According to the poll, 35% of respondents said global warming was a serious problem, down from 44% in April 2008. Even starker is the increase in voters' skepticism: Only 57% said they believe there is solid evidence that earth's average temperature has increased over the past few decades, compared with 71% who said that last year -- a 14-point drop. Also, just 36% said increases in global temperatures are the result of human activity, which was down from 47% last year.Is this the beginning of a trend, or the regular oscillation of opinion that accompanies any complex issue? This is the second Pew poll to find global warming a low-priority issue among the public at large. A poll taken earlier this year showed that "moral decline" and "lobbyists" were deemed more pernicious than climate change.