The Consensus on Climate Change

Sadly, a large percentage of Americans are under the impression that climate scientists do not agree on the reality of anthropogenic global warming (AGW). A lot of people are simply wrong about this. They think that there is a great deal of controversy among the scientists who study the Earth's climate. But there isn't. One way we know this is from a study done by John Cook, Dana Nuccitelli, Sarah A Green, Mark Richardson, Bärbel Winkler, Rob Painting, Robert Way, Peter Jacobs, and Andrew Skuce, called "Quantifying the consensus on anthropogenic global warming in the scientific literature"

In that study, the authors analyzed "the evolution of the scientific consensus on anthropogenic global warming (AGW) in the peer-reviewed scientific literature, examining 11,944 climate abstracts from 1991–2011 matching the topics 'global climate change' or 'global warming'." They learned that "66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming." Among the papers that expressed a scientific position on the topic, "97.1% endorsed the consensus position that humans are causing global warming."

The study was actually a bit conservative, as in order to be counted as part of that ~3% not supporting the consensus position on AGW a paper did not really have to be fully against the idea. Also, since the study was done, the consensus has increased. I asked study author Dana Nuccitelli about more recent changes in consensus, and he told me, "The consensus is growing over time, and reached 98% in 2011 (the last year included in our survey). So by now the minimizers/deniers are probably in the 1-2% range in the peer-reviewed literature (contrary to the 'crumbling consensus' claims)."

The other day I was giving talks at a local high school, and between classes, found myself chatting with a science teacher who had just completed a module on climate change and AGW. She asked me, "Isn't there now research that shows that the consensus isn't really as high as previously thought? Or is that bogus? Sounds bogus to me."

Yes. Bogus.

I'm not sure what research the teacher was referring to (it was just something she had heard about) but there is a paper just published in "Energy Policy" by economist Richard Tol, who as far as I can tell has been a naysayer of climate science for some time now. Tol's abstract says:

A claim has been that 97% of the scientific literature endorses anthropogenic climate change... This claim, frequently repeated in debates about climate policy, does not stand. A trend in composition is mistaken for a trend in endorsement. Reported results are inconsistent and biased. The sample is not representative and contains many irrelevant papers. Overall, data quality is low. Cook's validation test shows that the data are invalid. Data disclosure is incomplete so that key results cannot be reproduced or tested.

Nuccitelli has responded to Tol's paper, in a post at Skeptical Science called "Richard Tol accidentally confirms the 97% global warming consensus."

Concern Tol-ing

Tol is practicing a special kind of science denialism here, sometimes called "seeding doubt" or as I prefer it, "casting seeds of doubt on infertile ground." In other contexts this is called "concern trolling" or the "You're not helping" gambit. The first of two paragraphs of the Conclusion section of Tol's paper reads (emphasis added),

The conclusions of Cook et al. are thus unfounded. There is no doubt in my mind that the literature on climate change overwhelmingly supports the hypothesis that climate change is caused by humans. I have very little reason to doubt that the consensus is indeed correct. Cook et al., however, failed to demonstrate this. Instead, they gave further cause to those who believe that climate researchers are secretive (as data were held back) and incompetent (as the analysis is flawed).

Let's get straight that Cook et al is not flawed, despite Tol's complaints.

Tol's main complaint is in the coding of the abstracts. He claims that it is imperfect. Well, duh. This is, essentially, social science research, and coding of text is imperfect. Tol makes the claim that the imperfections, if corrected, might bring the consensus down to a dismal 91%. I'm pretty sure he's wrong about that, but if he is right, we are not impressed.

Tol's key point is that the papers that are coded as not making a claim include some that do. He then incorrectly calculates how many of of those, if coded "correctly" there would be, and using this, downgrades the consensus to 91%

Nuccitelli explains in detail, in his post, how Tol's re-analysis is badly done (see the amazing graphic at the top of this post) (go read it) and notes:

In reality, as our response to Tol's critique (accepted by Energy Policy but not yet published) shows, there simply aren't very many peer-reviewed papers that minimize or reject human-caused global warming. Most of the papers that were reconciled 'towards stronger rejection' went from explicit to implicit endorsement, or from implicit endorsement to no position. For abstracts initially rated as 'no position,' 98% of the changes were to endorsement categories; only 2% were changed to rejections.

Nuccitelli also notes that a separate study indicates that Tol's method is flawed in the sense that no matter what data are used, the consensus will be decreased as an artifact of the methodology. Nuccitelli notes " making this mistake, Tol effectively conjured approximately 300 papers rejecting or minimizing human-caused global warming out of thin air, with no evidence that those papers exist in reality. As a result, his consensus estimate falls apart under cursory examination."

Amazingly, when the Consensus research team fixed Tol's methodology but applied the same question about coding papers in the no-position category, and re-calculated the percent consensus, it went up by 0.1%. Also, as Nuccitelli points out the Cook et al paper is not alone, and there have been a number of other studies that show essentially the same level of consensus among papers and/or scientists.

So, the consensus is real and isn't going away. As is also the case with Anthropogenic Global Warming.

More like this

An important study has just been published1 examining the level of consensus among scientists about climate change. The issue at hand is this: What is the level of agreement in the scientific community about the reality of climate change and about the human role in climate change? The new paper,…
Given recent attention to the issue of consensus in climate change research, this is a good time to mention a paper that came out recently by John Abraham, John Cook, John Fasullo, Peter Jacobs, Scott Mandia and Dana Nuccitelli called "Review of the consensus and asymmetric quality of research on…
Well, I got this (some days ago; I got backlogged): As one of the more highly trafficked climate blogs on the web, I’m seeking your assistance in conducting a crowd-sourced online survey of peer-reviewed climate research. I have compiled a database of around 12,000 papers listed in the 'Web Of…
A new paper examines what is behind the ~2% of climate change related peer reviewed research that run contrary to widely accepted scientific consensus on climate change to see why those papers are wrong. There is a scientific consensus that increasing greenhouse gas concentration in the atmosphere…

Contrast this very appropriate standard for open science with that of GMO's controlled by patent law & licensing restrictions. The criterion for "a serious misdemeanour" is when a finding "helps to spread fear among the public that is not based on any firm conclusion".

If this standard were applied to the climate, 97% could be guilty of a serious misdemeanor.

By Buck Field (not verified) on 04 Jun 2014 #permalink

A detailed statistical critique of Tol's reasoning has been written and linked in a comment posted at Rabett Run:…

"Tol’s analysis appears to be flawed. The work fails both simple common-sense sanity checks, and basic testing to ensure that the method can reproduce the known results of the reconciliation step. The reduction in consensus percentage is primarily an artifact of the method, rather than arising from the shifts in the reconciliation step. The behavior of the method does not reflect Tol’s description of that behavior. The correction algorithm gives an initial impression of being correct, but on further analysis appears to be statistically meaningless."

By L Hamilton (not verified) on 04 Jun 2014 #permalink

Thanks, I was going to post that but I had to finish up this post and run to a meeting.

The growing consensus has also been confirmed by Powell.
In his original study of 13,950 peer-reviewed climate papers from 1991 to 2012, he found 24 that rejected human-caused global warming. In a more recent study of 2,259 papers from November 2012 to December 2013, he found only 1.…- only-1-9136-study-authors-rejects-global-warming

I can't make head or tail of Tol. He doesn't seem to be an ACC denier, but rather one who tends to underestimate the consequences, and he does appear to be extremely self-centered and easily slighted. If I remember correctly, his original opposition to the Cook paper was based on the exclusion of some of his own papers, because they were not judged to be climate papers.

By cosmicomics (not verified) on 04 Jun 2014 #permalink

"Ask the American Meteorological Society, the American Chemical Society, the National Academy of Sciences, the American Geophysical Union, and many, many others. Climate change is a reality."

By ray del colle (not verified) on 05 Jun 2014 #permalink

Tol has a comment in The Guardian. After using much energy to delegitimize the Cook consensus paper, he concludes by saying that consensus in science is irrelevant. In doing so he approaches the heads I win tails you lose logic of outright climate septics:
1. There is no consensus.
2. Consensus doesn't matter.…

Sou has written a sharp response:…

By cosmicomics (not verified) on 06 Jun 2014 #permalink

"66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming.” Among the papers that expressed a scientific position on the topic, “97.1% endorsed the consensus position that humans are causing global warming"....97% of 32.6% of papers that say yes. Wow talk about false data!! 66% had no opinion! So 1/3 of scientist say it is human caused. We live on a crusted fire ball and the climate will always change. Please, let's also find out what our beloved governments have done to damage our atmosphere with rockets and weapons and their testing. Instead of taking away from real quality of human life as far as transportation and electricity production. Fear mongers!!!

No, it is simply incorrect, and rather bone-headed, to say that 66 percent had no opinion. 66% did not address the issue BECAUSE THEY WERE ABOUT SOMETHING ELSE.

Yes, this is a little hard to understand for some so let me explain it another way. Say I wanted to see how many computer programmers used Python. I want to use blog posts by computer programmers to see if they use Python or not. So, I look at EVERY SINGLE BLOG POST EVER WRITTEN BY ANYONE EVER and see how many of them say "I am a computer programmer and I use Python" or otherwise indicate that they use python.

What I'll find is that 99.99999 percent of the blog posts say nothing about Python and are not even by computer programmers. SO I look at the 0.00001 percent that say something about this. Among those, I find that about 99% are by people indicating that they are computer programmers, but they don't happen to say what language they use. Of the remaining 0.0000001 percent it turns out that half of them use Python.

Therefore, according to your logic, 0.00000001 (or whatever, I've lost track of the zeros) of computer programmers use Python.

But no. I would not do such an idiotic survey. I'd narrow it down first to look only at blogs about computer programmers. Then I'd start counting.

THE CONSENSUS STUDY LOOKE AT ONLY PEER REVIEWED PAPERS THAT HAD SOME THING OR ANOTHER TO DO WITH CLIMATE CHANGE. Then, they look at those papers to see which ones could possibly have had any information about the acceptance/rejection of AGW. THEN they looked at that ... the relevant papers ... to see what their findings on the matter were.

I know this is really hard because it has numbers and stuff, and logic, and it is a tiny bit complicated. But really, most people can understand if they try just a little.

Also, you are confusing the idea of a study of PEER REVIEWED PAPERS which are a thing and Scientists, which is a different thing. Please try to keep that straight as well.


Thanks for setting me straight! (as I wipe the drool from my chin and drag my knuckles back to my cave). I believe there is some bias in that study. I also believe this planet is in constant climate change and wonder if 200 years of study of a planet this old can really make a firm analysis. Just keeping an open mind due to the fact my fresh water state has a lot of limestone....hmmm. and as far as this study, yep I guess that's what it finds. 97% of what was wanted to be found.

What is the bias you have identified and how did you identify it? Or is it just something you think must be true?

Mr. Laden, first off, I just found your blog yesterday and had a knee jerk reaction. Secondly, I just read some of your fishing posts and I find a kindred spirit. Thirdly, let say I am no way an expert or in the science field. Now with all this said I grew up in real Detroit, not some suburb, during the 70's and 80's I have a certain amount of street smarts and common sense. Let me say that I call John Cook into question and the method of proving a theory based on the amount of peer reviewed papers. As in your first response, the papers were 3894 out of 11944.The 11944 were authored by 29,083. These were found by using the search term ‘global climate change’ or ‘global warming’. I have not researched all of these or the 60% that held no opinion. It seems to me they are relative to climate change and global warming. This is 20 years of papers of which 3894 of 29083 were specific to the subject matter they wanted to find. 3796 confirmed what they wanted to find that it is human caused. Lets now talk about the integrity of peer review. Is it fair? Do scientific publishers and their referees prejudice against the non common belief, AGW is real. They are papers, not necessarily proven fact. Did you know eggs are now good for you, the whole egg. Science said something different but now it has changed. I wonder how many peer reviewed papers were written on egg white benefits. John cook also has another paper he co authored with Stephan Lewandowsky on debunking and psychology. This document "Debunking Handbook" essentially instructs one on how to steer the public to your thinking without causing a backfire with the message you are fighting. Seems fishy to me, almost religious. everyone is spouting 97% of climate scientist agree. When you fairly point out we are talking papers not people. This statement is a falsehood and not a survey of people as our leaders want us to believe. I have doubts of the causes and do wonder what rockets and their fuel blasting through our ozone is doing in the name of science. We have scrubbing technology for coal plants and the like and don't get me started on third world pollution. Kids in china mining gold from our "recycled" electronics. Finally, of interest to you is the recent find under lake Huron ( Prehistoric caribou hunting structure discovered beneath Lake Huron. 120 feet below the surface with a land bridge. The climate does indeed change. Are we the evil doers? Maybe, but a consensus?? What about our sun? it's activity or lack of not have some bearing. Just questioning the "facts". Thanks-Dave

1) you failed to show any kind of bias at all with that long post.
2) you make allegations about the peer review process and then proceed to back them up with absolutely no kind of data at all. Just random statements.
3) showing a hunting structure underwater in the great lakes is not somehow a debunking of AGW.
4) you suggest it might be the sun while showing you haven't read any of the vast body of scientific evidence showing we are getting less energy from the sun.

Thanks for coming out.

Dr Roy Clark of Ventura Photonics does a very scientific job of showing how the greenhouse effect influences surface temperature and goes on to point out his thoughts on climate models. Dr Joseph O Fletcher at 80 years of age gave a lecture in 2000 sharing his 50 years of experience from pole to pole and his 1963 to 1993 years at NOAA. It sheds a lot of light on heating from the sun versus greenhouse gases all based on real earth data. He really does relate climate change to real measurements and climate history. By the way he predicted the slow down in warming and expects a drop after 2020.

By Larry wilhelmsen (not verified) on 26 Sep 2016 #permalink

All Milankovitch Cycle and no GHG Emissions makes Roy Clark a bad scientist.

(Nice try at cherry-picking an "authority" and claiming he speaks for all of science. As if...)

By Brainstorms (not verified) on 26 Sep 2016 #permalink

Brainstorms: "All Milankovitch Cycle and no GHG Emissions makes Roy Clark a bad scientist."

But is he still a great banjo player?

By Desertphile (not verified) on 27 Sep 2016 #permalink

"By the way he predicted the slow down in warming and expects a drop after 2020."

Clark predicted the global average temperature would continue to do what every scientist in the related science venues has been observing it doing for 130+ years? Gosh, that's amazing! Why, no other scientists predicted that!

By Desertphile (not verified) on 27 Sep 2016 #permalink