2015 Hottest Year in Recorded History

Last year was the hottest ever recorded in history by far, scientists announced Wednesday. In the continental U.S., 2015 was the second-hottest year on record. “The whole system is warming up, relentlessly,” said Gerald A. Meehl, a scientist at the National Center for Atmospheric Research. The rising annual temperatures are reportedly caused by by human emissions of greenhouse gases, scientists said.