I want to give you full disclosure. When I sat down to record today's podcast, I was feeling a little sweaty. No, I wasn't nervous. But the thing is, even after showering, I was still feeling the effects of a workout in the hot Georgia sun. I was finding it really hard to cool down. So as it often happens, our conversation ended up starting off with the weather. What is the weather like where you are today?

Today it's rainy so it's been raining a lot. But yesterday, you know, it was a muggy low 90s.

You know, for a long time, talking about the weather was seen sort of as small talk, something superficial, something to fill in the silence. But today I decided to bring on Dr Gaurab Basu to talk just about that specifically extreme heat, because it seems to be affecting so many parts of the country right now. That includes my home base of Atlanta and near Boston, where Dr. Basu works as a physician, a Harvard Medical School assistant professor and a climate change expert.

So I was saying about this week, my son is in baseball camp right now and so seven years old, very excited. And it was really hot yesterday. And we're outdoors all day. And he had a great time. But he came home and he was really flushed was actually really describing the impact of the heat yesterday.

Here's the thing I've always struggled with, you know, getting flushed, sweaty on a hot summer day that could be seen as just sort of standard summer fare. And it is. But as you're about to hear this kind of heat, the one that we're talking about nowadays, it's far more than that.

Test scores decrease during hot days for kids at school. Gun violence and aggression are increased on hot days. So, you know, across the board mood disorders, schizophrenia, substance use disorder all worsening on dangerously hot days.

It's been called the silent killer, which is kind of dramatic, but people don't realize just how harmful heat can be. This summer, there have been so many reports where heat has turned everyday activities into something very dangerous, very deadly.

270 million people facing extreme and blistering conditions, set to get worse in the coming hours...

And hundreds of people are reported to have died in sweltering conditions in Saudi Arabia during the annual Muslim pilgrimage to Mecca.

Extreme heat is the most dangerous weather phenomenon we have in New York City. In the Northern hemisphere, new science finds that last summer was the hottest since the birth of Christ. Like Doctor Basu, I'm also a dad. I'm raising kids in a world that is getting hot. And as temperatures rise, anxiety about climate change, well, that's rising as well. Even with all of that as the backdrop, Doctor Basu is pretty hopeful about what lies ahead. And that's why I wanted to share this conversation with all of you. You see, it's easy to get anxious, it's even easier to get complacent. And Doctor Basu argues we should not do either.

This is an extraordinary time, Sanjay. We're talking in a year in which there are some 13 straight months of record breaking heat. We hit 1.5°C over the course of a year for the first time ever. So we are seeing kind of climate breakdown in an unprecedented way. And we are also seeing climate solutions breakthrough in a way that truly no one could have appreciated ten years ago.

On today's podcast, we're coming in hot with the science behind heat and how it impacts our bodies. Plus changes we can all make to take better care of ourselves, our loved ones and our planet as the temperatures rise. I'm Doctor Sanjay Gupta, CNN's chief medical correspondent, and this is Chasing Life. When you started getting into this kind of work. Well, what was it that surprised you the most where there are some revelations for you?

'Now, I'll just just acknowledge that I didn't appreciate how much heat matters to our health. The W.H.O. now says it's close to 500,000 people a year die from heat related disease around the world. I mean, it's a major issue. And we are we are massively under-counting the number of heat related deaths. And so I think my big revelation was, a primary care doc that takes real pride in knowing my patients, knowing their lives, being able to picture where they live and work. And I wasn't asking the right questions. You know, I wasn't asking, like, on a very hot day. How do you stay safe? I wasn't really counting my patients properly. So heat is like just on my mind. And the good news is we can be proactive about it. We know when heat waves are going to come a week before, so we can have nurses reaching out to patients who are most vulnerable to heat related disease. We can you know, we're two responsive in medicine to often. And we could be a more proactive because on the same day a heat someone could get very sick or die or not based on their preparation.

Let me ask you this. So just just sort of didactic, let you step outside. It's a hot day. You start sweating. How is that heat actually affecting our bodies and our brains?

'Yeah. So maybe the place to start is our body will fight tooth and nail to keep a equilibrium core temperature. Our body does not want to go up in temperature inside. And so it will work hard to keep that core temperature right where we want it. And so it'll react by changing our metabolic rate. Sweating is the biggest thing, right. Because sweating is the releasing of that heat, increasing our cardiac output, shunting blood flow from like our guts and our intestines to, you know, our skin, so that it's like recalibrating all its functions to kind of immediately react to that heat. And so it will kind of de-emphasize other important functions to kind of fight the heat off. Now, if you have heart disease, if you have other chronic issues, kidney disease, diabetes, your body's ability to react in that way, there's some challenges there. And so if you have underlying health issues that prevent you from doing that, or it's just so darn hot that even in spite of its best efforts, it can't do that. You move from a place of compensated heat stress to decompensated heat stress, which, if you're not able to keep up and get rid of that heat from the body, then you start increasing that temperature inside, and then you start playing with dangerous stuff like inflammatory pathways and cardiovascular harms and then organ failure. And, you know, the ultimate most dangerous thing is heat stroke, where the heat is just inside your body and it causes multi organ failure. So and that can kind of have a positive cascade where it keeps building. But your body's really trying to prevent that from happening by getting rid of that heat as fast as you can.

We know that heat is linked to problems like depression. It is linked to an inability to sleep as well at night. Why is that?

Yeah, the cognition stuff I think a lot about, you know, test scores decrease during hot days for kids at school. Gun violence and aggression are increased on hot days. So there's just so the brain is really so in the middle of all of this. And I appreciate you bringing up the mental health piece because studies are just showing across the board mood disorder, schizophrenia, substance use disorder all worsening on dangerously hot days. And so there's, you know, hypotheses right there. There's different studies out there. And I don't think there's a conclusive mechanism yet. But there's questions of the role of inflammation. I've even seen studies where they talk about, you know, how is heat playing with neuro transmitters during regulation. And I think part of it is just the brain is involved in all that thermo regulation. You know, it's the quarterback saying, all right, we got to change how we're doing everything here. So that takes a lot of fuel up. So there's parts of the brain that are really working hard. And then other parts of the brain that we require for cognition and things like that. Other questions of whether our cortisol levels are increasing and that's causing the mental fog and stuff like that, or blood pressure, you know, increasing might play a role. So there's a lot of hypotheses, but those are some of the kind of mechanisms that are on the table is causing some of these outcomes.

It's called the silent killer. Often heat because we I guess we're getting more data on how many people die of heat related illnesses or heat related deaths every year. But is it difficult to track? I mean, how good is the data, would you say right now, as a scientist.

We got real problems of of counting heat related disease and death. And here's why is that. You know, if you go to the CDC, I think if I'm right, it's something like they they probably said there was like. 1200 Americans who died from heat related disease. That's based on death certificates. So that's based on someone coming in with heat stroke. They came in with a core temperature of 104 degrees. All the signs were there, and they're writing on that death certificate in the emergency room. They died of heat stroke. That is not counting any of those folks who. They had coronary artery disease. They got knocked down a peg on one heat wave. They weren't feeling so great. Their cardiovascular system was trying to hang on. And then they had another heart attack, you know, a day later and come in with a heart attack. You know, their temperature is okay. So, I mean, there's questions of, like, undercounting by tenfold amount or so.

Don't judge me for asking this next question, because I think I think I'm right on this, but but people often talk about but it's a dry heat. Doctor Basu but it's a dry heat where I live. Not as problematic. How much of it is the heat versus the humidity?

I want to maybe emphasize the importance of humidity and maybe let me just explain to you, a wet bulb temperature incorporates humidity into it. So when we talk about temperature, how hot it is outside, we're always talking about just the normal temperature. We're not talking about wet fall. And we should really change that because it's important.

I do want to take a moment and explain the term wet bulb temperature. First of all, I really agree with Doctor Basu. We should be talking about it more. Most people haven't even heard of this. Some scientists say wet bulb temperatures can give us a better idea of how dangerous heat can be to humans, as opposed to just your standard thermometer. And that's because wet bulb temperatures take into account both heat and humidity. Instead of simply measuring the air's temperature. Wet bulb temperatures are measured by wrapping a wet cloth around the bulb of a thermometer. That's how it gets its name. As the water from the cloth evaporates. It cools down the bulb, pushing the wet bulb temperature down. But here's the thing more moisture in the air or humidity means less water will evaporate, and therefore the bulb won't cool down as quickly. And this mimics what happens to our bodies when it is both hot and humid outside.

But humidity is important because at the beginning of our conversation, we were talking about how important sweating is. And so it's really humid. Our ability to dissipate heat and sweat it off gets really limited, and the more humid the more true that is. And so I definitely do not want to say that a dry heat of 110 degrees in Phenix, Arizona is okay because there's so many factors. So there's no one answer here. But humidity is an additional burden that I think we do not, talk about enough to kind of identify as a unique, risk factor and should be aware of a part of how we're analyzing how dangerous a day could be. So. So, yeah, I think dry heat is better than wet heat, but both can be quite dangerous.

Yeah. I feel like we probably, as a general rule, maybe in the media, but weather, weather apps and things like that should be giving the wet bulb temperature as well. It's more data and I think it's, to your point, relevant. What do you among your own patients what do what warning signs do you look for? We hear that the very old, the very young people you mentioned who have underlying heart disease, things like that are going to be more at risk. Are there other things that that are less obvious?

I think about pregnant folks a lot. I think we we should really be thinking about the impacts of heat on obstetrical care and how we're counseling folks. I thing that I worry about Sunday also is nighttime heat. You know, we get so fixated with the, like, eye popping temperatures during the day. And obviously we should, but it's sometimes the heat at night which is not coming down as much as it should. And that might not catch our attention as much. Right. We're like fixated on the 100 degrees during the day. I went down to 85 at night or 88. But the nighttime is a time in which our body really needs time to recuperate. It might be working really hard, and we're feeling okay, you know, and maybe sweating a little bit, but, like, we got through the day, okay? Because our body is just making it happen and it really needs that night time to just chill out and just reset. And so you talked about sleep and that's, you know, a major way it impacts sleep. You know if we don't get that diastole that kind of rest at night, we're setting ourselves up for more danger for the coming days. So I picture an old patient with health issues sweating through the night, and that just feels so undignified. And so it behooves us to to make sure people are in safe places. Can cool off at night while they're sleeping. Well.

I do want to take a minute to just acknowledge, for a lot of people that we've talked to, turning on the air conditioning, even simply staying out of the sun, that really isn't a possibility for them. But one thing I have often wondered as the temperatures get hotter, will we humans change as well? Will we slowly evolve? Is it possible for us to build up heat tolerance? Well, I looked into this a bit. As it stands now, there is some early research to suggest that there is such a thing as acclimating to the heat, the process of gradually increasing the intensity or duration of work in a hot setting over a period of time, to essentially make you more tolerant of it. Obviously, there's a lot that needs to be done about climate change, not minimizing that at all. But yeah, do our bodies acclimate? And you said maybe they do and maybe it can even happen quickly. My brother lives in a much cooler climate than I do, and we both like to exercise and things like that. I'm pretty sure that I've. I'm different than he is at this point. I don't lose as many electrolytes. I am able to stay cooler and be outside longer. Notwithstanding the story I told you where I was sweating even though he was podcast. But he comes to visit me and he cannot deal with that at all.

Yeah. And you know that that the real world has taught us that over time, right? Like, you know, I have family. Like I was telling you, in Atlanta, when it goes from 90 to 95, I'm not too worried about that, but family or friends that are in places that are much cooler throughout the year, 85 to 95, you know, or going up to 85, let's say, you know, a lower high temperature in a place that's not used to it, you know, is is is more dangerous, you know? And so what that teaches us is that, yeah, people have built resilience, and they're able to kind of cope and their body has built up response mechanisms, right, to increase the cardiac output to sweat more quickly. You know, the physiology certainly that is very real, that there is a physiological acclimation to what you are used to around you.

Yeah. And I wonder sometimes of my great great grandkids physiologically will be different than me because of what has happened on the planet.

'Yeah. So listen, I think that, you know, I mean, there's good news in there, right? Like, and I want to kind of make sure I'm not de-emphasizing that, that hey, our body again, it sees things, it reacts, it compensates, it adjusts and can do it durably. That's real. You know, I'm still just worried about the kind of the quick changes that happen. Like the weather could be fine and then a heat wave come in. And maybe the thing that we just need to have caution for, I assume that I'm offering these as notes of caution, is that the people we want to make sure you're acclimating right, are the people with the underlying risk factors. Right. Those are the people who are at most risk of getting really sick from heat. So I just want to maybe put a word in of if we're counseling patients with underlying health issues to get a little bit of exposure, your body's kind of getting used to. They really got to know the right dose of that heat exposure. We definitely don't want to get anyone in a situation where they're getting sick as they're doing that. So I think it just deserves a lot of attention, medical attention and counseling to be done to to communicate carefully.

You know, I never really considered how much or how quickly our bodies might acclimate. It's kind of extraordinary if you think about it. But remember this you can acclimate back to being less tolerant of heat quickly as well. So if you're thinking of trying something like this, take Doctor Basu's advice. Always listen to your body and go slow. We're going to take a short break here, but when we come back, Doctor Basu and I are both dads first and foremost, how he views the future for his kids and yours more in just a moment. One of the reasons we wanted to talk to you is that you've been talking about this. You've been a voice in the climate change space for some time, and you're a doctor who treats patients. How did this all come about for you, Laura?

'Yeah, well, I'll tell you, I did not think about climate change for most of my life. Most of my career. I was a little embarrassed to say that, but, you know, I'm a primary care doctor that works at a community health center and really love taking care of my vibrant immigrant patient population there. I did global health in India and Liberia, so kind of identify as a global health doc. And so climate change was all around me, but I couldn't see it. And I was kind of in this mindset. I remember talking to friends of the environment is important, but there's people suffering and we got to take care of people. And that was a real misunderstanding because I now understand you can't take care of each other as people without taking care of our planet. And in 2018, there was that big U.N. report, the IPCC report. I think it was a light bulb moment for many people. For me, it was, it's like a thunderbolt moment, really. It really changed my life. I was it was like a Sunday morning in October and still, like, really palpable. You remember it. And I was waking up and just kind of grabbed my phone. And the first big headline, New York Times, was severe concerns about the impacts of climate change sooner than previously understood. And my wife was pregnant at the time. We have a two year old, and I had a visceral reaction, I'll tell you. Like I was shaking kind of as a wait a minute, like I did not understand this properly. I kind of thought someone out there had a plan - we were moving. We weren't moving as fast as we should, but we were making steady progress. We were getting there. And you know that news article linked to the actual report and I, I went downstairs and I like handed my phone to my wife and I, my hand was shaking as I was giving it to her, you know, saying, I think this is a lot worse than I understood. Then it just something change, you know, and I think some people understand this over time. For me, I couldn't see it. And then suddenly I could see it everywhere. And all these issues of human rights and global health and the health of my patients in my clinic, I just suddenly realized that this was in the middle of all these things I cared about. I let's just spent months and months after everyone went to sleep. I'd stayed up late at night and was just studying and trying to understand what what it meant for what I wanted to do. And the connection finally, for me, was that climate change was in the middle of all of that, and stopping these emissions and and taking care of our planet was just foundational to that stuff I cared about.

I have to tell you. So my kids are older than your kids. I'm older than you are. So my kids are 19, 17 and 15. And I remember my 17 year old who I guess was 11 or 12 at the time. She's, first of all, a kid who seemingly had her whole life organized at a very young age. She knew exactly what she wanted to do with their life and and how old she was going to be when she got married and where she wanted to live, and how many kids she wanted to have. It was it was it was a kind of a source of comedy, but that's just who she is. And then I think it was right around that time group. I remember sitting down to dinner one day with her and saying, so how's all the planning going, you know, for the rest of your life? And she made some common to me like that's not going to happen anymore. And I said well you know, what do you mean. And, and she basically I think at school that day it had some primer on what had happened with that climate change report. Yeah. At her level, you know, a sixth grade sort of level. And the impression she was left with was cat's out of the bag, and and we're not going to be able to to get a hold of this.

Yeah.

And it was a really interesting thing as a parent because on one hand you you always want to be Mr. Fix It. So how do you how do you handle that when you're talking to your kids?

Yeah. I'll start by saying I stay up late at night worried about this, and feel a tremendous sense of responsibility as an adult in the room and a sense of responsibility to all our children. And it is scary. And here's where I land on that Sanjay is that like the world has always been full of of immense suffering? When you look at poverty over the last decade and how much that's improved, you look at all life expectancies that there's tremendous suffering in the world. And, you know, my parents and grandparents, their life in India are great examples of this. And so every generation has these challenges of how we're going to make a better world and how we're going to fight against these great threats to our health and safety. And this is a pretty big one because it encompasses all of us on this great planet we live on. But I also think that it's critical in this work to realize the work of advocating for climate solutions is also about navigating hope and despair among all of us. And and that takes something different. That takes courage. It takes persistence. It takes imagination that we can transform the things that sometimes don't feel possible or actually happening all the time. And so I have a real concern about this, Sanjay, about the kids these days and the kind of information they're getting. And obviously, there's the folks who are denying climate change and science, and they've got their agenda. And there's also the folks are just spreading despair and doom and taking hope away from our children. And that is so wrong. If you're going to say the world is over, you better know that. Sure, you better know that that you're totally right about that. And the science does not say that. We have made extraordinary progress over the last ten years. You're really looking at apocalyptic outcomes three four degrees Celsius of warming by the end of this century. And we're not going to do that anymore, because solar is the cheapest form of energy that is just taking off in wind, in batteries. So those kind of transformative exponential growth changes are the kind that we need year in and year out, decade in, decade out. And I see the pathway forward of how we can have the best days in front of us where we are healthier, more safe, more just, and our planet is in better shape.

I gotta say, it's really it's really well said Gaurab. I've thought about this a lot. I've had this conversation with a lot of colleagues and friends and family members, and it is it feels existential. It feels overwhelming at times. And but I think the point that you're making that, first of all, part of addressing this is also addressing the, the value of, of optimism. I think there's some parallels, probably to just being a doctor. I mean, you have to give bad news to patients all the time, I'm sure. But if you abide by this principle that there are some intrinsic value to hope. Yeah. Then then I think it does frame how you present things. And it's not to be euphemistic. It's not to be Pollyanna in some way. But it is. It is. It's real. Right?

Yeah. I honestly, you know, this stuff feels dark and paralyzing, overwhelming, like you said. And so it it it makes it dig deep about your, your values, your beliefs about the world. Right. This is an extraordinary time, Sanjay. We're talking in a year in which there are some 13 straight months of record breaking heat. We hit 1.5°C over the course of a year for the first time ever. So we are seeing kind of climate breakdown in an unprecedented way, and we are also seeing climate solutions breakthrough in a way that truly no one could have appreciated ten years ago. So I feel urgent and passionate about this, and we've got to keep going with all the are guiding principles of society to move forward. And I feel conviction and courage. I would say more than anything, because we have everything we need. We have the solutions to turn. Cause I'm confident it's a heck of a lot of work. And I don't want to oversimplify this, but we know what we need to do. We've made a ton of progress since that day in 2018, and I'm I'm much more positive of the path forward today than I was when I started on this journey six years ago.

You have this incredible platform now, and you're you're obviously a leading voice on this. You're father, doctor. You talked about the fact that you're an optimistic guy as well.

Yeah.

The name of the podcast is Chasing Life. How do you chase life?

The risk of sounding cheesy here. I think we're built to take care of each other. I'm really. You know, it's from my family's story to my patients. I see people doing extraordinary things in their lives. What I would say is climate solutions is about chasing life. And so I would ask people to know your power in your community. It's not about being a doctor or a climate scientist or an expert in this. This is about expressing your concerns to your neighbors, to your schools, to your churches to say, hey, I'm really worried about this. Is there something small we can do? And if we can hold this thing together and everyone chips in just a tiny bit, in their own way and their own voice, I'm telling you, we have everything we need to have our best days ahead of us.

What a pleasure talking to you. Thank you so much for your time.

Thank you. Sanjay, it's great to be with you.

'So often issues like climate change can feel so big, maybe so unsolvable. But I think the point that we were getting at is that there is value in hope. Just in hope, there is intrinsic value. And as you heard from Doctor Basu, there is good reason for hope. This isn't misguided hope. And there is no room, no time, no value in despair. I hope that you agree and you got a little bit of optimism from today's episode. Now, before we say goodbye, we're starting a new segment titled Doctor Sanjay Gupta on Call, where you guessed it, I'm going to be on call. I'm going to be answering your questions along with some of the most knowledgeable people in the world. And we're going to talk about a bunch of different topics. You can ask us almost anything, whether it's about something you've heard on the podcast, something you've seen in the news, or maybe something that's just a burning medical question you've always wondered about. I'd love to hear from you. So record a voice memo and email it to ask sanjay@cnn.com, or you can give us a call (470) 396-0832 and leave a message. I'm here to help and I can't wait to hear from you. Chasing Life is a production of CNN audio. Our podcast is produced by Eryn Mathewson, Jennifer Lai, Grace Walker, and Jesse Remedios. Our senior producer and showrunner is Felicia Patinkin. Andrea Kane is our medical writer, Dan Dzula is our technical director. And the executive producer of CNN Audio is Steve Lickteig, with support from James Andrest, John Dionora, Haley Thomas, Alex Manisseri, Robert Mathers, Leni Steinhart, Nicole Pass-through, and Lisa Namerow. Special thanks to Ben Tinker, Amanda Sealy, and Nadia Kounang of CNN Health and Katie Hinman.