As a heat wave roasted the western United States this week, temperatures in California’s Death Valley soared to a blistering 130 degrees Fahrenheit, marking the hottest temperature measured anywhere on Earth since 1931 and the third hottest day ever recorded on our planet, period.

But Earth has seen warmer days in its past and it will experience them again in the future. During so-called hothouse periods, when the atmosphere was supercharged with greenhouse gases, the planet was much warmer than it is today and the worst heat waves were correspondingly nightmarish. And while human carbon emissions haven’t pushed Earth into a new hothouse state yet, climate change is making heat waves more frequent and severe, meaning Death