Arguments
The 97% consensus on global warming
What the science says...
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97% of climate experts agree humans are causing global warming. |
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Climate Myth...
There is no consensus
"[...] And I'll mention that the stat on the 97% of - of scientists is based on one discredited study." (Ted Cruz)
At a glance
What is consensus? In science, it's when the vast majority of specialists agree about a basic principle. Thus, astronomers agree that the Earth orbits around the Sun. Biologists accept that tadpoles hatch out from frog-spawn and grow into adult frogs. Almost all geologists agree that plate tectonics is real and you'd be hard-placed to find a doctor who thinks smoking is harmless.
In each above case, something has been so thoroughly looked into that those who specialise in its study have stopped arguing about its basic explanation. Nevertheless, the above examples were all once argued about, often passionately. That's how progress works.
The reaching of scientific consensus is the product of an often lengthy time-line. It starts with something being observed and ends with it being fully explained. Let's look at a classic and highly relevant example.
In the late 1700s, the Earth-Sun distance was calculated. The value obtained was 149 million kilometres. That's incredibly close to modern measurements. It got French physicist Joseph Fourier thinking. He innocently asked, in the 1820s, something along these lines:
"Why is Planet Earth such a warm place? It should be an ice-ball at this distance from the Sun."
Such fundamental questions about our home planet are as attractive to inquisitive scientists as ripened fruit is to wasps. Fourier's initial query set in motion a process of research. Within a few decades, that research had experimentally shown that carbon dioxide has heat-trapping properties.
Through the twentieth century the effort intensified, particularly during the Cold War. At that time there was great interest in the behaviour of infra-red (IR) radiation in the atmosphere. Why? Because heat-seeking missiles home in on jet exhausts which are IR hotspots. Their invention involved understanding what makes IR tick.
That research led to the publication of a landmark 1956 paper by Gilbert Plass. The paper's title was, “The Carbon Dioxide Theory of Climatic Change”. It explained in detail how CO2 traps heat in our atmosphere. Note in passing that Plass used the term "Climatic Change" all the way back then. That's contrary to the deniers' frequent claim that it is used nowadays because of a recent and motivated change in terminology.
From observation to explanation, this is a classic illustration of the scientific method at work. Fourier gets people thinking, experiments are designed and performed. In time, a hypothesis emerges. That is a proposed explanation. It is made on the basis of limited evidence as a starting point for further investigation.
Once a hypothesis is proposed, it becomes subject to rigorous testing within the relevant specialist science groups. Testing ensures that incorrect hypotheses fall by the wayside, because they don't stand up to scrutiny. But some survive such interrogation. As their supporting evidence mounts up over time, they eventually graduate to become theories.
Theories are valid explanations for things that are supported by an expert consensus of specialists. Gravity, jet aviation, electronics, you name it, all are based on solid theories. They are known to work because they have stood the test of time and prolonged scientific inquiry.
In climate science today, there is overwhelming (greater than 97%) expert consensus that CO2 traps heat and adding it to the atmosphere warms the planet. Whatever claims are made to the contrary, that principle has been established for almost seventy years, since the publication of that 1955 landmark paper.
Expert consensus is a powerful thing. None of us have the time or ability to learn about everything/ That's why we frequently defer to experts, such as consulting doctors when we’re ill.
The public often underestimate the degree of expert consensus that our vast greenhouse gas emissions trap heat and warm the planet. That is because alongside information, we have misinformation. Certain sections of the mass-media are as happy to trot out the latter as the former. We saw a very similar problem during the COVID-19 pandemic and it cost many lives.
For those who want to learn more, a much longer detailed account of the history of climate science is available on this website.
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further details
We know full well that we don’t have the time or capacity to learn about everything, so we frequently defer to the conclusions of experts. Without experienced people using their expertise to perform many vital tasks – and without new people constantly entering such occupations – society would quickly disintegrate.
The same is true of climate change: we defer to the expert consensus of climate scientists. Indeed, public perception of the scientific consensus with regard to global warming has been found to be an important gateway into other enlightened climate-related attitudes - including policy support.
Let's take a look at summaries of the key studies, featured in the graphic above, into the degree of consensus. These have been based on analyses of large samples of peer-reviewed climate science literature or surveys of climate and Earth scientists. These studies are available online through e.g. Google Scholar. That slightly different methodologies reached very similar conclusions is a strong indicator that those conclusions are robust.
Oreskes 2004
In this pioneering paper, a survey was conducted into all peer-reviewed abstracts on the subject 'global climate change', published between 1993 and 2003. The work showed that not a single paper, out of the 928 examined, rejected the consensus position that global warming is man-made. 75% of the papers agreed with the consensus position while 25% made no comment either way.
Doran & Zimmerman 2009
A survey of 3,146 Earth scientists asked the question, "Do you think human activity is a significant contributing factor in changing mean global temperatures?" Overall, 82% of the scientists answered yes. However, what was most interesting was the type of response compared to the level of expertise in climate science. Of scientists who were non-climatologists and didn't publish research, 77% answered yes. In contrast, 97.5% of actively-publishing climatologists responded yes. As the level of active research and specialization in climate science increases, so does agreement that humans are significantly changing global temperatures. The paper concludes:
"It seems that the debate on the authenticity of global warming and the role played by human activity is largely non-existent among those who understand the nuances and scientific basis of long-term climate processes. The challenge, rather, appears to be how to effectively communicate this fact to policy makers and to a public that continues to mistakenly perceive debate among scientists."
Anderegg et al. 2010
This study of 1,372 climate science researchers found that (i) 97–98% of the researchers most actively publishing in the field support the tenets of anthropogenic climate change (ACC) as outlined by the IPCC and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.
Cook et al. 2013
A Skeptical Science-based analysis of over 12,000 peer-reviewed abstracts on the subject 'global climate change' and 'global warming', published between 1991 and 2011, found that over 97% of the papers taking a position on the subject agreed with the consensus position that humans are causing global warming. In a second phase of the project, the scientist authors were emailed and rated over 2,000 of their own papers. Once again, over 97% of the papers taking a position on the cause of global warming agreed that humans are causing it.
Verheggen et al. 2014
Results were presented from a survey held among 1868 scientists studying various aspects of climate change, including physical climate, climate impacts, and mitigation. The survey was at the time unique in its size, broadness and level of detail. Consistent with other research, it was found that as the level of expertise in climate science grew, so too did the level of agreement on anthropogenic causation. 90% of respondents with more than 10 climate-related peer-reviewed publications (about half of all respondents), explicitly agreed with anthropogenic greenhouse gases (GHGs) being the dominant driver of recent global warming. The respondents’ quantitative estimate of the GHG contribution appeared to strongly depend on their judgement or knowledge of the cooling effect of aerosols.
Stenhouse et al. 2014
In a survey of all 1,854 American Meteorological Society members with known e-mail addresses, achieving a 26.3% response rate, perceived scientific consensus was the strongest predictor of views on global warming, followed by political ideology, climate science expertise, and perceived organisational conflict.
Carlton et al 2015
Commenting that the extent to which non-climate scientists are skeptical of climate science had not so far been studied via direct survey, the authors did just that. They undertook a survey of biophysical scientists across disciplines at universities in the Big 10 Conference. Most respondents (93.6%) stated that mean temperatures have risen. Of the subset that agreed temperatures had risen, the following question was then asked of them: "do you think human activity is a significant contributing factor in changing mean global temperatures?" The affirmative response to that query was 96.66%.
Cook et al. 2016
In 2015, authors of the above studies joined forces to co-author a paper, “Consensus on consensus: a synthesis of consensus estimates on human-caused global warming”. Two key conclusions from the paper are as follows:
(i) Depending on exactly how you measure the expert consensus, somewhere between 90% and 100% of climate scientists agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists. (ii) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming.
Lynas et al. 2021
In this paper, from a dataset of 88,125 climate-related peer-reviewed papers published since 2012, these authors examined a randomly-selected subset of 3000 such publications. They also used a second sample-weighted approach that was specifically biased with keywords to help identify any sceptical papers in the whole dataset. Twenty-eight sceptical papers were identified within the original dataset using that approach, as evidenced by abstracts that were rated as implicitly or explicitly sceptical of human-caused global warming. It was concluded that the scientific consensus on human-caused climate change, expressed as a proportion of the total publications, exceeds 99% in the peer reviewed scientific literature.
Myers et al. 2021
This study revisited the 2009 consensus among geoscientists, while exploring different ways to define expertise and the level of agreement among them. The authors sent 10,929 invitations to participate in the survey, receiving 2,780 responses. In addition, the number of scientific publications by these self-identified experts in the field of climate change research was quantified and compared to their survey response on questions about climate change. Perhaps not surprisingly, the study found that agreement on anthropogenic global warming was high at 91% to 100% and generally increases with expertise. Out of a group of 153 independently confirmed climate experts, 98.7% of those scientists agreed that the Earth is warming mostly because of human activities such as burning fossil fuels. Among the subset with the highest level of expertise, these being independently-confirmed climate experts who each published 20+ peer-reviewed papers on climate change between 2015 and 2019, there was 100% agreement.
Public Polls and Consensus
Opinion polls are not absolute in the same way as uncontestable scientific evidence but they nevertheless usefully indicate in which way public thinking is heading. So let's look at a couple taken 13 years apart. A 15-nation World Public Opinion Poll in 2009 PDF), with 13,518 respondents, asked, among other questions, “Is it your impression that among scientists, most think the problem is urgent and enough is known to take action?” Out of all responses, just 51% agreed with that. Worse, in six countries only a minority agreed: United States (38%), Russia (23%), Indonesia (33%), Japan (43%), India (48%), and Mexico (48%). Conversely, the two highest “agree” scores were among Vietnamese (69%) and Bangladeshis (70%) - perhaps unsurprisingly.
The two other options people had to choose from were that “views are pretty evenly divided” (24% of total respondents), or “most think the problem is not urgent, and not enough is known to take action“ (15%). American and Japanese respondents scored most highly on “views are pretty evenly divided” (43 and 44% respectively).
How such a pervasive misperception arose, regarding the expert consensus on climate change, is no accident. Regular readers of this website's resources will know that instead, it was another product of deliberate misinformation campaigning by individuals and organizations in the United States and other nations around the world. These are people who campaign against action to reduce carbon emissions because it suits their paymasters if we continue to burn as much as possible.
Step forward to 2022 and the situation has perhaps improved, but there's still some way to go. A recent poll, Public Perceptions on Climate change (PDF), was conducted by the Policy Institute, based at King's College London, UK. It quizzed samples of just over 2,000 people from each of six countries (UK, Ireland, Norway, Poland, Italy and Germany). The survey asked the question: “To the best of your knowledge, what percentage of climate scientists have concluded that human-caused climate change is happening?” The following averages were returned: the UK sample thought 65%, the average of the whole survey was 68% and the highest was Ireland at 71%. Clearly, although public perception of expert consensus is growing, there's still plenty of room for strategies to communicate the reality and to shield people from the constant drip-feed of misinformation.
Expert and Public Consensus
Finally, let's consider the differences between expert and public consensus. Expert consensus is reached among those who have studied complex problems and know how to collect and work with data, to identify what constitutes evidence and evaluate it. This is demanding work requiring specific skill-sets and areas of expertise, preparation for which requires years of study and training.
Public consensus, in contrast, tends to occur only when something is blindingly obvious. For example, a serial misinformer would struggle if they tried running a campaign denying the existence of owls. Everyone already knows that of course there are owls. There is public consensus because we see and hear owls, for real or on the TV or radio. But complex issues are more prone to the antics of misinformers. We saw examples of misinformation during the COVID pandemic, in some cases with lethal outcomes when misinformed people failed to take the risks seriously. There's a strong parallel with climate change: it is imperative we accept the expert consensus and not kick the can down the road until the realisation it is real becomes universal – but utterly inescapable.
Update May 26, 2023: The "At a glance" section was updated to improve readability.
Last updated on 26 May 2023 by John Mason. View Archives
LeonD - I expect you're doing a 'drive-by', rather than actually engaging in conversation, but I would ask you to consider just what proportion of peer-reviewed biology papers make explicit statements for or against the validity of evolution in their abstracts? And whether you, for some reason, think the large percentage of such papers not restating known facts is in some fashion disagreement with evolution?
The same holds of climate science. In fact, I suspect the estimated percentage of disagreement on climate is biased towards the negative (that the percentage might be lower than 3%), since authors disagreeing with the consensus have far more reason to mention AGW than authors who treat it as a known and understood background to the data.
Bzzzt.
The source is the paper itself:
http://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024
Specifically Table 5
I am referring to the self-rated results but the abstract results are even less in favour of AGW.
LeonD - I'll repeat my question: do you think the high percentage of biology papers that fail to state a position on evolution are in fact evidence that biologists disagree with it? Or that the infinitesimal number of modern physics studies stating a position on the existence of atoms represents evidence of major disagreement there?
There's no need to repeat known facts, especially in the limited space of a paper or even more so the 200-500 words of an abstract - your argument is absurd.
I cannot find the reference at the moment, but as I recall Naomi Oreskes noted that as a scientific consensus grows the explicit mention of that consensus declines - because, again, there's no need to repeatedly tell your audience that water is wet, or that a clear sky is blue...
My mistake, I thought they were querying the authors on their own views not on what their papers were saying.
LeonD... I think that's a very common mistake. Relative to the Cook13 paper, many people fail to discern the difference between "position" and "opinion."
For a survey of scientific opinions, rather than the published work, see Doran 2009, whose survey found that among scientists who had more than half of their recent work on climate (i.e., who are actively researching the matter), 97% agreed that:
KR @707, I think insufficient attention has been paid to uncertainty intervals with regard to the concensus. In particular, in the case of Doran, Kendall and Zimmerman (2009), the sample size for question two, ie, the question on attribution, is only 77.
Calculating uncertainty depends not only on the sample size, but also (weakly) on the size of the total population. In the case of climate scientists, the total number of climate scientists in the world is an unknown. However, based on a literature review, Verheggen et al (2014) found the emails of approximately 8000 people, of which approximately 7600 where climate scientists (the other 400 being contacted because they where known "skeptics". On that basis, the total number of climate scientists in the world is likely to be greater than 5000, but less than 50000.
Using these figures and a confidence interval calculator, it is possible to determine that the 99% confidence interval is approximately is between + 2.6% and - 4.64 to 4.68%. The larger of the two figures assumes 50 thousand climate scientists. Of course the confidence interval calculator assumes a normal distribution, which is not possible in this case because there cannot be more than 100% concensus. That is likely to mean the lower bound is understated by a small amount, but the 95% confidence interval almost certainly has a lower bound less than or equal to 4.7% based on these figures.
More troubling for Doran is the actual question, which is:
By asking if human activity is "a significant factor", it allows that other influences are as, or even more significant.
Taking significance to be "statistically significant", it asks whether global temperature increase since the "pre-1800s" would have been less than that observed by a statistically significant amount absent human influence. Given the statistical uncertainty in determining pre-1800s temperatures (see graph below) that requires greater than 50% of the warming be attributed to anthropogenic factors. I think this means the question must be understood colloquially, where "significant" does not imply "statistically significant".
Colloquially, something contributing 25% of the effect would be considered "a significant contributing factor". Arguably something contributing just 10% of the effect would also be considered "a significant contributing factor" but that is more dubious. Taking the 25% benchmark, we can compare Doran et al to Verheggen et al, in which just over 90% agree that 25% or more of the warming is due to anthropogenic factors. Allowing for the inclusion of approximately 5% known "skeptics" without regard of their scientific qualifications (and in most cases absent relevant scientific expertise), that result is qualitatively equivalent to Doran et al's.
The upshot is that unless we are making the weak claim that the consensus is that anthropogenic factors are a significant factor in recent warming, we should no longer be citing Doran et al, and hence the 97% figure, for the percentage of scientists who accept the concensus position. That is particularly the case given Bray and von Storch (2010) and Verheggen et al (2014), both of which post date Doran et al, have larger sample sizes and support a consensus figure in the high 80 percents. In particular, Verheggen et al, excluding those invited because of their known "skeptical" opinion and without regard to their scientific qualification, find a concensus figure of 87% (85-89%).
Tom Curtis - I would agree that little attention has been paid to the uncertainty ranges on consensus estimates. However, as you yourself have noted WRT Doran, with perhaps the smallest sample, the uncertainty is <5% - meaning that even at the extrema we are still looking at a >90% consensus on AGW in the literature, and in at least some surveys of the expert opinions. (As I understand it, B. Verheggen is of the opinion that the lower number in their survey was actually due to a much more detailed/specific question, rather than the mean range thought appropriate - that the respondents didn't think they could narrow it down to the specificity given)
And when you look at actual attribution studies in AR5, the fraction of warming due to AGW has a mean of 110%, with less than a 5% chance of anthropogenic causes being responsible for less than 50% of observed warming. That makes AGW not just a significant, but a dominant cause.
Quite frankly, the various arguments on consensus (and denial thereof by the pseudoskeptics) are equivalent to discussing the number of angels who can dance on a pin, given that by any measure the scientific consensus on AGW is as high as that on ozone depletion by CFCs, acid rain, or the dangers of smoking tobacco, in all of which we found the consensus sufficient to act.
We know enough to take appropriate action.
KR @709, Verheggen et al argue that the percentage of respondents excluding undetermined results (ie, "unknown", "I do not know" and "other") for both the qualitative and quantitative responses are equivalent. Specifically, 84 +/- 2% of respondents agreed that 50% or more of "global warming since the mid 20th century" can be attributed to "human induced increases in atmospheric greenhouse gas (GHG) concentrations"; while 86 +/- 2% agreed that greenhouse gases had a moderate or strong warming contribution to the "reported global warming of ~0.8 degrees C since pre-industrial times".
As an aside, the unequal time periods for the quantitative and qualitative questions substantially weaken that argument. However, I think it is a no brainer that "I do not know" and "other" responses should not be included. On the other hand, arguably "unknown" responses claim scientific ignorance (ie, it has not been determined adequately by scientists) rather than mere personal ignorance, and so should not be included. Against that, an "unknown" response may merely indicate the respondent thinks it is not yet determined whether the greenhouse gas contribution was 75-100 or 100-125% (quantitative question) or a moderate or strong warming contribution (qualitative question). Therefore while presumable some respondents answering "unknown" do not agree with the consensus, it is problematic including the "unknown" figures because doing so assumes that all who so answered disagreed with the consensus which is not at all certain.
More important are the figures with no "unconvinced", ie, those deliberately invited to participate because of their "skeptical opinion" rather than because they are just scientists. Excluding both "undetermined" responses and "unconvinced" invitees, 87 +/-2% agreed that 50% plus of recent warming has been due to anthropogenic greenhouse gases. That does not lie in the uncertainty range of Doran et al. As Verheggen et al. is much more recent then Doran et al, we must therefore either conclude that there has been an approximately 10% slide in agreement with the concensus among climate scientists; or that differences in the questions made a substantial (approximately 10%) difference in the response. The later is what I argue above, based on the difference between "a significant contributor" and "the major contributor".
I completely agree with your final two paragraphs, but do not think that reason to by imprecise or selective when quoting determination of the size of the concensus. That is, to the best of our current knowledge, ~87% of climate scientists (on attribution), and ~97% of climate science papers. IMO those figures show that the approximately 13% of climate scientists who do not agree with the IPCC on attribution do not do so based on publishable evidence. Put another way, it means that political opinion has influenced the scientific views of some climate scientists, but against the IPCC position, not for it (ie, in the opposite direction of the bias claimed by "skeptics").
Response to sjw40364 on the appropriate thread.
Okay so while a sceptic is mostly interested in checking (and if necessary refuting) new scientific claims, it is reasonable to discuss the "consensus" issue due to its importance to science as a whole.
Ironically, there is no consensus on the meanings of the terms used to define this consensus. Does it mean a majority? Or just an important and strongly agreed minority? Do voices with authority carry sway, or is it democratic. Does it need to be "overwhelming" and is it, in fact? Is it absolute or is there internal dissent? Which human beings count as scientists? Which institutions act as gatekeepers thereof and what is their motivation?
Rather than work trough all of these, I will simply ask the reader to consider whether it is healthy that you are being asked to accept the speakers' tacit definitions on these matters, as well as their unstated assumptions. You are being guided toward what is really more of a psychological sensation than any fact-based argument - the sensation of being part of something big and powerful. Maybe a sense of belonging and safety. Maybe moral superiority. Maybe the clarity that comes from being decisively led.
If the reader is ready to understand their own (and their peers') fralties in such areas, then I do not need to discuss the history of systems of control and subjudication. If not, there's no point getting in to it except to suggest you may wish to begin with the Milgram experiment.
Instead, I will take a single example, from the current article, of a flagrent manipulation of the meaning of "consensus" and surrounding terms: the 97% pie-chart.
You thought it said 97% of scientists, right? No. It's 97% of papers. That's right there in the jpeg image itself but you didn't notice it. What else didn't you notice?
If you read the underlying study, what 97% really agree with is somthing along the lines of "do you agree that (a) humans emit CO2 and (b) that the greenhouse effect is real". Your present author does, and so would be a part of the consensus!
The trick here is a toxic mix of pedantry and tactical naivety - as so often seen among precotious fifteen-year-olds, but in this case carefully hidden within a typically dull metholodgy section in a paper. It is *pedantically* true that human CO2 plus greenhouse effect implies *probably* *some* human generated warming. But has human generated warming been *shown* to occur? Not implied. Is it problematic? Not implied. Significant? Not implied. Even detectable? Not implied. Nor does the position in the question even imply that there won't be compensating factors or that warming would even be harmful anyway.
In summary, consensus taken in general is too subject to the frailties of the human condition for any wise person to pay any attention to it. Specific factoids, such as the 97% pie-chart (and there are others) may seem to lend concrete validity, but as soon as you check them you find nothing meaningful, only trickery.
Should we accept climate consensus because consensus exists around, say evolution? A real sceptic can answer this easily: the whole point of science is to investigate methodically the questions whose answers are *not* obvious on the surface. No scientist would ever be so intellectually lazy as to reason that since the climate consensus "sort-of looks like" the Darwinian consensus, that their underlying scientific validities should also match.
Climate consensus is much more like a rainbow. Amazing to look at; vast and magical. But how many times do you have to check for that pot of gold before you accept there's really *nothing there at all*!
A.R.S.Says @ #712 :
To be blunt: the word consensus has a very plain, straightforward meaning in the English language.
Your expressed "logic" is a complete failure, since you seem unable to connect words and concepts and realities.
(btw, I must commend your sense of humour in choice of your nom-de-plume ~ the abbreviation is priceless.)
[JH] Inflamatory & off-topic.
I'm looking for the data on climate change. I haven't been able to find it. I don't care how many agree, I want to know what evidence they base their opinion on. I was taught to question, not swallow. Please just post the data on climate, not the politics of popularity. Thank you.
[DB] Data and codes are openly available, and have been for years:
http://www.realclimate.org/index.php/data-sources/#Climate_data_raw
http://www.realclimate.org/index.php/data-sources/#Climate_data_processed
http://www.realclimate.org/index.php/data-sources/#GCM_code
http://oco.jpl.nasa.gov/science/dataproducts/
http://podaac.jpl.nasa.gov/
http://daac.gsfc.nasa.gov/
https://earthdata.nasa.gov/about/daacs
https://www.wmo.int/pages/themes/climate/climate_models.php
Note that the Muir Russell Commission was able to do a full global reconstruction from the raw data linked to from the above page, WITHOUT ANY CODE, in a mere 2 days (when asked, they replied "any competent researcher could have done the same).
The Auditors over at McIntyre's Climate Audit have been struggling with their "audit" reconstruction for many years now.
KiAnCa @ #714 : You have my sympathies, for your desire to gain good quality scientific information about the amount of global warming going, and how severely the problem is building. As you have doubtless already noticed, the mainstream media generally does a poor job in supplying realistic information ~ and it gives an inordinate amount of space to anti-science propagandists (with lawyer-type rhetoric designed to make you think black is white, or that there are so many "doubtful" shades inbetween, such that there is nothing meaningful in this whole universe).
You will find a vast amount of science-based info on this website . . . but you have my sympathy, because that info is not presented as a giant-size single meal where you simply chew your way through from one end of the pie to the other end.
Best (a) if you go to the Home page, central top region, and click on the small box titled "The Big Picture" . . . and then follow to areas that interest you,
or (b) on the Home page, click on the nearby box titled "Newcomers, start here" . . . and look down to the second heading, titled "Good starting point for newbies" where [second line of the paragraph] you can click on "Warming Indicators" and from that go to "Evidence for Global Warming (intermediate)" . . . where you can follow your interests. I must point out that this particular section generally holds info up to about 2010 ~ and so doesn't directly mention all the additional weight of scientific info in the last five years [i.e. all the newer "hot year" global records and even faster Ice Melt and sea-level rise]. No great matter, since the "sufficient evidence" was already overwhelmingly convincing, long before that date [indeed, in a recently publicised scandal, it appears that Exxon already had convincing evidence of the CO2/Warming problem by 1979],
or (c) if your scientific education is already above average, then you can simply skip to the "Arguments" [on Home page] and pursue any of the 170+ "arguments" [arranged by Climate Myth] which interest you, and delve further from there. The Myths are quite entertaining, because the info there does neatly deflate all the rubbish/nonsense talked by the small number of shills & mavericks who oppose the mainstream science (i.e. the mainstream science which results in virtually all the climate scientists being in accord with the consensus of 97% . . . or nowadays more likely 99% )
Good hunting ~ and please use the appropriate thread's Comments Section for any questions that you want clarified.
One of the human finger prints cited in the first week of the Denial course was that the atmospheric warming this century is unique in the fact of warming lower atmosphere and cooling upper atmosphere. What evidence from past warming episodes establises that this is unique to the current warming. How do we know what happened in the upper stmosphere in the past warming/ increased CO2 events?
[Rob P] - A cooling upper atmosphere and warming lower atmosphere is a signature unique to the enhanced (increased) Greenhouse Effect. If we had a Tardis, we would be able to go back in time to the Paleoecene-Eocene Thermal Maximum (PETM) about 55-56 million years ago, a time of substantial natural global warming, and observe the Greenhouse Effect growing stronger.
The enhanced Greenhouse Effect we are now measuring is a human fingerprint because the source of it is the continued emission of greenhouse gases, primarily carbon dioxide, produced by industrial activity. See the SkS post: Climate Change Cluedo.
Thanks for Responce @Rob P and for the link to Climate Cluedo. I get that carbon isotopes are critical in determining CO2 sources and ways of determining concentrations but my question speicifically was what is it about a cooling upper atmosphere in conjunction with a warming lower atmosphere that is unique. Another way to ask this might be, why is the upper atmosphere cooling with increased GHG levels while the lower atmosphere continues to rise at a sharp rate compared to background seasonal oscilations? And how do we know that in the past when the lower atmosphere warmed, so to did the upper atmospthere, or did it just stay the same. (I only found three hits on the Cluedo page when searching "upper atmos" and they were all in comments. no hits for "lower atmos")
What you should be looking for is "stratospheric cooling". It is not an easily understood concept, but there are several attempts around the internet to explain it. At basic level, It falls out of the equations for radiative transfer if you increase a greenhouse gas. Other forcings that change the surface temperature like changing albedo, solar influx, or aerosols do not produce this effect.
John writes: "Science achieves a consensus when scientists stop arguing"
Actually that's a bit simplistic. A scientifi consensus is formed after a series of scientists are able to reproduce the work of the scientist advancing a hypothesis. This is done by publishing confiming/denying results in refreed journals. Tom make that possible, the person advancing the hypothesis first fully explains it, then describes how it was tested (the "mehtodology"), the observed data and the results.
A scientific consensus isn't formed by simple agreement between scientists, it's evidence based and very much dependent on repeatable experiment. So while the consensus that CO2 is a "greenhouse" gas, meaning that like water vapor and methane it absorbs and radiates solar energy in known quanta, there is no consensus on the effect or "sensitivity" Earth's climate has to increases or decreases in it. Which is the problem.
We know CO2 absorbs IR. Water vaport (H20) observes much more, so much more that IR astronomers put their telescopes as high as possible, on Mauna Kea, Medium Altitude soborbital platforms like the KAO and SOPHIA, and in low Earth orbit in order to get above H20. IR astronomers aren't particularly worried about CO2 because its effect is so small it just doesn't matter.
[PS] Myths about water vapour are addressed under "water is the most powerful greenhouse gas". Make your arguments there. Offtopic comments will be deleted.
"Tom" doesn't make it possible. "To make"
"methodology" not "mehtodology"
"vapor" not "vaport"
"suborbital" not "soborbital"
I was proof reading my post here on the last page of comments when I encountered this gem:
"One of the human finger prints cited in the first week of the Denial course was that the atmospheric warming this century is unique in the fact of warming lower atmosphere and cooling upper atmosphere"
Not sure who came up with this but it's trully choice. So how many folks were measuring the temperature of Earth's stratosphere 200 years ago? 500 years ago? 2000? 20,000 years ago?
Whoever made up that fun fact should get a prize, it's a real whopper.
[PS] try reading for understanding rather than demostrating misunderstanding before banding about accusations. The surface temperature of any planet can be altered by changing solar input, albedo, GHG composition or aerosols. Increases in GHG composition is unique in that it is only forcing change that will warm the surface but cool stratosphere.
It would be very nice if this site allowed comments to be edited.
@Pfc. Parts
I gather from you're tone your here to troll not to learn, understand or convey science. But if you're interested in the source you can listen the full interview with Ben Santer (lead author of the historic 1995 IPCC) here:
https://www.youtube.com/watch?v=EOrUYQhGzT8
He states, no known natural mechanisms or combination of natural causes have that sustained effect, that human fingerprint, in this unquie way.
to Pfc.Parts @722 : you make a fair point, with your comment "It would be very nice if this site allowed comments to be edited."
On balance though, that would not be a good idea ~ and I am sure you can picture the chaos and non-sequiturs which would occur as posters go back and modify their posts, even with innocent intent (let alone the malicious intent). Nope: to be fair to all, a non-self-modified posting system is definitely far better.
Mind you, it could be reasonable to allow a poster to later insert a very obvious "corrigendum" paragraph at the end, to deal with clumsy bloopers / typos / or poorly-expressed phrasing . . . and this would help the flow of understanding in the commentary [rather than having such corrections appear later and quite possibly be half-buried by other intervening posts]. Such corrigendum would require clear demarcation and date/time label.
But . . . there would probably need to be a 24 or 48-hour cut-off for such "grafted-on" corrections. And even there, I am sure you can picture how some posters would try to play games and thoroughly abuse such a system. So, overall, it's simpler to keep this as they are : and it also makes for a simpler and less vulnerable control of the comments column.
[apologies for this off-topic excursion]
If you read the sentence stating 97% support, it's a self selecting subset of the data,
"of papers stating a position on human caused global warming"
of all the papaers in the Cook study, only 0.5% Explicitly support and quantify AWG as > 50%., (64 out of 11944)
of all papers stating a position, that number jumps to a whopping 1.5%. (64 out of 3974)
can someone explain to me how that equates to "consensus"