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With more extreme heat, air conditioning becomes a matter of life and death

According to NASA, last month was the hottest June documented in the past 139 years. And the National Weather Service forecasts record highs, at potentially deadly levels, through the coming weekend. How is climate change related to the extreme heat, and how can individuals and governments prepare for more days of it? William Brangham talks to Astrid Caldas of the Union of Concerned Scientists.

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  • Judy Woodruff:

    With temperatures across the U.S. and around the globe setting record highs this week, William Brangham looks at what science tells us about where we could be headed.

  • William Brangham:

    That's right, Judy.

    Last month was the hottest June on record going back 139 years, according to NASA. And, today, halfway into July, the National Weather Service forecasts potentially deadly temperatures throughout the weekend across much of the United States.

    This week, a study by the Union of Concerned Scientists warned that the number of extreme heat days could more than double by mid-century, just 30 years away, if we don't change how much of those heat-trapping gasses we emit.

    For more on where we are and where we might be going, I'm joined by Astrid Caldas. She's a senior climate scientist at the Union of Concerned Scientists.


  • Astrid Caldas:

    Thank you.

  • William Brangham:

    The skeptics are going to say, look, it's summertime; of course it's hot.

    What can you say — what does the science say about this particular kind of a heat wave over this much of the U.S. and how it relates to climate change?

  • Astrid Caldas:

    Well, this particular heat wave is due to a meteorological phenomena that happens in the atmosphere. So this can happen independently of climate change.

    However, this heat dome that's leading to this heat wave is trapping warmer air, because, as we know, the last 18 years, all the years in this century have been record-breaking years in terms of warming.

    So the thermometer is going up, temperatures are going up. So the heat waves are likely going up also.

  • William Brangham:

    And this trend of more heat waves, longer heat waves, hotter heat waves is what the climate models have always projected, right? This is what we are now seeing.

  • Astrid Caldas:

    That's correct.

    We are seeing more — more extreme heat days. We are seeing more consecutive extreme heat days. And we are slated to see a lot more of these extreme heat days, as you said, if we don't take any measures to reduce the emissions that we pump into the atmosphere, because extreme heat is one of the extreme impacts of climate change that responds very well to the emissions in the atmosphere.

    So, if we have more emissions in the atmosphere, more greenhouse gases, warmer. But if we reduce, they reflect that, and the extreme heat is reduced.

  • William Brangham:

    We know that cities are particularly vulnerable to heat waves. All that concrete and asphalt gets baked in the sun during the day, and then it emits that heat over the night, even when the sun is down.

  • Astrid Caldas:


  • William Brangham:

    And that's particularly dangerous for people.

    Are there things that cities can do from an infrastructure perspective to help protect people from these dangers?

  • Astrid Caldas:

    Well, the idea of green cities is not a new idea.

    As much as you can reduce the amount of heat that is absorbed by those surfaces to be re-emitted at night, the better. And, of course, planting trees is always a good thing.

    Increasing the amount of shade in cities, getting white roofs or green roofs, all this reduces the amount that is absorbed. But, ultimately, in terms of particularly urban centers, infrastructure is going to be built better or adapted to be more resilient to the type of heat that we are expecting to see in the future.

  • William Brangham:

    Another issue, obviously, with a heat wave like this is air conditioning.

    We know it's lifesaving. We know more and more people need it, especially in the developing world. But there's a double-edged sword to air conditioning. It's incredibly energy-intensive. And it's also an emitter of greenhouse gases.

    So how do we wrestle with that in a world that's getting hotter?

  • Astrid Caldas:

    Yes, this is very critical, because we need the air conditioning. More areas in the United States are getting air conditioners, because they're starting to feel the heat, as I always say.

    Seattle last year got a big boom in the sales of air conditioning. Areas that…

  • William Brangham:

    Seattle, Washington, did?

  • Astrid Caldas:

    Seattle, Washington, yes.

    So areas that never had air conditioning traditionally, historically, are starting to get so hot that people are starting to buy air conditioning. This puts a strain on our power grid. That makes the power grid emit more, of course, because we're using electricity, so there's more emissions.

    And in addition to that, the substances that are used in those refrigerators and this air conditioning also, the coolants, are quite potent greenhouse gases also. And they are also contributing to the global warming.

    So, more air conditioning, more emissions, more global warming, need more air conditioning again. And that goes on and on and on.

  • William Brangham:

    A snake swallows its tail.

  • Astrid Caldas:

    Yes, absolutely. It's very tricky.

  • William Brangham:

    Astrid Caldas of the Union of Concerned Scientists, thank you.

  • Astrid Caldas:

    Thank you, William.

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