An email (I believe from The Heartland institute) is going around that says: "In January 2012, the AMS surveyed its members via email and found 52 percent believe global warming is happening and is mostly human-caused, while 48 percent do not." It's a misleading distilation of a misleading Forbes article by James Taylor.
I read the survey cited and the amount of trickery used to arrive at those numbers is pretty shocking.
The 52/48 numbers are nowhere to be found in the American Meteorological Society survey. They are arrived at by crafty cherry-picking from the following paragraph:
"A very large majority of respondents (89%) indicated that global warming is happening; in contrast few indicated it isn’t happening (4%), or that they “don’t know” (7%). Respondents who indicated that global warming is happening were asked their views about its primary causes; a large majority indicated that human activity (59%), or human activity and natural causes in more or less equal amounts (11%), were the primary causes. Relatively few respondents indicated that the warning is caused primarily by natural causes (6%), although a substantial minority (23%) indicated they don’t believe enough is yet know to determine the degree of human or natural causation."
So 70% (or 62% of all respondents) believe human activity is a factor in global warming. The 52% comes from multiplying 89% by 59% and omitting the 11% that believe natural causes in addition to human causes are a primary factor. The 48% is arrived at by subtracting 52 from 100, but as you can see above simply writing "48% do not" is a huge cheat that omits a lot of nuance and wrongly implies that 48% of respondents are climate-change deniers.
The Forbes article pretends this survey is comprehensive and representative of the scientific community as a whole. It repeatedly refers to the survey respondents as "meteorologists" and "scientists" and omits the following information:
* Only 1/4 AMS members responded to the survey.
* AMS membership does not require you to be a scientist or professional. A BA in any science related to climate suffices no matter when you got it or what your profession is.
* Only half the respondents have PhDs.
Here's what the study itself says on what experts believe:
"Our findings regarding the degree of consensus about human-caused climate change among the most expert meteorologists are similar to those of Doran and Zimmerman (2009): 93% of actively publishing climate scientists indicated they are convinced that humans have contributed to global warming. Our findings also revealed that majorities of experts view human activity as the primary cause of recent climate change: 78% of climate experts actively publishing on climate change, 73% of all people actively publishing on climate change, and 62% of active publishers who mostly do not publish on climate change. These results, together with those of other similar studies, suggest high levels of expert consensus about human-caused climate change (Farnsworth & Lichter 2012, Bray 2010)."
This paragraph is, of course, not referenced by the Forbes piece. Taylor gives a lot of lip service in his article to respecting science, but ignoring or misrepresenting inconvenient data is not how good science works.
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Postscript:
The main points of the survey are that political ideology and perceptions of consensus (as well as expertise) seem to correlate with views on climate change. The conservative email (which includes the AMA logo to give the impression it is an AMA mailing) summarizes the ideology factor as follows: "The survey also found that scientists with professed liberal political views were far more likely to believe global warming is human-caused than others." That's a cute bit of one-sidedness that suggests those who don't believe in human-caused climate change are objective, but of course a more likely flipside is that the deniers tend to be politically conservative.