How to save a billion lives from extreme heat

A review of interventions and their price tags, from the personal to the planetary

I recently learned that the US spends $4.9 trillion every year on healthcare, or 17.6% of our GDP. In 2023, we spent a comparatively meager $820 billion on defense. And our spending on climate adaptation and resilience topped out at just $23 billion. But for anyone who’s paying attention, these three categories and their costs are starting to converge in the most unpleasant of ways.

Today, I want to talk about climate change and public health, how costs factor in, and how the solutions might surprise you.

Extreme heat — a silent and expensive killer

Image Source: National Oceanic and Atmospheric Administration, Climate.gov

New research estimates that extreme heat will cost the US an additional $1 billion in healthcare expenditures every summer as more people experience health complications and require care. But what does that mean? Are millions of people going to show up at hospitals with heat stroke?

Extreme heat impacts public health in a multitude of ways. For me, it was helpful to organize them into first, second and third order effects of extreme heat conditions.

Primary effects

The primary effects of extreme heat are the obvious effects of heat exposure like heat exhaustion and heat stroke. These are usually the minority of cases that show up at hospitals and clinics during extreme heat events.

Secondary effects

The second order effects of extreme heat happen when people have underlying conditions that can be aggravated by heat: cardiovascular disease, diabetes, hypertension, pregnancy and old age. Around 48% of the US population has cardiovascular disease, 12% have diabetes, and 47% have hypertension with some overlap between these three highly prevalent conditions. The numbers are sheer insanity on their own, and deserve a pause.

Translating these percentages, we get:

• 158 million people have cardiovascular disease

• 39 million people have diabetes

• 155 million people have hypertension

Given the significant overlaps between these groups, in total an estimated 209 million people in the US have CVD, diabetes or hypertension, and are therefore at heightened risk during extreme heat.

It’s not just the conditions themselves, either. Common medications that people take for these diseases also increase their risk of bad outcomes — for example beta-blockers can limit the body’s ability to sweat and respond to heat stress, and ACE inhibitors can lead to heat-related kidney damage.

But how much additional risk are we talking about here? Many people, myself included, hear “extreme heat” and tend to imagine the sweaty discomfort we’ve felt during a heat wave, but let’s be clear: discomfort and inconvenience aren’t what we mean by extreme heat risk.

Cardiovascular disease

• The 158 million Americans with CVD are 2–5X more likely to experience heart attacks or strokes compared to the general population during extreme heat.

• Heat aggravates preexisting conditions by increasing blood viscosity, forcing the heart to pump harder to dissipate heat, and potentially triggering arrhythmias.

Diabetes

• During extreme heat events, the 39 million Americans who have diabetes are 2–3X more likely to experience heat-related death outright.

• That’s because dehydration concentrates blood sugar (even further) and increases the risk of hyperglycemia and diabetic ketoacidosis, both of which are life-threatening.

• For the up to 70% of diabetics who have diabetic neuropathy (nerve damage), it can be hard to sweat efficiently or even to sense overheating — putting the body at greater risk of heat stroke.

• Extreme heat also puts injectable insulin at risk, since insulin is a cold chain product.

• For more on this, I highly recommend Ratter-Rieck, Roden and Herder’s paper, “Diabetes and climate change: current evidence and implications for people with diabetes, clinicians and policy stakeholders”

Hypertension

• The 155 million Americans with hypertension are 2X more likely to face hospitalization or mortality from extreme heat.

• People with high blood pressure have a harder time cooling down because of impaired blood vessel elasticity.

• As mentioned above, antihypertensive medications like beta blockers and ACE inhibitors can make heat stress much worse.

In other words, for 209 million Americans, a heat wave isn't just gross and sticky — it's a potential emergency that creates a cumulative, population-level impact due to the sheer sizes of these groups. Even modest increases in risk could translate to tens of thousands of additional deaths or hospitalizations during major heat waves that are increasingly hitting larger geographical swaths.

The 2003 heat wave that hit France caused 1,500 excess deaths per day during its peak, totaling 71,449 additional deaths over its 6-week course — similar to the earliest (but not the peak) COVID numbers in Europe. While COVID's peak numbers dwarf heat's direct impact at the national and international scales, heat waves are highly localized and concentrated and could impose similar levels of stress — and cost — on healthcare systems in affected regions.

*As a total aside, many people don’t know that my main non-climate passion is cardiovascular disease and metabolic health, where I’ve spent more than 200 hours reading, listening and measuring! Thank you for allowing me to indulge my hobby here on Climate Money, and for more and better content on this topic, I highly recommend spending some time on PeterAttiaMD.com, checking out Peter Attia’s bestselling book Outlive, or following the incredible lipid luminary Tom Dayspring on social media.

The above second order effects of extreme heat are responsible for a large percentage of the uptick in hospitalizations during heat waves, but extreme heat goes even further than this.

Tertiary effects

The third order effects of extreme heat get even more… interesting. From the Center for American Progress and Virginia Commonwealth University report, The Health Care Costs of Extreme Heat:

“Heat-related power outages and blackouts deactivate home medical devices, such as oxygen pumps and dialysis machines, on which people with chronic diseases rely. A recent study estimated that electrical grid failures during heat waves could double heat-related mortality in some cities. Heat waves also affect mental health and are associated with higher rates of crime and violence.”

In my recent conversation with Anna Bershteyn, assistant professor at NYU and leader of a new interdisciplinary effort to combat deaths from extreme heat called Project HEATWAVE, she pointed to the role of behavioral factors. For example, extreme heat can lead people to pursue higher risk behaviors out of desperation, increasing drowning risk by 17%.

Due to these multiple layers of impact, extreme heat causes sharp spikes in costly ambulance rides, ER visits and hospital admissions. In the CAP and Virginia Commonwealth University report, researchers looked at heat events in Virginia and found that the increase in heat events between 2016 and 2020 led to 400 more ambulance rides, 7,000 more ER visits and 2,000 more hospital visits across that 4-year period.

Some of these costs are borne directly by consumers, insured or uninsured, and all contribute to the ballooning of American healthcare costs that overshadow every other sector of our economy — even outpacing the already astonishing growth of US GDP.

In previous commentary, I’ve noted that climate change is expected to cost an individual born today between $500,000 to $1 million over the course of their lifetime due to cost-of-living increases and lost income. This sucks.

So what can we do about extreme heat?

A solution set that ranges from ice packs to SRM

Project HEATWAVE’s approach is to compile a menu of options tailored to budgetary, geographical, cultural, and infrastructure constraints, with solutions that range from ice packs to halt heat stroke to stratospheric aerosol injection to reduce planetary radiative forcing. This makes extreme heat unique as a public health threat in its demand for a broad, creative toolbox.

Extreme heat is often framed as a straightforward planning and resilience issue — a few more air conditioners, a little better urban planning, and a few extra cooling centers. But this view is geographically narrow because it assumes the vantage point of the developed zones of the Global North. It misunderstands not just the heterogeneity but also the scale of the problem. Extreme heat is a planetary force multiplier that disproportionately affects the vulnerable and the poor — from individuals without adequate shelter up to nations without adequate grids.

The misery of Kutupalong refugee camp — now a de facto permanent home to over 900,000 Rohingya refugees — snarls in the face of our existing solution set. Ice vests where there’s no refrigeration? Cooling centers where every building is a makeshift combination of tarp and bamboo? Reflective paint when surfaces are being washed away regularly by torrential rain and floods? No good for the 6.6 million people across the world living in refugee camps, or the 1.1 billion living in slums and informal settlements.

In these contexts, extreme heat is salt on an already festering wound of injustice. For the billions of un-rich people who are already experiencing extreme heat mortality risk, the ultimate realistic and fair response may come down to systemic interventions— ones that might permanently reshape our relationship to the planet.

What happens when you really listen to the Global South

Here is where solutions like solar radiation management enters the conversation. I’ve become increasingly interested in SRM not because I’m an Elon, but because it’s clear that our other efforts are simultaneously not working and that millions of people are already experiencing climate change as a mortal threat. I don’t believe in “cooling credits” or startups that purport to send balloons into the air as a way to sell them (for why, check out my podcast episode with SRM luminary Kelly Wanser), but I do believe we should be learning as much as we possibly can about this potential emergency medicine for the planet.

And it turns out that many scientists and researchers in the Global South agree with me.

At first blush, SRM sounds like Silicon Valley’s latest science fiction answer to climate change, technocratic hubris meets profit motive. But in reality, SRM isn’t just the domain of tech billionaires and academics hailing from the US and the UK.

In my recent conversation with Andy Parker, the founder and CEO of the Degrees Initiative, an NGO that empowers scientists in the Global South to do research on solar radiation management, I learned that who's doing the asking > the questions we ask > the answers we seek.

Andy has been working on SRM since 2009, when he led the secretariat for the Royal Society's Geoengineering the Climate Report — but his real breakthrough contribution has been his work demonstrating that not all cutting edge climate research has to come from the American Ivys, Oxford and Cambridge.

Andy’s organization provides grant funding to scientists and researchers in Africa, Latin America and Southeast Asia to ask hard and important questions about climate change and geoengineering as it relates to the billions of people living in those most affected regions. Degrees transforms these regions and their scholars from mere passive recipients of climate fallout to critical stakeholders in shaping how we confront climate change.

If you’ve followed SRM at all, you might know about the International Solar Geoengineering Non-Use Agreement that called for a moratorium on all SRM research that was signed by over 500 prominent scholars from Europe and the US. One of its key arguments was that solar geoengineering could disproportionately and adversely affect the Global South, and even its research created moral hazard and jeopardy.

But when Degrees talked to actual scientists and researchers via workshops held throughout Africa, South and Southeast Asia, and Latin America, they heard a different story. Overwhelmingly, scholars in these regions believed we should study and understand geoengineering as best we can — not that the we should deploy it tomorrow or ever, but that the real moral hazard would be in not studying its patchwork of risks and opportunities, leaving billions of people unprepared for decisions that may ultimately get made by wealthier nations. The Degrees mission understands that it’s not just about For What, but also For Whom and By Whom.

What heat forces us to confront

Extreme heat is a uniquely clarifying crisis. It reveals that planetary health is the baseline for everything else we value and valorize, and that it’s not just how we deal with it but how far we’re willing to go and whose voices shape the solutions.

Whether you’re Peter Attia who cares deeply about reducing deaths from cardiovascular disease and metabolic syndrome or you’re an agricultural industrialist who doesn’t want to lose a season’s worth of row crops, whether you’re one of the 200 million Americans with CVD, diabetes and hypertension or a lean Burkinabé with none of those conditions, it will affect you. Planetary health is everyone’s baseline.

In the new year, I’ll be asking more of these questions — not just about the monetary business of climate, but about how deep thinkers confront systems level problems by using every discipline in our toolbox. I hope you’ll follow along here at Climate Money and at our podcast Climate on the Edge.

Till the next one, I wish you a restful and reflective end of 2024.