Guardian: The number of Americans who believe in global warming has plummeted, falling 20% in two years, a survey said today. Only 57% of Americans believe there is solid scientific evidence that the Earth’s atmosphere is warming, said the poll of 1,500 people by the Pew Research Centre for the People & the Press. That is a fall of 77% from 2007. The number of people who believe that human activity is causing global warming also fell to just 36%. The public uncertainty about …