The author of today’s post, Lisa Moore, Ph.D., is a scientist in the Climate and Air program.
On Wednesday, the DailyTech Blog said that an update to a 2004 survey shows that the scientific community is moving away from a consensus that humans are causing global warming. The survey was submitted to the journal Energy and Environment, but is as yet unpublished.
So is it true? In a word, no, because scientific consensus cannot be surmised from subjective surveys.
The new survey, by Klaus-Martin Schulte, updates a survey by Naomi Oreskes. Oreskes searched journal articles from 1993 to 2003 on the term "global climate change", then categorized the results based on their abstracts. She found that 75 percent either explicitly or implicitly accepted that human activity is causing global warming. Schulte repeated Oreskes' method on journal articles from 2004 to February 2007 and found that the number had dropped to 45 percent.
The problem is, these surveys are unreliable – there is too much subjectivity in making the categorizations. As AccuWeather.com points out, Benny Peiser, analyzing the same data as Oreskes, came up with very different results. Peiser said that only 30 percent of articles explicitly or implicitly accepted human-caused global warming. If you believe Peiser, then scientific consensus around human-caused global warming has increased, not decreased.
In any case, surveys such as these are an invalid way to discover what the majority of scientists think. The most reliable indicator is the consensus opinion of large and respected scientific bodies. To give a few examples… The IPCC [PDF], the American Geophysical Union, the American Meteorological Society, and the National Academy of Sciences [PDF] (which the White House calls the "gold standard of independent scientific review") all say that human activity is causing global warming. These organizations are composed of and governed by scientists, and could not take this position if it didn't represent the consensus view of the scientific community.