05/08/2008 - The latest national survey by the Pew Research Center for the People & the Press finds that the proportion of Americans who say that the earth is getting warmer has decreased modestly since January 2007, mostly because of a decline among Republicans. Republicans are increasingly skeptical that there is solid evidence that the earth has been warming over the past few decades: just 49% of Republicans say there is evidence that the earth's average temperature has been rising, down 13 points since January 2007.
Overall, 71% of Americans say there is solid evidence of higher global temperatures, compared with 77% at the beginning of last year. There is less of a consensus about the cause of global warming. Roughly half of Americans (47%) say the earth is warming because of human activity, such as the burning of fossil fuels.
But nearly as many people (45%) say that rising global temperatures are either mostly caused by natural environmental patterns (18%), say they do not know the cause of warming (6%), or say that no solid evidence of warming exists (21%).
The survey, conducted April 23-27 among 1,502 adults, finds that the already substantial partisan divide over global warming has widened in the past year. Fully 84% of Democrats and 75% of independents say there is evidence that the earth's temperatures have been rising, compared with just 49% of Republicans.
Among Republicans, far more moderates and liberals than conservatives say there is evidence of global warming (69% vs. 43%). However, the proportion of both groups expressing this view has declined since January 2007.
Read the complete findings An Increase in GOP Doubt About Global Warming Deepens Partisan Divide on the Pew Research Center Web site.