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From scientific arguments to scepticism: Humans’ place in the Greenhouse

This article investigates the different roles attributed to humanity in the climate change debate, through the depiction of the greenhouse effect . Our hypothesis is that the stance associated with different genres will not only demonstrate different conceptualisations of the greenhouse effect but also convey different views on humans’ capacity (or lack of capacity) to mitigate climate change. The corpus under study is composed of texts pertaining to three genres which display particular viewpoints: scientific papers present a documented view on the phenomenon, online forum discussions present exchanges between users who endorse or question particular characteristics of the Greenhouse , and sceptical newspaper articles explicitly deny the existence of an anthropogenic phenomenon. Through a corpus-based, cognitive and pragmatic analysis of the metaphorical expression greenhouse effect , the research shows that humans’ place(s) in the Greenhouse is a significant part of environmental argumentative strategies.

1. Introduction

This article proposes an investigation of the varying use of the metaphorical expression greenhouse effect in climate change discourse. This particular metaphor is in focus because the expression greenhouse effect may describe either a concept that is related to environmental disruption (i.e. anthropogenic climate change) or a concept that is related to a natural process enabling life on Earth. Therefore, I distinguish the metaphor greenhouse effect from other climate change metaphors such as carbon footprint ( Koteyko, 2010 ), runaway effect ( Van Der Hel et al., 2018 ) or war on pollution ( Atanasova and Koteyko, 2017 ). Indeed, these metaphors are all associated with the phenomenon of climate change and human alteration of the environment. In this article, I thus ask how metaphor users rely on the varying meaning of the expression greenhouse effect depending on the stance adopted in the texts. My hypothesis is that, while scientists may draw a distinction between a natural and an anthropogenic greenhouse effect, sceptical arguments may merge these two concepts to dispute the idea of an anthropogenic phenomenon (more details below).

The arguments analysed below are related to the role of humanity in the modification of the Greenhouse . In the corpus under study, we see that sceptical strategies can either deny humans’ responsibility or these may ignore the association between the greenhouse effect and climate change. These arguments attribute different roles to humans: humans can be depicted as the BUILDERS of a dangerous Greenhouse or as the DESTROYERS of the natural Greenhouse , or they can only be described as the CONTENT of the Greenhouse , deprived of any agency.

To appreciate the association between different stances and different perspectives on humanity in the Greenhouse , this article focuses on the arguments reported in three genres. These three genres present a graduation from objectivity, argumentation and scepticism. First, scientific papers represent documented views on the greenhouse effect and objective viewpoint is an essential criterion for scientific legitimacy ( Knudsen, 2015 ). Second, online forum discussions highlight the characteristics of the greenhouse effect , which can be questioned or disputed. Third, sceptical media offer an explicit bias on the greenhouse effect which aims at convincing readers that the anthropogenic greenhouse effect is not real.

Relying on cognitive linguistics, pragmatics and discourse analysis, I demonstrate how a scientific metaphor can convey opposite arguments in different contexts. The following section will explain the significance of metaphors in discourses describing a scientific topic, I then provide more information about my corpus and my methodology, and I present the different uses of the metaphor in the three genres. The discussion will highlight the interrelation between the different roles attributed to humans and different stances.

2. Climate change and metaphors

What is a metaphor.

My review of existing literature about climate change metaphors must first establish the significance of metaphors as a figurative device in discourse. From a cognitive perspective, a metaphor involves two conceptual domains: the target domain represents the literal concept which may be too complex or too abstract to be described literally. This target domain is associated with a source domain that represents a figurative, ‘alien’ concept which is more concrete and which is more familiar to the metaphor recipient ( Lakoff, 1993 [1979]). For example, the metaphorical compound carbon footprint depicts the impact and extent of carbon pollution (i.e. the target domain) with reference to a concrete, visible footprint (i.e. the source domain). The presence of this compound in a plurality of texts about climate change ( Koteyko, 2010 ) makes it easier for metaphor recipients to understand and quantify the impact of carbon pollution.

Pragmatic views on metaphors have established that the association between the two domains (called a ‘mapping’; Lakoff, 1993 [1979]) is performed through a transfer of characteristics from one domain to another ( Glucksberg, 2001 ). While the cognitive view does not necessarily tackle the significance of metaphors in context, pragmatics and discourse analysis have demonstrated that the meaning of the metaphor varies depending on the context in which it is used. Therefore, the target domain of the metaphor will be perceived according to certain characteristics shared with the source domain which are relevant in a particular context. For example, depending on the topic discussed in the texts, the carbon footprint aforementioned may refer to a large footprint or to a small footprint ( Augé, 2022 ).

The metaphorical meaning can be exploited and disputed to promote various arguments. These various arguments reveal the presence of metaphor scenarios in discourse ( Musolff, 2016 ). Scenarios include metaphorical expressions in argumentative discourses. They highlight the way the source domain (i.e. the concrete concept) can be perceived from different viewpoints to influence recipients’ opinions on a topic ( Musolff, 2016 : 30–31). For example, while the metaphorical compound carbon footprint is a significant concept in climate change discourse, this compound can be adapted to criticise specific polluters, attributing the footprint to a Carbon Bigfoot ( Koteyko et al., 2009 : 43). The expression drives the recipients’ attention towards polluters instead of pollution and it conveys particular arguments regarding the responsibility of polluters.

In the next section, I offer an overview of the existing findings related to climate change metaphors.

Climate change discourse

Through the mapping of a complex target domain and a concrete source domain, metaphors play an essential role in discourses about science ( Knudsen, 2015 ). In the context of climate change, these help to describe environmental concepts to a wide readership with limited scientific background (as opposed to a scientific readership). Since climate change is a global dangerous phenomenon, populations’ understanding of scientific concepts is essential to convince them to reduce pollution. Metaphors can help in this process through the reliance on familiar words to explain concepts such as the amount and impact of pollution, extreme weather events and their causes, or the evolution of climate. It is thus unsurprising to observe a wide variety of metaphors in climate change discourse: the tipping point metaphor describes the evolution of climate change towards a point where the phenomenon is out of control ( Van der Hel et al., 2018 ), the carbon footprint describes the amount and impact of carbon pollution ( Koteyko, 2010 ; Nerlich and Hellsten, 2014 ), green-washing describes economically biased processes that present marketed products as environmentally friendly ( Pérez-Sobrino, 2013 ), and the personification Mother Earth describes humans’ dependence on nature ( Augé, 2019 ).

Since climate change is still a disputed topic associated with a plurality of discourses (scientific, political, journalistic or environmentalist) and a plurality of opinions, related metaphors are accordingly involved in the promotion of various arguments. For instance, scholars demonstrate how WAR metaphors associated with climate change can convince recipients of the urgency to find solutions, as in: ‘How to win the war on global warming?’ ( Mangat and Dalby, 2018 : 3). Atanasova and Koteyko (2017) show that this metaphor is predominantly associated with environmentalist arguments in newspapers. In addition, Flusberg et al.’s (2017) survey shows that WAR metaphors are more likely to convince recipients to act upon climate change as opposed to other metaphors such as RACE metaphors, as in ‘When will Americans go after excessive energy use and surge ahead on problems?’ (p. 772). Indeed, the metaphorical idea of winning a race comprises positive, yet non-essential characteristics compared with the metaphorical idea of winning a war , which comprises necessary characteristics for survival ( Flusberg et al., 2017 : 772). Alternatively, RELIGION metaphors in climate change discourse have been shown to promote scepticism in the media, as in the following: ‘They (G8 leaders) are like medieval preachers proclaiming to baying crowds that the end of the world in nigh’ ( Atanasova and Koteyko, 2017 : 460). Nerlich (2010) establishes that RELIGION metaphors represent a significant part of climate change discourse when these focus on scandals like the scandal of the Climategate. 1 The complexity of the problem and the existing scientific uncertainties regarding climatic evolution were mapped with the uncertainty regarding religious dogma. However, other scholars demonstrate that RELIGION metaphors have been used to dispute such sceptical arguments to present scientists as prophets capable of interpreting signs ( Foust and Murphy, 2009 : 153–156). Nay and Brunson’s (2013) survey demonstrates that MEDICINE metaphors may also effectively convince recipients to protect the forests (p. 165), as in the following: ‘An ecological system is healthy and free from distress syndrome if it is stable and sustainable’ ( Ross et al., 1997 : 119). MEDICINE metaphors can promote compassion among recipients who can interpret environmental disruption according to their own experience of sickness ( Augé, 2021 ).

While I acknowledge the significant contribution of existing research about climate change metaphors, this overview suggests that metaphorical environmentalist arguments have mainly been observed in the use of non-specific metaphors such as WAR, RELIGION, RACE and MEDICINE. The next section will focus on the particularities of the greenhouse effect metaphor.

The greenhouse effect

With attention paid to the greenhouse effect , existing literature demonstrates that this concept is constitutive of climate change scientific theory ( Nerlich and Hellsten, 2014 ). The source domain GREENHOUSE comprises a wide variety of characteristics, which can map with climate change: the concept Greenhouse describes a container in which specific temperatures are to be kept to enable particular plants to grow. Romaine (1996) relates the expression to the mapping EARTH AS A CONTAINER (p. 181). The particularities of the source domain GREENHOUSE involve an additional mapping emerging from the EARTH-CONTAINER, which identifies HUMANS AS PLANTS (i.e. the plants are the typical content of the Greenhouse; Romaine, 1996 : 181). Nerlich and Hellsten (2014) demonstrate how the source domain GREENHOUSE helps metaphor recipients to see a concrete representation of the impact of pollution (p. 28). Deignan et al. (2019) indicate that the greenhouse effect metaphor is used by different discourse communities. They show that this metaphor seldom occurs in academic articles about climate change while educational texts and interviewed students use this particular metaphor more frequently ( Deignan et al., 2019 : 385–388). They also note that the greenhouse effect metaphor may lead to misunderstandings. The interviewed students referred to the greenhouse effect as a thin layer around the planet which does not let heat out, while greenhouse gases are rather ‘dispersed’ in the atmosphere, according to the linguists’ academic corpus ( Deignan et al., 2019 : 394). Such a misunderstanding of the scientific concept is supplemented by a ‘domestication’ process observed in the media, where climate change is misrepresented as a local phenomenon ( Brown, et al. 2011 : 664–665; Olausson, 2009 ).

This article offers a different viewpoint on the greenhouse effect . I see that existing literature has mostly focused on its explanatory function. Here, I investigate the argumentative role of this metaphor in scientific discussions, online forum discussions and sceptical media commentaries. I aim at showing that the greenhouse effect metaphor is not only a ‘technical term’ but has a significant role to play in the promotion of arguments about anthropogenic climate change.

3. Methodology

To investigate the different arguments related to the metaphorical expression greenhouse effect , I build a corpus of texts composed of scientific articles, online discussions and newspapers.

To access scientific articles, I relied on the Web of Science ( n.d. ), which gives access to a plurality of research articles. I limited my selection to papers published in the journal Nature released between 1990 and 2019. Nature has been selected for this study to discuss exemplary uses of the metaphor in a scientific context. This journal has been of particular interest, as opposed to other scientific journals like Science or Climate Change , because I noticed many references to these papers in the media (see below) and because my research on Web of Science has demonstrated that Nature is the journal that most frequently relies on the expressions ‘climate change’ and ‘global warming’ in the titles of the associated papers. Such explicit references to the phenomenon are helpful to non-scientists to rapidly identify the main topic discussed in the articles which can, then, be included in the corpus. To access these articles, I used particular keywords: ‘climate change’ OR ‘global warming’ as the topic, and ‘greenhouse effect’ as a term included in these articles. This procedure resulted in a corpus composed of 153 scientific articles.

Online discussions about the environment were selected from the electronic corpus provider SketchEngine ( Kilgarriff, 2014 ). SketchEngine is an online corpus provider, which gives access to different electronic corpora of texts produced in different languages and different contexts (i.e. general contexts, political contexts, scientific contexts, historical contexts or online discussions). These corpora allow the analyst to search for a particular search term (here, ‘greenhouse effect’) to observe a plurality of data which rely on this term in different contexts. Among the available electronic corpora, I selected the corpus EnTenTen which is an electronic corpus of data produced in English. The data comprised in the corpus EnTenTen have all been collected from the Internet (e.g. blogs, forums, online commentaries, advertisements). EnTenTen gathers data, which have been produced from 2008 to 2018 (latest version of the corpus produced in 2015). Thanks to the functions provided by SketchEngine , the researcher may focus on data collected during a specific time, in a specific language and on a specific online source. For the purpose of my research, I discarded the data occurring in specialised contexts such as scientific blogs as well as data occurring in online press releases (explicitly identified as such in SketchEngine advanced search tools). I thus focused on the data produced by ‘lay’ people, that is, general blogs, online commentaries and forums (as indicated in the sources provided by SketchEngine ). I first performed a search using the function WordSketch , which presents the most frequent collocates of the search term (here, ‘greenhouse effect’; see Table 1 ). This research yielded 8433 occurrences in the electronic corpus, which have been automatically classified according to the collocates. These collocations help to see automatically generated categories of the different uses of the search term. These categories thus offer a first overview of the different contexts and, more precisely, the different concepts with which ‘the greenhouse effect’ can be associated. I then performed a more intensive search, paying attention to the contextual information provided for each type of collocations. This contextual information helped me to establish the source from which the data have been extracted (blogs, commentaries, forums, identified in the ‘information’ settings available for each data), with attention paid to the characteristics of the source (I can infer that scientists or journalists may also rely on blogs, commentaries and forums) to avoid including data that would be similar to the data I investigate in the other genres (scientific papers and media). In addition, this information warrants the assumption that the expression is used in a context associated with climate change, with particular attention paid to specific words indicating a contextual link, that is, ‘pollution’, ‘environment’, ‘climate’, ‘weather’ or ‘global’. When doubts persisted regarding the context of use, the decision was not to include the related data in my corpus. An overview of the collocations provided by EnTenTen is displayed in Table 1 .

Overview of the collocates of ‘greenhouse effect’ ( EnTenTen ).

Newspaper articles have been retrieved from the database Nexis ( n.d. ). This database allows researchers to access articles from different countries and produced over a 40-year timespan. For the present purpose, I selected English language newspapers with the keywords ‘climate change’ OR ‘global warming’ AND ‘greenhouse effect’. The period of publication starts in 1990 and ends in 2019. I focused on English language newspapers because I do not aim at establishing a link between environmental arguments and cultures. I thus selected newspapers displaying texts produced in the English language, although admittedly United Kingdom, United States or Australian stances may highlight cultural variations. In addition, I selected articles whose headlines explicitly showed a sceptical stance towards climate change. For example, I selected articles which described the phenomenon or associated decisions as a ‘scam’, a ‘con-trick’, ‘hot air’, a ‘fake’ news, or a ‘wrong’ claim. Instances of such sceptical arguments can be best described in headlines such as ‘The climate change scam: what should I believe and why’ ( News Wire , US, 24 September 2015). This selection resulted in the inclusion of 297 articles in my corpus.

To interpret the metaphorical expression in context, I used the Metaphor Identification Procedure VU University Amsterdam (MIPVU) ( Steen et al., 2010 ). MIPVU proposes four steps to determine whether an expression can be established as metaphorical:

1. Reading the text 2. Selecting lexical units 3. Interpreting these units in context and searching for a more ‘basic’ meaning in other contexts 4. Interpreting the ‘basic’ meaning in the context under study. ( Steen et al., 2010 : 4–6)

The emphasis on the role played by the communication level on the interpretation of a metaphorical expression required additional steps: the researcher can consult dictionary entries to determine the referential meaning of the utterance in context ( Reijnierse et al., 2018 ).

Once I distinguished metaphorical occurrences of greenhouse effect from non-metaphorical occurrences in our corpus, I observed the co-text of the occurrences. This initial observation permitted an overview of the role played by humans within the mapping EARTH AS A GREENHOUSE in scientific papers, online discussions and sceptical newspaper articles.

Even though the timespan of the publication of texts and the number of texts and occurrences significantly vary from one genre to another, I emphasise that the scope of this research is corpus-based ( Tognini-Bonelli, 2001 ): I aim at presenting various uses of the metaphor greenhouse effect in the different genres to observe the roles attributed to humans, but our findings do not tackle the overall use of the metaphor in the totality of my corpus. Therefore, when an occurrence was established as metaphorical but did not promote particular argument or was not explicitly related to humans’ contribution, I did not include it in my corpus. In addition, when doubt persisted regarding the interpretation, the occurrence was not included either. Following this selection, I obtained a corpus of 71 occurrences in scientific papers, 392 occurrences in online discussions and 95 metaphorical occurrences in newspapers. The findings presented in the following sections highlight how the place of humans within the Greenhouse may differ depending on the arguments promoted in each text.

4. Scientific arguments

The papers selected from the journal Nature show a distinction between the natural greenhouse effect and its anthropogenic version related to climate change. We see that ‘the greenhouse effect’ can be explicitly characterised with particular qualifications: these rely on adjectives such as ‘natural’, ‘anthropogenic’, ‘human-made’, ‘beneficial’ or ‘threatening’. These adjectives highlight that the concept greenhouse effect is a unique effect that is progressively transformed by human activities. Such a transformation is adequately described in the following example:

(1) Although models (and simple theory) indicate that such a change, which would increase mid-latitude land precipitation, might be expected to accompany an anthropogenic greenhouse warming , most models seem to underestimate the magnitude of this circulation change. (. . .) Physically, therefore, it has long seemed plausible that the distribution of relative humidity would remain roughly constant under climate change, in which case the Clausius–Clapeyron relation implies that specific humidity would increase roughly exponentially with temperature. ( Nature , volume 419, 224–232 (12 September 2002), Myles R. Allen and William J. Ingram)

In extract (1), the scientists refer to a ‘greenhouse warming’ instead of a ‘greenhouse effect’. While both expressions depict a global system that warms the planet, the former phrase emphasises the negative impact of the warming. Indeed, while the greenhouse effect is an expression which can be applied to both natural and unnatural processes, greenhouse warming expresses the increase in temperatures, which differs from the temperatures provided by greenhouse effect . The addition of the adjective ‘anthropogenic’ identifies the human origin of this increase. The scientists thereby linguistically emphasise the (negative) evolution of the greenhouse effect which is referred to by two distinct expressions to differentiate the warming processes. Hence, humans’ active role is perceived as the origin of the ‘change’, and this change comes with negative characteristics explained in the remainder of the extract: ‘increase mid-latitude land precipitation’, ‘specific humidity would increase roughly exponentially with temperature’. Scientists attest that human activities have not only increased warming but also modified the functioning of the greenhouse effect to the point that this effect is now characterised as an ‘anthropogenic warming’.

In other extracts, the scientists focus on the identification of gases and pollution as the MATERIAL of the human-made Greenhouse . In such cases, humans’ role is even more significant as humans become the BUILDERS of the unnatural Greenhouse or the DESTROYERS of the natural Greenhouse . These characterisations can be observed in the extract presented below:

(2) Previous studies have concluded that climate change owing to increasing greenhouse-gas concentrations will have a detrimental effect on the ozone layer over the next few decades (. . .) We emphasize, however, that while CFC levels remain artificially high, the ozone layer will continue to be vulnerable to the enhanced destruction resulting from a greenhouse cooling of the stratosphere . ( Nature , volume 410, 799–802 (12 April 2001), Neal Butchart and Adam A. Scaife)

In extract (2), the scientists describe ‘greenhouse-gas concentrations’ as the origin of climate change. Although human activities are not explicitly mentioned, the link established between the concentrations and climate change shows that the expression refers to the unnatural Greenhouse . In such cases, humans are not only seen as the BUILDERS OF THE UNNATURAL GREENHOUSE but also as the DESTROYERS OF THE NATURAL GREENHOUSE. Indeed, while humans’ addition of gases is modifying the GREENHOUSE-EARTH (‘owing to increasing greenhouse-gas concentrations’; ‘CFC levels remain artificially high’), this addition is also described as destroying some components of the NATURAL GREENHOUSE, the ozone layer. The GREENHOUSE is here mapped to another target concept: the cooling stratosphere, which indicates that the UNNATURAL GREENHOUSE also causes the cooling of components. Hence, the addition of MATERIAL (CFCs) transforms not only the characteristics of the GREENHOUSE-ATMOSPHERE but also the characteristics of the GREENHOUSE-STRATOSPHERE. Therefore, humans’ active role in the GREENHOUSE is emphasised as they implicitly perform the dual functions of BUILDERS and DESTROYERS of the GREENHOUSES.

In different articles, scientists rely on the metaphor to describe the evolution of the greenhouse effect . Since the exact characteristics of this evolution are linked with significant uncertainties, scientists dispute existing claims regarding the need to prepare for an apocalyptic Greenhouse world ( Foust and Murphy, 2009 ) without adopting preventive solutions. The metaphor EARTH AS A HEATED CONTAINER aims at illustrating an imaginary state of future climate, as in:

(3) But I am not aware of any scientist or environmental activist who have ever used the phrase ‘runaway global warming’ in the context of Earth (the jargon is usually reserved for the oven-like super-greenhouse effect on Venus ); and, needless to say these dissembling activists and scientist-hysterics go unnamed and uncited in Parsons’ text. ( Nature , volume 381, 384–386 (30 May 1996), Stephen H. Schneider) 2

In extract (3), the scientist describes the greenhouse effect as an OVEN to depict the warmth on the planet Venus, which prevents life on this planet. This conceptualisation aims at criticising Edward Parson, a Professor of Law and Environment. 3 This criticism is a reply to Parson’s stance about (supposed) scientific characterisation of the greenhouse effect on Earth as a RUNAWAY effect.

This scientific characterisation is denied by Stephen Schneider who attributes a RUNAWAY characteristic to the climatic conditions of Venus. He emphasises the impossibility of applying this characteristic to the Earth through the use of the source domain OVEN. This source domain is effective in illustrating a very high degree of heat, which is fatal to humans. Since the warming on Earth does not prevent human life, the temperatures cannot be equated to OVEN-LIKE temperatures and the greenhouse effect cannot be described as a RUNAWAY effect.

The scientist relies on exaggeration to contradict Parson’s claims. He also questions the existence of ‘dissembling activists and scientists-hysterics’ who supposedly coined this analogical qualification. The characterisation of these scientists as ‘hysterics’ emphasises the absurdity of the comparison between the climatic conditions on Venus and the conditions on Earth.

These three examples from Nature show that scientists give a prevalent role to humanity in the Greenhouse . This role is associated with increasing warmth within the CONTAINER and We see a criticism related to human activities: humans are described as BUILDING a Greenhouse that endangers their life while they also DESTROY a Greenhouse that offer(ed) them a pleasant environment to live in. We also see that scientific stance may dispute humans’ lack of capacity to act upon the greenhouse effect : characterisation of humans as the passive victims ‘cooked in an oven’ is explicitly criticised to promote existing solutions. In the following section, I will study the uses of the metaphor in online discussions.

5. Arguments from online discussions

The occurrences of the metaphorical expression greenhouse effect in online discussions offer an overview of the characteristics of the concept, which can be debated by online users. We see that debates about the g reenhouse effect can encompass humans’ responsibility to mitigate the effects. We also see how sceptical stances can be moderated or contradicted through online exchanges. Although I cannot always access the full exchanges from which the selected data originate, the varying use of the metaphor can highlight the negotiation of the characteristics of the Greenhouse . For instance, the example below shows that sceptical stance can be associated with a promotion of humans’ responsibility:

(4) I love the minimalistic idea of living with less. I believe that the best way to save on home expenses is to live in a house in the country. You can produce your own organic food, your own fuel for heating, your own power from alternative sources like solar panels. While I don’t believe in such bullcrap like human-induced greenhouse effect , I want to reduce my impact on the environment. I want to use as little fossil fuels as possible, having my own plot of land will allow me to produce my own biomass. ( EnTenTen , token: 13073468485)

In extract (4), the metaphor user denies the ‘human-induced’ characteristics of the greenhouse effect . Here, the alteration of temperatures is not perceived as a clue of the transformation of the Greenhouse . Indeed, climatic changes are not mentioned to give prevalence to the role of humans within the Greenhouse . While the stance of the extract is sceptical ( ‘bullcrap’), the metaphor user presents environmental actions as a reasonable human behaviour. Cutting down fossil fuels and living in a sustainable manner are actions which can be assimilated, in the extract, to CLEANING-SANITISING ONE’S HABITAT. I can observe an argumentative strategy which places humans in the role of the inhabitants of the shared Greenhouse . This conceptualisation implies that while the anthropogenic cause of climate change is denied, humans are yet attributed the responsibility to take care of the planet. Such a responsibility can be emphasised further in the discussions, especially when the metaphor is used in a politically oriented context showing the users’ opinions on environmental decisions. This emphasis is observed in the example below:

(5) In addition if carbon dioxide contributes 20% to the terrestrial greenhouse effect , then what a waste of time a carbon tax will be in Australia, especially if the ‘others’ don’t follow suit. It is fiction to believe we will set an example and the others will follow, Australia already tried that with free trade and level playing fields; as a result our manufacturing industries are a basket case and agriculture is following close behind. ( EnTenTen , token: 2675720970)

In extract (5), the metaphor user refers to the conceptualisation of humans as the BUILDERS of the unnatural Greenhouse through a criticism related to the ‘carbon tax’. This tax aims at forcing carbon emitters to financially contribute to climate change mitigation. However, the metaphor user is critical of such a contribution: he or she highlights that the identification of HUMANS AS BUILDERS only holds because of humans’ carbon emissions. Yet, he or she emphasises that carbon represents a minor element of the MATERIAL of the Greenhouse (‘20%’). Hence, in view of this percentage, the association between HUMANS-BUILDERS and carbon emissions implies that humans cannot be identified as the main BUILDERS. An additional argument refers to humanity as the global CONTENT OF THE GREENHOUSE to promote global responsibility. This denial aims at arguing against the carbon tax, which is grounded in a (political) belief that humans have a prominent role in the CONSTRUCTION of the Greenhouse (and are, therefore, expected to stop this CONSTRUCTION).

Alternatively, the dangerous levels of heat increases are exploited by online users who can refer to climate change as a series of threats caused by humans’ consumption. This unreasonable consumption is perceived as MISCHIEVOUS ACTIONS which must be reprimanded by a higher authority, as in the following:

(6) The global climate is changing. And it is rapidly morphing as the temperature rises too quickly. Over centuries, our dependence on carbon fuel is finally playing the death knell loud and clear. The overall greenhouse effect is causing a spike in the temperature of the Earth’s atmosphere and this is causing the polar caps to melt. Scientists anticipate that if the polar caps melted entirely, all the clear freshwater will mingle with the salty sea water to create a concoction that we couldn’t survive on at all. Rather, it will risk tainting the fresh water sources we still count on today. (EnTenTen, token: 6016353006)

In extract (6), the metaphor user pictures humans’ gas emissions as MISCHIEVOUS ACTIONS, which have long been unnoticed (‘finally’). However, the link established by scientists between emissions and climate change leads the metaphor user to infer that environmental threats represent a PUNISHMENT. The paradox highlighted in the extract between humans’ acknowledgement of such a link and their continuing reliance on gases is described as a LETHAL DEPENDENCE. The metaphor user does not consider the possibility of reduction and, therefore, does not question the impact of the ‘death knell’. I can also identify a conceptual association between the greenhouse effect and FOOD-related lexicon through the characterisation of the climatic effects as a DEADLY CONCOCTION. Here, the Greenhouse becomes a HEATED CONTAINER which imprisons humans following their misbehaviour. Such an imprisonment is followed by a series of lethal events – described in the extract as deliberate reprimands performed by a personified version of climate change – which constitute climate’s response to humans’ actions.

These three examples show that online discussions offer relevant data regarding the varying argumentative use of the metaphorical expression greenhouse effect . We see how scepticism may only be attributed to particular characteristics of the greenhouse effect , such as reduction policies. In the following section, I will discuss the argumentative uses of the metaphor in highly sceptical contexts.

6. Sceptical arguments

Sceptical newspaper articles are also of particular interest. This genre has been selected among other possible sceptical discourses because articles’ headlines allow the researcher to rapidly establish the sceptical stance. Here, I focus on how scepticism may alter humans’ place in the Greenhouse . I see that sceptical journalists favour a depiction of humans as the passive inhabitants of the Greenhouse : these views may either deny the existence of a dangerous phenomenon or question the possibility for humans to mitigate the evolution of the greenhouse effect . For instance, the example below emphasises the role of the planet in keeping humans’ habitat adapted to human life:

(7) The two scientists compared the predictions about what the atmosphere ‘should’ do to what satellite data showed the atmosphere actually did do during the 18 months before and after warming events since 2000. They found – shock! – that the computer models vastly overestimated the greenhouse effect . Turns out that the Earth is far more capable of equalizing its own temperature than environmentalists would have us believe. ( The New York Post , Matt Paterson, 2 August 2011)

Extract (7) questions scientific findings related to the evolution of the greenhouse effect . The journalist uses scientific admitted overestimation to promote sceptical arguments related to humans’ contribution to dangerous warming. Indeed, the greenhouse effect is exclusively perceived in relation to climate change and, more precisely, to irreversible future climate change. As noted in our discussion of scientific examples, we see that these predictions are surrounded by uncertainties. In turn, the journalist depicts the greenhouse effect as a process, which does not bear any dangerous characteristics: according to the journalist, this effect will evolve without representing a threat to humans’ survival. I also see that possible human actions to mitigate the effect are not even mentioned. These actions are only inferred through a vague reference to ‘environmentalists’ who promote worrying views on the climate. Here, the Earth is the main protagonist of the narrative: through personification (‘is far more capable’), the planet is perceived as a benevolent character who is the sole entity capable of modifying the climate. Yet, as climate change may lead to its destruction, the journalist claims that the planet has a defensive system preventing catastrophic warming. The anthropogenic characteristic of the greenhouse effect is not explicitly denied: since the Earth is expected to ‘equalise’ its temperatures, I can infer that the journalist still considers humans’ alteration. However, the scepticism is related to the significance of humans’ alteration, which does not outreach the Earth’s capacities to provide adapted temperatures.

Scepticism may also be related to the reality of climate change as a phenomenon comprising temperature increase and anthropogenic causes. This is exemplified in the extract below:

(8) Flying into Churchill, the weather seems cold enough. If minus 5C means the greenhouse effect is upon us , heaven knows what it was like before. ( Daily Mail , David Jones, 8 December 2007)

In extract (8), the journalist presents the greenhouse effect as a perceptible clue of climate change. Since the journalist cannot perceive such a clue (‘minus 5C’), he questions the very existence of the Greenhouse (‘upon us’). Here, the natural effect is not considered: the journalist only refers to the claims that humans have BUILT a Greenhouse which endangers their survival. Since this BUILT CONTAINER is characterised by warm temperatures, the experience of cold weather represents an event that leads sceptics to question the reality of this human action. In addition, the inference regarding the experience of temperate weather in the past (‘before’) is conceived as a proof that humans are not BUILDING A GREENHOUSE. Therefore, the sceptical stance is related to the existence of the anthropogenic greenhouse ; in other words, the journalist disputes the fact that humans (or nature) have an active role in the modification of climate and that climate is changing.

We see that, in these two extract, the journalists mainly consider humans’ alteration and temperature increase. However, they do not focus on the lethal consequences of the phenomenon. These lethal consequences are described in other articles through the conceptualisation of the EARTH AS A HEATED CONTAINER. This is demonstrated in the example below:

(9) Many people are worried about the greenhouse effect of carbon dioxide. The real problem is that scientists are not telling the truth about carbon dioxide. Early in the earth’s history the earth was boiling hot and the major gas in the atmosphere was carbon dioxide. So the greenhouse effect of carbon dioxide isn’t as effective as supposed because with the extremely high amount of carbon dioxide in the atmosphere the earth cooled off. ( News release Wire , 6 May 2005)

In extract (9), the journalist describes the greenhouse effect through references to an anthropogenic, climate change–related phenomenon (‘many people are worried about the greenhouse effect of carbon dioxide’) and references to a natural, non-threatening phenomenon (‘early in the earth’s history’). The existence of an unnatural Greenhouse BUILT by humans is denied: the ‘scientists’ quoted in the extract are identified as spreaders of fake news regarding the danger of humans’ alteration. First, I see that humans’ alteration is exclusively perceived through carbon pollution (‘greenhouse effect of carbon dioxide’). Yet, the journalist claims that humans do not play any role in the CONSTRUCTION of the Greenhouse since the MATERIAL they are adding (according to the scientists) was already present ‘early in the earth’s history’ (which might refer to a time when humanity did not exist). Second, the impact of this ADDITION OF MATERIAL (i.e. carbon dioxide) is not explicitly described as dangerous. I here see a problem in the journalist’s argumentation. Indeed, he or she first claims that the greenhouse effect of carbon dioxide was associated with threatening temperature increase (‘the earth was boiling hot’), but he or she denies that the greenhouse effect was the cause since it did not prevent the Earth from ‘cooling off’. Hence, even though the journalist aims at denying the impact of the greenhouse effect , he or she still endorses the fact that temperatures may significantly vary to the point that humans may not survive. In addition, from a cognitive viewpoint, another argumentative problem appears: the journalist denies the fact that the greenhouse effect has an impact on the Earth’s temperatures while the source domain GREENHOUSE still bears characteristics associated with a WARM CONTAINER. These argumentative issues appear because the journalist focuses on humans’ addition of carbon, and he or she argues that humans are only passive INHABITANTS who might suffer from uncontrollable climatic cycles. Yet, this occurrence still presents a threatening view on the climate which can ‘boil’ the Earth (contradicting extract 7). As a result, this lack of human control not only promotes human inaction towards carbon reduction (see also extract 5) but also emphasises the extent of the danger related to climate change.

These three extracts show that sceptical arguments in the media may focus either on the lack of real danger associated with the greenhouse effect – humans may not need to reduce their emissions – or on humans’ contribution to the BUILDING of the Greenhouse – natural climatic evolution represents a clue that humans cannot control the climate. In the following section, I will further discuss the different roles attributed to humanity in the three genres.

7. Discussion

Considering existing research on the greenhouse effect metaphor, this article demonstrated the variety of characteristics associated with source domain GREENHOUSE in climate change discourse. Depending on the stance adopted in the texts, I see that different genres attribute different roles to humans in the Greenhouse . Therefore, metaphors which are constitutive of climate change theories cannot be attributed a single, scientific meaning ( Deignan et al., 2019 ): this meaning is exploited by different discourse producers to promote environmental arguments ( Musolff, 2016 ).

Considering Romaine’s (1996) finding about the identification of HUMANS AS PLANTS CONTAINED IN THE GREENHOUSE, I see that scientific uses and online discussions do not significantly endorse such a characterisation, even when they promote arguments questioning climatic claims (in online forums). However, this mapping is relevant to sceptical journalists who criticise claims related to humans’ alteration of the Greenhouse . The GREENHOUSE concept allows PLANTS to grow but PLANTS are not expected to have any influence on the GREENHOUSE that contains them. In addition, PLANTS are non-human, inanimate, and material referents. These HUMANS-PLANTS therefore correspond to humans’ passive role in the Greenhouse narrative. Sceptical journalists relied on the mapping HUMANS AS PLANTS to convince recipients not to adopt environmental policies and not to feel threatened by the phenomenon. Alternatively, in online forums, users may argue against certain policies (i.e. the carbon tax) but still endorse the image of humans contributing (yet, partially) to the CONSTRUCTION of the Greenhouse .

While the GREENHOUSE concept was figuratively extended to become an EARTH-CONTAINER providing adapted temperatures to its CONTENT, the fact that pollution has altered the climate means that the GREENHOUSE does not provide adapted temperatures anymore. This subsequently alters the identification of HUMANS AS PLANTS. Humans are conceptualised as the INADEQUATE CONTENT OF THE GREENHOUSE, following appropriate knowledge about the characteristics of PLANTS, which grow within a greenhouse , and the characteristics of PLANTS, which do not grow in a greenhouse . The impact of humans’ activities has promoted a different view on humans’ role in the Greenhouse . This active role may slightly differ in scientific papers and in online discussions.

First, in scientific extracts, pollution is perceived as a MATERIAL added by humans to the Greenhouse . This MATERIAL implicitly demonstrates humans’ contribution to the BUILDING of the GREENHOUSE. In online discussions, humans are also identified as the BUILDERS, but this process may or may not have any incidence on the Greenhouse – which can still be described through its natural characteristics.

Second, in scientific extracts, humans are attributed a prominent role: they are not only represented as the BUILDERS of the Greenhouse – leading to scientific arguments regarding the alteration of living conditions – they are also depicted as the DESTROYERS of the natural Greenhouse which provided adapted temperatures. This conceptual DESTRUCTION in scientific descriptions of the greenhouse effect is related to an emphasis on the threatening consequences of human activities, which may lead to irreversible climate change. Hence, the claim that scientists may not promote threatening images of climate change ( Weingart et al., 2000 ) can be contradicted by my findings: I showed that scientists’ documented view on the phenomenon enables them to offer a detailed metaphorical picture of humans’ alteration of the environment. In addition, my findings echo existing literature about scientific representations of humanity: I see that scientists depict humans as a species capable of altering the climate. Yet, while they draw an explicit distinction between a natural, anthropogenic or stratospheric Greenhouse ( s ), such a distinction does not occur regarding humanity. Humanity – as a whole – contributes to the (DE)CONSTRUCTION, discarding individual or national pollution rates (see Besley et al., 2018 ; Dawson, 2018 ). Scientists dispute the image of humans as PLANTS as they aim to demonstrate humans’ active role not only in the alteration of climate but also in the application of solutions.

The threat represented by future climate change – which transforms into ‘climate chaos’ ( Dahl and Fløttum, 2014 : 415) – has promoted particular metaphorical descriptions. These descriptions favour metaphorical pictures of a former NATURAL GREENHOUSE-EARTH which has fully achieved its transformation into a HEATED CONTAINER. Such a picture of hypothesised evolutionary trends may contradict the scientific stance which focuses on experiment, models, and tests ( Knudsen, 2015 ). Online users and sceptical journalists relied on this mapping to identify a danger which may either be a direct response from the climate to humans’ activities or represent the uncontrollable characteristic of the climate, discarding humans’ presence in the Greenhouse . The role of humans as the powerless CONTENT promotes a re-occurrence of the identification of HUMANS AS PLANTS. Yet, this view on humans’ passive role is not endorsed in scientific descriptions. I can see how the metaphor may be used to fit scientific observations, and how the metaphor has been extended in argumentative discourses to produce metaphorical conceptualisations resulting in non-scientific descriptions of climate change. This discussion highlights a graduation from the prominent roles attributed to humans advertised in science, the questioning and endorsement of certain characteristics related to these roles in forums, to the promotion of the negligible role played by humans in sceptical articles.

I should finally acknowledge that my corpus-based approach ( Tognini-Bonelli, 2001 ) does not allow me to make any exhaustive claims about scientific, journalistic or online uses of climate change metaphors. Yet, the examples discussed in this article demonstrate the varying places attributed to humans through the uses of a specific metaphor, depending on particular stances on climate change. In addition, the selection of particular sources ( Nature, EnTenTen, Nexis ) does not allow me to offer a diachronic view on metaphorical descriptions. It would be relevant to use comparable sources for the corpus to observe how the metaphor has evolved over time. For instance, forthcoming research will focus on the impact of controversial events on the use of metaphors in different discourses about climate change. This article demonstrated that questioning climate change can lead to the questioning of humans’ environmental capacities. Through the use of a metaphor, environmental control may be attributed to human agents or to a personified version of the ecosystem.

Author biography

Anaïs Augé is a linguist interested in metaphor studies, corpus analysis, political and scientific discourse studies, and cultural communications. She does research on the representation of environmental issues and its impact on communities in different regions of the world.

1. The Climategate scandal took place in 2009 when climate scientists from the University of East Anglia saw their emails hacked and spread to the media. The content of these emails highlighted scientists’ doubts and pressures, and this impacted the public opinion: the discussion of this scandal in the media promoted a rise of scepticism.

2. Extract (3) questions the mapping of the source domain RUNAWAY to the target domain EARTH CLIMATE. Here, the scientist argues that the target domain VENUS CLIMATE is more appropriate.

3. Edward Parson’s biography is available at: https://www.ucsusa.org/about/people/edward-parson

Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding: The author(s) received no financial support for the research, authorship and/or publication of this article.

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What is the greenhouse effect?

planets

Scientists have determined that carbon dioxide plays a crucial role in maintaining the stability of Earth's atmosphere. If carbon dioxide were removed, the terrestrial greenhouse effect would collapse, and Earth's surface temperature would drop significantly, by approximately 33°C (59°F).

Greenhouse gases are part of Earth's atmosphere. This is why Earth is often called the 'Goldilocks' planet – its conditions are just right, not too hot or too cold, allowing life to thrive. Part of what makes Earth so amenable is its natural greenhouse effect, which maintains an average temperature of 15 ° C (59 ° F) . However, in the last century, human activities, primarily from burning fossil fuels that have led to the release of carbon dioxide and other greenhouse gases into the atmosphere, have disrupted Earth's energy balance. This has led to an increase in carbon dioxide in the atmosphere and ocean. The level of carbon dioxide in Earth’s atmosphere has been rising consistently for decades and traps extra heat near Earth's surface, causing temperatures to rise.

  • The Greenhouse Effect (UCAR)
  • NASA's Climate Kids: Meet the Greenhouse Gases! (downloadable and printable cards)
  • NASA's Climate Kids: What Is the Greenhouse Effect?

Encyclopedia of the Environment

Overview of the physics of the atmospheric greenhouse effect

What exactly is the greenhouse effect ? Radiation can be described as a flow of elementary particles, photons, each of which has a certain energy, proportional to the frequency of the radiation (see The thermal radiation of the black body ). In the atmosphere, when a photon meets a molecule, it can capture its energy, but only under certain conditions. The first is the presence of a permanent electrical dipole moment . What is it about? In any molecule we can distinguish the ensemble of positive electrical charges, the protons of its atoms, and the ensemble of negative electric charges, the electrons. Each of these two ensembles can be associated with a barycentre and, if the two barycentres do not coincide, the molecule has a non-zero electric dipolar moment. On the other hand, when these two barycentres occupy the same position, as in the symmetrical diatomic molecules N 2 and O 2 which are the most frequent in the atmosphere, the electric dipolar moment is zero and these molecules cannot participate significantly in energy exchanges with photons.

Besides, more complex molecules, such as H 2 O, CO 2  and CH 4 , have vibrational modes that allow them to absorb energy. In the case of H 2 O, in a stable position the two H-O bonds form an angle of 120°; they can absorb energy by flapping on either side of their average position, like butterfly wings. The CO 2  molecule is linear and symmetrical, with two double bonds: O=C=O. It is then the positions of the O atoms that can oscillate in order to absorb energy, either by bending on either side of the average position, or by moving away from and approaching the C atom, symmetrically or not. Other species in the atmosphere, such as methane CH 4 , also have vibrational modes that allow them to absorb the energy of certain photons.

The second condition is related to the quantum character: the energy of the photon must be equal to the energy jump of the vibrational mode of the molecule . This implies that molecules can only pick up certain wavelengths. This is why some can absorb the Earth’s infrared radiation in bands of well-defined wavelengths, called absorption windows, separated by transparency bands (Figure).

Within the atmosphere, molecules that have captured a fraction of the Earth’s infrared radiation exchange it with their neighbours during collisions. This results in some heating of this gaseous medium, which contributes to the temperature distribution. And the atmosphere radiates some of this energy to the land and to oceans (150 W/m 2 ), which is the greenhouse effect . The respective contributions of the various molecules are very different. Note, for example, that, per unit mass, the contribution of water vapour is 6 times greater than that of carbon dioxide, and that that of methane is 21 times greater. Considering the respective contents of these gases in the atmosphere (0.1 to 5% for H 2 O, 0.035% for CO 2  , about 10 -6 for CH 4 ) and their molar masses, it is clear that the most important contribution to the greenhouse effect comes from water (about 75%).

This focus was written by René MOREAU  Emeritus Professor in Grenoble-INP, SIMaP Laboratory (Science and Engineering of Materials and Processes), member of the Academy of Sciences and the Academy of Technologies and BELORIZKY Elie , Former Professor at the Joseph Fourier University, LIPhy (Interdisciplinary Laboratory of Physics), UGA

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Understanding Global Change

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Greenhouse effect

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Life as we know it would be impossible if not for the greenhouse effect, the process through which heat is absorbed and re-radiated in that atmosphere. The intensity of a planet’s greenhouse effect is determined by the relative abundance of greenhouse gases in its atmosphere. Without greenhouse gases, most of Earth’s heat would be lost to outer space, and our planet would quickly turn into a giant ball of ice. Increase the amount of greenhouse gases to the levels found on the planet Venus, and the Earth would be as hot as a pizza oven! Fortunately, the strength of Earth’s greenhouse effect keeps our planet within a temperature range that supports life

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What is the greenhouse effect, earth system models about the greenhouse effect, how human activities influence the greenhouse effect, explore the earth system, investigate, links to learn more.

For the classroom:

  • Teaching Resources

definition of greenhouse hypothesis

Global Change Infographic

The greenhouse effect occurs in the atmosphere, and is an essential part of How the Earth System Works. Click the image on the left to open the Understanding Global Change Infographic . Locate the greenhouse effect icon and identify other topics that cause changes to, or are affected by, the greenhouse effect.

definition of greenhouse hypothesis

Adapted from the Environmental Protection Agency greenhouse effect file

Greenhouse gases such as methane, carbon dioxide, nitrous oxide, and water vapor  significantly affect the amount of energy in the Earth system, even though they make up a tiny percentage of Earth’s atmosphere.  Solar radiation that passes through the atmosphere and reaches Earth’s surface is either reflected or absorbed . Reflected sunlight doesn’t add any heat to the Earth system because this energy bounces back into space.

However, absorbed sunlight increases the temperature of Earth’s surface, and the warmed surface re-radiates as long-wave radiation (also known as infrared radiation). Infrared radiation is invisible to the eye, but we feel it as heat.

If there were not any greenhouse gases in the atmosphere, all that heat would pass directly back into space. With greenhouse gases present, however, most of the long-wave radiation coming from Earth’s surface is absorbed and then re-radiated in all directions many times before passing back into space. Heat that is re-radiated downward, toward the Earth, is absorbed by the surface and re-radiated again.

Clouds also influence the greenhouse effect. A thick, low cloud cover can enhance the reflectivity of the atmosphere, reducing the amount of solar radiation reaching Earth’s surface, but clouds high in the atmosphere can intensify the greenhouse effect by re-radiating heat from the Earth’s surface.

Altogether, this cycle of absorption and re-radiation by greenhouse gases impedes the loss of heat from our atmosphere to space, creating the greenhouse effect. Increases in the amount of greenhouses gases will mean that more heat is trapped, increasing the amount of energy in the Earth system (Earth’s energy budget), and raising Earth’s temperature. This increase in Earth’s average temperature is also known as global warming.

This Earth system model is one way to represent the essential processes and interactions related to the greenhouse effect. Hover over the icons for brief explanations; click on the icons to learn more about each topic. Download the Earth system models on this page. There are a few ways that the relationships among these topics can be represented and explained using the Understanding Global Change icons ( download examples ).  

The greenhouse effect, which influences Earth’s average temperature, affects many of the processes that shape global climate and ecosystems.  This model shows some of the other parts of the Earth system that the greenhouse effect influences, including the water cycle and water temperature .

Humans directly affect the greenhouse effect through activities that result in greenhouse gas emissions. The Earth system model below includes some of the ways that human activities increase the amount of greenhouse gases in the atmosphere. Releasing greenhouse gases intensifies the greenhouse effect, and increases Earth’s average air temperatures (also known as global warming). Hover over or click on the icons to learn more about these human causes of change and how they influence the greenhouse effect.

Click the scene icons and bolded terms on this page to learn more about these process and phenomena.

Learn more in these real-world examples, and challenge yourself to  construct a model  that explains the Earth system relationships.

  • Ancient fossils and modern climate change
  • How Global Warming Works
  • NASA:  Global Climate Change:  A Blanket Around the Earth
  • UCAR Center for Science Education: The Greenhouse Effect
  • IPCC:  What is the Greenhouse Effect?
  • Indicators of Change (NCA.2014)
  • Human influence on the greenhouse effect
  • The Carbon Cycle and Earth’s Climate

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1. Introduction

A) the scientific process.

Climate scientists, like other scientists, use a cyclical process to advance their understanding. Usually it starts with a question, a lack of understanding. They form hypotheses based on previous knowledge or experience. Formulating a good hypothesis is usually not trivial. A useful hypothesis must be testable. That is, there must be the possibility to obtain evidence that confirms or falsifies the hypothesis. In climate science the evidence is most often quantitative data based on measurements (observations) or model simulations. The data is then analyzed to test the hypotheses. Once a hypothesis is falsified a different hypothesis may be formulated and tested. A hypothesis that has been confirmed by many different studies becomes a well-established theory.

Practically, after a considerable amount of time gathering and analyzing data the results of a study are written up into a manuscript, which is submitted to a scientific journal. The journal editor sends the manuscript to other researchers who are experts in the topic, who will read the manuscript and provide the editor with a critical assessment. Typically, the editor wants to know if the evidence provided in the manuscript supports the conclusions drawn by the authors. In most cases the manuscript will be changed by the authors considering the reviewers comments. Once a revised manuscript has been send back to the journal, the editor may send it back to the reviewers to make sure their comments were adequately addressed. This process can repeat itself several times. Once all the reviewers and the editor are happy with the manuscript it will be accepted for publication and ultimately published. This peer-review process can take a long time, several months to a year or more, but it improves the quality of the published articles.

b) Weather and Climate

Weather and climate are related but they differ in the time scales of changes and their predictability. They can be defined as follows.

Weather is the instantaneous state of the atmosphere around us. It consists of short-term variations over minutes to days of variables such as temperature, precipitation, humidity, air pressure, cloudiness, radiation, wind, and visibility. Due to the non-linear, chaotic nature of its governing equations, weather predictability is limited to days.

Climate is the statistics of weather over a longer period. It can be thought of as the average weather that varies slowly over periods of months, or longer. It does, however, also include other statistics such as probabilities or frequencies of extreme events . Climate is potentially predictable if the forcing is known because Earth’s average temperature is controlled by energy conservation. For climate, not only the state of the atmosphere is important but also that of the ocean, ice, land surface, and biosphere.

In short: ‘Climate is what you expect. Weather is what you get.’

c) The Climate System

Earth’s climate system consists of interacting components (Fig. 1). The atmosphere , which is the air and clouds above the surface, is about 10 km thick (more than two thirds of its mass is contained below that height). The ocean covers more than two thirds of Earth’s surface and has an average depth of roughly 4 km. Contrast those numbers with Earth’s radius which is approximately 6,400 km and you’ll find that Earth’s atmosphere and ocean are very thin layers compared to the size of the planet itself. In fact, they are about 1,000 times thinner. They are comparable perhaps to the outer layer of an onion or the water on a wet soccer ball. Yet all life is constrained to these thin layers. The major ocean basins are the Pacific, the Atlantic, the Indian, and the Southern Ocean. Ice and snow comprises the cryosphere , which includes sea ice, mountain glaciers and ice sheets on land. Sea ice is frozen sea water, up to several meters thick, floating on the ocean. Ice sheets on land, made out of compressed snow, can be several kilometers thick. The biosphere includes all living things on land and in the sea from the smallest microbes to trees and whales. The lithosphere , which is the solid Earth (upper crust and mantle), could also be considered an active part of Earth’s climate sytem because it responds to ice load [1] and impacts atmospheric carbon dioxide (CO 2 ) concentrations and climate on long timescales through the movements of the continents.

A picture of Earth from space.

The components interact with each other by exchanging energy, water, momentum, and carbon thus creating a deliciously complex coupled system. Imagine water evaporating from the tropical ocean heated by the sun (Fig. 1). The air containing that water rises and cools. The water condenses into a cloud. The cloud is carried by winds over land where it rains. The rain sustains a forest. Trees are dark, having a low albedo . This influences the amount of sunlight absorbed by the Earth. Dark surfaces absorb more sunlight and get warmer compared to bright surfaces such as desert sand or snow. Air warmed by the surface rises and affects the wind.

d) Processes

Fig. 2 illustrates some of the important processes that contribute to the complex interactions within the climate system. Earth’s energy source is the sun. Both solar and terrestrial radiation are affected by gases, aerosols , and clouds in the atmosphere. Thus, the atmospheric composition affects the heating and cooling of the earth. Heating and cooling affect the temperature and circulation of the atmosphere and oceans. Circulations of the air and sea affect temperatures and precipitation over both ocean and land, which impact the biosphere and cryosphere. Atmosphere and oceans exchange heat, water (evaporation and precipitation), and momentum. Wind blowing over the ocean pushes the surface water ahead. Air temperatures and snow fall affect the growth and melting of glaciers and ice sheets. Water from melting ice flows through rivers into the ocean affecting its salinity, its density and movement. Variations in solar irradiance can cause global climate to change. Volcanoes can eject large amounts of aerosol into the atmosphere with climatic implications. Humans are influencing the climate system through emissions of greenhouse gases , aerosols , and land use changes .

Climate system schematic

The complexity makes studying the climate system challenging. Scientists from many  disciplines contribute such as physicists, chemists, biologists, geologists, oceanographers, atmospheric scientists, paleoclimatologists, mathematicians, statisticians, and computer scientists. To me, the challenges and interdisciplinary nature of climate science are fascinating and fun. I learn something new about it every day.

Recorded Lectures

Weather and Climate

Le Treut, H., R. Somerville, U. Cubasch, Y. Ding, C. Mauritzen, A. Mokssit, T. Peterson and M. Prather, 2007: Historical Overview of Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

  • What are the two main differences between weather and climate?
  • How big is Earth? How thick is the atmosphere, how deep the ocean?
  • What are the components of Earth’s climate system?
  • List processes that cause interactions between the components: atmosphere-ocean, atmosphere-biosphere, atmosphere-cryosphere, ocean-biosphere, ocean-cryosphere.
  • Name three processes ( forcings ) that can cause global climate to change.

Go to one of the following websites and explore temporal variations of surface temperature observations in a location of your interest. Plot today’s data, yesterday’s, last week’s, last month’s, last year’s, the last decade’s, as far back as you can and make some notes on what you observe. Note regular, predictable cycles such as the diurnal and annual cycle in contrast with irregular, unpredictable variations such as day-to-day and year-to-year fluctuations. What causes the regular cycles? Try to order the variations with respect to their amplitude (strength). Discuss with fellow students and instructor.

Hourly and daily data are available at visualcrossing.com . Enter a location of your interest and select “history” to get recent data. At the next step you can select different time periods. Unfortunately, hourly data are not shown for periods longer than 3 days, but you can sign up and download the data and plot them yourself. This is what I did below in Figure 3. I  plotted them using Google Sheets . Are you able to identify diurnal (daily) cycles in temperature? Although some nights can be warmer than some days and sometimes days and nights have similar temperatures, on average days are warmer than nights. Thus the average diurnal cycle is part of climate. It is forced by the diurnal cycle of solar irradiance. Does pressure have a diurnal cycle? Answer: no . What is the typical timescale of pressure variations? Often it is about a week or so. This timescale is associated with the transition of weather systems (high and low pressure systems) passing by.

Timeseries graph of weather data for Corvallis, Oregon from March 2023. Time is on the horizontal axis from March 1st to March 28th.

Daily temperature data are usually reported as a daily maximum, a daily minimum and an average. An example for Corvallis is shown in Fig. 4. It shows a clear seasonal cycle with temperatures in winter colder than in summer (duh).

Timeseries graph of daily temperatures in Corvallis, Oregon 2021-2023. Horizontal axis ranges from 2021 to 2023. Vertical axis ranges from -10 deg C to 50 deg C.

Averaging many years of these weather data yields a climatology. For Corvallis it shows average temperatures around 40°F (4°C) in winter and 65°F (18°C) in summer (Fig. 5). It also shows a larger diurnal cycle in summer than in winter. What could be the reason for th at? Answer: less cloud cover in summer. Clouds lead to cooler days and warmer nights, thus decreasing the diurnal cycle. Curves are smooth in the climatology. In contrast to Fig. 4 the weather variations have been averaged out.

Timeseries of climatological daily temperature data from Corvallis. Horizontal axis is time of year starting on January 1st and ending on December 31st.

Now try a forecast of temperature for next August and next January. What is your gues s? Answer: a good guess would be the climatology, i.e. 65°F for August and 40°F for January. Thus the average seasonal cycle is climate and it is predictable because it is forced by the seasonal cycle of solar radiation. However, deviations from the climatology for a certain day next year are unpredictable weather.

Statistical properties of climate can be summarized in a frequency histogram. Let’s explore those with an example. I have downloaded daily average temperature data from May 1st from 1985 to 2016. The following list (or vector mathematically speaking) of 30 years (N=30) of temperature data T = ( T 1, T 2, … , T N) = (52, 52, 44, 52, 52, 54, 48, 52, 50, 56, 59, 46, 64, 58, 55, 48, 54, 54, 63, 54, 51, 54, 42, 52, 52, 48, 48, 48, 66, 56). Here N = 1 corresponds to 1985, N = 2 to 1986 and so on. In order to construct the frequency histogram we first need to choose bin sizes. I propose to choose 6 bins: 40-44, 45-49, 50-54, 55-59, 60-64, and 65-70. Now simply count how many years fall into each bin. I get 2, 6, 14, 6, 2, 1. Using python I produced the following graph (Fig. 6).

Climate change can be expressed as a change in the mean, which would correspond simply to a shift of the whole histogram to warmer or colder temperatures. However, it can also change the shape of the histogram. For example by making the distribution wider or narrower. This would increase or decrease the occurrences of extreme events. And, of course, it can both change the mean and the width. Most of the time, including in this text, discussions of climate change consider only changes in the mean. But we should keep in mind that changes to the tails of the distribution may be equally important because it is those tails that can have large impacts (heat waves, cold spells, droughts, floods, etc).

Histogram of 30 year (1985-2016) temperatures in Corvallis on May 1st. Most years (14 out of the 30) the temperature is between 50 and 55°F. The mean of the distribution is 52.8°F, its standard deviation of σ =5.4°F represents its width (about 2/3 of all years have temperatures within ±1 σ of the mean). The histogram, although it approximates well a Gaussian (normal) distribution, is slightly asymmetric such that very warm years (65-70) occur slightly more often than very cold extremes (35-40). The tails of the distribution are the upper and lower bins. They represent rare or extreme events. Only one year was warmer than 65°F. This year (2014) can be regarded as an extreme event. It was a record warm year in Oregon.

Now let’s explore effects of spatial scales on climate variations. Go to NOAA’s Climate-At-A-Glance website and start with the city tab selection. We want to compare the annual average temperature change in a city of your choice (e.g. Salem in Oregon), averaged over the larger region of a state, for the U.S. as a whole, and the globe. Use the “City Mapping” tab to select a city. For “Timescale” select “Annual”. Check the “Display Trend” box. This will include a trend line on the graph. Compare the trends and year-to-year variations. Are the trends larger for the global ocean or for the global land?

Compare the year-to-year variations and trends in regionally and globally averaged temperatures (Figs. 7-12) to the local diurnal cycle, day-to-day weather fluctuations (Fig. 3), and to the seasonal cycle (Figs. 4-5). Even though the global temperature trends (~0.1°C/decade) are much smaller than diurnal, day-to-day or seasonal fluctuations, which can be 10°C or more, we will see in the remainder of this course that global temperature changes of a few degrees C will have important impacts on natural systems and human societies.

Timeseries graph of surface temperature in Salem, Oregon from 1895 to 2022.

  • The weight of the ice depresses the lithosphere, which provides a feedback to the ice by lowering its surface elevation. Traditionally it has been thought that this feedback acts on long (millennial and longer) timescales, but recent research indicates that in certain regions such as West Antarctica, where the lithosphere is thin and the mantle viscosity is low the lithosphere can respond on much shorter (decadal to centennial) timescales. ↵

Rare weather or climate events such as hurricanes, typhoons, floods, droughts, and tornadoes that can often be damaging.

Reflectivity. Snow, ice, clouds and other bright surfaces have a high albedo, which leads to most sunlight being reflected to space. Ocean and vegetation on land have low albedos. They absorb lots of the suns radiation, which leads to warming.

Small particles in the air. Aerosols reflect sunlight back to space and therefore lead to cooling of the surface (negative forcing). Aerosols originate from natural (dust, ash from volcanic eruptions, wave breaking) and anthropogenic (smoke) sources.

Greenhouse gases are molecules that are able to absorb and emit electromagnetic radiation in the infrared part of the spectrum (longwave). Water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are Earth’s most important greenhouse gases.

Humans' effects on the climate system through modifications of the land surface e.g. through deforestation and agriculture.

Radiative forcing (ΔF) is a change in energy fluxes F (in W/m2) at the top-of-the-atmosphere that causes climate change. It is defined as positive (negative) if it leads to warming (cooling). The radiative forcing for a doubling of CO2 is ΔF2xCO2 = 3.7 W/m2. Other examples are increased solar radiation (positive), increased aerosols (negative) or increased surface albedo (negative), e.g. due to land use changes.

Introduction to Climate Science Copyright © 2019 by Andreas Schmittner is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

Climate Matters • April 16, 2014

The Greenhouse Effect

The Greenhouse Effect

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The basic explanation for why CO2 and other greenhouse gases warm the planet is so simple and has been known science for more than a century. Our atmosphere is transparent to visible light — the rainbow of colors from red to violet that make up natural sunlight. When the sun shines, its light passes right through the atmosphere to warm the Earth.

The warm Earth then radiates some of its energy back upward in the form of infrared radiation — the “color” of light that lies just beyond red that our eyes can’t see (unless we’re wearing infrared-sensitive night-vision goggles). If all of that infrared radiation escaped back into space, the Earth would be frozen solid. However, naturally occurring greenhouse gas molecules, including not just CO2 but also methane and water vapor, intercept some of it — re-emitting the infrared radiation in all directions, including back to Earth. That keeps us warm.

When we add extra greenhouse gases to the atmosphere, though, we increase the atmosphere’s heat-trapping capacity. Less heat escapes to space, more returns to Earth, and the planet warms.

There’s really no scientific doubt about this process, which is known as the greenhouse effect. What scientists don’t know is exactly how strong the effect is. That’s because trapping heat is just the first step. As the planet warms, it changes. Ice on land and on the ocean melts back, letting the Earth absorb more heat than it did before. Oceans warm, but currents carry some of that warm water below the surface, where it’s temporarily hidden away. Oceans also stop absorbing CO2 as easily, so more stays in the atmosphere, adding to the greenhouse effect. The atmosphere itself holds more water vapor when it warms, so concentrations of that greenhouse gas increase. But some of that vapor forms into clouds, which reflect sunlight before it can even hit the Earth.

All of these secondary effects (and more) are known as feedbacks, which can speed up global warming or slow it down. And since they’re not all understood with perfect certainty, scientists can only give a range of likely temperature changes for the next century, not a specific number. There’s wide agreement, though, that the temperature will continue to rise  between 0.54°F and 8.64°F above the 1986-2005 average by the end of this century , depending on how our emissions grow (note however, the low number is only possible if we actively suck carbon out of the air). Scientists also agree that the consequences are likely to be severe.

What Is the Greenhouse Effect?

Reference Article: Facts about the greenhouse effect.

Artist's rendering of the sun shining on Earth's surface.

Earth is said to be in a perfect "Goldilocks zone" away from the sun (not too cold, and not too hot), which enables life to thrive on the planet's surface. But Earth's balmy temperatures would not be possible without the greenhouse effect, which traps solar energy on Earth's surface and keeps the planet warm. 

The greenhouse effect arises from Earth's atmosphere . Visible light from the sun , as well as invisible ultraviolet and infrared wavelengths, can penetrate the gaseous layer that blankets our world. Roughly 70% of these energetic rays are absorbed by Earth's oceans, land and atmosphere, while the remaining 30% are immediately reflected back into space, according to NASA Earth Observatory .

As the planet's surface heats up, it releases some of the infrared energy that it had absorbed, but that energy doesn't make it back out of Earth's gaseous atmosphere. Instead of shooting back out into space, the infrared energy closely hugs our planet and, therefore, raises Earth's overall temperature. This is similar to how a human-built glass greenhouse works, trapping heat from the sun to keep plants warm in the winter.

Without an atmosphere, our world would be as cold as the lifeless moon , which has an average temperature of minus 243 degrees Fahrenheit (minus 153 degrees Celsius) on its far side. Because of the greenhouse effect, Earth maintains an overall average temperature of around 59 F (15 C).

Greenhouse gases and climate change 

Greenhouse gases include several naturally occurring molecules — like water vapor, carbon dioxide, methane, nitrous oxide and ozone — as well as several manufactured ones, like chlorofluorocarbons, according to the Australian Department of the Environment and Energy . Over the past century or so, human activities — such as the burning of fossil fuels, intensive agriculture, livestock raising and land clearing — have dramatically increased the concentrations of greenhouse gases in Earth's atmosphere, to the point where it's changing our planet's climate.

Since the middle of the 20th century, greenhouse gases produced by humans have become the most significant driver of climate change, according to the U.S. Environmental Protection Agency . Carbon dioxide levels in the atmosphere have increased by more than 40% since the start of the Industrial Revolution, from roughly 280 parts per million (ppm) to more than 400 ppm today.

The last time Earth's atmosphere had similar carbon dioxide concentrations was during the Pliocene epoch, between 3 million and 5 million years ago, according to the Scripps Institution of Oceanography in San Diego. That's at least 2.8 million years before modern humans roamed the planet. Fossils show that forests grew in the Canadian Arctic during the Pliocene, and savannas and woodlands spread over what's now the Sahara desert .

While some people still doubt the reality of human-induced climate change, the evidence for it is overwhelming. Since the 1850s, the average global surface-air temperature has risen by around 1.4 F (0.8 C), and ocean temperatures are now at the highest levels ever recorded.

Increases in greenhouse gases in the coming decades are expected to harm human health , increase droughts, contribute to sea level rise, and decrease national security and economic well-being throughout the world.  

The greenhouse effect on other planets 

Because the greenhouse effect is a natural process, it affects other bodies in the solar system , too. And, in some cases, that provides a warning about how things can go awry. A perfect example of this is Venus , which is roughly the same size as Earth and not that much closer to the sun.

Billions of years ago, when the sun was cooler and dimmer, Venus may have had a temperate climate that could have allowed for liquid water oceans on its surface. Simulations suggest that the planet's average temperatures ranged from a low of 68 F (20 C) to a high of 122 F (50 C) for about 3 billion years, potentially even allowing Venus to support life .

But as the sun aged and grew brighter, excess water vapor would have entered Venus' atmosphere . This potent greenhouse gas trapped heat and raised the planet's surface temperature, leading to a vicious feedback cycle in which hotter temperatures led to more water vapor in the atmosphere, further heating the world — a process known as the runaway greenhouse effect . 

When Venus' oceans vaporized, its planetary plate tectonics would have ground to a halt, as there was no water left to help lubricate the shifting of geological plates. The increasingly thick atmosphere might have created a drag on Venus' rotation period, leading to its bizarrely slow spin, in which a year goes by with only two days passing. The dense cloud cover also led to hellish surface temperatures on present-day Venus, with an average of 700 F (370 C) — hot enough to melt lead. 

"I think Venus is an important warning: Greenhouse atmospheres are not theoretical," Ellen Stofan, director of the Smithsonian's National Air and Space Museum and former chief scientist at NASA, previously told Space.com .

On Mars , greenhouse gases such as water and carbon dioxide might have been released during ancient impact events . Some scientists speculate that such wallops could have raised Mars' overall temperature enough for the planet to have liquid water on its surface for significant lengths of time. However, because Mars is smaller than Earth, it's gravitational pull is weaker. Therefore, these gases drifted away, and eventually, the Red Planet reverted back to the cold and dry world it is today.

Saturn's distant moon Titan , which has a thick nitrogen atmosphere with about a thousand times greater concentration of methane as Earth, is also subject to the greenhouse effect. With data from the European Space Agency's Huygens probe, which landed on Titan in 2005, researchers are getting a better understanding of how methane absorbs short-wavelength infrared radiation and are using that information to develop climate change models of our planet.

The greenhouse effect is also expected to warm the worlds of other star systems . Many astronomers speak of a narrow habitable zone around a star — the area where a planet would be at the perfect distance to maintain liquid water on its surface, between 0.95 and 1.4 times the Earth-sun distance . However, others have argued that such models need to be broadened. A thick atmosphere of molecular hydrogen, which is a potent greenhouse gas, could potentially give a world clement temperatures even if it were 15 times farther from the sun than Earth is.

Additional resources:

  • Try playing NASA's "Greenhouse Gas Attack!" game to learn more about the excess greenhouse gases in Earth's atmosphere. 
  • Watch this video to learn how the Japan Aerospace Exploration Agency (JAXA) is measuring greenhouse gases from space .
  • Read more about the greenhouse effect on other planets , from the University of Calgary. 

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

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Adam Mann

Adam Mann is a journalist specializing in astronomy and physics stories. His work has appeared in the New York Times, New Yorker, Wall Street Journal, Wired, Nature, Science, and many other places. He lives in Oakland, California, where he enjoys riding his bike. Follow him on Twitter @adamspacemann or visit his website at https://www.adamspacemann.com/ .

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Admin said: How planets trap heat like a greenhouse. What Is the Greenhouse Effect? : Read more
  • Worzel The figure of 280 ppm for CO2 at the beginning of the industrial revolution was based on samples from ice cores. Ice is not an impermeable material, so gasses can escape, and do, so that figure was far too low. It has since been updated, and is now estimated at around 360 pm. Therefore the increase since industrial revolution is only around 40 ppm. This amount is far too small to have any effect on climate whatsoever. Also the climate warms, the oceans release CO2. So IF CO2 caused the climate to warm, that in turn would cause the oceans to release more CO2, which in turn would cause more warming, and so on. This is a positive feedback process, which would cause the global temperature to rise exponentially until the planet baked. This has not occurred in 600 million years, since the planet emerged from the ''Snowball Earth'' event, even when CO2 levels were 7000 ppm, or 17 times the present tiny 400 ppm, of which human input is a miserable 40 ppm. During that time CO2 and global temperature have varied in opposite directions, for millions of years, contrary to the theory. Therefore as the observed facts do not support the theory that CO2 causes global warming, the theory is WRONG! In addition, the level of CO2 and global average temperature, now, and throughout this interglacial period, is the lowest since the Permian extinction, 270 million years ago. Also, the planet has been in an ever deepening Ice Age for around 40 million years, so the chance of a mythical, ''runaway greenhouse'' effect is ZERO! This ice age is not to be confused with the Malenkovitch cycle of approximately 90,000 years glacial, followed by 10,000 years interglacial period which the planet is in now, and is due to end in the near future. Reply
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What Is the Greenhouse Effect?

Watch this video to learn about the greenhouse effect! Click here to download this video (1920x1080, 105 MB, video/mp4). Click here to download this video about the greenhouse effect in Spanish (1920x1080, 154 MB, video/mp4).

How does the greenhouse effect work?

As you might expect from the name, the greenhouse effect works … like a greenhouse! A greenhouse is a building with glass walls and a glass roof. Greenhouses are used to grow plants, such as tomatoes and tropical flowers.

A greenhouse stays warm inside, even during the winter. In the daytime, sunlight shines into the greenhouse and warms the plants and air inside. At nighttime, it's colder outside, but the greenhouse stays pretty warm inside. That's because the glass walls of the greenhouse trap the Sun's heat.

definition of greenhouse hypothesis

A greenhouse captures heat from the Sun during the day. Its glass walls trap the Sun's heat, which keeps plants inside the greenhouse warm — even on cold nights. Credit: NASA/JPL-Caltech

The greenhouse effect works much the same way on Earth. Gases in the atmosphere, such as carbon dioxide , trap heat similar to the glass roof of a greenhouse. These heat-trapping gases are called greenhouse gases .

During the day, the Sun shines through the atmosphere. Earth's surface warms up in the sunlight. At night, Earth's surface cools, releasing heat back into the air. But some of the heat is trapped by the greenhouse gases in the atmosphere. That's what keeps our Earth a warm and cozy 58 degrees Fahrenheit (14 degrees Celsius), on average.

definition of greenhouse hypothesis

Earth's atmosphere traps some of the Sun's heat, preventing it from escaping back into space at night. Credit: NASA/JPL-Caltech

How are humans impacting the greenhouse effect?

Human activities are changing Earth's natural greenhouse effect. Burning fossil fuels like coal and oil puts more carbon dioxide into our atmosphere.

NASA has observed increases in the amount of carbon dioxide and some other greenhouse gases in our atmosphere. Too much of these greenhouse gases can cause Earth's atmosphere to trap more and more heat. This causes Earth to warm up.

What reduces the greenhouse effect on Earth?

Just like a glass greenhouse, Earth's greenhouse is also full of plants! Plants can help to balance the greenhouse effect on Earth. All plants — from giant trees to tiny phytoplankton in the ocean — take in carbon dioxide and give off oxygen.

The ocean also absorbs a lot of excess carbon dioxide in the air. Unfortunately, the increased carbon dioxide in the ocean changes the water, making it more acidic. This is called ocean acidification .

More acidic water can be harmful to many ocean creatures, such as certain shellfish and coral. Warming oceans — from too many greenhouse gases in the atmosphere — can also be harmful to these organisms. Warmer waters are a main cause of coral bleaching .

definition of greenhouse hypothesis

This photograph shows a bleached brain coral. A main cause of coral bleaching is warming oceans. Ocean acidification also stresses coral reef communities. Credit: NOAA

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Consulting   Geologist

The shattered greenhouse: how simple physics demolishes the "greenhouse effect"..

This article explores the "Greenhouse Effect" in contemporary literature and in the frame of physics, finding a conspicuous lack of clear thermodynamic definition. The "Greenhouse Effect" is defined by Arrhenius' (1896) modification of Pouillet's backradiation idea so that instead of being an explanation of how a thermal gradient is maintained at thermal equilibrium, Arrhenius' incarnation of the backradiation hypothesis offered an extra source of power in addition to the thermally conducted heat which produces the thermal gradient in the material. The general idea as expressed in contemporary literature, though seemingly chaotic in its diversity of emphasis, shows little change since its revision by Svante Arrhenius in 1896, and subsequent refutation by Robert Wood in 1909. The "Greenhouse Effect" is presented as a radiation trap whereby changes in atmospheric composition resulting in increased absorption lead to increased surface temperatures. However, since the composition of a body, isolated from thermal contact by a vacuum, cannot affect mean body temperature, the "Greenhouse Effect" has, in fact, no material foundation. Compositional variation can change the distribution of heat within a body in accordance with Fourier's Law, but it cannot change the overall temperature of the body. Arrhenius' Backradiation mechanism did, in fact, duplicate the radiative heat transfer component by adding this component to the conductive heat flow between the earth's surface and the atmosphere, when thermal conduction includes both contact and radiative modes of heat transfer between bodies in thermal contact. Moreover, the temperature of the earth's surface and the temperature in a greenhouse are adequately explained by elementary physics. Consequently, the dubious explanation presented by the "Greenhouse Effect" hypothesis is an unnecessary complication. Furthermore, this hypothesis has neither direct experimental confirmation nor direct empirical evidence of a material nature. Thus the notion of "Anthropogenic Global Warming", which rests on the "Greenhouse Effect", also has no real foundation.

1.0 Introduction: What on Earth Is the "Greenhouse Effect"?

Confusion and lack of thermodynamic definition.

Although the "Greenhouse Effect" is of crucial importance to modern climatology and is the putative cornerstone of the Anthropogenic Global Warming hypothesis, it lacks clear thermodynamic definition. This forecasts the likelihood that the name is misapplied. Even general descriptions of the "Greenhouse Effect" may seem confused when compared to one another. In the first year university geology text by Press & Siever (1982, p. 312) we read:

"The atmosphere is relatively transparent to the incoming visible rays of the Sun. Much of that radiation is absorbed at the Earth's surface and then reemitted as infrared, invisible long-wave rays that radiate back away from the surface (Fig. 12-14). The atmosphere, however, is relatively opaque and impermeable to infrared rays because of the combined effect of clouds and carbon dioxide, which strongly absorbs the radiation instead of allowing it to escape into space. This absorbed radiation heats the atmosphere, which radiates heat back to the Earth's surface. This is called the 'greenhouse effect' by analogy to the warming of greenhouses, whose glass is the barrier to heat loss."

This explanation is fundamentally confusing because it is seemingly contradictory, as impermeable materials cannot absorb on the minute to minute timescale that applies to the "Greenhouse Effect", even if such an impermeable material has a very high fluid storage capacity or porosity. According to Press & Siever's explanation above, the atmosphere is relatively impermeable due to the presence of clouds and carbon dioxide, which are part of the atmosphere. How then, can the part of the atmosphere that makes it impermeable to infrared, simultaneously facilitate infrared absorption? Moreover, the idea of thermal permeability is a product of the 19 th century pseudoscientific notion that heat was actually a fluid (called "caloric"). This led to a great deal of misunderstanding amongst the scientifically illiterate when it came to the findings of Fourier (e.g. Kelland, 1837). We may compare this description of the "Greenhouse Effect" with that of Whitaker (2007, pp. 17-18), which lacks the misplaced 19 th century usage:

"The incoming solar radiation that the earth absorbs is re-emitted in the form of so-called infra-red radiation - this is where the vital 'greenhouse effect' begins. Because of the chemical structure of the greenhouse gases in the atmosphere, they absorb the infra-red radiation from the Earth, and then emit it, into space and back into the atmosphere. The atmospheric re-emission helps heat the surface of the Earth - as well as the lower atmosphere - and keeps us warm."

This explanation describes the "Greenhouse Effect" as "vital", perhaps because, as Whitaker points out, it warms the earth's surface. Wishart (2009, p. 24) explains that this "Greenhouse Effect" is useful for a completely different reason:

"The Moon is another excellent example of what happens with no greenhouse effect. During the lunar day, average surface temperatures reach 107ºC, while the lunar night sees temperatures drop from boiling point to 153 degrees below zero. No greenhouse gases mean there's no way to smooth out temperatures on the moon. On Earth, greenhouse gases filter some of the sunlight hitting the surface and reflect some of the heat back out into space, meaning the days are cooler, but conversely the gases insulate the planet at night, preventing a lot of the heat from escaping."

In Wishart's explanation above, the Greenhouse Effect" is no longer a warming mechanism but a thermal buffer that moderates the extremes of temperature. In fact, Plimer (2001) uses the term "greenhouse" to denote interglacial periods (e.g. Plimer, 2001, p. 80). In describing the conditions when life evolved on earth 3800 million years ago, Plimer (2001, p. 43), like Wishart, is more reminiscent of Frankland (1864) and Tyndall (1867):

"The Earth's temperature had moderated because the atmosphere was rich in carbon dioxide and water vapour created a greenhouse."

The above quotes demonstrate a confusing array of "Greenhouse Effect" definitions, including the first one which seems to contradict itself. Plimer (2009, p. 365) really describes this situation very well when he writes:

"Everyone knows what the greenhouse effect is. Well ... do they? Ask someone to explain how the greenhouse effect works. There is an extremely high probability that they have no idea. What really is the greenhouse effect? The use of the term 'greenhouse effect' is a complete misnomer. Greenhouses or glasshouses are used for increasing plant growth, especially in colder climates. A greenhouse eliminates convective cooling, the major process of heat transfer in the atmosphere, and protects the plants from frost."

The "Greenhouse Effect" was originally defined around the hypothesis that visible light penetrating the atmosphere is converted to heat on absorption and emitted as infrared, which is subsequently trapped by the opacity of the atmosphere to infrared. In Arrhenius (1896, p. 237) we read:

"Fourier maintained that the atmosphere acts like the glass of a hothouse, because it lets through the light rays of the sun but retains the dark rays from the ground."

This quote from Arrhenius establishes the fact that the "Greenhouse Effect", far from being a misnomer, is so-called because it was originally based on the assumption that an atmosphere and the glass of a greenhouse are the same in their workings. Interestingly, Fourier doesn't even mention hothouses or greenhouses, and actually stated that in order for the atmosphere to be anything like the glass of a hotbox, such as the experimental aparatus of de Saussure (1779), the air would have to solidify while conserving its optical properties (Fourier, 1827, p. 586; Fourier, 1824, translated by Burgess, 1837, pp. 11-12 ).

In spite of Arrhenius' misunderstanding of Fourier, the Concise Oxford English Dictionary (11 th Edition) reflects his initial opening description of the "Greenhouse Effect":

" Greenhouse Effect noun the trapping of the sun's warmth in the planet's lower atmosphere, due to the greater transparency of the atmosphere to visible radiation from the sun than to infrared radiation emitted from the planet's surface."

These descriptions of the "Greenhouse Effect" all evade the key question of heat transfer. Given that the "Greenhouse Effect" profoundly affects heat transfer and distribution, what are the thermodynamic properties that govern the "Greenhouse Effect" and how, exactly, is this "Greenhouse Effect" governed by these material properties? Moreover, all of the elements expressed in the preceding quotations can be found in Arrhenius' proposition of the "Greenhouse Effect". While Arrhenius credits Tyndall with the thermal buffer idea expressed in Plimer (2001) and Wishart (2009), he then goes on to express the more complicated idea described in Press & Siever (1982) and Whitaker (2007). The "atmospheric re-emission" that "helps heat the surface of the earth" of Whitaker (2007, pp. 17-18) is the key to Arrhenius' original proposition, which revolves around the backradiation notion first proposed by Pouillet (1838, p. 42; translated by Taylor, 1846, p. 61). However, Pouillet used this idea to explain rather than add to the thermal gradient measured in transparent envelopes while, as we shall see, Arrhenius treated backradiation as an addition to the conductive (i.e. net) heat flow indicated by the thermal gradient.

2.0 How the "Greenhouse Effect" Is Built upon Arrhenius' Legacy of Error: Misattribution, Misunderstanding, and Energy Creation

Arrhenius' first error was to assume that greenhouses and hotboxes work as a radiation trap. Fourier explained quite clearly that such structures simply prevent the replenishment of the air inside, allowing it to reach much higher temperatures than are possible in circulating air ( Fourier, 1824, translated by Burgess, 1837, p. 12 ; Fourier, 1827, p. 586). Yet, as we have seen in the previous quotation of Arrhenius, this fundamental misunderstanding of greenhouses is attributed by Arrhenius to Fourier.

2.1 Misattribution versus What Fourier Really Found

Contrary to what Arrhenius (1896, 1906b) and many popular authors may claim (Weart, 2003; Flannery, 2005; Archer, 2009), Fourier did not consider the atmosphere to be anything like glass. In fact, Fourier (1827, p. 587) rejected the comparison by stipulating the impossible condition that, in order for the atmosphere to even remotely resemble the workings of a hotbox or greenhouse, layers of the air would have to solidify without affecting the air's optical properties. What Fourier (1824, translated by Burgess, 1837, p. 12) actually wrote stands in stark contrast to Arrhenius' claims about Fourier's ideas:

"In short, if all the strata of air of which the atmosphere is formed, preserved their density with their transparency, and lost only the mobility which is peculiar to them, this mass of air, thus become solid, on being exposed to the rays of the sun, would produce an effect the same in kind with that we have just described. The heat, coming in the state of light to the solid earth, would lose all at once, and almost entirely, its power of passing through transparent solids: it would accumulate in the lower strata of the atmosphere, which would thus acquire very high temperatures. We should observe at the same time a diminution of the degree of acquired heat, as we go from the surface of the earth."

A statement to the same effect can be found in Fourier (1827, p. 586). This demonstrates the sheer dissonance between these statements and what proponents of the "Greenhouse Effect" claim that Fourier says in their support. Moreover, I am not the first author to have discovered this fact by reading Fourier for myself (e.g. Fleming, 1999; Gerlich & Tscheuschner, 2007 and 2009). Furthermore, in his conclusion, the optical effect of air on heat is dropped by Fourier (1824, translated by Burgess, 1837, pp. 17-18) and Fourier (1827, pp. 597-598) which both state:

"The earth receives the rays of the sun, which penetrate its mass, and are converted into non-luminous heat: it likewise possesses an internal heat with which it was created, and which is continually dissipated at the surface: and lastly, the earth receives rays of light and heat from innumerable stars, in the midst of which is placed the solar system. These are three general causes which determine the temperature of the earth."

Fourier's fame has, in fact, nothing to do with any theory of atmospheric or surface temperature. This fame was earned years before such musings, when Fourier derived the law of physics that governs heat flow, and was subsequently named after him. About this, Fourier (1824, p. 166; Translation by Burgess, 1837, p. 19) remarks:

"Perhaps other properties of radiating heat will be discovered, or causes which modify the temperatures of the globe. But all the principle laws of the motion of heat are known. This theory, which rests upon immutable foundations, constitutes a new branch of mathematical sciences."

As you can see, Fourier admits that his work is constrained to the net movement of heat. In fact, nowhere does Fourier differentiate between radiative and, for example, "kinetic" heat transfer, because the means to tell the difference were not available when Fourier studied heat flow. What this tells us is that Fourier's Law, and only Fourier's Law, can describe the transfer of heat between bodies in thermal contact. Thus the distribution of heat between the atmosphere and the surface of the earth, with which it has thermal contact, cannot be correctly calculated using the radiative transfer equations derived from Boltzmann (1884) because the thermal contact of these bodies makes this a question of Fourier's Law. However, to better understand this it is necessary to explore the motion of heat and the modes of heat transfer more thoroughly than did Arrhenius.

2.2 Aethereal Misunderstanding versus Subatomic Heat Transfer

Arrhenius (1906b, pp. 154 and 225) still clung to the aether hypothesis, which refers to the unspecified material medium of space. Arrhenius' adherence to this hypothesis remained firm in spite of its sound refutation by Michelson & Morley (1887). This leaves the conceptual underpinning of radiation in Arrhenius' "Greenhouse Effect" to Tyndall (1864, pp. 264-265; 1867, p. 416), who ascribes communication of molecular vibration into the aether and communication of aethereal vibration to molecular motion. This interaction conceptually separates radiated heat from conducted heat so that radiation remains separate and distinct from conductive heat flow - effectively isolating conductive heat flow from the radiative mode of heat transfer. Thus no consideration is made for internal radiative transfer as a part of conductive transfer, in the context of aethereal wave propagation. However, Arrhenius' contemporaries, having moved beyond the debunked aether hypothesis, had a much more realistic perspective of the interactions between radiation, heat, and subatomic particles.

During the life of Arrhenius' "Greenhouse Effect", the scientific community understood that radiation was electromagnetic (Maxwell, 1864; Heaviside, 1881; Hertz, 1888), and by the time Arrhenius first published on the subject of the "Greenhouse Effect", Thompson (1896) had extended his idea of electrons to photoelectric effects on gases due to ionizing radiation, known then as röntgen rays. The photoelectric effect, by which a current or charge could be generated in certain materials by their exposure to electromagnetic radiation, was a matter of inquiry at the time. The emission of radiation in discrete quanta, though first suggested by Boltzmann in 1877, was mathematically formalised by Planck (1901). Einstein (1905) experimentally confirmed Planck's Equation after adapting it to the photoelectric effect, which was the subject of his study. However, ideas concerning the internal structure of the atom and it's relationship to ionisation, magnetism, photoelectric interactions, and discrete quanta of electromagnetic radiation were under intense development at the time (Thomson, 1902; Thomson, 1903; Thomson, 1904). By the time Bohr (1913) corrected the problems in Thomson's atomic model, the relationship between changes in electron shell (i.e. orbit) potential and photoelectric emission of radiation were a foregone conclusion. The relevance of these discoveries to the question of heat transfer is that unlike the notion of aethereal heat transfer, emission of electromagnetic energy quanta by atoms and molecules in materials confirmed that the radiative mode of heat transfer was as much a part of thermal conduction as any other mode of heat transfer.

In order to understand how heat moves through materials, we must first examine the structure and behaviour of the material media at a sub-atomic level. An atom comprises a nucleus within a shell. The shell is due to "Thomson's corpuscles", later known as electrons, which are negatively charged particles that orbit a nucleus with a positive charge corresponding to the number of these electrons. These orbital paths are also known as electron shells and, when shared by more than one atom, electron shells form the chemical bond between those atoms. When a "photon", or rather an electromagnetic wave pulse, passes through the electron shell -which is the region defined by the corresponding mathematical function called an orbital- one of a number of things may occur. It may pass through the "shell", it may be deflected by the "shell", or it may be absorbed by an electron in the "shell". When an electromagnetic wave pulse or 'photon' of light or heat is absorbed by an electron, the energy imparted to the electron is converted to kinetic energy, which moves the electron out to an orbital level commensurate with the energy gained. If we consider, from the mass of both electron and nucleus, that the centre of mass is somewhere between the electron and the nucleus, then this centre of mass does not coincide with the centre of positive charge, about which the electron orbits. Imagine a circumstance in which this centre of mass remains static, while the nucleus revolves around it. As the electron shell is centred on the nucleus, then in this case the shell and the entire atom or molecule is thus seen to wobble or vibrate about a particular point. The higher the electron shell, the more intense this wobble or vibration becomes. As a consequence, the absorption of electromagnetic radiation by a material manifests itself as what appears to be a corresponding net increase in the kinetic energy of constituent molecules.

If we take the processes we have just examined and apply them to more than one molecule, we may then perceive as Waterson (1843, 1846, 1892) did, that through collisions between molecules, the material must either expand or its internal pressure will increase. By this we may infer the kinetic propagation of heat through a medium by the collision of its molecules, as the momentum of one molecule is transferred to another in the collision. This is not the only consequence of molecular collision. Such a collision may transfer the kinetic energy from an electron of the inbound molecule to an electron of the outbound molecule. It is also possible that the collision may destabilise one or both electron shells resulting in the corresponding drops to lower electron potentials. When an electron falls to a lower orbit or electron shell of lesser potential, a "photon" or pulse of electromagnetic radiation is emitted. That electromagnetic wave pulse then propagates through the material until it is either absorbed by another molecule or escapes from the material. However short-lived, such radiation quanta carry a proportion of heat flow in all materials. Whether we are talking about air, glass, or steel, a component of internal heat transfer is via internal radiation, however short the path of that radiation may be. Ergo, thermal conduction is not solely the kinetic transfer of heat, but also the transmission and reception of radiation within a material or materials in thermal contact. This is confirmed by the fact that conductive heat transfer, as defined by Fourier (1822), is only concerned with total heat flow and therefore describes the sum of both radiative and kinetic transfer without addressing either specifically. This differs markedly from the separation of radiative and kinetic transfer implicit in the ethereal model of heat transfer proposed by Tyndall and favoured by Arrhenius. This divergence of Arrhenius' idea of heat transfer from the facts of contemporary science forecasts a major error in Arrhenius' thermodynamics.

2.3 Obfuscated Energy Creation versus "Kirchhoff's Law"

It is an interesting fact that Arrhenius (1896 and 1906b) obfuscates his critical backradiation mechanism of the "Greenhouse Effect" by focusing the reader's attention on the idea he falsely attributed to Fourier, which is now found in the dictionary; namely, that the atmosphere admits the visible radiation of the sun but obstructs the infrared radiation from the earth. However, Arrhenius' calculations are based on surface heating by backradiation from the atmosphere (first proposed by Pouillet, 1838, p. 44; translated by Taylor, 1846, p. 63), which is further clarified in Arrhenius (1906a). This exposes the fact that Arrhenius' "Greenhouse Effect" must be driven by recycling radiation from the surface to the atmosphere and back again. Thus, radiation heating the surface is re-emitted to heat the atmosphere and then re-emitted by the atmosphere back to accumulate yet more heat at the earth's surface. Physicists such as Gerlich & Tscheuschner (2007 and 2009) are quick to point out that this is a perpetuum mobile of the second kind - a type of mechanism that creates energy from nothing. It is very easy to see how this mechanism violates the first law of thermodynamics by counterfeiting energy ex nihilo , but it is much more difficult to demonstrate this in the context of Arrhenius' obfuscated hypothesis.

Suffice it to say that heat is lost at the earth's surface when it is radiated to the atmosphere. The atmosphere having gained this heat loses it when it is re-radiated, half into space and half back to earth because radiation is omnidirectional - being emitted by a molecule in any direction. However, such heat losses are not represented in the "Greenhouse Effect", which recycles this heat instead. According to this hypothesis, this heat joins yet more heat absorbed from direct solar radiation during the relay - much of which is simultaneously emitted and recycled again. The intensity of terrestrial radiation absorbed by the atmosphere is thus increased and, taken in addition to that absorbed by the earth's surface, now totals more than the radiation available from the sun (e.g. Kiehl & Trenberth, 1997; Trenberth et al., 2009). The logic is seductive, yet flawed. Radiation is simply the amount of power per square metre. This power cannot be used and stored at the same time. Power cannot be raised without intensifying the source or adding another source of energy. You can prove this at home by observing the consequences when you unceremoniously unplug the power lead from your amplifier (while listening to some music). Without the additional source of power, it simply cannot amplify the signal from the radio receiver or the DVD pickup.

Authors who defend the "Greenhouse Effect" attempt to characterise it as a form of heat congestion (e.g. Archer, 2009). The problem with this defense is that no amount of heat congestion can result in an average power output exceeding the average power input. The defense is also subject to the limitations of "Kirchhoff's Law". "Kirchhoff's Law" dictates that while emissivity and absorptivity are always equal for a given material or body, the equality of absorption (not absorptivity) and emission (not emissivity) of radiation defines thermal equilibrium between bodies that are not in thermal contact. Even the misconception that selective absorptivity makes it easier for radiation to get in than to escape, breaks down when both the atmosphere and the surface of the earth are treated as a whole body. Regardless of internal complexities, a whole body ultimately can only emit the exact amount of radiation it receives, or a lesser amount corresponding to a lower pre-equilibrium temperature if thermal equilibrium has not been reached. By increasing absorption, emission is increased - which was confirmed experimentally by Stewart (1858, 1860a, 1860b) and Kirchhoff (1859 & 1860). Moreover, this greater emission has a cooling effect on the atmosphere and Frankland (1864, p. 326) asserts that without this loss of heat by emission to space, atmospheric water vapour could not condense into clouds and precipitation. This cooling by radiative emission is further confirmed by Ellsaesser (1989) and Chillingar et al. (2008). Thus surface evaporation and subsequent condensation at altitude has a powerful cooling effect, which in addition to convection, offsets the high degree of heating that occurs at the surface.

Inasmuch as we raise the absorptivity of the atmosphere, we equally raise its capacity to emit radiation to space. This was understood by Tyndall, Frankland and Fourier, as well being experimentally confirmed by Pouillet (1838, p. 44; translated by Taylor, 1846, p. 63). This concept of "Kirchhoff's Law" possibly dates back to the experimental work of Leslie (e.g. 1804, p. 24). However, the inclusion of "Kirchhoff's Law" in Fourier (1822) is highly suggestive of a much earlier source given the abundance of pre-existing qualitative thermodynamic principles that were subsequently quantified by Fourier. The principle that a material's absorptivity is equal to it's emissivity, thus, has a long history with many experimental confirmations. This same law of physics, experimentally conifrmed by numerous scientists, dictates that the temperature of the atmosphere cannot be changed simply by increasing absorptivity. "Kirchhoff's law" thereby functions as the key to understanding the behaviour of passive body temperature in constant incident radiation. Moreover, when Arrhenius (1896, p. 255) added the radiative transfer between the earth's surface and the atmosphere to the conductive transfer between the earth's surface and the atmosphere, he effectively duplicated the radiative transfer quantity, because it was already included in the conductive transfer quantity ("M"). This quantity is representative of net heat flow in accordance with Fourier's Law which, further, does not distinguish between kinetic and radiative modes of heat transfer across a thermal contact.

Not only did Arrhenius duplicate heat, thereby invoking an energy creation mechanism to equip carbon dioxide with a power source it does not have, he propagated an erroneous explanation of how greenhouses work, which he falsely attributed to Fourier. Moreover, Arrhenius used this erroneous explanation as an alternative focal point for his "Hothouse Effect". With respect to the "Greenhouse Effect", as it later became known, this misdirection proved most effective in drawing scrutiny away from the weakest proposition of the idea - as attested by its consequent Concise Oxford Dictionary definition. It is upon this litany of error and misdirection that the "Greenhouse Effect" and the implicitly "anthropogenic" nature of global warming and climate change is based. Having ascertained the various mechanisms of the "Greenhouse Effect", we are ready to test this hypothesis against the laws of physics as they apply to real and repeatable experimental results of a physical and material nature.

3.0 Elementary Physics versus the "Greenhouse Effect"

Heat distribution amongst materials in thermal contact is controlled by respective thermal conductivities rather than any putative optical properties. The relationship between thermal gradient -the change in temperature per unit length- and heat flux -the rate of energy flow across a unit area- is key to understanding the relationship between thermal conductivity and heat distribution within a material or materials in thermal contact. This is limited by the overall power available via the heat flux, which may come from another body in thermal contact or as radiation from a body isolated by a vacuum. However, the amount of heat available to a system due to increased absorption, is lost to corresponding emission. Thus a change in materials without a change in incident radiation -the radiation that falls on a body- can, at most, alter the distribution of heat within those materials.

3.1 The Physics of Nitrogen, Oxygen, and Carbon Dioxide

The relationship between conductivity and net heat transfer explains why physicists, as Gerlich & Tscheuschner (2007 and 2009) point out, only consider the question of heat and temperature in terms of measurable physical properties such as thermal conductivity and heat capacity, unless that heat is being radiated across a vacuum. The latter case presents a question only answered by the Stefan-Boltzmann Equation, explained below. However, in terms of bodies in thermal contact, such as the atmosphere and the surface of the earth, the assertions of Arrhenius with respect to backradiation must necessarily be accompanied by a great variation in thermal conductivity in order to account for a comparably greater change in thermal gradient. This question is addressed in Gerlich & Tscheuschner (2007 and 2009, pp. 6-10), which shows an insufficient difference in the thermal conductivities of carbon dioxide, nitrogen, and oxygen to account for the claims of Arrhenius.

Carbon dioxide does, in fact, have a lower thermal conductivity than either nitrogen or oxygen (by roughly 36%, calculated from the figures of Gerlich & Tscheuschner, 2007 and 2009). So a large increase (i.e. by hundreds of thousands of parts per million) in atmospheric carbon dioxide concentration that would increase the thermal gradient accordingly, could produce a measurable surface warming. As this cannot change the amount of heat flowing through the system, the effect would be manifest by a decrease in atmospheric temperature offset by a corresponding increase in surface temperature. However, a meagre doubling of the presently insignificant levels of atmospheric carbon dioxide cannot have a measurable effect. In fact, geological history records that other factors have a much greater influence on global climate than carbon dioxide.

If carbon dioxide produced the backradiation claimed by Arrhenius, thermal conductivity measurements of carbon dioxide would be so suppressed by the backradiation of heat conducted into this material, that the correspondingly steep temperature gradient would yield a negative thermal conductivity of carbon dioxide. In reality, a 10,000ppm increase in carbon dioxide could, at most, reduce the conductivity of air by 1%. Given the actual difference between the thermal conductivities of carbon dioxide (0.0168) and zero grade air (0.0260), a 10,000ppm increase in carbon dioxide would lower the thermal conductivity of zero grade air by 0.36%. That would represent a 0.36% increase in thermal gradient, or a surface warming of 0.18% and a ceiling cooling of 0.18% of the total difference in temperature between the top and bottom of the affected air mass. In the case of a tropospheric carbon dioxide increase of 10,000ppm, that would correspond to a warming of 0.125ºC, or one eighth of a degree Celsius at the earth's surface, offset by a cooling of 0.125ºC at the tropopause. On the scale of doubling the troposphere's carbon dioxide, the surface warming predicted by this simple and materialistic thermodynamic approach is on the order of 0.004ºC.

3.2 Extending the Stefan-Boltzmann Equation to Incidence of Radiation

Beyond the material medium of the atmosphere, heat is transferred across the vacuum of space by electromagnetic radiation. In fact, radiation is the only way heat can cross a vacuum and this radiative transfer of heat is governed by the Stefan-Boltzmann Law. As we shall see, this is critical to calculating body temperature from heat entering an otherwise thermally isolated body. It also dictates the temperature of the ideal greenhouse. However, as the Stefan-Boltzmann Law concerns radiation emitted, we must first extend this law to relate temperature to incident radiation. This is achieved by applying the the principle of equal absorptivity and emissivity best known as "Kirchhoff's Law".

"Kirchhoff's Law" can be used to simplify the Stefan-Boltzmann Equation (Boltzmann, 1884) yielding a form that is surprisingly elegant. The significance of Kirchhoff's Law lies in the fact that emissivity not only constrains the proportion absorbed, but the readiness with which the body may emit (Kirchhoff, 1859; Kirchhoff, 1860, translated by Guthrie, 1860). Thus as emissivity decreases for the same emission of radiation, the temperature rises. However, given a constant incident radiation, the proportion by which temperature is raised by lack of emissivity is balanced by the reduced proportion of absorbed radiation. Substituting incident radiation multiplied by emissivity for emitted radiation in the Stefan-Boltzmann Equation arises the following way:

Where: W b = Radiation (heat flux) in Wm -2 emitted by the body in question if it is a perfect black body W i = Radiation (heat flux) in Wm -2 incident upon the body in question W e = Radiation (heat flux) in Wm -2 emitted by the body in question T = Absolute Temperature in ºK of the body in question ε = Emissivity = Absorption / (Absorption + Reflection) of the body in question σ = Stefan's Constant = 0.000000056704 W m = Mean incidence of radiation over the entire surface of the body in Wm -2 A x = Mean cross-sectional area of radiation incident on the body in m 2 A t = Topographical area of the body in m 2

W b = σT 4      Stefan's Law relating black body radiation to temperature (Stefan, 1879) W e = εW b    Emissivity is the proportion of hypothetical black body radiation emitted W b = W i      And at thermal equilibrium, black body radiation is equal to incident radiation W e = εW i     Ergo emissivity is also the proportion of incident radiation emitted W e = σεT 4    As the Stefan-Boltzmann Equation (Boltzmann, 1884) elaborates on emitted radiation: εW i = σεT 4

Thus a body's temperature response to incident radiation is entirely independent of emissivity, such that

This is confusing because it looks just like Stefan's Law for black bodies. However, as the radiation in question is not the body's emitted radiation as used by Stefan (1879), but is instead the incident radiation, it applies not only to black bodies but in general - as shown by the simple derivation. However, this case is strictly for omnidirectional radiation, which is only incident when all the radiation is diffuse or scattered. Radiation from a given source is directional and when the source is distant, the radiation is measured in a plane perpendicular to incidence. As a body is a three dimensional object with a much larger surface area than the area across which incident radiation falls, the emitted radiation of a body is always correspondingly lower in intensity then the incident radiation. As the area of incidence is less than the area of emission, we must further modify our equation so:

W i A x /A t = σT 4 W m = W i A x /A t W m = σT 4

As you can see, the temperature of a body in constant incident radiation cannot be raised by compositional changes, and solely depends on the intensity of the radiation. This confirms the duplication of energy and to some degree, the perpetuum mobile inherent in the "Greenhouse Effect."

3.3 Returning to Wood's Experiment to Test Pouillet's Backradiation Hypothesis & Arrhenius' Greenhouse Effect

We may well ask if it is at all possible for backradiation to coexist as a significant process alongside contact transfer. It would certainly seem possible within the limitations of thermal gradients. However, if we revisit the experiment conducted by Robert Wood in 1909, an entirely different picture emerges. Wood constructed two miniature greenhouses identical in all but one respect. One used a plate of halite to transmit light into the interior, while the other used a plate of glass to transmit light into the interior (Wood, 1909). While glass absorbs more than 80% of infrared radiation above 2900nm, halite does not and is regarded as quite transparent to infrared. The point of the experiment was to test whether the halite's lack of absorption and re-emission of infrared radiation relative to that of glass would have any effect on the temperature of the greenhouse.

Taking Pouillet (1838) and Arrhenius (1906a) into account, we may extend the backradiation hypothesis to this particular situation. In this case, the glass lets through the light of the sun but absorbs 85% of the terrestrial infrared radiation radiation returning to space - at least that emitted above 2900nm. We may suppose that this 85% is of the half of the radiation that is absorbed above 2900nm and is augmented by about 15% of the other half of the outgoing infrared radiation based on the numbers from Nicalau and Maluf (2001). That is a total absorption of 50% of the outgoing radiation. This radiation is subsequently emitted from the glass itself; half radiated outside and half radiated back inside the miniature greenhouse. The amount of radiation reaching the bottom of the greenhouse is equal to that directly received from the sun plus the 25% radiated back by the glass. Although halite is more transmissive than glass in the visible spectrum, this is offset by the fact that halite is much more reflective than glass in the visible spectrum (Lane & Christensen, 1998). The difference in light transmission is less than 5%. Thus in the case of this experiment, the glass greenhouse bottom can be said to have received at least 120% (100-5+25) of the radiation received by the halite greenhouse bottom according to the Arrhenius' revision of Pouillet's hypothesis. Thus we expect the temperatures of the respective greenhouses to reflect this significant difference in hypothetical radiation reaching the respective bases.

In Wood's experiment, the halite greenhouse interior temperature rose to 65ºC or 338ºK (Wood, 1909). Applying the Stefan-Boltzmann equation as shown above, to the relationship between incident radiation and body temperature we may determine from: W m = σT 4

That: W m = 0.000000056704 x 338 4 W m = 740 Wm -2

Now, according to the backradiation hypothesis and the measurable optical properties of glass and halite, this 740 Wm -2 should be supplemented, in the glass greenhouse, by 20% in backradiation from the glass. Thus we may surmise, via Arrhenius' variation on Pouillet's backradiation idea, that the radiation at the bottom of the glass greenhouse in the first stage of Wood's experiment was 888 Wm -2 . This predicts the temperature of the glass greenhouse as follows: T = {W m /σ} 0.25

Given W m = 888 Wm -2 : T = {888/0.000000056704} 0.25 = 353.8ºK = 80.6ºC

As you can see, Arrhenius' hypothetical backradiation should raise the glass greenhouse temperature 15ºC above the halite greenhouse temperature, in Wood's experiment. In fact, the first stage of the Wood experiment resulted in the glass greenhouse being slightly cooler than the halite greenhouse. Considering the possibility that this could be due to the fact that the glass filters some of the sun's radiation that is not filtered by the halite, Wood proceeded to conduct a second stage in his historic experiment. This time, he filtered the radiation entering both greenhouses with a sheet of glass. This had the effect of reducing the internal temperature of the halite greenhouse to 55ºC or 328ºK. Thus the radiation incident on the bottom of the halite greenhouse is as follows: W m = σT 4

That: W m = 0.000000056704 x 328 4 W m = 656 Wm -2

Allowing for additional 20% of backradiation gives us W m = 788 Wm -2 in the glass greenhouse, predicting: T = {W m /σ} 0.25

Given W m = 788 Wm -2 : T = {788/0.000000056704} 0.25 = 343.3ºK = 70.2ºC

Once again, the backradiation hypothesis predicts a temperature difference of 15ºC but in this second stage of the Wood experiment no significant difference in temperature was recorded between the glass greenhouse and the halite greenhouse. From the recorded results of the Wood experiment, we can only conclude that the backradiation hypothesis of Arrhenius creates heat ex nihilo , but only in theory.

3.4 Is the "Greenhouse Effect" Really Necessary?

The temperature of the earth's surface is often explained using the "Greenhouse Effect". However, having refuted the "Greenhouse Effect", we may wonder if it was necessary in the first place. The earth orbits the sun in the vacuum of space. There is no aether as Fourier, Tyndall and Arrhenius believed. Moreover, there is no heat capacity or thermal conductivity in space. The only way for heat to escape the planet is by emission to space. That makes the temperature of the absorbing mass of the earth a question of radiative heat transfer. Hereafter, I will refer to the that portion of the earth's mass which absorbs solar radiation as the " solarsphere " because the atmosphere does not include the surface layer warmed by the sun on a day to day basis and there is no other term to encompass both. The method of calculation is to treat the solarsphere as an absorbing body subject to incident radiation from the sun.

Given the solar constant of 1368 Wm -2 (Fröhlich & Brusa, 1981) and the fact that the cross-sectional area of solar radiation incident upon the earth is roughly one quarter of the earth's surface area, it is unsurprising to observe that authors such as Kiehl & Trenberth (1997) arrive at 342 Wm -2 as the mean quantity of solar radiation that falls on the entire surface of the earth. Using this, we may calculate the expected geographical and altitudinal mean temperature of the earth's solarsphere .

W m = σT 4 T 4 = W m /σ T = {W m /σ} 0.25

Given W m = 342: T = {342/0.000000056704} 0.25 = 278.7ºK = 5.5ºC

This figure, is an average or mean temperature for all times, latitudes, and altitudes of the the earth's solarsphere . Just as the balance point or centre of gravity is found at the centre of mass, this average temperature may be found at the centre of heat capacity. In materials of similar heat capacity, this can be found near the centre of mass. Thus, in order to determine how well our 5.5ºC result -calculated above- corresponds to observed reality, we must first determine the average observed temperature at the barometric median in the part of the earth penetrated by solar energy.

From the diagrams supplied by Vallier-Talbot (2007, pp. 25-26), we may roughly determine the centre of mass for a one square metre column extending from two metres below the surface to 50 kilometres above the surface. Soils and clays amount to roughly 2 tons per cubic metre, with the atmospheric column having to weigh 10 tons in order to yield a mean barometric pressure of roughly 1000 hectopascals at the surface. The total column weighs 14 tons with the centre of gravity corresponding to the barometric median at 700 hPa. Referring once again to Vallier-Talbot (2007, p. 26) we may determine that on average, this pressure corresponds to an elevation of roughly a mile or 1600m above the surface. Given the observed average atmospheric thermal gradient of -7ºC with every 1000m of elevation above the surface (Vallier-Talbot, 2007, p. 25), we may calculate the average absorbing mass temperature as it occurs at the altitude of the barometric mean for our absorbing column. No doubt you've worked out that the temperature drop over a tropospheric ascent is 11ºC per mile, and we all know that the average surface temperature is 15ºC (Arrhenius, 1896, p. 239; Burroughs, 2007, p. 124). Notwithstanding 100 years of apparently constant mean temperature from Arrhenius to Burroughs, we may determine that the observed temperature at the altitude corresponding to the centre of absorbing mass is 4ºC or 277ºK. This, via the reasoning above, extends to an observed average absorbing mass temperature for planet earth of 4ºC or 277ºK. This is slightly cooler than the mean absorbing mass temperature calculated above from the solar constant (278.7ºK, 5.5ºC) even if we do allow for 0.5º warming over the last century. However, if we were to consider the impact of convective cooling, I think we can agree that the temperature we derive from the Stefan-Boltzmann equation is well within the tolerance we must allow for such tests.

Adding the tropospheric thermal gradient of 11ºC per mile we got from Vallier-Talbot (2007) above, our temperature (278.7ºK, 5.5ºC), calculated from the Stefan-Boltzmann Equation using the Solar Constant, yields a calculated surface temperature of around 16.5ºC. The fact that this is warmer than the observed mean surface temperatures of Arrhenius and Burroughs (15ºC) leaves no room for such dubious free energy mechanisms as Arrhenius' "Greenhouse Effect". The surface temperature of the earth can be much more simply explained without resorting to such complex and unverifiable entities as radiative amplification and power recycling via backradiation of the "Greenhouse Effect". Absorptivity of any of the parts can vary, but that only alters the overall emissivity, which in turn leaves unchanged, the gross power flowing though the system. Once equilibrium is reached it is only the power flowing through a thermally isolated system that controls and maintains mean temperature. This is because comtinuing and ongoing power is required to offset the amount of heat that is lost spontaneously and continuously due to emission of radiation.

Our calculation of mean surface temperature without the "Greenhouse Effect" above (16.5±0.5ºC corresponding to 16-17ºC) is made without considering the effect of carbon dioxide. According to Arrhenius (1906a, translated by Gerlich & Tscheuschner, 2009, pp. 56-57) the observed temperature should be 20.9ºC higher than that yielded by a calculation such as this, owing to the carbon dioxide in the atmosphere. The observed surface temperature of 15ºC (Arrhenius, 1896; Burroughs, 2007) is actually 1-2ºC lower than the calculated mean surface temperature of 16-17ºC. The lower atmosphere will always be warmer than the upper atmosphere because higher material density in the lower atmosphere dictates a much higher thermal conductivity, absorption and density of heat. In contact with an opaque surface warmed by the bulk of the heat absorbed from the sun, it is not difficult to explain why the surface is so much warmer than the altitude corresponding to the centre of mass in the solarsphere . Moreover, the Ideal Gas Law (PV = nRT) dictates that the temperature of a gas containing a given amount of heat invariably increases with pressure. As the highest atmospheric pressure is at the surface, it makes sense that the higher temperature is there, especially if obstruction to radiative outflow decreases with altitude.

Turning our attention to the example of Langley's greenhouse experiment on Pike's Peak in Colorado (mentioned by Arrhenius, 1906b), we may be tempted to ask how it is that a greenhouse can reach such high temperatures. Qualitatively, we may attribute the difference between the 15ºC mean surface temperature and the 113ºC observed in Langley's greenhouse to the fact that noon-time radiation at the surface is three to four times as intense as the mean radiation over the whole of the earth's surface. Repeating our calculation method, this time for the midday conditions of a greenhouse:

T = {W m /σ} 0.25

Given W m = 1368: T = {1368/0.000000056704} 0.25 = 394.1ºK = 121.0ºC

As you can see, our application of the Stefan-Boltzmann Equation predicts that incident Solar radiation at 1368 Wm -2 should produce a maximum daytime temperature of 394.1ºK or 121.0ºC in a greenhouse fully protected from heat losses to conduction. Although Langley's temperature is lower by eight degrees, it is near enough and, allowing for conductive heat loss, remains a testament to the insulating effectiveness of double glazing.

What is demonstrated in the above examples, is the fact that surface temperature and the temperature in a greenhouse can be explained without resorting to the extraneous entity called the "Greenhouse Effect". This is significant in light of Ockham's Razor, which states:

Entia non sunt multiplicanda praeter necessitatem.

This reads in English as:

Entities are not to be multiplied beyond necessity.

Although the terminology may seem unfamiliar in light of 20 th century usage, if we look at the words for what they mean we can, nonetheless, understand this statement. This suggests, in modern palance, that it is simply not valid to hypothesise beyond what is strictly necessary to explain the material evidence we possess. A hypothesis that does go beyond the support of material evidence violates this principle in that the evidence is already explained by a simpler theory. This is one of the most fundamental and definitive principles of science.

4.0 Conclusion: a Greenhouse with neither Frame nor Foundation Cannot Stand

In the frame of physics, a "greenhouse effect" as such, can only be used to describe a mechanism by which heat accumulates in an isolated pocket of gas that is unable to mix with the main body of gas. The elimination of convection within the troposphere by stratification, and the consequent temperature rise at the surface, presents us with a natural, if not hypothetical, example of a "greenhouse mechanism" in the frame of physics. Pseudoscience, popular misconception and political misuse of the term "greenhouse effect" have given it quite a different and unrelated meaning.

The Hothouse Limerick There was an old man named Arrhenius Whose physics were rather erroneous He recycled rays In peculiar ways And created a "heat" most spontaneous! Timothy Casey, 2010 Since its original proposition by Arrhenius, the definition of the "Greenhouse Effect" has been chaotic and, as such, has successfully obfuscated the weakest and most important part of that proposition. Namely, that terrestrial heat radiated into the atmosphere is there absorbed and re-emitted back to earth to raise surface temperatures beyond what is possible from the incident radiation alone. In fact the physics, as we have examined them, only allow compositional changes to redistribute heat within the absorbing mass of the earth if no change in mean incident radiation occurs. This predicts that atmospheric warming due to increased opacity can only result in surface cooling, which effectively does no more than alter the thermal gradient, thereby redistributing the heat without adding or subtracting from it. This was confirmed by observations of surface cooling during eruptions that ejected ash and carbon dioxide into the stratosphere (Angell & Korshover, 1985) and by observations of stratospheric warming as a consequence of these same eruptions (Angell, 1997). The "Greenhouse Effect" would predict that backradiation from this warmer stratosphere would instead warm the surface significantly. Evidently, this did not occur. If the power recycling mechanisms that typify the "Greenhouse Effect" really existed, we could build cars that ran on nothing but their own recycled momentum and free energy machines could be built to create energy out of nothing more than spent energy. With a viable "Greenhouse Effect" a windscreen would not need a demister as the heat back-radiated by the glass would prevent ice and water drops from condensing and double-glazed windows filled with carbon dioxide would be self heating. In reality, heat flows and is conducted via two modes of heat transfer. One mode of heat flow is by contact transfer, and the other is by radiative transfer. By taking the radiative transfer part of conductive transfer and adding it to the total amount of conductive transfer between the surface of the earth and the atmosphere, Arrhenius (1896) duplicated a portion of the existing heat pro rata to the degree of absorption by carbon dioxide when, in fact, this portion of radiative transfer is already included in the conductive transfer figure.

In the real physics of thermodynamics, the measurable thermodynamic properties of common atmospheric gases predict little if any influence on temperature by carbon dioxide concentration and this prediction is confirmed by the inconsistency of temperature and carbon dioxide concentrations in the geological record . Moreover, when the backradiation "Greenhouse Effect" hypothesis of Arrhenius is put to a real, physical, material test, such as the Wood Experiment, there is no sign of it because the "Greenhouse Effect" simply does not exist. This is why the "Greenhouse Effect" is excluded from modern physics textbooks and why Arrhenius' theory of ice ages was so politely forgotten. It is exclusively the "Greenhouse Effect" due to carbon dioxide produced by industry that is used to underpin the claim that humans are changing the climate and causing global warming. However, without the "Greenhouse Effect", how can anyone honestly describe global warming as "anthropogenic"?

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  • Biology Article
  • Greenhouse Effect Gases

Greenhouse Effect

Table of Contents

What is the Greenhouse Effect?

Greenhouse gases, causes of greenhouse effect, effects of greenhouse effect, runaway greenhouse effect, greenhouse effect definition.

“Greenhouse effect is the process by which radiations from the sun are absorbed by the greenhouse gases and not reflected back into space. This insulates the surface of the earth and prevents it from freezing.”

A greenhouse is a house made of glass that can be used to grow plants. The sun’s radiations warm the plants and the air inside the greenhouse. The heat trapped inside can’t escape out and warms the greenhouse which is essential for the growth of the plants. Same is the case in the earth’s atmosphere.

During the day the sun heats up the earth’s atmosphere. At night, when the earth cools down the heat is radiated back into the atmosphere. During this process, the heat is absorbed by the greenhouse gases in the earth’s atmosphere. This is what makes the surface of the earth warmer, that makes the survival of living beings on earth possible.

However, due to the increased levels of greenhouse gases, the temperature of the earth has increased considerably. This has led to several drastic effects.

Let us have a look at the greenhouse gases and understand the causes and consequences of greenhouse effects with the help of a diagram.

Also Read:  Global Warming

“Greenhouse gases are the gases that absorb the infrared radiations and create a greenhouse effect. For eg., carbondioxide and chlorofluorocarbons.” Greenhouse Effect Diagram

Greenhouse gases

The Diagram shows Greenhouse Gases such as carbon dioxide are the primary cause for the Greenhouse Effect

The major contributors to the greenhouse gases are factories, automobiles, deforestation , etc. The increased number of factories and automobiles increases the amount of these gases in the atmosphere. The greenhouse gases never let the radiations escape from the earth and increase the surface temperature of the earth. This then leads to global warming.

Also Read:  Our Environment

The major causes of the greenhouse effect are:

Burning of Fossil Fuels

Fossil fuels are an important part of our lives. They are widely used in transportation and to produce electricity. Burning of fossil fuels releases carbon dioxide. With the increase in population, the utilization of fossil fuels has increased. This has led to an increase in the release of greenhouse gases in the atmosphere.

Deforestation

Plants and trees take in carbon dioxide and release oxygen. Due to the cutting of trees, there is a considerable increase in the greenhouse gases which increases the earth’s temperature.

Nitrous oxide used in fertilizers is one of the contributors to the greenhouse effect in the atmosphere.

Industrial Waste and Landfills

The industries and factories produce harmful gases which are released in the atmosphere.

Landfills also release carbon dioxide and methane that adds to the greenhouse gases.

definition of greenhouse hypothesis

The main effects of increased greenhouse gases are:

Global Warming

It is the phenomenon of a gradual increase in the average temperature of the Earth’s atmosphere. The main cause for this environmental issue is the increased volumes of greenhouse gases such as carbon dioxide and methane released by the burning of fossil fuels, emissions from the vehicles, industries and other human activities.

Depletion of  Ozone Layer

Ozone Layer protects the earth from harmful ultraviolet rays from the sun. It is found in the upper regions of the stratosphere. The depletion of the ozone layer results in the entry of the harmful UV rays to the earth’s surface that might lead to skin cancer and can also change the climate drastically.

The major cause of this phenomenon is the accumulation of natural greenhouse gases including chlorofluorocarbons, carbon dioxide, methane, etc.

Smog and Air Pollution

Smog is formed by the combination of smoke and fog. It can be caused both by natural means and man-made activities.

In general, smog is generally formed by the accumulation of more greenhouse gases including nitrogen and sulfur oxides. The major contributors to the formation of smog are automobile and industrial emissions, agricultural fires, natural forest fires and the reaction of these chemicals among themselves.

Acidification of Water Bodies

Increase in the total amount of greenhouse gases in the air has turned most of the world’s water bodies acidic. The greenhouse gases mix with the rainwater and fall as acid rain. This leads to the acidification of water bodies.

Also, the rainwater carries the contaminants along with it and falls into the river, streams and lakes thereby causing their acidification.

This phenomenon occurs when the planet absorbs more radiation than it can radiate back. Thus, the heat lost from the earth’s surface is less and the temperature of the planet keeps rising. Scientists believe that this phenomenon took place on the surface of Venus billions of years ago.

This phenomenon is believed to have occurred in the following manner:

  • A runaway greenhouse effect arises when the temperature of a planet rises to a level of the boiling point of water. As a result, all the water from the oceans converts into water vapour, which traps more heat coming from the sun and further increases the planet’s temperature. This eventually accelerates the greenhouse effect. This is also called the “positive feedback loop”.
  • There is another scenario giving way to the runaway greenhouse effect. Suppose the temperature rise due to the above causes reaches such a high level that the chemical reactions begin to occur. These chemical reactions drive carbon dioxide from the rocks into the atmosphere. This would heat the surface of the planet which would further accelerate the transfer of carbon dioxide from the rocks to the atmosphere, giving rise to the runaway greenhouse effect.

In simple words, increasing the greenhouse effect gives rise to a runaway greenhouse effect which would increase the temperature of the earth to such an extent that no life will exist in the near future.

Also Read:  Environmental Issues

To learn more about what is the greenhouse effect, its definition, causes and effects, keep visiting BYJU’S website or download the BYJU’S app for further reference.

Frequently Asked Questions

What is global warming.

The gradual increase in temperature due to the greenhouse effect caused by pollutants, CFCs and carbon dioxide is called global warming. This phenomenon has disturbed the climatic pattern of the earth.

List gases which are responsible for the greenhouse effect.

The major greenhouse gases are: 1) Carbon dioxide 2) Methane 3) Water 4) Nitrous oxide 5) Ozone 6) Chlorofluorocarbons (CFCs)

What is the greenhouse effect?

What are the major causes of the greenhouse effect.

Burning of fossil fuels, deforestation, farming and livestock production all contribute to the greenhouse effect. Industries and factories also play a major role in the release of greenhouse gases.

What would have happened if the greenhouse gases were totally missing in the earth’s atmosphere?

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ENCYCLOPEDIC ENTRY

Climate change.

Climate change is a long-term shift in global or regional climate patterns. Often climate change refers specifically to the rise in global temperatures from the mid-20th century to present.

Earth Science, Climatology

Fracking tower

Fracking is a controversial form of drilling that uses high-pressure liquid to create cracks in underground shale to extract natural gas and petroleum. Carbon emissions from fossils fuels like these have been linked to global warming and climate change.

Photograph by Mark Thiessen / National Geographic

Fracking is a controversial form of drilling that uses high-pressure liquid to create cracks in underground shale to extract natural gas and petroleum. Carbon emissions from fossils fuels like these have been linked to global warming and climate change.

Climate is sometimes mistaken for weather. But climate is different from weather because it is measured over a long period of time, whereas weather can change from day to day, or from year to year. The climate of an area includes seasonal temperature and rainfall averages, and wind patterns. Different places have different climates. A desert, for example, is referred to as an arid climate because little water falls, as rain or snow, during the year. Other types of climate include tropical climates, which are hot and humid , and temperate climates, which have warm summers and cooler winters.

Climate change is the long-term alteration of temperature and typical weather patterns in a place. Climate change could refer to a particular location or the planet as a whole. Climate change may cause weather patterns to be less predictable. These unexpected weather patterns can make it difficult to maintain and grow crops in regions that rely on farming because expected temperature and rainfall levels can no longer be relied on. Climate change has also been connected with other damaging weather events such as more frequent and more intense hurricanes, floods, downpours, and winter storms.

In polar regions, the warming global temperatures associated with climate change have meant ice sheets and glaciers are melting at an accelerated rate from season to season. This contributes to sea levels rising in different regions of the planet. Together with expanding ocean waters due to rising temperatures, the resulting rise in sea level has begun to damage coastlines as a result of increased flooding and erosion.

The cause of current climate change is largely human activity, like burning fossil fuels , like natural gas, oil, and coal. Burning these materials releases what are called greenhouse gases into Earth’s atmosphere . There, these gases trap heat from the sun’s rays inside the atmosphere causing Earth’s average temperature to rise. This rise in the planet's temperature is called global warming. The warming of the planet impacts local and regional climates. Throughout Earth's history, climate has continually changed. When occuring naturally, this is a slow process that has taken place over hundreds and thousands of years. The human influenced climate change that is happening now is occuring at a much faster rate.

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New to Climate Change?

Greenhouse gases.

Greenhouse gases are gases—like carbon dioxide (CO 2 ), methane, and nitrous oxide—that keep the Earth warmer than it would be without them. The reason they warm the Earth has to do with the way energy enters and leaves our atmosphere . When energy from the sun first reaches us, it does so mainly as light. But when that same energy leaves the Earth, it does so as infrared radiation, which we experience as heat. Greenhouse gases reflect infrared radiation, so some of the heat leaving the Earth bounces off the greenhouse gases in our atmosphere and comes back to the Earth’s surface. This is called the “greenhouse effect,” in a comparison to the heat-trapping glass on a greenhouse.

The greenhouse effect is not a bad thing. Without it, our planet would be too cold for life as we know it. But if the amount of greenhouse gases in the atmosphere changes, the strength of the greenhouse effect changes too. This is the cause of human-made climate change: by adding greenhouse gases to the atmosphere, we are trapping more heat, and the entire planet gets warmer.

The focus on “carbon”

For climate change, the most important greenhouse gas is carbon dioxide, which is why you hear so many references to “carbon” when people talk about climate change. There are three main reasons CO 2 is so central to the global warming happening today. First, there is just so much of it: we now add over 35 billion tons of CO 2 to the atmosphere every year, mostly by burning carbon-rich fuel like coal and oil that had previously been trapped in the ground. Second, it lasts a long time in the atmosphere. The CO 2 we emit today will stay above us reflecting heat for hundreds of years. This means that, even if we stop all new CO 2 emissions tomorrow, it will take many lifetimes before the warming effect of our past emissions fades away.

Finally, many different industries rely on carbon-rich fuels or other processes that give off CO 2 . That includes burning fossil fuels for electricity and heat and to power our vehicles, but it also includes manufacturing concrete and steel , the refining process for raw oil and gas, fermentation (for instance, to make alcohol or pharmaceuticals), and the decay of plant matter (like after trees are cut down ). All of these sectors can make changes to emit less CO 2 , but the same solutions won’t work for all of them.

Infographic: Other greenhouse gases. CO2 is the biggest cause of human-made climate change, but other greenhouse gases are important too. They come from different sources, linger in the atmosphere for different amounts of time, and may be more or less potent at trapping heat. Greenhouse gases are usually counted in “CO2 equivalents” (CO2e). One CO2e is the amount of heat an equal amount of CO2 would be expected to trap over the next 100 years.

Updated May 22, 2023. This Explainer was adapted from “ Explained: Greenhouse Gases ” by David Chandler, which originally appeared in MIT News.

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Doctors and patients fearfully proceed with IVF after Alabama court rules embryos are children

After three miscarriages in less than a year, Gabby Goidel said she was diagnosed with unexplained genetic infertility.

For reasons that aren't clear to doctors, any fetus she carries has a higher-than-average likelihood of genetic abnormalities, she said, so there is a slim chance she'd be able to carry a pregnancy to term without in-vitro fertilization.

To avoid the possibility of additional miscarriages, Goidel and her husband, Spencer, decided last year to pursue in vitro fertilization in their home state of Alabama.

IVF allows doctors to test embryos for genetic abnormalities, then implant only the ones that are healthy.

The Goidels were on track to freeze embryos later this month, and they planned to only store the ones that were genetically normal.

But on Friday, the Alabama Supreme Court ruled that frozen embryos created through IVF are considered children under state law, meaning that people could theoretically be sued for destroying an embryo.

The Goidels began to worry whether they might be forced to store — or even use — embryos they had intended to discard.

"Most of our embryos are not going to be genetically normal," said Goidel, a 26-year-old property manager in Auburn. "My hope would be that we could let those embryos naturally pass, but now it’s, 'Do we have to save them?' I don’t necessarily want to implant a child that I know is going to miscarry."

Roughly half of first-trimester miscarriages are due to a chromosomal abnormality in the fetus. In addition to vaginal bleeding, abdominal pain and cramping, miscarriages can increase the risk of anxiety, depression, post-traumatic stress disorder and suicide.

An uncertain future for IVF patients

In the wake of the Alabama ruling, many patients and providers are unsure of how to navigate the IVF process, given that embryos are often discarded if they have genetic abnormalities or after patients decide they will not need to use them. The decision raises questions about whether those who undergo IVF will have to store all their embryos indefinitely — but experts said the answer is not yet clear.

Storing frozen embryos can cost between $350 to $1,000 per year .

The court's decision was issued in a case in which a person removed embryos from storage at a fertility clinic and dropped them on the floor accidentally.

Gail Deady, senior staff attorney at the Center for Reproductive Rights, said that because of that, the ruling "does not appear to create criminal liability for IVF providers."

Instead, she said, "what it does implicate is the Wrongful Death Act, which is civil liability and negligence," meaning people could be sued for the destruction of embryos and have to pay monetary penalties.

Nevertheless, “anyone who cares about reproductive autonomy should be terrified of this decision,” Deady added.

Dr. Mamie McLean, a reproductive endocrinologist at Alabama Fertility, said she is concerned about the survival of IVF services in Alabama. Clinics may need to raise prices if they have trouble staffing providers or have to pay more for medical malpractice insurance, she said. As a result, fewer people may be able to afford IVF and fewer insurers may be willing to cover treatments.

The cost of insurance to defend against wrongful death lawsuits “might actually prevent us from practicing, it would be so high,” said Dr. Brett Davenport, a reproductive endocrinologist at Fertility Institute of North Alabama.

Davenport, too, worries the new law could penalize doctors for helping people start families.

“I am a very pro-life reproductive endocrinologist, and yet this still seems quite absurd to me,” he said.

Legal experts worry the ruling could set the stage for harsher abortion restrictions in the future, as well, such as penalties for women who get abortions. (Right now, state law only penalizes providers who administer abortions.)

"The next step will be to say, 'Well, if an embryo is a person [outside the uterus], clearly it's a person in utero," said Priscilla Smith, director of the Program for the Study of Reproductive Justice at Yale Law School.

“I don’t want to be dramatic and say it’s totally Handmaid’s Tale, but more and more, you’re in the situation rather where the state controls your behavior," Smith said.

Where to put embryos?

After the Alabama Supreme Court decision, Meghan Cole, an attorney in Birmingham, made a plan to move her remaining embryos to another state. Cole has a rare blood disorder that prevents her from safely carrying a child, so she’s planning to use a surrogate. That embryo transfer is scheduled for next week, and she still has other embryos in storage.

“I was scared for what the future held for the embryos that we’re still going to have in storage,” she said. “My first thought was, ‘OK, I need to transfer my embryos out-of-state and have them frozen somewhere else so I don’t open myself up to liability.’”

Cole said she selected which embryo to use with Alabama’s legal landscape in mind.

“We are picking a boy to transfer because these rules and laws that are coming out that are affecting women’s health kind of scare me for a daughter,” she said.

Deady said there's no reason yet why patients in Alabama should be afraid of getting IVF — but providers are proceeding cautiously.

McLean said there are even some concerns about the ability to freeze embryos in the first place, given the ruling. An alternative to freezing or discarding embryos, she said, would be to create fewer of them. But in that case, patients would likely require more rounds of IVF to get pregnant, which is both expensive and physically demanding.

Alabama's legal landscape has made the Goidels reconsider whether they want to raise kids there.

“We’re this very traditional family that just wants to have a kid, so I didn’t realize ever that this was going to be a question of morality,” Goidel said.

“We really envisioned starting a life here and probably retiring here,” she added. “We’re very much questioning whether or not we want to leave.”

definition of greenhouse hypothesis

Aria Bendix is the breaking health reporter for NBC News Digital.

IMAGES

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  6. Greenhouse Effect Definition

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VIDEO

  1. Explaining The Greenhouse Effect

  2. Greenhouse effect and greenhouse gases| Global change| AP Environmental science| Khan Academy

  3. Demystifying the Atmospheric Greenhouse Effect: Toward a New Physical Paradigm in Climate Science

  4. What is the greenhouse effect and how does it work?

  5. Greenhouse Effect and Global Warming

  6. The Greenhouse Effect

COMMENTS

  1. Greenhouse effect

    greenhouse effect, a warming of Earth 's surface and troposphere (the lowest layer of the atmosphere) caused by the presence of water vapour, carbon dioxide, methane, and certain other gases in the air. Of those gases, known as greenhouse gases, water vapour has the largest effect. The origins of the term greenhouse effect are unclear.

  2. From scientific arguments to scepticism: Humans' place in the Greenhouse

    This article investigates the different roles attributed to humanity in the climate change debate, through the depiction of the greenhouse effect.Our hypothesis is that the stance associated with different genres will not only demonstrate different conceptualisations of the greenhouse effect but also convey different views on humans' capacity (or lack of capacity) to mitigate climate change.

  3. Greenhouse Effect

    Many scientists use the term "climate change" instead of "global warming.". This is because greenhouse gas emissions affect more than just temperature. Another effect involves changes in precipitation like rain and snow. Patterns in precipitation may change or become more extreme.

  4. What is the greenhouse effect?

    The greenhouse effect is the process through which heat is trapped near Earth's surface by substances known as 'greenhouse gases.'. Imagine these gases as a cozy blanket enveloping our planet, helping to maintain a warmer temperature than it would have otherwise. Greenhouse gases consist of carbon dioxide, methane, ozone, nitrous oxide ...

  5. Overview of the physics of the atmospheric greenhouse effect

    This results in some heating of this gaseous medium, which contributes to the temperature distribution. And the atmosphere radiates some of this energy to the land and to oceans (150 W/m 2 ), which is the greenhouse effect. The respective contributions of the various molecules are very different. Note, for example, that, per unit mass, the ...

  6. Greenhouse effect

    Greenhouse gases such as methane, carbon dioxide, nitrous oxide, and water vapor significantly affect the amount of energy in the Earth system, even though they make up a tiny percentage of Earth's atmosphere. Solar radiation that passes through the atmosphere and reaches Earth's surface is either reflected or absorbed.Reflected sunlight doesn't add any heat to the Earth system because ...

  7. 1. Introduction

    a) The Scientific Process. Climate scientists, like other scientists, use a cyclical process to advance their understanding. Usually it starts with a question, a lack of understanding. They form hypotheses based on previous knowledge or experience. Formulating a good hypothesis is usually not trivial.

  8. The Greenhouse Effect

    When we add extra greenhouse gases to the atmosphere, though, we increase the atmosphere's heat-trapping capacity. Less heat escapes to space, more returns to Earth, and the planet warms. There ...

  9. PDF CHAPTER 7. THE GREENHOUSE EFFECT

    Figure 7-10.eps. CHAPTER 7. THE GREENHOUSE EFFECT. We examine in this chapter the role played by atmospheric gases in controlling the temperature of the Earth. The main source of heat to the Earth is solar energy, which is transmitted from the Sun to the Earth by radiation and is converted to heat at the Earth's surface.

  10. What Is the Greenhouse Effect?

    The greenhouse effect on other planets . Because the greenhouse effect is a natural process, it affects other bodies in the solar system, too. And, in some cases, that provides a warning about how ...

  11. The Greenhouse Theory of Climate Change: A Test by an ...

    According to the greenhouse theory of climate change, the climate system will be restored to equilibrium by a warming of the surface-troposphere system and a cooling of the stratosphere. The predicted changes, during the next few decades, could far exceed natural climate variations in historical times. Hence, the greenhouse theory of climate ...

  12. What Is the Greenhouse Effect?

    A greenhouse captures heat from the Sun during the day. Its glass walls trap the Sun's heat, which keeps plants inside the greenhouse warm — even on cold nights. Credit: NASA/JPL-Caltech. The greenhouse effect works much the same way on Earth. Gases in the atmosphere, such as carbon dioxide, trap heat similar to the glass roof of a greenhouse.

  13. Part 1: The Greenhouse Effect

    Examine Figure 1 at right. The Greenhouse Effect is comprised of multiple energy transfers. First, the Sun emits electromagnetic radiation (light) that interacts with the Earth's atmosphere and surface. Second, Earth's surface emits radiation that both escapes to space and interacts with Earth's atmosphere. Finally, Earth's atmosphere itself ...

  14. The Shattered Greenhouse

    Confusion and Lack of Thermodynamic Definition. Although the "Greenhouse Effect" is of crucial importance to modern climatology and is the putative cornerstone of the Anthropogenic Global Warming hypothesis, it lacks clear thermodynamic definition. ... Moreover, when the backradiation "Greenhouse Effect" hypothesis of Arrhenius is put to a real ...

  15. What Is Greenhouse Effect?

    A greenhouse is a house made of glass that can be used to grow plants. The sun's radiations warm the plants and the air inside the greenhouse. The heat trapped inside can't escape out and warms the greenhouse which is essential for the growth of the plants. Same is the case in the earth's atmosphere. During the day the sun heats up the ...

  16. Climate Change

    Climate change is the long-term alteration of temperature and typical weather patterns in a place. Climate change could refer to a particular location or the planet as a whole. Climate change may cause weather patterns to be less predictable. These unexpected weather patterns can make it difficult to maintain and grow crops in regions that rely ...

  17. Greenhouse

    Also called: greenhouse, building designed for the protection of tender or out-of-season plants against excessive cold or heat. In the 17th century, greenhouses were ordinary brick or timber shelters with a normal proportion of window space and some means of heating. As glass became cheaper and as more sophisticated forms of heating became ...

  18. PDF Refutation of The "Greenhouse Effect" Theory on A

    The object of this study is to demonstrate the nonexistence of the so-called "greenhouse effect" (GHE) based on established physical laws of thermodynamics and material hydrostatics as well as relevant experimental data. The GHE hypothesis, widely promoted in recent years, claims that atmospheric gases, particularly carbon dioxide (CO2)

  19. What Is Anthropogenic Global Warming? : ScienceAlert

    Explainer. By Mike McRae. (Hramovnick/iStock) Anthropogenic global warming is a theory explaining today's long-term increase in the average temperature of Earth's atmosphere as an effect of human industry and agriculture. For well over a century, scientists have been concerned that as the concentration of greenhouse gases in the atmosphere ...

  20. (PDF) Laws of thermodynamics challenge greenhouse-gas and climate

    The greenhouse-gas hypothesis (GGH), i.e., CO2 is the cause of global warming by ~1K from ~1950-2023, is popularly believed to be established scientific truth. It is generally assumed that heat ...

  21. Greenhouse gas

    greenhouse gas, any gas that has the property of absorbing infrared radiation (net heat energy) emitted from Earth's surface and reradiating it back to Earth's surface, thus contributing to the greenhouse effect. Carbon dioxide, methane, and water vapour are the most important greenhouse gases. (To a lesser extent, surface-level ozone, nitrous oxides, and fluorinated gases also trap ...

  22. PDF Laws of thermodynamics challenge greenhouse-gas and ...

    the greenhouse-gas hypothesis and also the climate-change hypothesis (CCH) and emphasise ... definition of "global warming" to within the accuracy that mean air temperature can be

  23. Greenhouse Gases

    Greenhouse gases are gases—like carbon dioxide (CO 2), methane, and nitrous oxide—that keep the Earth warmer than it would be without them. The reason they warm the Earth has to do with the way energy enters and leaves our atmosphere. When energy from the sun first reaches us, it does so mainly as light. But when that same energy leaves the ...

  24. IVF doctors, patients fearful after Alabama court rules embryos are

    According to the decision, people in Alabama could theoretically be sued for destroying a frozen embryo, raising questions about in-vitro fertilization.