How much do the presidential candidates know about climate change?

Climate change will be a hot topic during the 2016 presidential election campaign. The candidates have already started  talking about climate science in debates, press conferences, and interviews. An overwhelming majority of Americans (87%) say it is important that candidates for President and Congress have a basic understanding of the science informing public policy issues.

Associated Press reporter Seth Borenstein contacted scientists to fact-check presidential candidates’ statements on climate change.

We asked Climate Feedback contributors to carry out Borenstein’s exercise by:

  • checking the facts in the candidates’ public statements (not their opinions or ideology)
  • giving each candidate a score on a scale of 0–100 for “accuracy and understanding of climate change”

Each candidate was assigned a randomly generated number, and scientists were instructed not to determine the identity of the quoted candidate before completing the exercise. Their annotated speeches can be found here. The list of candidates and the list of statements was compiled by Seth Borenstein. We added a few quotes to the original selection so that the scientists would have more factual claims to check. In this analysis, we explore how robust such an evaluation could be. We intend to repeat and broaden this approach in the future to keep track of the accuracy and understanding of presidential candidates on climate change.


Note: This is not an endorsement of the candidates’ policies. We are simply checking their understanding of climate change and the accuracy of these specific statements.


Here’s what we found:

Some candidates clearly lack an understanding of climate science.

The scientists agreed that five candidates’ understanding of climate change is seriously lacking. All scientists gave these candidates a below-average rating, a strong indication that people should be very careful when these candidates make public statements on climate change.



Dr. Rasmus Benestad: “Contrary to the candidate’s assertion, there are strong scientific evidence for the effects of greenhouse gases, be it from lab measurements, classical and quantum physics, or from direct observations of the atmosphere.”

Read all the scientists’ comments about this candidate

Ted Cruz climate_change

Prof. David Battisti: “This candidate shows a profound ignorance of the observational records, the climate science — and indeed of the scientific method.”

Read all the scientists’ comments about this candidate

Ben Carson climate_change

Prof. Michael Mann: “The notion that we don’t even know if Earth is warming is pure anti-science. Individual avoided score of zero with the somewhat enlightened acknowledgement that we have “a responsibility to protect our environment.”

Read all the scientists’ comments about this candidate

Donald Trump climate_change

Dr. Ryan Sriver: “The candidate lacks basic understanding about the differences between local weather and global climate.”

Read all the scientists’ comments about this candidate

Marco Rubio climate_change

Dr. William Anderegg: “Accepts some of the science but ignores other science when inconvenient.”

Read all the scientists’ comments about this candidate


Some candidates show a high-level understanding of climate science.

The scientists agreed that three candidates demonstrate a high understanding of climate change. All scientists gave them an above-average rating, a strong indication that these candidates’ public statements on climate change are mostly accurate.

Hillary Clinton climate_change

Prof. Kevin Trenberth: “Very good understanding of situation and pragmatic.”

Read all the scientists’ comments about this candidate

Bernie_Sanders climate_change

Dr. Victor Venema: “The claim that the Earth will not be habitable is too strong. Climate change is a stressor, only in combination with other stressors and human stupidity would it become this bad. Otherwise no complaints on the science.”

Read all the scientists’ comments about this candidate

Martin_Omalley climate_change

Prof. David Battisti: “It is not possible to determine from the statements provided whether the candidate understands the science, but the candidate clearly accepts the science conclusions (warming has happened and will continue to happen due to human activity) and has clearly determined it is a problem that must be dealt with.”

Read all the scientists’ comments about this candidate

For other candidates, we need more information to confidently evaluate their understanding of climate science:

For this candidate, the high rating mostly derives from his 2011 quotes. More recent statements would be required to confidently assess this candidate’s level of understanding of climate change.

Chris_Christie climate_change

Dr. Ryan Sriver: “I like the [candidate’s] 2011 quote about deferring to the experts [“when you have over 90 percent of the world’s scientists who have studied this stating that climate change is occurring and that humans play a contributing role, it’s time to defer to the experts”]. Not sure how to assess the new comments… very political and not much scientific substance.”

Read all the scientists’ comments about this candidate

Several scientists indicated that there are not enough factual statements to clearly determine this candidate’s understanding of climate change.

Carly_Fiorina climate_change

Dr. Twila Moon: “Difficult to judge this candidate’s understanding. He/she does provide false statements that action would provide no impact.”

Read all the scientists’ comments about this candidate

This candidate has made public statements about climate change that are not consistent over time, further analysis will be required.

Jeb_Bush climate_change

Dr. William Anderegg: “Acknowledges some of the science, some of the time.”

Read all the scientists’ comments about this candidate

This candidate produced only a few statements about climate change, more quotes would be needed to precise the candidate’s understanding of climate change.

John_Kasich climate_change

Dr. Rasmus Benestad: “The statement about “a theory that is unproven” is misguided. One could use the same phrase about weather forecasting, medicine or gravity. Is there any science that “can be proven”? The candidate should be challenged to present one.”

Read all the scientists’ comments about this candidate


A note on the statistical significance of this analysis.

8 out of 12 candidates received very similar ratings in both Climate Feedback’s and the Associated Press’ experiments. This is a strong indication that the approach is quite robust: more than 15 scientists rated the presidential candidates statements independently and all converged to similar conclusions. While 8 candidates received very similar ratings in the two evaluations, 4 of Climate Feedback’s ratings (CF) differ significantly from those reported by Seth Borenstein (AP):

  • Chris Christie: AP rating=54, CF rating=75 (+/- 11*)
  • Jeb Bush: AP rating=63, CF rating=36 (+/- 15*)
  • Rand Paul: AP rating=38, CF rating=14 (+/- 6*)
  • O’Malley: AP rating=91, CF rating=76 (+/- 12*)

These differences are due to the additional quotations which Climate Feedback added to the AP selection. This illustrates the sensitivity of the results to the choice of quotations.

Clearly, more analysis will be needed to increase the confidence we have in the results for these candidates.


The 10 reviewers who analyzed all the candidates’ statements are: Prof. J. Abraham, Dr. W. Anderegg, Prof. D. Battisti, Dr. R. Benestad, Prof. M. Mann, Dr. T. Moon, Prof. R Sriver, Dr. K. Trenberth,  Dr. V. Venema, Dr. E. Vincent.


* The confidence interval level is based on a bootstrap technique randomly drawing from the set of ratings.

Published on: 24 Nov 2015 | Editor:

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