You’ll notice that Obama’s tweet took the claim further. He claimed that not only is climate change real and man made, but also that it is dangerous. The 97% figure has also been referenced from a study by Kendall Zimmerman in 2008, 8 years before Cook’s study brought about the same 97% statistic.

Claiming a 97% consensus is a big deal, especially when purporting to represent the globally respected scientific community. I set out to find where these stats came from, and if they support the claims made by Oliver, Obama, and others.

The study conducted by Zimmerman was very straight forward. A questionnaire was sent to 10,257 earth scientists, from a database built by Keane and Martinez [2007]. In order to maximize the response rate, the survey was designed to take two minutes to complete, and was conducted by a professional survey website. The survey contained two primary questions:

1. When compared with pre 1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?

2. Do you think human activity is a significant contributing factor in changing mean global temperatures?

3146 of the 10,257 individuals polled responded to the survey. 90% of those polled answered “risen” to the first question, and 82% answered yes to question 2.

These are high percentages, but they still do not reach 97%. The origin of that number is found later in the study.

The respondents of the survey were asked to list their scientific field of expertise. The answers to the survey questions of those who listed climate science as their area of expertise were then analyzed (79 total). Here are the results:

96.2% (76 of 79) answered “risen” to question 1 and 97.4% (75 of 77) answered yes to question 2.

Taking a poll of 77 individuals and claiming consensus is at a bare minimum misleading.

For the purposes of this post, I will ignore the 1st question of the survey for 2 reasons: 1) It is not the origin of the infamous 97% stat. 2) It is an undeniable fact that global temperatures have risen since the 1800’s. The globe has increased in temperature roughly 1.5 degC in the last 150 or so years.

The second question in Zimmerman’ study asks if the scientists believe that human activity is a significant contributing factor in the rise. However, the study does not even define what “significant contributing factor” means. Each contributor in the survey was left to their own judgement when it comes to the interpretation of the term. What would be reasonable to define as a significant factor? 50%? 30%? Maybe 15%?

The second study was done by John Cook et. al. (2013), entitled ‘Quantifying the Consensus on Anthropogenic Global Warming in the Scientific Literature‘, and was published by IOP Science. The study examined 11, 944 abstracts from 1991-2011 matching the topics ‘global climate change’ or ‘global warming’. Take note that the study observed only the abstracts, and not the substance of the studies themselves. This has been a major source of criticism for Cook. The following is a quote from the study’s abstract:

“We find that 66.4% of abstracts expressed no position on AGW (Anthropogenic Global Warming), 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming.”

This means that two thirds of the reviewed studies provided no opinion on AGW at all. The study is also widely criticized for it’s lack of scope. The literature available on climate science far exceeds the 12,000 papers that were reviewed. There is also the possibility that Cook’s team inaccurately deemed studies as having no opinion, when they may in fact provide evidence against the prevailing theory that Cook was out to prove. The following was written by Professor Richard Tol in the Guardian:



“Cook’s sample is not representative. Any conclusion they draw is not about “the literature” but rather about the papers they happened to find”

Cook also made the decision to lump together data from groups who he interpreted to believe humans were the main cause of global warming, with those who he interpreted to believe humans were a cause of global warming.

Not to mention that Cook received significant backlash from the very authors he was reviewing!

“Cook’s survey included 10 of my 122 eligible papers. 5/10 were rated incorrectly. 4/5 were rated as endorse rather than neutral.” – Professor Richard Tol.

“That is not an accurate representation of my paper…… It would be incorrect to claim that our paper was an endorsement of CO2-induced global warming.” Dr. Craig D. Idso, author of ‘Ultra-enhanced spring branch growth in CO2-enriched trees: can it alter the phase of the atmosphere’s seasonal CO2 cycle?‘

Scafetta: “Cook et al. (2013) is based on a strawman argument because it does not correctly define the IPCC AGW theory, which is NOT that human emissions have contributed 50%+ of the global warming since 1900 but that almost 90-100% of the observed global warming was induced by human emission”.

“What my papers say is that the IPCC view is erroneous because about 40-70% of the global warming observed from 1900 to 2000 was induced by the sun.” – Dr. Nicola Scafetta, author of ‘Phenomenological solar contribution to the 1900–2000 global surface warming‘

In his segment Oliver uses the 97% statistic as a trump card. He literally brings out 96 scientists, to sit along side Bill Nye, to debate a single “climate change skeptic”. The token “skeptic” on stage is then asked by Oliver to state his case. “I just don’t think the science is settled”, he responds. “And what about the overwhelming majority of the scientific community?”