Last year was the hottest on record, according to NASA. It’s the third year in a row to set a new high for the yearly average temperature on Earth.

Since the late 1800s, temperatures on Earth have increased by about 1.1°C (2°F). “The whole planet is warming up,” says Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies in New York.

The vast majority of scientists agree that the recent warming is human-made. As we burn fossil fuels—such as coal, oil, and gas—carbon dioxide and other greenhouse gases are released into the air. These gases act like a blanket around our planet, trapping heat in the atmosphere.

To find out how 2016 stacked up against previous years, Schmidt and colleagues analyzed temperature measurements from more than 6,000 weather stations and ocean buoys around the globe. Although local temperatures varied from place to place and season to season, data showed that overall the year was the warmest ever recorded.