13% of Americans have never heard of global warming,

even though their country is the world’s top source of greenhouse gases, a 46-country survey showed on Monday. Some 57 percent of people around the world considered global warming a “very serious problem” and a further 34 percent rated it a “serious problem.” People in Latin America “were most worried while U.S. citizens were least concerned with just 42 percent rating global warming ‘very serious.’”