All five of the hottest years on record have occurred in the last five years, according to global temperature data released Wednesday by NASA and the National Oceanic and Atmospheric Administration.
While 2018 was slightly cooler than the three prior years, Earth still had its fourth-warmest year since scientists began keeping records in 1880, the federal agencies said. Their separate analyses add to decades of evidence that the burning of fossil fuels, the clearing of forests and other human activities are releasing heat-trapping greenhouse gases into the atmosphere and causing the planet to warm.
If you smooth out these year-to-year variations and look at the big picture, the overall trend in the past few decades is one of accelerating change, said Alex Hall, who directs the Center for Climate Science at UCLA and was not involved in either government analysis. We are seeing more and more warming that is happening at a faster and faster rate.