Sobering stuff from the Pew Research Center.

A recent Pew Research survey showing a sharp decline in the proportion of the public saying there is solid evidence of global warming has triggered considerable speculation about why these views are changing. The poll was released a day after 18 leading scientific organizations released a letter reaffirming what they see as scientific consensus on climate change.

The survey found 57% saying there is "solid evidence that the average temperature on earth has been getting warmer over the past few decades." In April 2008, 71% said there was solid evidence of global warming, and in 2006 and 2007, 77% expressed this view.

Why do fewer Americans believe the earth is warming? No single factor emerges from Pew Research Center surveys, but rather a range of possible explanations, including a sour economy and, perhaps, a cooler than normal summer in parts of the United States.

First, it is important to note that signs of a change in public opinion — on the environment generally and global warming more specifically — were evident long before Pew Research’s new survey. In March, Gallup’s annual environment survey found an increase in the percentage of Americans who say the seriousness of global warming is “generally exaggerated” — from 30% in 2006 to 41% this year. Similarly, Fox News found the percentage of registered voters saying they “believe global warming exists” has fallen from 82% in January 2007 to 69% in May of this year.

Pew Research surveys show that as economic concerns have surged, fewer people view the environment as a top policy priority. In our annual survey on the public’s policy agenda, just 41% rated protecting the environment as a top priority; just a year earlier, 56% rated it as a top priority. Yet other issues also were overshadowed as more people focused on the economy and jobs. There were sharp declines as well in the proportions rating dealing with illegal immigration (down 10 points), reducing health care costs (10 points) and reducing crime (eight points) as top priorities for the president and Congress.