Nature Quest: Are Summers Getting Hotter?

Much of the country is deep in the middle of a heat wave right now. And every summer, Duane Stilwell's town in Arizona seems to get hotter. It has him worried — and he's not the only one. Since 1980, the average number of heat waves https://repository.library.noaa.gov/view/noaa/61592 in the U. S has doubled and the average length of a heat wave season hasincreased from 40 days to 70 https://web.archive.org/web/20250611192628/https://www.globalchange.gov/indicators/heat-waves. Future summers, experts say, will be even hotter https://www.npr.org/2022/07/23/1113142529/opinion-blistering-summers-are-the-future. But why exactly is that happening, and what can people do to protect themselves from the heat? This episode is part of Nature Quest, a monthly segment that answers listeners' questions about their local environment. If you have a question, send a voice memo to [email protected] mailto:[email protected] that includes it, your name and where you live. We might make it into our next Nature Quest episode! Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

  This message comes from Doppel. Social engineering attacks come in disguise, but Doppel sees through them. The Agentic platform shuts down threats, turns employees into first line defenders, and more. Learn more at D-O-P-P-E-L dot com. You're listening to Short Wave from NPR.

• 0:24Emily Kwong?

  Hey, everyone. Emily Kwong here with producer Hannah Chin, who is bringing us this month's listener question for Nature Quest, my favorite series ever. Okay, Hannah, who's the question coming from?

• 0:35Speaker 02

  This question comes from Dwayne Stillwell. He's 68, and he's lived a lot of different lives in a lot of different places.

• 0:42Speaker 03

  I've lived in Cleveland, in Chicago, New York City.

• 0:45Speaker 02

  Dwayne grew up working summers as a delivery boy in the lush green of Mexico City. He taught chemistry in the dry heat of California, and he even worked as a railway swittemint, tamping down snow in below freezing temperatures in the Midwest. Basically, he is no stranger to extreme weather. And when he retired and moved to the American Southwest five years ago, he kind of thought he was there to stay, that Guadalupe, Arizona, just outside of Phoenix, was his forever home.

• 1:12Speaker 03

  I pretty much thought this was going to be the last place I'd have to move. And I'm tired of moving, you know?

• 1:21Emily Kwong?

  Yeah, I feel that. He's lived a lot of places. He's ready to settle.

• 1:25Speaker 02

  But now, he's not so sure. Because Emily, over the past four years, the summers where Dwayne lives have become longer and hotter and more dangerous. Last year, Dwayne said there were 113 days in a row above 100 degrees Fahrenheit. His fig trees stopped producing fruit, some of the cacti in his yard started dying, and his neighbor, who's an older guy who lives across the road with his family, passed from heat stroke.

• 1:52Speaker 03

  It's forbiddingly hot. In other words, you know that if you stay outside, you can die.

• 1:58Speaker 02

  Since 1980, the average number of heat waves in the US has doubled, and the length of an average heat wave season has increased from 40 days to 70. We are facing a future with more summers like this.

• 2:13Speaker 02

  So this month's nature quest? Extreme heat. How it's linked to climate change, why humidity makes it worse and more deadly, and how you heatproof your life for the future. You're listening to Short Wave from NPR.

• 2:35Speaker 00

  Stay tuned for the following announcements and messages from our sponsors.

• 2:39Speaker 04

  This message comes from Bowlin Branch. Change the way you sleep with soft, 100% organic cotton bedding from Bowlin Branch. Designed to help you fall asleep faster and never sleep hot while wrapped in luxurious comfort, airy blankets, cloud-like duvets, and breathable sheets. Experience pure comfort and feel your bedding get softer with every wash. Discover the difference with 15% off your first order at bowlinbranch.com with code NPR. Exclusions apply. See site for details. This message comes from Google Workspace with Gemini. One subscription that does it all. Personalized AI and premium business versions of Gmail, Google Docs, Drive, and more.

• 3:21Speaker 04

  Try it free for 14 days at goo.gle/workspacewithgemini.

• 3:28Speaker 00

  This message comes from Mint Mobile. While others have been hiking your bill, Mint Mobile has kept their wireless plans starting at $15 a month. Switch to Mint Mobile and get three months of premium wireless service for $15 a month. Go to mintmobile.com/switch. Upfront payment of $45 for three-month plan required. $15 per month equivalent. New customer offer, first three months only, then full price plan options available. Taxes and fees extra.

• 3:54Speaker 02

  OK, Short Wavers, we are on a nature quest. This is our monthly segment that brings you a question from a fellow short waiver who is paying attention to the environment around them and the ways that it's changing. And this month, Emily Kwong is looking into extreme heat.

• 4:09Emily Kwong?

  Yeah, I want to take you back to the summer of 2022, when COVID restrictions started to loosen and that Kate Bush song, "Running Up That Hill," was everywhere.

• 4:22Speaker 02

  I love an 80s bop.

• 4:23Emily Kwong?

  Right? I remember listening to that song thinking, this is so good. And also, this 80s synth will not save me. It is just too hot. I have to go inside.

• 4:33Speaker 02

  Yeah. I mean, it was that same summer that I think heat records were breaking around the world in Europe and in China. I even remember the US Secretary of Commerce at the time, Gina Raimondo, she said that this summer is likely to be one of the coolest summers of the rest of our lives.

• 4:50Emily Kwong?

  Yeah, hot as it was. So I want to talk about the physics of why this is happening and why the Earth, which does have natural variations in temperature, cannot simply correct for this much warming.

• 5:02Speaker 05

  As my PhD advisor would say, if you believe in thermometers, you believe in global warming. It is an observation of what is occurring.

• 5:11Emily Kwong?

  This is Justin Mankin. He's a climate scientist and professor of geography at Dartmouth. And he reminded me that greenhouse gas is just a term that scientists use to describe any gas in Earth's atmosphere that traps heat. So water vapor is a greenhouse gas.

• 5:24Speaker 02

  Oh, I didn't know that.

• 5:25Emily Kwong?

  Yeah, but the gases that have been on the rise since the Industrial Revolution because of humans emitting fossil fuels, the gases we're all so worried about, are carbon dioxide, methane, and nitrous oxide. You can think of our atmosphere almost like a bathtub. It gets full. And typically, Earth's forests and oceans and soil act like a drain. They sequester carbon in the long term, bring our planet back into equilibrium, the bathtub empties. But because human activity is emitting more greenhouse gases, the drain is getting clogged.

• 5:56Speaker 02

  Oh, so the bathtub, like our atmosphere, is filling up.

• 6:01Emily Kwong?

  Yeah, just as the water level in a bathtub fills up to push water down a clogged drain, so too does the Earth warm.

• 6:08Speaker 05

  The planet needs to heat up to ensure that the amount of energy we're receiving from the Sun is balanced by the amount of energy Earth is sending out to space.

• 6:17Emily Kwong?

  Justin says this is called radiative balance.

• 6:20Speaker 02

  Radiative what?

• 6:22Emily Kwong?

  It's kind of how the Earth and Sun do what they do. And it's governed by the unchanging laws of physics. So one law says that all matter that has a temperature radiates energy. The sun, which is very hot, radiates energy. The earth absorbs that energy and heats up too. And another law of physics says that hotter objects will emit more energy, essentially shed that energy to achieve radiative balance.

• 6:47Speaker 02

  Okay, so the earth has to shed its heat?

• 6:50Emily Kwong?

  Yes, and that's because of the law of the conservation of energy, right? Energy cannot be created or destroyed. What goes in has to equal what comes out, so the earth must achieve equilibrium. And we experience that as warming. Hotter temperatures here on earth.

• 7:04Speaker 02

  Right. And longer summer heat waves.

• 7:07Emily Kwong?

  And also humidity, which is going up in some places.

• 7:11Speaker 02

  Right, because when the humidity is worse, our bodies are less efficient at evaporating sweat.

• 7:15Emily Kwong?

  Yeah.

• 7:16Speaker 02

  And then if our sweat doesn't evaporate, our systems literally can't cool down.

• 7:20Emily Kwong?

  Yeah, and when our bodies can't cool down, that is when you put yourself in danger of heat exhaustion, or heat stroke, or even death. And when we talk about heat-proofing our future, the most important thing to think about is that your location, your geographic location, will be the biggest factor in determining how you experience extreme heat.

• 7:40Speaker 02

  I mean, Emily, you and I have talked about the urban heat island effect, where buildings and roads and other infrastructure basically trap heat and make these urban areas hotter.

• 7:49Emily Kwong?

  Yeah.

• 7:50Speaker 02

  This disproportionately affects poorer communities and communities of color, because those areas already tend to have fewer parks and trees.

• 7:56Emily Kwong?

  Right, so a key adaptation to extreme heat is to green the landscape, especially urban landscapes, by expanding parks and community gardens and installing green roofs.

• 8:08Speaker 05

  Vegetation siphons water from below the land surface and sends it to the atmosphere through transpiration, which is a form of evaporation. And evaporation cools, and so it's a really effective way of wicking heat away from the surface.

• 8:24Emily Kwong?

  And there's another adaptation I want to talk about, Hannah. Cooling centers. Cooling centers are air-conditioned, public or private spaces. They're a real tool in the state of Arizona. Nick Staub is the incident commander for extreme heat response in Maricopa County, where our listener Dwayne lives. And the reason I wanted to talk to him is because by the department's count, heat-related deaths in Maricopa Did go down last year, and it is in large part because the county is making an effort to care for those who are most vulnerable.

• 8:55Speaker 06

  Those who are at highest risk in our community are those who are unsheltered, those who are, you know, spending their nights out on the street.

• 9:02Emily Kwong?

  Typically at night, you know, the temperature drops and people's bodies have a chance to recover from the heat exposure during the day. But Nick gets worried when he sees a forecast with a string of high overnight temperatures of nights above 90 degrees Fahrenheit. And people who don't have regular access to shelter aren't the only high-risk groups. Other groups include children, older adults, people who are pregnant, people who work outdoors, and many more. Kim McMahon, the Public Weather Services Program Manager at the National Weather Service, put it this way.

• 9:33Speaker 07

  The more susceptible you are, the more exposed you are, the greater your chances of feeling those impacts from heat, starting to get heat rash, starting to get heat exhaustion before, say, somebody who works in an air-conditioned office building.

• 9:48Emily Kwong?

  So in response to these heat-related deaths, the Maricopa County Department of Public Health decided to expand their heat relief network. A whole bunch of organizations came together to keep cooling centers open longer into the evenings, on weekends, holidays. The county also opened up these respite centers, places with blankets where people can lie down and even sleep for a few hours.

• 10:11Speaker 02

  Right, so that they can rest and they can cool off.

• 10:14Emily Kwong?

  Mm-hmm.

• 10:15Speaker 06

  And then we put a big effort into advertising the heat relief network as well as getting consistent street signage printed so that we could put them outside of the centers so people could see those signs and know it was a cooling center.

• 10:28Emily Kwong?

  Hmm, so did it work? Like, has it been successful? It has. At least in 2024, the number of heat-related deaths that they counted went down. But...

• 10:39Speaker 06

  We still had over 600 heat-related deaths in 2024. So while we are encouraged by the reversal of the trajectory, there is still a lot of work to be done.

• 10:51Emily Kwong?

  And of course, as with all public health data, undercounts are always a possibility. Summers in Arizona will only get hotter, and not everyone may want to stay.

• 11:00Speaker 02

  Right. I mean, everybody is different. Every community is different.

• 11:04Emily Kwong?

  Mm-hmm.

• 11:05Speaker 02

  You mentioned that several European countries have these heat early warning systems.

• 11:09Emily Kwong?

  Yeah.

• 11:09Speaker 02

  And I'm pretty sure we have something similar in the US, because I know I have gotten texts about, like, extreme heat.

• 11:14Emily Kwong?

  Yes, let's end on this. Early warning systems. So in the US, we have a system of weather emergency alerts, which can be sent directly to your device as a text message or a notification about a flash flood or a thunderstorm, or an extreme heat advisory. And one of the main participants in this system is the National Weather Service.

• 11:31Speaker 02

  Huh, OK. So how does the National Weather Service think about heat? Like, what are they doing to address it?

• 11:37Emily Kwong?

  Well, the National Weather Service is responsible for all weather forecasting in the US. They do science. And one of the tools they use is the heat index. The heat index is a measure of how hot it feels to the human body when relative humidity is combined with air temperature.

• 11:51Speaker 02

  Oh, that's why, like, if I scroll down on the weather app on my phone, like, when I look at the daily forecast and then I swipe up, there's this feels-like temperature, and it's sometimes a little bit different.

• 12:01Emily Kwong?

  Yeah, it's like the heat vibe, you know? And it often feels more accurate because humidity is factored in. So that's the forecasting system. But then you also need a warning system, right?

• 12:10Speaker 02

  Right.

• 12:10Emily Kwong?

  Over the years, each local forecast office of the National Weather Service has developed a unique set of thresholds for when in that community the outdoor conditions trigger a heat watch, or a warning, or advisory. But it's not a foolproof measure, Nick pointed out to me, for assessing your personal risk.

• 12:29Speaker 06

  We see a significant number of heat-related deaths on days that are not an extreme heat warning, which is why our messaging to the public is, you need to plan all summer long.

• 12:41Emily Kwong?

  The heat index values are calibrated for shady locations, which means this heat early warning system does not fully account for people being in direct sunlight. And that can be 15 degrees hotter than in the shade.

• 12:52Speaker 02

  Wow. OK, so basically, don't wait for that text message to change your outdoor plans.

• 13:01Speaker 02

  I mean, under these circumstances, I guess I'm wondering, what can people realistically do about it? Like, if they know a heat wave is coming and they're worried?

• 13:09Emily Kwong?

  Yeah, so assess, you know, where you live, your individual heat tolerance. But if you know it's about to get really hot, you have to take precautions. For Nick in Arizona, it's about treating all Maricopa County summers like a heat watch is constantly in effect.

• 13:24Speaker 05

  Plan your outdoor activities wisely. Don't be outside during the heat of the day.

• 13:29Emily Kwong?

  Install dark curtains, take cold showers, check in on friends and family and neighbors to make sure they're doing OK while the heat wave is doing its thing. It's all good advice, but I was not totally satisfied with some of these answers.

• 13:42Speaker 02

  Huh. Wait, how come?

• 13:44Emily Kwong?

  Because individuals and local governments can only do so much. We cannot cold shower our way out of this.

• 13:51Speaker 02

  OK.

• 13:52Emily Kwong?

  Justin says ultimately, it is fossil fuel emissions that are the root of the problem.

• 13:57Speaker 05

  Mitigating our greenhouse gas emissions is going to be the clearest way to prevent additional warming and extreme heat risks. And we have the tools to do it. We have had policies in place to help achieve it. And neglecting the problem is not going to make it go away.

• 14:17Emily Kwong?

  It's only going to make the world hotter.

• 14:21Speaker 02

  Emily Kwong, thank you so much for bringing us this reporting.

• 14:24Emily Kwong?

  You're welcome, Hannah. Thank you, Dwayne, for the great question.

• 14:30Emily Kwong?

  Shortravers, if you have a question about changes in your environment, email it to us at [email protected] and we'll consider it for a future Nature Quest episode. The series comes out the last Tuesday of every month. Special thanks also to the National Weather Service and to Alejandra Barunda and Julia Simon on NPR's Climate Desk.

• 14:49Speaker 02

  This episode was produced by Hannah Chin, that's me, and Rachel Carlson. It was edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts. Jimmy Keely was the audio engineer. Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Hannah Chin.

• 15:05Emily Kwong?

  And I'm Emily Kwong. Thanks for listening to Shore Wave from NPR.

• 15:21Speaker 04

  Stay tuned for the following announcements and messages from our sponsors.