Though 57% of those polled said they believe global temperatures are on the rise, that's down from 71% who felt that way in April 2008, the Pew Research Center for the People & the Press reports today.

And, Pew says, "fewer also see global warming as a very serious problem — 35% say that today, down from 44% in April 2008."

The researchers' overall conclusion: "There has been a sharp decline over the past year in the percentage of Americans who say there is solid evidence that global temperatures are rising."

Why has that happened?

Pew's research director, Andrew Kohut, tells the Associated Press that:

"The priority that people give to pollution and environmental concerns and a whole host of other issues is down because of the economy and because of the focus on other things. ... When the focus is on other things, people forget and see these issues as less grave."

The national telephone survey of 1,500 adults was done from Sept. 30 to Oct. 4. Pew says the margin of error on each result is +/- 3 percentage points.