Have what seem to be warmer winters and even hotter summers been influencing peoples' belief about global warming? A poll conducted by the University of Michigan and Muhlenberg College says yes, even though climate experts say everyday weather observations are not necessarily evidence of climate change.
According to the UofM statement, 62 percent of those surveyed said they believe that there is trustworthy scientific evidence that the earth is warming. This is the highest level of confidence participants have shown in favor of global warming data since the fall of 2009, but this is still 10 percentage points less than when the poll was first conducted in 2008. Here is more explanation of previous surveys conducted by the team for the past four years:
When the initial survey was done in the fall of 2008, 72 percent of Americans said they believed there was solid evidence that average temperatures on Earth have been getting warmer over the past four decades.
The number declined to 65 percent in the fall of 2009 and fell further to 58 percent a year later. But the most recent survey shows that in the fall of 2011, the number rebounded to 62 percent, ending the period of decline.
Nearly half the people who say they believe in global warming base it on their own personal observations of the weather. Climate scientists say daily local weather isn't evidence of climate change. But they also claim long-term climate change is so dramatic that people do recognize and experience it. UofM notes that according to this latest National Survey of American Public Opinion on Climate Change, half of Americans cite personal experience, such as weather observations, as the main basis for their belief in global warming.
In addition to weather, the survey also states that physical evidence, such as melting icecaps, are considered observations that can contribute to belief in global warming. In fall 2008, 19 percent of participants reported that evidence of ice melt contributed to their belief in global warming while in fall 2011, 14 percent considered this melt a factor.
Of the factors that are considered to "have a very large effect on individual views" of global warming, the survey reports melting glaciers as the highest (59 percent in fall 2011; 63 percent in fall 2008), followed by warmer temperatures in recent years (39 percent in fall 2011; 42 percent in fall 2008) and severe droughts (35 percent in fall 2011; 47 percent in fall 2008).
But is that the whole story? Not only is the number down from 2008 and most people incorrectly cite everyday weather observations to formulate their opinions, but consider that recent improvements in data collection technology has also revealed that the polar ice caps are melting less than originally thought. U.S. World News reported that researchers at the University of Colorado-Boulder found that 30 percent less ice is melting than earlier projections. It does claim that ice melt that has occurred between 2003 and 2010 is enough to cover the whole of the United States with a foot and a half of water -- or fill Lake Erie eight times.
Additionally, the survey results do not explicitly state whether the question posed to participants specifies belief in global warming as caused by man-made activities. Some hold that the earth is undergoing natural and cyclical warming, and therefore do believe that the earth is warming, though not necessarily as result of anthropogenic factors.
The survey does note, however, that seasonal fluctuation -- asking participants about belief in global warming in the spring (just after winter) versus the fall (just after summer) -- appears to be a factor:
Among those that maintain the position that global warming is not occurring there is a higher number that claim personal observations as the primary cause of this view during surveys fielded in the spring than in the fall. For example, after the relatively cold and snowy winters of 2010 and 2011 over 40% of those claiming that global warming is not happening cited personal observation as the main reason for their position on the matter.
UofM reports that 3 out of 4 people associating their political beliefs with the Democratic Party think the evidence being presented supports global warming, whereas 47 percent of Republicans believe the data is solid and 42 percent don't consider it proof enough.
The survey of 887 people who were called randomly in the United States has a margin of error of plus or minus 3.5 percentage points.
The Associated Press contributed to this report.