Extreme weather left its mark across the planet in 2016, the hottest year in recorded history. Record heat baked Asia and the Arctic. Droughts gripped Brazil and southern Africa. The Great Barrier Reef suffered its worst bleaching event in memory, killing large swaths of coral.

Now climate scientists are starting to tease out which of last year’s calamities can, and can’t, be linked to global warming.

In a new collection of papers published Wednesday in the Bulletin of the American Meteorological Society, researchers around the world analyzed 27 extreme weather events from 2016 and found that human-caused climate change was a “significant driver” for 21 of them. The effort is part of the growing field of climate change attribution, which explores connections between warming and weather events that have already happened.

To judge whether global warming made a particular extreme weather event more likely to occur, scientists typically compare data from the real world, where rising greenhouse gases have heated the planet over the past century, against a modeled counterfactual world without those rising emissions. This technique has gained broader acceptance among climate scientists in the last decade.