A new study says killer heat is getting worse.
A comprehensive examination of more than 1,900 deadly heat waves says that hot spells like the one now broiling the American West are bigger killers than previously thought and will be more frequent.
Study author Camillo Mora says that even though it will get hotter, such waves may not be as lethal in the future as people become accustomed to the heat.
Mora calculates that nearly one in three people on Earth now experience 20 days a year when the heat can reach deadly levels.
But by the end of the century, he says, nearly three out of four people will endure such stretches if global warming continues at its current pace.
The study is in Nature Climate Change.