WASHINGTON (AP) — Nearly 4 out of 5 Americans now think temperatures are rising and that global warming will be a serious problem for the United States if nothing is done about it, a new Associated Press-GfK poll finds.

Belief and worry about climate change are inching up among Americans in general, but concern is growing faster among people who don't often trust scientists on the environment. In follow-up interviews, some of those doubters said they believe their own eyes as they've watched thermometers rise, New York City subway tunnels flood, polar ice melt and Midwestern farm fields dry up.

Overall, 78 percent of those surveyed said they thought temperatures were rising and 80 percent called it a serious problem. That's up slightly from 2009, when 75 percent thought global warming was occurring and just 73 percent thought it was a serious problem. In general, U.S. belief in global warming, according to AP-GfK and other polls, has fluctuated over the years but has stayed between about 70 and 85 percent.