The US House of Representatives Congressional Committee on Science, Space, and Technology held a hearing on the IPCC process last Thursday. The Republicans on the committee invited three witnesses to speak (Richard Tol, Daniel Botkin, and Roger Pielke Sr.), while the Democrats were allowed one witness (Michael Oppenheimer). The focus during the hearing shifted several times to the 97% expert consensus on human caused global warming; committee chairman Lamar Smith (R-TX) even included some inaccurate statements denying the consensus in his opening remarks.

The witnesses generally focused on the subject at hand – the IPCC process – during their prepared testimonies, but Rep. Rohrabacher (R-CA) asked them in the question and answer session about the 97% expert consensus that humans are the main cause of global warming.

Richard Tol answered first, but his answer probably didn't satisfy Rohrabacher. Tol admitted,

"I mean it's pretty clear that most of the science agrees that climate change is real and most likely human-made"

Tol has also previously acknowledged,



"The consensus is of course in the high nineties"

However, while he admits it's real, Tol quibbles whether the consensus is precisely 97%. Ever since my colleagues and I published our consensus study a year ago, Tol has seemed determined to find fault with it. He submitted a critique to the journal that published our paper, Environmental Research Letters. However, the journal rejected Tol's comment twice, finding it unsuitable for publication. The peer-review referee comments are available on Tol's blog, saying for example,

"Rather than contribute to the discussion, the paper instead seems oriented at casting doubt on the Cook paper, which is not appropriate to a peer-reviewed venue, and has a number of important flaws ... Many of the claims in the abstract and conclusion are not supported by the author’s analyses."

These comments are consistent with Tol's own admission that he took a "destructive" approach toward our paper rather than try and replicate our results. We even went as far as to create a public webpage where anybody can review and rate the same abstracts as we did to make replication as easy as possible.

In fact, the Environmental Research Letters reviews included 24 critiques and suggestions regarding how Tol could improve his paper. Tol reports that after two additional rejections, he finally found a journal to publish his paper. It will be interesting to see if he addressed the 24 Environmental Research Letters reviewer critiques, or if he simply shopped a flawed paper around until finding a publisher willing to overlook its shortcomings.

Nevertheless, Tol accepts that the expert consensus on human-caused global warming is real. It was thus a bit of an own-goal for the Republican committee members to invite him and inquire about the consensus, given that they seem determined to deny that it exists.



Based on their post-hearing press release, the Republicans on the committee seem satisfied believing that our study "has been debunked," and Tol made several unfounded claims disparaging our study during the question and answer session. He did however make one accurate statement,

"The 97% estimate is bandied about by basically everybody."

Due to the fact that the general public is largely unaware of the expert consensus on human-caused global warming, and people are more likely to accept the science and support action to address the problem if they're aware of the consensus, it's a very important fact. Our study is the most comprehensive quantification of this expert consensus to date, so not surprisingly it's been "bandied about" widely:



Retweet if you agree it's time to #ActOnClimate. pic.twitter.com/xZxi6KdInY — Barack Obama (@BarackObama) July 11, 2013

In reality, 97% of scientists agree that we face serious human generated climate change http://t.co/soQCnJB61B — Elon Musk (@elonmusk) May 25, 2013

It remains to be seen whether Tol can substantiate his accusations about our research. The expert referees who reviewed previous versions of his paper found that he had failed to do so.



In any case, whether the number is 97% or 96% or 98%, Tol acknowledges that the overwhelming scientific consensus is a reality, probably to the chagrin of the Republican committee members who invited him to testify. Now we just need those policymakers to accept the reality of human-caused global warming and join the debate regarding what we should do about it.