On Tuesday, the Competitive Enterprise Institute (CEI) sent NASA a formal complaint, asking the agency to withdraw the false claim that 97 percent of climate scientists agree that humans are the primary cause of global warming and climate change. The 2013 study purporting to demonstrate that number was fatally flawed and proved no such thing.
“The claim that 97% of climate scientists believe humans are the primary cause of global warming is simply false,” CEI attorney Devin Watkins said in a statement. “That figure was created only by ignoring many climate scientists’ views, including those of undecided scientists. It is time that NASA correct the record and present unbiased figures to the public.”
According to the CEI complaint, NASA’s decision to repeat the false claim violated the Information Quality Act (IQA). Specifically, NASA claimed that “[n]inety-seven percent of climate scientists agree that climate-warming trends over the past century are extremely likely due to human activities.” The claim appears on the NASA website on the page “Climate Change: How Do We Know?”
The claim traces back to a study led by John Cook entitled “Quantifying the consensus on anthropogenic global warming in the scientific literature” and published in the journal Environmental Research Letters in 2013.
The study is fundamentally dishonest, as the CEI complaint explains. The study analyzed all published peer-reviewed academic research papers from 1991 to 2011 that use the terms “global warming” or “global climate change.” The study placed the papers into seven categories: explicit endorsement with quantification, saying humans are responsible for 50+ percent of climate change; explicit endorsement without quantification; implicit endorsement; no position or uncertain; implicit rejection; explicit rejection with qualification; and explicit rejection without qualification.
The study found: 64 papers had explicitly endorsed anthropogenic global warming (AGW) with quantification (attributing at least half of climate change to humans); 922 papers had explicitly endorsed AGW without quantifying how much humans contribute; 2,910 papers had implicitly endorsed AGW; 7,930 papers did not state a position and 40 papers were uncertain; 54 papers implicitly rejected AGW by affirming the possibility that natural causes explain climate change; 15 papers explicitly rejected AGW without qualification; and 9 papers explicitly rejected AGW with quantification, saying human contributions to global warming are negligible.
So how did Cook and his team come up with the 97 percent number? They added up the first three categories (3,896 papers), compared them to the last three categories (78 papers) and the papers expressing uncertainty (40 papers), and completely ignored the nearly 8,000 papers that did not state a position.
Of the papers Cook’s team characterized as stating a position, 97 percent (3,896 of the 4,014 papers) favored the idea of man-made global warming.
See the problem? The study completely discounted the majority of the papers it analyzed (66.4 percent — 7,930 of the 11,944 papers analyzed). With those papers included, only 32.6 percent of the papers explicitly or implicitly endorsed AGW (3,896 of 11,944 papers).