The survey, which was conducted for STATS by Harris Interactive®, also found increased concern among climate scientists since the Gallup organization asked them many of the same questions in 1991.
Between March 19 through May 28, 2007 Harris Interactive conducted a mail survey of a random sample of 489 self-identified members of either the American Meteorological Society or the American Geophysical Union who are listed in the current edition of American Men and Women of Science. A random sample of this size carries a theoretical sampling error of +/- four percentage points. A detailed description of the study’s methodology as well as that of the earlier Gallup survey is available on request.
Scientists agree that humans cause global warming
Eighty-four percent say they personally believe human-induced warming is occurring, and 74% agree that “currently available scientific evidence” substantiates its occurrence. Only 5% believe that that human activity does not contribute to greenhouse warming; the rest are unsure.
Scientists still debate the dangers
A slight majority (56%) see at least a 50-50 chance that global temperatures will rise two degrees Celsius or more during the next 50 to 100 years. (The United Nations’ Intergovernmental Panel on Climate Change cites this increase as the point beyond which additional warming would produce major environmental disruptions.)
Based on current trends, 41% of scientists believe global climate change will pose a very great danger to the earth in the next 50 to 100 years, compared to 13% who see relatively little danger. Another 44% rate climate change as moderately dangerous.
Seventy percent see climate change as very difficult to manage over the next 50 to 100 years, compared to only 5% who see it as not very difficult to manage. Another 23% see moderate difficulty in managing these changes.
A need to know more
Only 29% express a “great deal of confidence” that scientists understand the size and extent of anthropogenic [human] sources of greenhouse gases,” and only 32% are confident about our understanding of the archeological climate evidence.
Climate scientists are skeptical of the media
Former Vice President Al Gore’s documentary film “An Inconvenient Truth” rates better than any traditional news source, with 26% finding it “very reliable” and 38% as somewhat reliable. Other non-traditional information sources fare poorly: No more than 1% of climate experts rate the doomsday movie “The Day After Tomorrow” or Michael Crichton’s novel “State of Fear” as very reliable.
Are climate scientists being pressured to deny or advance global warming?
Three percent report that they were pressured by public officials or government agencies to “embellish, play up or overstate” evidence of global warming: Two percent report such pressure from funders, and two percent from supervisors.
Changing scientific opinion
We repeated several of their questions verbatim, in order to measure changes in scientific opinion over time. On a variety of questions, opinion has consistently shifted toward increased belief in and concern about global warming. Among the changes:
All sample surveys and polls, whether or not they use probability sampling, are subject to multiple sources of error which are most often not possible to quantify or estimate, including sampling error, coverage error, error associated with non-response, error associated with question wording and response options, and post-survey weighting and adjustments. Therefore, Harris Interactive avoids the words “margin of error” as they are misleading. All that can be calculated are different possible sampling errors with different probabilities for pure, unweighted, random samples with 100% response rates. These are only theoretical because no published polls come close to this ideal.
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