You're listening to Shortwave from NPR.

Hey, Shirt Wavors, Regina Barber here with Lauren's summer,

one of NPR's climate correspondence.

Hey, Lauren.

Hey, Dina.

So today, we're starting with an experiment that's designed to make you sweat.

Well, I am an already sweaty person,

and actually thinking about climate change doesn't help,

but you know I'm going to do it, I'm ready.

Okay. Well, then this is going to be like the perfect Venn diagram of that.

It's at Penn State University inside this climate-controlled room.

And if you're in the study, you go in and you either sit there

or walk slowly on a treadmill.

Okay, that doesn't sound so bad. I could do that.

Yeah, well, here's what Professor of Physiology, Larry Kenney, does next.

We start to increase the humidity every five minutes in a stepwise fashion.

Okay, that sounds awful. As a West Coaster, I am very bad with humidity.

Yeah, I am too. And in that room, it's getting really muggy.

And then the test subjects, they've also all this tiny electronic device

that shaped like a pill, and it records their core temperature.

Cool. And what Kenney is looking for is what he calls the critical environmental limit.

The combination of temperature and humidity beyond which either they can't sweat enough

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