Yale Project on Climate Change Communication:

Our most recent survey, conducted in April, 2014, finds that by more than a three-to-one margin, more Americans think global warming is happening than think it is not. Currently, 64% of Americans think global is happening, a number that has been relatively stable over the past three years.

The reality of climate change – worldwide and in the United States – is a well-established scientific fact. The first finding in the recently released 2014 National Climate Assessment (written and reviewed by hundreds of climate experts over the past 4 years), for example, concluded: “Global climate is changing and this is apparent across the United States in a wide range of observations.”

Our survey also shows that Americans’ certainty that the Earth is warming has increased over the past three years. Currently, of those who think global warming is happening, nearly two in three (62%) say they are either extremely (30%) or very (32%) sure that it is. Three years ago, in May 2011, fewer (54%) were as sure. And over the same three-year period, those who think global warming is not happening have become substantially less sure of their position (from 52% in May 2011, to 41% today).

These findings are notable in light of the fact that the survey was conducted shortly after much of the country experienced a particularly cold winter, including the “polar vortex”, suggesting that Americans’ growing certainty that global warming is happening was relatively unaffected by their recent experience of extreme cold weather.