Many of us have heard the assertion that 97 percent of scientists agree that climate change or anthropogenic global warming (AGW) is being caused by emissions of greenhouse gasses that result from our modern lifestyle. Since some have questioned the validity of that statistic, this article seeks to understand where the 97 percent figure comes from.
Back in April 2013, an article was published in the journal Environmental Research Letters by John Cook, et. al. that claimed that “Among abstracts expressing a position on AGW, 97.1% [percent] endorsed the consensus position that humans are causing global warming.” This finding came from a meta-analysis of 11,944 climate abstracts from 1991–2011.
This certainly sounds impressive, and lends credence to the notion that nearly all scientists support the idea that we, as humans who emit greenhouse gasses, are responsible for climate change or global warming. However, we need to delve into Professor Cook’s analysis a little deeper.
Of the 11,944 abstracts he examined, 2/3 (66.4 percent) expressed no opinion on human induced climate change, while 32.6 percent endorsed the idea that climate change was being induced by mankind. The other 1 percent either rejected the idea of human induced climate change or were uncertain about the role of mankind in climate change.
So, only 4013 abstracts expressed an opinion on the role of humans in climate change and 3,894 of the abstracts indicated that humans were responsible, thus the 97 percent support. However, if the number of abstracts supporting the idea were divided by the total number of abstracts examined, the percent of scientific papers supporting the claim of AGW falls to 33 percent. This is further complicated by the fact that some of those 11,944 abstracts were by authors who published multiple abstracts on the subject. Therefore, only 33 percent of the abstracts support the theory that climate change is primarily the result of humans and whether that figure represents the percent of scientists is unknown.
Why does this matter?
Increasingly, we see the 97 percent of scientists agree figure in the media and more popular literature leading some to conclude that human induced climate change is a fact, not a theory! Since there are few things that over 90 percent of scientists agree upon, many people accept the theory as fact. However, if only 1/3 of scientists indicate that they are convinced that climate change is the result of our human activities, the subject becomes more hypothetical, still awaiting further evidence.
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