Seventy-two percent currently say global warming is occurring, compared to 26 percent who say it is not. In the previous survey, the ratio was 80 percent to 18 percent. A "cap and trade" program aimed at reducing greenhouse emissions is supported by a 53 percent to 42 percent margin, a number that has been consistent dating back to June of this year but lower than the 59 percent to 34 percent margin in July 2008.

A Pew Research Center survey published last month found the percentage of Americans believing there is solid evidence of global warming dropping from 71 percent in April 2008 to 57 percent. Sixty-five percent nevertheless described it as a somewhat or very serious problem, but that was down from 73 percent in April of last year.

President Obama plans to go to Copenhagen next week to attend the early rounds of a U.N. climate summit, which is drawing delegations from 192 countries. Fifty-five percent of Americans believe that the U.S. should act on global warming even if other countries do less; 21 percent say the U.S. should take action only if other countries do; and 22 percent say the U.S. should not take action at all, according to the Post/ABC poll.