There are still a surprisingly large number of people who think that scientists haven’t reached a consensus on climate change. In making their case, some of those contrarians point to an online petition, signed by over 31,000 “scientists,” which states:
There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate. Moreover, there is substantial scientific evidence that increases in atmospheric carbon dioxide produce many beneficial effects upon the natural plant and animal environments of the Earth.
So wow, huh? A petition with the signatures of more than 31,000 scientists seems quite impressive. I mean, if 31,000 scientists say climate change is a bunch of hooey, who am I to argue? But as Glenn Kessler wrote in his “Fact Checker” column for The Washington Post, “Only 9,000 of the [31,000+] signers actually have PhDs, and the list of signers’ qualifications shows only a relatively small percentage with expertise on climate research. One study estimated that under the petition’s rather expansive definition of a ‘scientist,’ more than 10 million Americans would be qualified to sign it.” That same study found that only 39 individual climatologists—that is, people who actually study climate for a living—signed the petition. The remainder of the 31,000 signers came from the following fields:
- Computers and Math
- Physics and Aerospace
- Biochemistry, Biology, and Agriculture
- General Science
Meanwhile, a peer-reviewed study published in the Proceedings of the National Academy of Sciences (PNAS) found that “97-98% of the [nearly 1,400] climate researchers most actively publishing in the field support the tenets of ACC [anthropogenic (human-caused) climate change] outlined by the Intergovernmental Panel on Climate Change.” Similarly, scientists who analyzed nearly 12,000 climate studies that appeared in peer-reviewed scientific journals, between 1991 and 2011, concluded: “Among papers expressing a position on AGW [anthropogenic global warming], an overwhelming percentage (97.2% based on self-ratings, 97.1% based on abstract ratings) endorses the scientific consensus on AGW.”
So, on the one hand, you have between 97 and 98 percent of 12,000 published climate scientists agreeing that humans are causing climate change, and, on the other, you have 39 climatologists (not 39 percent of 31,000, mind you, just 39 individuals) signing an online petition that says there’s no “convincing scientific evidence” that humans are causing climate change. Now, which of those two positions do you think is more likely to be correct?
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I mention the petition and the peer-reviewed studies because I’m convinced that it’s crucial we recognize that climate change is real and that we’re causing it. If we face the truth, we’re more likely to do whatever is necessary to change our course and avert disaster.
Need more evidence that climate change is an existential threat? Check out this article from today’s Washington Post:
“How Earth Itself Has Dramatically Upped the Stakes for the Paris Climate Accord,” by Chris Mooney and Brady Dennis.
Need more arguments to use on climate deniers? Check out: “Yes, You Should Listen to Bill Nye Instead of Sarah Palin on Climate Change.”
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 Global Warming Petition Project. “31,487 American scientists have signed this petition, including 9,029 with PhDs.” http://www.petitionproject.org/index.php
 Kessler, Glenn. “Rick Perry’s Made-Up ‘Facts’ About Climate Change.” Washington Post, August 18, 2011. https://www.washingtonpost.com/blogs/fact-checker/post/rick-perrys-made-up-facts-about-climate-change/2011/08/17/gIQApVF5LJ_blog.html
 Angliss. “Guest Post: Scrutinizing the 31,000 Scientissts in the OISM Petition Project. March 11, 2010. http://www.skepticalscience.com/scrutinising-31000-scientists-in-the-OISM-P
 Anderegg, William R. L., James W. Prall, Jacob Harold, and Stephen H. Schneider. “Expert Credibility in Climate Change.” PNAS. June 21, 2010. http://www.pnas.org/content/107/27/12107.abstract
 Cook, John, Dana Nuccitelli, Sarah A. Green, et al. 2013. “Quantifying the Consensus on Anthropogenic Global Warming in the Scientific Literature.” Environmental Research Letters. Vol. 8, p. 6.