Americans are now almost evenly split over what they believe to be the major contributor to global warming, according to a new Gallup Poll released Thursday.
Fifty percent of respondents believe human activities are causing a rise in the earth's temperature, while 46 percent say the rise is due to natural causes. Gallup reports that as early as 2003, 61 percent of Americans believed global warming was due to human activities and 33 percent to natural causes.
"Most Gallup measures up to 2008 had shown increasing concern over global warming on the part of the average American, in line with what one might have expected given the high level of publicity on the topic," Gallup said in its release about the poll. "But the public opinion tide turned in 2009, when several Gallup measures showed a slight retreat in public concern about global warming. This year, the downturn is even more pronounced."
The poll also found that Americans are becoming increasingly skeptical over the existence of global warming and how much of a threat it poses, despite the overwhelming scientific consensus that man-made global warming is real and poses significant challenges.
For example, the number of Americans who say the seriousness of global warming has been accurately portrayed is waning. About 48 percent of Americans now contend that the effects of global warming are generally exaggerated, up from 41 percent in 2009 and 31 percent in 1997.
Gallup also said the "average American is now less convinced than at any time since 1997 that global warming's effects have already begun or will begin shortly."
Slightly more than a half of Americans, 53 percent, say the negative effects of global warming have already begun or will become visible in a few years (65 percent said so two years ago). Meanwhile, 35 percent of Americans believe global warming will either never happen or won't happen in their lifetimes.
There are several possible explanations for this stark turnaround in public opinion within the last two years.
One of these is the recent controversy surrounding "Climategate," when some alleged the exposed e-mails from the Climate Research Unit in England were evidence that scientists were distorting data to support global warming.=http:>
Other explanations could be the record-shattering snowfall from this winter and the fact that global warming has become an increasingly partisan issue.
"It may be that the continuing doubts about global warming put forth by conservatives and others are having an effect," Gallup states.
The Gallup Poll was conducted between March 4-7 and was based on telephone interviews with 1,014 adults. The margin of error was plus or minus four percent.