Fewer Republicans believe that the Earth is warming than last year, according to a new poll released by the Pew Research Center.

According to the poll, 44 percent of Republicans believe that there is solid evidence of global warming, down 8 percent from a similar poll taken in October. Overall, 69 percent of Americans believe that the Earth is warming, up two percentage points from October, bolstered by a 2 percent increase in Democrats and a 6 percent uptick among Independents.

About 4 in 10 Americans believe global warming is mostly caused by human activity; nearly a quarter believe it's being caused by natural earth patterns. Overall, belief in global warming among Americans has increased 21 percent—from 57 percent to 69 percent—since hitting a low in 2009. Belief in global warming hit an all time high in 2006 and 2007, when more than three quarters of Americans believed the Earth was warming.

Though overall belief in global warming has increased, fewer Americans see global warming as a "serious problem," according to the poll. A third of respondents said it was a "very serious" problem, down 15 percent from 2012.

The poll was taken during March, which has gone on record as being unseasonably cool in many parts of the country. Several recent polls suggest that Americans are less likely to believe in global warming after cool days.