Nowadays, when there’s a killer heat wave or serious drought somewhere, people wonder: Is this climate change at work? It’s a question scientists have struggled with for years. And now there’s a new field of research that’s providing some answers. It’s called “attribution science” — a set of principles that allow scientists to determine when it’s a change in climate that’s altering weather events … and when it isn’t.

The principles start with the premise that, as almost all climate scientists expect, there will be more “extreme” weather events if the planet warms up much more: heat waves, droughts, huge storms.