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  • There's a reason that summers in the city are so hot.

  • And it's probably easiest to explain why with thermal vision.

  • It shows the heat all around me and also the coldness of this ice cream cone.

  • Cities are often hotter than their suburbs due to a phenomenon known as the heat island effect.

  • All of that asphalt, concrete, dark rooftops and tall buildings, they absorb and store heat.

  • And there are a lot of people using a lot of energydriving cars, riding subways, running the AC.

  • All of these materials and activities either create or retain heat.

  • And all that stored heat causes steeper nighttime highs when people would otherwise have a chance to cool down.

  • The way all these heat-storing elements are laid out matters quite a bit.

  • In cities laid out in grids, like Phoenix, Chicago, or Washington, D.C., the buildings are closer together, like closely packed coals in a fire, keeping heat in.

  • More space between buildings creates more circulation.

  • Another way to combat this heat island effect is through green space.

  • Parks, trees, plants, they don't absorb as much heat.

  • They actually send water back into the atmosphere.

  • Between all those hot buildings, that cools things off.

  • Another solution is color.

  • Light colors reflect sunlight back into the atmosphere instead of storing it as heat.

  • It's easiest to see in crosswalks, and it's true for the color of buildings and other urban surfaces, too.

  • And one long-game way to combat the heat island effect is to avoid using air conditioning when you don't need it.

  • AC uses a ton of electricity and creates a feedback loop.

  • When we get that electricity from coal or natural gas, that puts more carbon dioxide into the atmosphere, which warms the planet making cities even hotter.

  • But this isn't just about comfort.

  • Today, heat waves kill more people than any other extreme weather event.

  • More than tornadoes, hurricanes and even floods.

  • City populations keep growing, and those cities are only getting hotter.

  • This is Let's Talk, NPR's news explainer show.

  • Make sure to subscribe to our YouTube channel and check out other shows.

  • I'm Christopher Joyce, and this is NPR.

There's a reason that summers in the city are so hot.

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