Heat Waves America's Deadliest Weather Disaster; Don't Have To Be

"Heat waves are quickly becoming one of the world's deadliest weather phenomena. In the United States, extreme heat now kills more people each year than tornadoes, hurricanes, or flooding. And a massive heat wave, like the one that hit Europe in 2003, can kill tens of thousands in a blow.

What's more, without big changes, scientists are predicting that heat waves will get far more lethal as global warming unfolds. One study projects that US heat-wave deaths could rise to 3,500 per year or more by mid-century if the planet keeps heating up.

One reason for that? More and more people are moving to cities. And cities are heating up even faster than surrounding rural areas due to the "urban heat island" effect. All that concrete and asphalt tends to absorb additional heat. On top of that, as cities get hotter, more people use air conditioning — and the waste heat from that A/C can warm a city up a couple of extra degrees, making things even hotter for people who don't have it."

Brad Plumer reports for Vox September 8, 2014.