Scientists say 2020 was either the hottest year on record or a close second or third. Several weather groups Thursday calculated that 2020 globally was extremely hot, but just how hot depended on who was measuring and how they were doing it. Some groups, including NASA, said it was the hottest year, while others including the U.S. and British weather agencies, said it was a close No. 2. Either way, they said the hottest six years on record have been the last six, and that Earth is clearly warming because of the burning of coal, oil and natural gas.