James Lawrence Powell har undersökt publicererade artiklar med nyckelorden "global warming" eller "global climate change". Kortfattat beskriver han kategoriseringen enligt:
I read whatever combination of titles, abstracts, and entire articles was necessary to identify articles that "reject" human-caused global warming. To be classified as rejecting, an article had to clearly and explicitly state that the theory of global warming is false or, as happened in a few cases, that some other process better explains the observed warming. Articles that merely claimed to have found some discrepancy, some minor flaw, some reason for doubt, I did not classify as rejecting global warming. Articles about methods, paleoclimatology, mitigation, adaptation, and effects at least implicitly accept human-caused global warming and were usually obvious from the title alone.
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