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

The latest national survey by the Pew Research Center for the People & the Press, conducted Sept. 30-Oct. 4 among 1,500 adults reached on cell phones and landlines, finds that 57% think 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 rising global temperatures.

Over the same period, there has been a comparable decline in the proportion of Americans who say global temperatures are rising as a result of human activity, such as burning fossil fuels. Just 36% say that currently, down from 47% last year.

The decline in the belief in solid evidence of global warming has come across the political spectrum, but has been particularly pronounced among independents. Just 53% of independents now see solid evidence of global warming, compared with 75% who did so in April 2008. Republicans, who already were highly skeptical of the evidence of global warming, have become even more so: just 35% of Republicans now see solid evidence of rising global temperatures, down from 49% in 2008 and 62% in 2007. Fewer Democrats also express this view — 75% today compared with 83% last year.

Despite the growing public skepticism about global warming, the survey finds more support than opposition for a policy to set limits on carbon emissions. Half of Americans favor setting limits on carbon emissions and making companies pay for their emissions, even if this may lead to higher energy prices; 39% oppose imposing limits on carbon emissions under these circumstances.

This issue has not registered widely with the public. Just 14% say they have heard a lot about the so-called “cap and trade” policy that would set carbon dioxide emissions limits; another 30% say they have heard a little about the policy, while a majority (55%) has heard nothing at all.

The small minority that has heard a lot about the issue opposes carbon emissions limits by two-to-one (64% to 32%). More Republicans (20%) and independents (17%) than Democrats (8%) have heard a lot about cap and trade. Among the much larger group that has head little or nothing about the issue, most support it (50% little, 58% nothing).

With less than two months before the United Nations Climate Change Conference in Copenhagen, a majority (56%) of Americans think the United States should join other countries in setting standards to address global climate change while 32% say that the United States should set its own standards.

Shifts on Global Warming

Opinions about global warming changed little between 2006 and 2008. In August 2006 and January 2007, 77% said there was solid evidence that the earth’s temperatures were increasing; that figure fell modestly to 71% in April of last year.

Among those who saw solid evidence of global warming, most said it was largely caused by human activity, such as burning fossil fuels; in all three of those surveys, 47% of the public expressed this view. Far smaller percentages — including just 18% in 2008 — said it was mostly caused by natural environmental patterns.

Currently, 57% say there is solid evidence of rising global temperatures, while 33% say there is no solid evidence. Fewer than four-in-ten (36%) now say global warming is mostly caused by human activity such as burning fossil fuels, while 16% say it is occurring mostly because of natural environmental patterns.

A majority (53%) of independents say there is solid evidence of warming, including 33% who say it is mostly caused by human activity. But this is far lower than in April 2008 when 75% said global warming was happening and 50% said it was due to human activity.

The proportion of Republicans saying there is solid evidence of global warming declined from 62% in 2007 to 49% in 2008. The balance of opinion among Republicans has shifted, with a majority (57%) now saying there is no hard evidence of global warming. The drop among moderate and liberal Republicans has been particularly steep; 41% now say there is solid evidence of global warming, compared with 69% last year. The decline among conservative Republicans has been more modest (from 43% to 32%).

Opinions among Democrats have changed less. Three-quarters of Democrats (75%) say there is solid evidence the earth is warming, including 50% who say that it is mostly because of human activity. In April 2008, 83% of Democrats said the earth is warming and 58% attributed it to human actions. More liberal Democrats than conservative and moderate Democrats say the earth is warming (83% vs. 72%), and far more liberal Democrats say that global warming is caused by human activity (69% vs. 43%).

There also are strong regional differences in opinions about global warming; fewer people living in the Mountain West (44%) and the Midwest (48%) say there is solid evidence of warming than in other regions. Similarly, there have been sharp declines since April 2008 in the proportion who say the earth is warming in the Mountain West (75% to 44%) and the Great Lakes region (69% to 49%). Both regions have also seen large drops in the percentage who say that warming is caused by human activity. (For a breakdown of states and regions, see “About the Survey” on pewresearch.org/politics.)

Fewer See Warming as Very Serious Problem

A majority (65%) of the public continues to view global warming as a very (35%) or somewhat (30%) serious problem. But in April 2008, 73% expressed this view, including 44% who thought it was a very serious problem. About a third (32%) says global warming is not too serious (15%) or not a problem at all (17%). Last year, 24% said it was little or no problem. From 2006 to 2008, these numbers had been quite stable.

Partisan differences also are evident on evaluations of the seriousness of global warming. About half (49%) of Democrats say global warming is a very serious problem, down from 57% in April 2008. Far fewer conservative and moderate Democrats say global warming is a serious problem than did so last year, widening the gap between them and liberal Democrats. Currently, 39% of conservative and moderate Democrats say it is a very serious problem compared with 70% of liberal Democrats. A third of independents now say global warming is a very serious problem, a decline of 13 points from last year.

Only 14% of Republicans say that global warming is a very serious problem, down from 22% in April 2008. Just 20% of moderate and liberal Republicans now say that global warming is a very serious problem, down from 35% last year. Only 10% of conservative Republicans now say global warming is a very serious problem.

People living in the Midwest (30%) and the Mountain West (26%) are the least likely to view global warming as a very serious problem. There have been modest declines across regions, but they are particularly steep in the West (52% April 2008 to 36% now).

Young people are now far more likely than older Americans to view global warming as a very serious problem. Across all age groups, except those younger than age 30, the percent who think warming is a very serious problem has declined since April 2008.

As expected, views about the seriousness of global warming are also related to whether people think there is solid evidence the earth is warming and whether it is human caused. A third of those who do not think there is solid evidence of global warming say it is a very or somewhat serious problem, while 65% say it is not too serious or not a problem at all.

By comparison, 65% of those who say that the warming is mostly caused by natural patterns in the earth’s environment say global warming is at least a somewhat serious problem. Nearly all (97%) who think the earth is warming mostly because of human activity say it is a problem. These numbers are largely unchanged from April 2008.

In January 2009, global warming ranked at the bottom of the public’s list of policy priorities for the president and Congress this year. Only 30% of the public said it should be a top priority, down from 35% a year ago. More than twice as many Democrats (45%) as Republicans (16%) rank global warming as a top priority, along with 25% independents. Global warming is the lowest-rated priority for both independents and Republicans and ranks sixteenth for Democrats among 20 issues.

Cap and Trade Barely Registers

As the health care debate has dominated the public’s attention, awareness about cap and trade legislation is quite low. A majority (55%) of the public has heard nothing at all about the cap and trade policy being considered by the president and Congress that would set limits on carbon dioxide emissions. Only 14% have heard a lot and 30% a little about this policy.

More Republicans (20%) and independents (17%) than Democrats (8%) have heard a lot about cap and trade although more Democrats have heard a little. Conservative Republicans are hearing the most; more than a quarter have heard a lot (28%) about the policy.

More people who say there is no solid evidence of global warming have heard a lot about cap and trade than those who think temperatures are rising (24% vs. 10%). But more of those who say that warming is caused mostly by human activity have heard a little about the proposed policy than those who say there is no evidence of warming (36% vs. 27%).

The most recent survey of the public’s knowledge by the Pew Research Center, released Oct. 14, found that just 23% of the public could correctly identify that the cap and trade legislation being discussed in Congress deals with energy and the environment; 48% were unsure and 29% said incorrectly that it deals with health care, banking reform or unemployment. More Republicans (27%) and independents (29%) correctly identify cap and trade as dealing with energy and the environment than Democrats (15%).

Carbon Emissions Limits Favored

Half of the public favors setting limits on carbon dioxide emissions and making companies pay for their emissions, even if it may mean higher energy prices. About four-in-ten (39%) oppose this and 11% are unsure or do not offer an opinion.

Conservative Republicans are the only political group in which a majority (60%) opposes setting limits on carbon dioxide emissions. Most moderate and liberal Republicans (51%) favor this policy, as do an identical percentage of independents and a majority of Democrats (58%).

There also are wide regional differences in opinions about cap and trade. More people living near the Pacific coast (62%) and the Northeast (56%) favor limiting carbon emissions, even if it may mean higher energy prices than those living in the South (46%), Midwest (44%) and Mountain West (42%). More college graduates favor this policy than those with a high school education or less (59% vs. 43%), but there are very few differences by age.

Opinion about cap and trade is related to views about global warming. About three-fourths (74%) of those who think the earth is warming and it is mostly caused by human activity favor cap and trade legislation. By comparison, 41% of those who say warming is due to natural patterns in the earth’s environment favor limiting carbon emissions. But even 31% of those who say there is no solid evidence of rising temperatures favor cap and trade.

Public Supports Global Initiatives

A majority (56%) of Americans thinks the United States should join other countries in setting standards to address global climate change while 32% say the U.S. should set its own standards; 5% say neither and 6% are unsure. These numbers are similar to those in 2001 and 1997 when the public was asked about setting standards to improve the global environment.

More Democrats (66%) than independents (53%) or Republicans (47%) say the U.S. should join other countries in setting standards to address global climate change. Three-quarters of those who say the earth is warming mostly because of human activity think the U.S. should join with other countries in setting standards to address global climate change. By comparison, 51% of those who say warming is due to natural patterns in the earth’s environment and 42% who say the earth is not warming think the U.S. should join other countries in setting standards to address climate change.

View the topline and survey methodology at pewresearch.org/politics.