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
Richard Tol accidentally confirmed the 97% global warming consensus. An "own-goal" if there ever was one.
LINK 1
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realelybritt, you should have followed the link included in the paper you referred. All this is old news. Cook et al published a response to Tol 2014, here are the highlights:
T14′s consensus value is based on a math error that manufactures ~300 nonexistent rejection papers.
•T14 infers data drift using an inappropriate statistic that poorly correlates with consensus.
•Analysis of appropriate consensus statistics reveals no significant data drift.
•T14 wrongly conflates abstract ratings and author self-ratings; differences are detailed in C13.
•Re-analysis without T14′s errors confirms 97±1% consensus on AGW
Both sides of this argument seem to be exagerating their own subjective evidence and the weight of support for their views. This indicates a lack of real certainty. It seems also that many on both sides have a vested interest. In the majority of scientific experiments, before a conclusion can be drawn there needs to be a control. There is no 2nd planet Earth without man made co2 to make an accurate comparison of climate change. Therefore, even if the 97% consensus claim is true, it can hardly be considered credible.
[PS] Sloganeering. please provide evidence to support your assertion that science is exagerating subjective evidence. Your claim that science has some kind of vested interest is verging on a conspiracy theory. Vast areas of science do not work the way you suppose (eg geology) so it would be better to learn how the scientific method actually works. In essence, you predict the outcome of an observation from known physics, make the observation and compare to prediction. This is been done in countless ways to build modern climate theory.
Nothing is certain in science - but a scientific consensus, particularly when strong is the only rational basis for policy.
How many of those identified by Cook through his unscientific interpretaion have been approached to confirm their views on anthropogenic climate change? I suspect that would sink his dodgy statistics once and for all.
[JH] Inflammatory sloganeering striked through. Inflammatory tone and sloganeering are both prohibited by the SkS Comments Policy.
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Foundusually @779 : Quite evidently you have no understanding of the scientific consensus, and have not managed to read the award-winning Cook et al 2013 paper (where your question is answered).
Please educate yourself.
I have come across a climate denier who makes statements such as:
It is difficult to know what exactly is the scientific consensus on the predictions about the effects of climate change in the future.
I have read estimates that the global sea level is expected to rise anywhere from 6 inches to 6 feet by the year 2100.
What I am looking for is a consensus among climate scientists about the specific effects of climate change in the coming several decades.
I'm sure there is a souce here on Skeptical Science if someone could kindly point me to it.
Sea level rise estimates are largely based on the future emissions concentration pathways that we would need a crystal ball to foresee. Hence the estimates are dependant on those future decisions society makes. And those decisions matter a very great deal to future SLR by 2100.
Per the NCA4, Volume 1, Chapter 12, Table 12.1:
For reference, we are currently following RCP 6.0 pathways, so I would look at the Intermediate-High set of values.
@ 782 Daniel,
Thanks so very much that's a great resource!
The best part about using it on a denier is that you can tell him that the information was released by the Trump Administration...I never fail to remind them of that.
While I do believe there's sufficient consensus, I'd like to see the following considerations addressed. I'm pretty sure it's nothing new, but still it's not something widely discussed in popular science media, so any hints appreciated.
1. "Attractor" theory - since CO2 AGW is the predominant one, other alternative theories may not receive the attention and resources thay may potentially deserve, resulting in low number of papers, etc.
2. Peer influence - putting pseudoscience outliners aside, I find it plausible those wit mildly dissenting views will feel some pressure to conform to the level they wouldn't if the topic wasn't so controversial.
So again, I fully agree there's strong consensus and believe AGW is almost certainly real, methodologically when determining the level of consensus, the above two variables need to be controlled for. I'm just not sure if & how it was done.
Pl @785 ,
1. The original "attractor" theory (held up until the 1930's) was that the Earth's climate was self-correcting i.e. homeostatic within narrow limits. But that was disproven, as experimental & observational & paleo-climatic evidence mounted up. Satellite-based evidence has re-inforced that, too.
2. "Peer influence" is not a problem ~ because genuine scientists have a natural tendency to be contrarian & genuinely skeptical.
The consensus is pretty much unanimous for climatologists, because nowadays (unlike 50 or 100 years ago) the evidence for "CO2/AGW" is conclusive. There are no longer any "alternative theories" that hold any validity ~ the plausible alternative have been disproven (e.g. GW from variation in cosmic ray intensity; homeostatic cloud formation as an "Iris Effect"; long-cycle ocean current effects).
If you take time to learn more about the mechanisms influencing global climate, you will recognize that the (mere handful of) "dissenting" climatologists are offering only empty dissent . . . because they have nothing valid to back up their dissent. They are just running on automatic . . . such as the well-known retired Professor Lindzen, who has an Old Testament religious belief that the Earth has been designed to remain close to the Garden of Eden climate status. A few others suffer from extremist political beliefs, motivating them to cherry-pick / ignore the plain evidence.
Please note that the respected scientific journals welcome dissenting views provided that there is reasonable supportive evidence. (Journals and scientists gain prestige & fame by demonstrating valid contrarian evidence.)
But alas, every contrarian idea has failed the validity test, and there are extremely strong reasons why no "undiscovered" factor exists.
Eclectic @786,
My comment was mainly about the method of determining the level of consensus.
Point 1 ("attractor" theory) addressed my assumption, that the method includes statistics about numbers of articles - which can be strongly biased by such "attractor". If there was another attractor in rather distant past, it has little to do with this argument. However, I also assume that such bias may have been controlled for - I'm simply asking for brief explanation how.
Point 2 (peer influence) - I know in the ideal world, scientists have such characteristics as you claim, in real world they often follow direction or advice of their more senior peers, topics are to significant extent determined by projects / programs, etc. Again, I'm not saying this is a big issue, but it's most likely not totally negligible either. I'm interested in how such bias was / would be addressed when determining the level of consensus.
On a related note - a foot soldier of science may find it more productive to focus on particulars rather than spending time questioning consensual claims. I'm probably not the only one seeing a bit of positive feedback loop in there.
Regarding lack of valid alternative theories - I fully agree. There are softer claims than that though - "the field is young, it's not established science yet, the link to human activity is not conclusive yet" and similar. Only miniscule part of general public is able to determine that themselves, so I find preaching the importance of scientific consensus probably the most effective way. I.e. the arguments for it (specific consensus and it's level in climate science) better be airtight. Therefore my original comment.
Pl @787 ,
of course you are quite correct that there are institutional pressures towards conformity. As well as the genetically-inherited tendency of humans to "team up" in a tribal manner : just witness the current mindless tribalism in political matters ~ "full steam ahead and damn the facts!" ;-)
But your question suggests you are insufficiently aware of the drive towards contrarianism by scientists as individuals. The up-and-coming scientist seeks not money, but reputation / respect / fame / prestige. Yes, a Nobel Prize may well be awarded in 10 years' time or more . . . but scientific acclaim this year is a powerful inducement for publishing clever / innovative / iconoclastic work. And the competition is fierce !
Similarly, there is no shortage of respected journals that are ready & willing to publish novel dissenting papers (always provided the ideas have some reasonable evidentiary backing . . . and are not just fruitcake speculation.) A journal gains in prestige by being the first to publish groundbreaking work.
Between the scores of journals and the 10,000+ climate-related scientists, there is really nothing for you to fear that any worthy contrarian idea will be suppressed.
Yes, there are a few real scientists who speak against the mainstream climate science, but they have no actual evidence to back up their viewpoint ~ and if you look more closely at them, you find a sorry collection of crackpots / religious nutcases / political extremists / and a few aging "emeritus" types (even a rare Nobel Laureate) whose maverick-inclined personalities have become warped by the early changes of senility. [ I myself know a once-respected researcher, PhD equipped etc, who is a member in good standing of a local branch of the Flat Earth Society.]
But let's not get bogged down in Ad Homs ~ however apt & amusing. The basic problem is that the climate contrarians are still fighting last century's battles ~ and they have no facts to support themselves.
All they can muster is rhetoric & the unjustified "soft claims" you mention . . . in their attempt to sway the susceptible.
( btw, since the consensus of climate experts is extremely close to the 100% mark, I am wondering what you can mean by "the method of determining the level of consensus". What can you be thinking of ? )
Eclectic @786,
I think you made some of these points above already, you are somehow overstating my claims, I think my two points are more subtle in their supposed effect.
To be clear, I like playing devil's advocate more than preaching to the choir, so you can take that context into account when responding.
Re motivation of scientists - that's probably more complex, my guess would be that the primary driving factor is usually interest in the topic and natural curiosity, so not necessarily fame and pursuing contrarian views. But this is a bit off topic, so I'll leave it at that.
Let me focus on your last question - what do I think of when writing "the method of determineng the level of consensus":
I've skimmed through one of the papers linked above, you can see they are discussing such methods in length. They don't seem to address the two points I made above (attractor theory and peer influence), unless I missed it in the text.
Stamping a specific number with % sign to a consensus is non-trivial task. For example, processing abstracts using some simplistic method may potentially skew the result a lot, so I would personally prefer surveying scientists, allowing non-binary response, weighting the data by their level of expertise in the field and ability to critically think... - which would be very difficult, if not impossible to pull off.
Therefore my question(s) in first comment I made. The paper I linked to don't seem to address that and I'm lazy to study all consensus survey papers on my own, so I was hoping someone who knows the answers may chime in.
Pl @789 ,
I would certainly not wish to overstate your claims.
At the same time, it would be best if you clarified your claims far more precisely than you have in post #789 and prior. Otherwise, we are mutually tackling a Hydra-headed creature called a consensus, and doing so in an uncoordinated manner.
From my position as somewhat of a "naive realist", the primary meaning of (climate) consensus is in the basic sense of : the scientific consensus of our modern knowledge of climate physics. In other words, the current understanding of the science (of climate). In essence, the science is found in the (summation of) scientific papers published in reputable peer-reviewed scientific journals. Twas ever thus !
That is why a number of studies (including the very clever Cook et al., 2013 with its notorious 97% ) have looked at what is found in the many thousands of published papers. BTW, the Cook study was outstandingly excellent, because it cross-checked its findings by asking the actual authors what they considered their own papers showed. And yet it is important to remember that the Cook paper of 2013 was centered on a median paper "age" of approximately 2005 date ~ and the "consensus" has moved on by a considerable amount in the 12+ years since then.
Some other studies were even older than that.
However, it is even more important to remember that the scientific consensus (on climate matters) is the science itself ~ and that it is not a vote or a percentage or an opinion poll. (As you yourself have implied, we can easily end up in a futile tangle of shades of definition, if we are merely assessing "opinions" by scientists of all stripes.)
A survey of opinions is only a proxy of the scientific consensus. Taking a vox pop of scientists shows (as we would expect!) that "the level of consensus correlates with expertise in climate science" [Cook et al., 2013]. Obviously here, Cook is using consensus in its loose meaning of "opinion". It is understandable that the non-scientists & politicians of this world would have a desire to deal with a brief proxy of the complex science of climate ~ and a "percentage consensus" is a handy first approximation. But it is only a proxy, and we should never mistake it for the underlying science.
As your linked 2016 reference (to the IPCC) states: "human influence has been the dominant cause of the observed warming since the mid-20th century." That is a fair summation, though expressed in an overly-conservative manner. And - as you yourself say - "stamping a specific number with % sign to a consensus is [a] non-trivial task". To which I would add: it is both non-trivial and essentially irrelevant.
I'm going to be blunt here, and I hope that this doesn't cross any moderation lines. The voices that most loudly and most often deny climate science seem (in my very personal opinion!) to fall into four categories, often several at once.
Lobbyists, loons, ideologues, and opportunists.
Such people show up repeatedly in the few surveyed papers objecting to climate science consensus, often cross-referencing other deniers or just themselves.
Lobbyists are self-evident; often residing in 'think tanks' that receive business funding. Loons hold obviously counter-factual positions, ignoring the majority of data in deference to their pet theories. Ideologues include for example libertarians, Randian capitalists, and others who object to climate science because they view any response to climate change as increasing the role of governments - not an objection to the science, but rather to the correction methods implied. That also includes teleological religious types who feel that the world was made for us to use, or who think a Rapture is imminent and why bother with the ecology. Opportunists are simply folks who find it more personally profitable/rewarding to object to climate science, rather than pursue more mainstream (and factually based) approaches - the average scientist doesn't get invited to travel around the world, or provide frequent Congressional testimony.
There's just no hard science making sustainable objections to the consensus climate views. None that I've seen, at least, and I've been looking. I won't name names WRT the preceding classifications, but I think that most people following the 'debate' can find a few loud climate deniers who fall into one or more of those categories.
I would gladly read anything with a scientific basis that supportably points out issues with the climate consensus - it's not a joyful outlook, sad to say. But I just haven't seen anything that holds up to examination.
Quite agree, KR @791 . . . and longish post follows.
There are probably rather more than four categories of denialist . . . but the madness/badness of the human psyche is so commonplace, that it would be tiresome for you (or anyone) to allocate further mental effort to refine categories beyond your four !
As you say, KR, science-deniers (and here I include some well-educated scientists who nevertheless deny climate science directly or indirectly) have a tendency to occupy more than one category.
Perhaps they start off in a single category, and then some amplification or or positive feedback process causes them to swell and overflow into neighbouring categories? Do you know of any psychological study which quantifies the TCLS (Transient Climate Lunacy Sensitivity = number of years until Climate Lunacy has doubled in an individual denialist) . . . or quantifies the ECLS (Equilibrium Climate Lunacy Sensitivity) ?? Though I suspect that the ECLS is a difficult matter to quantify, because ECL is only reached at the moment of death.
If I am permitted to name names which fit primarily into your fourth category, it would be easy to pick Richard L and Judith C ~ being scientists who in earlier decades have made some contribution to climate science, but whose contribution history has been more ordinary than illustrious. Yet they are only human, and doubtless enjoy the perks & celebrity status awarded by the general denialist community (who have a desperately thin field of champions to choose from).
Now a "Fourther" who has puzzled me is Dr Koonin ~ does he justify a fifth category, or is it merely a case of "opportunism"? Perhaps he suffers from LDS (Limelight Deprivation Syndrome) as he moves out of public life . . . but then again, LDS would also explain some of the motivation of emeritus professors & other retirees who occupy category 4.
Returning more closely on topic : we have the multi-category award winner Mr Monckton. Lord M has been lauded by (Mr Watts and his cronies at) WUWT website, for his innumerate [in both meanings!] and strenuous denunciations of the consensus demonstrated by Cook et al., 2013.
Now, at various times I have touted the excellent Youtube video series produced by science journalist Potholer54 on climate matters & climate myth debunking. In particular, Potholer has an amusing 5-part video exposure of the mendacity of Lord M. (Look for "Monckton Bunkum".) And I gather that Potholer also posted on WUWT, to show the utter falsity of Lord M's positions & calculations (especially regarding Consensus figures) . . . and before very long, Mr Watt banned & expunged Potholer from the website. I did not witness these events ~ but I know that Potholer makes a point of always being civil or showing icy politeness. So it seems Mr Watts was infuriated by the relentless logic provide by Potholer . . . and Lord M's denunciations of Consensus are still extant on WUWT (or were so, last time I looked).
Eclectic @790,
"Consensus" can mean either the proposition itself, or the fact that there's an agreement. For me, the former is rather clear ("AGW is a thing"), the quantification of the latter is what I'm commenting.
The paper I was linking to is also "Cook et al", but from 2016, so perhaps an updated and upgraded version.
Where our views may differ is your last sentence, where you consider measure of consensus "essentially irrelevant". I may agree that it is not absolutely essential in case of AGW, where it's rather obvious that a widespread consensus exists. I still think it is relevant, especially as questioning the consensus is one of the lines of attack from deniers.
Generally speaking, measuring consensus as a concept of skeptical thinking is also very relevant, but I think it's pretty obvious.
So circling back to my original comment, I still don't see couple of variables influencing the measure (I have given two examples) being addressed.
In addition to the two examples, there'd be more. I already alluded to natural non-binary nature of scientific claims. Skimming through the Cook 2016 article, I also didn't find it explicitly addressed. We would probably agree that it's something completely different to claim "90+% of scientists agree, that the probability of AGW is above x" when the x is 50% compared to say x=99%.
Pl @793 ,
< "Consensus" can mean either the proposition itself, or the fact that there's an agreement. For me, the former is rather clear ("AGW is a thing"), the quantification of the latter is what I'm commenting. > unquote .
"Consensus" is potentially a very large Venn Circle indeed, and we would do well to define it more closely and pragmatically. (Semantic confusion can easily be a Black Hole that swallows up any effectual discussion.)
"AGW is a thing" is far from correct. AGW is much more than "a thing" in the colloquial sense ~ AGW is a physical reality. Likewise, choosing to label the Consensus as a proposition, is a choice of even more nebulous terminology.
As I mentioned in an earlier post, for climate purposes Consensus is essentially a term for the established science. (There have been rare occasions when the established non-climate science has been overthrown or enormously modified - think Newtonian/Einsteinian physics of motion - but the established climate science is the product of a century of work by countless thousands of modern scientists, not the work of a single English genius in the 17th Century . . . and the chance of the mainstream climate science being seriously overthrown by startling new insights, is such a vanishingly small chance, as to be ridiculously fanciful.
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In looser terminology, "Consensus" is often used in climate matters as a type of numerical proxy for the scientific position. It is this latter meaning which gives rise to public confusion/uncertainty about the actual underlying science (a confusion magnified by numerous propagandists who injected much deliberate obfuscation).
The purpose of the Cook et al., 2013 study was to achieve an improvement over earlier studies/surveys : to achieve a more definitive figure for the numerical consensus, and to greatly reduce the scope for any [as you yourself quote:] "lines of attack from deniers". The Cook study was very clever - and award-winning - and produced the very widely cited 97% figure, which has become notorious (and which has become infuriating & nauseating, to all the science-deniers).
As might be expected, the denialists' fury has resulted in massive eruptions of Motivated Reasoning. The gigantic brain of Lord Monckton (and cronies) has produced very "creative accounting" which has variously redefined the Cook 97% figure down to 33% or 13% or 4% or similar absurd figures. Yet that's hardly surprising, coming from intellects which are in full denial about the physical properties of CO2.
As I mentioned earlier, the 2013 Cook study is now quite dated ~ centered on approximately 2005. More modern studies [e.g. 2014] show a consensus well above 99%. And more importantly, the "contrarians" have still produced nothing valid in the way of support for their skepticism. Nothing at all.
Pl , the 2016 link you gave earlier (to Cook and other consensus investigators) is merely a meta-analysis.
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"Circling back" to your original comments ~ Pl , I had hoped I had already answered your "two examples" ; answered them directly as well as en passant. If that is not so (in your own mind), then perhaps I have not expressed myself clearly enough. Or perhaps you are doubling-down on your "Devil's Advocacy". Either way, you will need to state your objections in a far more precise & thorough manner.
At the same time, you might care to expand on the "non-binary nature" you mentioned ~ although once you have eliminated the obscurity, it might well be that we find it rather off-topic for this thread.
"A couple of variables." Who cares? Splitting hair about the consensus is likely the least useful way one could spend time on climate change (except for reading WUWT perhaps). Anyone with a functioning brain and some critical thinking skills looking at the science will quickly see where the weight of the evidence resides. There are now some much more pressing imperatives than quantifying and/or qualifying the consensus. The lack of scientific consensus is just another defunct lie from deniers. The rest is details, of truly little interest.
Eclectic @794,
first, you must excuse some inaccuracy in my text, English is not my strongest skill. By "AGW is a thing" as a simplified statement of the consensus proposition I simply mean "GW is happening and human influence on it is significant" - or similar statement where I don't expect any disagreement.
You did not address my original points though - you expressed your view and opinions - which BTW I don't have many reasons to disagree with - but what I was looking for was to see, how these variables (and maybe I added another one in later comments) were controlled for in studies establishing the level of consensus - I haven't seen that in the study I linked to, nor in the comments.
Also, I wouldn't call it "objections" - I'm simply interested in some details of the "consensus measurement" methodology.
Regarding the "non-binary nature", it's rather trivial, see final paragraph of @793. No true scientist can claim something with absolute 100% confidence, despite human brains have tendency to use such heuristic. It's not an off-topic here, because - let me quote myself: We would probably agree that it's something completely different to claim "90+% of scientists agree, that the probability of AGW is above x" when the x is 50% compared to say x=99%.
Philippe Chantreau @795,
assuming you are commenting my "nitpicking" here. I believe I already stated I don't consider these considerations critical to the actual topic of AGW and I don't claim it has high priority on any related to-do list. However, I also consider the question how a consensus in measured and how the resulting "numerical level" is adjusted for apparent systemic biases to be relevant - both in general (as some kind of methodological best practice, regardless of the field) and also in the field of climate science, if not for anything else, at least to prevent possible attacks from deniers. I'm afraid people waste time on many less useful things than that.
Philippe Chantreau is quite correct that the question of the Consensus has become trivial and largely irrelevant. The science (of AGW) is settled enough for practical purposes [the practical purposes being the political policies for dealing with the climate situation]. And the "numerical consensus" is well over 99% and climbing ever closer to 100%.
Nevertheless, this thread here stays open for those who wish to split hairs about what are nowadays irrelevant trivialities. ;-)
Pl , you are correct in stating that AGW is "a thing" in the sense of a reality. But the "A Thing" phrase is so widely applied to all sorts of abstract concepts & ephemeral fashions, that it becomes quite ambiguous and unhelpful in our discussion here.
The surveys assessing the state of the (climate) science show that the (scientific) consensus, as measured by the published scientific papers in recent years, is in effect 100%. Over the years, there's been a tiny (and reducing) number of "contrarian" papers ~ and these papers have been mutually contradictory in their expressed concepts, and have utterly failed to present any valid evidence to support themselves.
In the far looser terminology of the Consensus in the form of an opinion poll of scientists . . . surely the only worthwhile poll can be made of scientists who are well-informed on climate science and who have definite expertise in this field.
Even rather old studies [such as the Cook 2013 study] show that the greater the climate expertise of the scientists, the closer to 100% is their "consensus of opinion".
And surely the whole concept of numerical consensus loses any useful meaning if the assessments include more and more of the ill-informed and the deliberately ignorant. Surely there can be no real value in a consensus that includes the opinions of blowpipe-toting hunters in the upper Orinoco River or iPhone-toting hipsters in the upper Missouri River.
Pl , the "non-binary" question you mention, is one that has been much discussed in years past. This, and your "original points", are all examples of imprecision of expression; and I must yet again beg you to clarify what you are driving at.
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The truth is not found thru a vote, just ask Ptolemy ;-)
As been stated many time here, the point of consensus studies is to counter myth that consensus doesnt exist.
The Scientific consensus might be wrong but it is the only basis for rational policy especially when it is strong.