By increasing the energy stored in our atmosphere, climate change is expected to generate more severe storms and heat waves. Severe storms and heat waves, however, also happen naturally. As a result, it’s tough to figure out whether any given event is a product of climate change.

A corollary to that is that detecting a signal of climate change using weather events is a serious challenge. Are three nor’easters in quick succession, as the East Coast is now experiencing, a sign of a changing climate? Or is it simply a matter of natural variability?

A team of researchers has now looked at heat waves in the US, trying to determine when a warming-driven signal will stand out above the natural variability. And the answer is that it depends. In the West, the answer is “soon,” with climate-driven heat waves becoming the majority in the 2020s. But for the Great Plains, the researchers show that a specific weather pattern will push back the appearance of a warming signal until the 2070s.