The situation has gotten so bad, we now have…drum roll…night warming: We’ve likely all heard of the many metrics used to gauge how bad global warming is becoming. These include CO2 levels in the air, rising sea levels, and of course, hotter days. But another metric is now worrying scientists and that’s the warming of the summer nights. In parts of the US, night time temperatures have reached records of up to 38°C, according to the New York Times. What is also alarming, is the fact that night time temperatures are rising at nearly double the daytime rate.

Why should you even care? Well, for one, rising nightime temperatures can be deadly. “The combination of high daytime and high nighttime temperatures can be really lethal because the body doesn’t have a chance to cool down during the nighttime hours,” said Lara Cushing, professor of environmental epidemiology at San Francisco State University. Older people, the sick, and young children are especially at risk of overheating during high summer night temperatures. Also at risk are agricultural, construction and other outdoor workers, who can no longer avoid the heat by shifting their hours to work earlier or later in the day.

And for those thinking they are fortunate enough to have avoided the problem with an air conditioner, that’s exactly the type of thinking that has gotten us here. Air-conditioners expel hot air into the atmosphere, exacerbating the problem. The impact of heavy use of ACs on power usage and the burning of fossil fuels that goes with it isn’t doing climate change any favors either.