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His intellectual influences include longtime climate action skeptics — and Bill Gates’ favorite author.

Donald Trump’s nominee for Secretary of Energy, Chris Wright, is a nerd — and he’ll tell you about it. “I’m Chris Wright, and my short bio is, I started out as a science geek, I transitioned to a tech nerd, and then I’ve been an energy entrepreneur my whole life,” he told energy journalist Robert Bryce on the Power Hungry podcast in 2020. “In addition to an energy nerd, I’ve been a climate nerd for quite some time,” he said in a talk hosted by Veriten, the energy consulting firm in 2023.
This is a far cry from Trump’s first Energy Secretary, the former Texas Governor Rick Perry, who famously failed to remember on the Republican primary debate stage the third of the three agencies he sought to eliminate (it was the Department of Energy) and who reportedly didn’t know that the Energy Department’s responsibilities — and budget — then lay heavily with maintaining the country’s nuclear stockpile.
But Wright’s extensive energy experience — studying nuclear fusion at the Massachusetts Institute of Technology and working early in his career on solar and geothermal engineering (his company, Liberty Energy, the fracking powerhouse he founded in 2011, has invested in the next-generation geothermal company Fervo, and Wright sits on the board of the nuclear company Oklo) — has not won him any plaudits from environmental groups or Democrats who focus on climate change. After Trump announced his nomination, the Sierra Club called Wright a “climate denier who has profited off of polluting our communities and endangering our health and future.” Illinois Rep. Sean Casten, one of the House’s most vocal proponents of climate action, also called Wright a “climate denier who prioritizes the wants of energy producers over the needs of American consumers.”
Few Republicans — and certainly few high-level Trump appointees — are as conversant in climate and energy data as Wright. That may make him an even more effective advocate for Trump’s “energy dominance” strategy, built around increased production of fossil fuels and, almost certainly, fewer subsidies for clean energy and electrification.
Typically when a person gains some notoriety by coming out against immediate, large-scale climate action and restrictions on fossil fuel extraction, climate advocates try to link that person to the fossil fuel industry and its long history of deliberate and knowing climate denial. Wright’s associations, however, are perfectly straightforward: Liberty Energy fracks oil and gas in the United States and Canada on behalf of large oil companies. He thinks the company’s contribution to the good of the world consists of its producing more hydrocarbons — full stop.
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Wright calls this philosophy “energy sobriety,” fully conceding that climate change is real while also diminishing the urgency of mounting a response. In seemingly countless speeches, interviews, and legislative testimonies, as well as in Liberty Energy’s annual “Bettering Human Lives” report — its version of an environmental, social, and governance review — Wright is perfectly comfortable acknowledging climate change while also patiently assaulting many key pillars of climate policy as it’s practiced in the United States, Europe, and other countries in the developed world seeking to sharply reduce greenhouse gas emissions.
While Wright’s written and spoken record adds up to tens of thousands of words and hours of talks, it can be distilled into a few core ideas: Energy consumption makes people better off; energy access, especially in the developing world, is a greater global challenge than climate change; and existing alternatives to hydrocarbons are not capable of replacing the status quo energy system, which still overwhelmingly relies on fossil fuels, with little prospect of a rapid transition.
He cites a wide range of thinkers, including members of a group of scholars — including the Danish political scientist Bjorn Lomborg (whose book, False Alarm, is “fantastic,” Wright said in a Liberty talk), University of Colorado science policy scholar Roger Pielke, Jr. (“a real intellectual”), and the Canadian energy scholar and historian Vaclav Smil (“the greatest energy scholar of my lifetime by far”) — who share elements of this deflationary view of climate change.
Lomborg and Pielke have long been bêtes noires of the climate movement, mostly as the subjects of years of furious back and forth in every form of media for the past two-plus decades. (Though in Pielke’s case, there was also an investigation in 2015 over alleged conflicts of interest led by House Democrat Raul Grijalva, who is retiring from Congress this year.) Lomborg has for decades argued that climate change ranks relatively low on global challenges compared to, say, global public health, while Pielke contends that many climate change policy advocates overstate what the Intergovernmental Panel on Climate Change actually says about the connection between climate change and extreme weather, a point that has made him the object of intense criticism for going on 15 years.
Smil, meanwhile, is deeply skeptical of any effort to wean the world from fossil fuels considering their role in the production of steel, cement, plastics, and fertilizers — the materials that he describes as essential to the modern world. Smil also counts among his fans Bill Gates (“Vaclav Smil is my favorite author”), who is also one of the biggest funders and promoters of climate action through his research and investment group Breakthrough Energy and funding for companies like TerraPower, which is currently building the country’s first next-generation nuclear facility in Wyoming.
Pielke called both Wright and Doug Burgum, Trump’s nominee for Secretary of the Interior and the designated head of a planned National Energy Council “super competent. They know energy, and that’s a fantastic starting point,” he told me.
“There is polarization of the climate debate, and the idea that fossil fuels are evil and the fossil industry are arch-villains — that’s part of the framing from the progressive left about how climate wars are to be fought,” Pielke said. “I’m not particularly wedded to that sort of Manichean evil vs. good framing of the debate.”
But the differences are real. Wright strongly contests much of what is the mainstream of climate policy. While he acknowledges that increased concentrations of carbon dioxide cause higher temperature, he says it’s “actually sort of slow-moving in our lifetimes” and a “relatively modest phenomenon that’s just been wildly abused for political reasons,” he said in a talk to the conservative policy group American Legislative Exchange Council.
While the Department of Energy has only limited authority over energy policy, per se, especially the permitting and public lands issues that typically concern fossil fuel companies, Wright does have some levers he can pull. He will likely act quickly to approve more export facilities for liquified natural gas, though the Energy Department’s recently released study of LNG’s long-term effects — particularly on domestic energy prices — may complicate that somewhat. Beyond that, he will inherit a massive energy research portfolio through the national labs, putting him in charge of developing the energy technology that he says are currently insufficient to replace oil and gas.
“I’ve worked on alternatives. I’d love it if fusion energy arrives,” Wright said in an interview with the conservative website Power Line. “I love energy technology, and I think there’s good things going on, but it’s now become political.”
He believes that reaching net zero greenhouse gas emissions by 2050 is “neither achievable nor humane,” he wrote in the foreword to the 2024 edition of “Bettering Human Lives.” He also disagrees with the idea of subsidizing the world’s predominant forms of alternative energy, solar and wind.
“Wind and solar are never going to be dominant sources of energy in the world,” Wright told Bryce on the 2020 podcast. The “main impact” of subsidies for wind and solar, Wright said in another 2023 podcast episode with Bryce, “is just to make our electricity grids less reliable and electricity prices more expensive, and to do nothing for the demand for oil and very little for the demand for natural gas.”
“Oil and gas make the world go round,” he added. “[People] want higher quality of lives. That’s what drives the demand for oil and gas.”
Bryce, a persistent critic of green energy policies, told me in an email that he thinks Wright is “the right person for the DOE. He’s not apologetic about being an energy humanist. Regardless of what anyone thinks about climate change, it is obvious that we are going to need a lot more energy in the future, and the majority of that new supply will come from hydrocarbons.”
While Wright’s arguments certainly have wide purchase among his peers in the energy industry executive corps, he nevertheless stands out from the rest for his willingness to express them. In contrast to the stance taken by large, multinational energy companies, which are willing at least to pay lip service to carbon reduction goals and have, at times, embraced branding and marketing strategies to make them seem like something other than oil and gas companies (e.g. ExxonMobil’s algae-based fuel initiative and BP’s notorious “Beyond Petroleum” campaign), Wright and his company see their contribution to a better world as their work extracting oil and gas.
Other executives “don’t want to deal with the criticism that will come with taking a higher-profile stance,” Bryce told me. “They don’t have time or the inclination. It takes a lot of time, courage, and conviction to engage with the media, get on the speaking circuit, and do so in a thoughtful way.”
Wright’s emphasis on the energy poverty faced by poor countries could potentially serve as a diplomatic bridge to the developing world, especially in Africa, where some observers think there’s space for the United States to start funding natural gas development through the International Development Finance Corporation. For Wright, expanding energy production — and specifically fossil fuel development — is crucial to providing cheap energy to the developing world. He mentions in almost every talk the billions of people who use wood, dung, or other biofuels on open fires to cook indoors, causing 3 million premature deaths per year.
“The biggest problem today is a third of humanity doesn’t have hydrocarbons,” Wright told Bryce in 2023. In a 2023 speech to the American Conservation Coalition, a conservative environmental group, he described strictures against financing fossil fuel development as “not just ignorant or bad policy” but “immoral.” His solution: distributing propane stoves as widely as possible, in part through his Bettering Human Lives Foundation.
Here might be the greatest challenge for advocates of climate action: Even if most of the world’s leaders have accepted the reality of anthropogenic climate change, much of the world, especially outside North America and Europe, is still eagerly increasing its use of fossil fuels. In the United States, coal plant shutdowns are being pushed out further and natural gas investment may soon pick up again to power new demand for electricity. Globally, coal use is set to grow over the next few years. That’s thanks in large part to demand from China, the world’s largest emitter and second-largest cumulative emitter behind the United States, defying predictions that demand there was near peaking. The biggest new source of oil demand is India, a country with a per-capita gross domestic product less than 1/30th of the United States.
And so the greatest danger to aggressive action to lower global emissions may not be Chris Wright and his “sober” ideas at the helm of the Department of Energy. It may be that much of the world agrees with him.
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Can she appease AI skeptics, economic development advocates, and renewables boosters?
New York Governor Kathy Hochul tried to pick out a middle way with her data center moratorium, carefully charting a course between the demands of industry, advocacy groups, and voters who are increasingly suspicious of the data center and artificial intelligence industries. Did she succeed? Only time will tell.
Hochul’s first-in-the-nation permitting pause has been hailed by data center opponents who want to re-orient American politics around the artificial intelligence backlash and lamented by the technology sector and its allies, including several in the Trump administration. President Donald Trump himself wrote on Truth Social, “New York State has made a terrible decision.” adding that the “Radical Left Dumocrats must not be allowed to cause us to lose Data Centers, AI, and all of this incredible new Technology, to China.”
Before we discuss what Hochul did, we must first discuss what she didn’t do.
What Hochul’s moratorium is not is her signature on the Responsible Data Center Development Act, a data center moratorium that passed both houses of the state legislature in June. That moratorium had a lower energy use threshold for the moratorium: 20 megawatts, compared to Hochul’s 50 megawatts.
One of that bill’s sponsors, democratic socialist Kristen Gonzalez, appeared alongside Hochul when she signed the executive order Tuesday and hailed the governor for “protecting everyday New Yorkers with a first in the nation moratorium on new large data centers.” When asked about this discrepancy by reporters, Hochul said that “we want to make sure we didn’t touch the data centers that are powering hospitals and schools and research centers,” and specifically mentioned data centers used by “bank back-office operations.”
Protecting bank back-office operations is not typically top of mind for democratic socialists. Gonzalez’s office did not respond to a request for comment.
The goal of the moratorium, Hochul said, is to develop a process for data centers to pay their way in terms of grid costs and electricity rates.
“We expect this process, which we already launched, to be completed within the year,” she said. “Once this policy’s in place, the moratorium will be reviewed and lifted.”
What is still unclear is how this moratorium interacts with renewables development, especially upstate where there is enough open space for both wind and solar power as well as large data centers.
While the New York governor has pulled back on the state’s climate goals as renewable energy and transmission has come under the dual assault of the Trump administration and rising costs, Hochul has made a point of promoting clean power development across the state, especially nuclear and hydropower, which can be built and maintained close to her western New York home base.
A New York data center industry could — emphasis on could — be a major customer for renewable power in the state, especially as there’s little prospect of large-scale new natural gas development.
During her speech announcing the moratorium, Hochul emphasized that “we’ve invested so much in other forms of power to meet the current needs of New Yorkers and our businesses,” and that “New York will require data centers to either produce their own energy or pay a premium to tap into our grid.”
The executive order itself lays out a process whereby, once the moratorium is lifted, new data centers may be required “to fund new clean electric generation and/or battery storage dedicated to their operations, consistent with the State’s clean energy goals, including customer-sited distributed energy resources, to the greatest extent feasible.”
When discussing her energy and economic policies on Bloomberg’s “Odd Lots” podcast this week, Hochul connected her data center moratorium with economic development efforts, especially upstate, where large data centers are more likely to be sited.
Referring to Micron’s $100 billion Syracuse-area semiconductor manufacturing project, Hochul told hosts Joe Weisenthal and Tracy Alloway, “I’ll work with you to get the power you need.” (The state approved a transmission line for the project last year.)
“If I have to choose between powering a largely vacant data center with the same amount of power I can have with a Micron with 1,000 jobs, I can tell you right now where I’m going,” Hochul said. “They can come under the conditions we lay out.”
But it may be just as likely data center developers take the hint and avoid a state with expensive power and high costs of doing business in the best of times.
“I don’t think we know yet how this will impact what’s known as behind-the-meter or off-the-grid power solutions: natural gas, cogeneration, solar, wind, battery storage,” Jeffrey Moerdler, a partner at the law firm Haynes Boone who chairs the data center practice, told me. “I assume it will hold up data centers powered by alternative energy sources.”
As for whether Hochul can successfully keep the one-year moratorium a year (temporary policies have a tendency to become permanent), develop new rules to address her concerns about grid costs and local opposition, and then have data centers line up to get back into New York, Moerdler was skeptical.
“It’s going to take years to make up for that shift” against data center development, he told me, predicting that the moratorium could lead to “many years of new data centers not locating here because they already started during that one-year period somewhere else.”
Something else that must be noted in all of this: “New York is not a high priority location for data centers.” Whether the state’s governor wants it to be remains to be seen.
Where is the smoke worst, where will it go next, and what causes that color?
Before wildfire smoke turns the skies to a jaundiced yellow-gray, it might look almost pretty. Midday light grows diffuse, taking on a crepuscular golden hue. Shadows soften and stretch long. The sunsets are particularly incredible: radiant, neon red.
But as with oleander and poison dart frogs, beautiful things are often the most dangerous. The same wildfire particulates that scatter the light will, once dense enough, turn the air around you orange, then black. They will get into your lungs — slipping past your nose hairs and mucus, the body’s defenses that stop larger particulates — and provoke your immune system into an attack. The tiny air sacs at the ends of the bronchioles in your lungs, where the gas exchange of “breathing” actually happens, will become inflamed. You will become short of breath. You will cough. The smallest smoke particulates may even enter your bloodstream.
And if you are like 24,000 other Americans every year, this will kill you.
Though wildfire smoke exposure might seem to be more of a nuisance to a healthy person than anything else, experts agree it should be taken seriously. “In my profession, wildland firefighting, you make a decision that you run into that,” Nicholai Allen, a firefighter and founder of Safe Soss, a home-hardening product line, told me. “But for my family and my children, I don’t want them breathing in the smoke that’s traveling that far. We have air purifiers, and we’re taking similar precautions.”
On Wednesday, more than 100 million people in the Midwest and Northeast face unhealthy smoke conditions from fires burning up to 2,000 miles away. Here’s what you need to know.
The smoke is largely coming from 150 or so lightning-ignited fires in Ontario and northeastern Minnesota. Triple-digit temperatures, dry conditions, and high winds have fanned a “wall of fire” across the region, as the firefighting newsletter The Hotshot Wakeup put it, even as Canada is, on the whole, tracking behind its five-year average for area burned so far. Most of the fires sending smoke to the U.S. this week are still out of control and spreading rapidly.

A high-pressure area over the central U.S. and a low-pressure area over Eastern Canada are acting as a funnel, pulling bad air east across the Great Lakes region and into the populous Acela Corridor. Conditions are worst closest to the fires: Around 8 a.m. on Wednesday morning, Duluth, Minnesota had a “hazardous” air quality rating of 785 out of 800. By the afternoon, Toronto had the worst air quality of any major city in the world, and drivers in northern Michigan have been advised to slow down and turn on their low-beam headlights because visibility has been so reduced by the smoke. The eastern-moving plume has also blanketed large portions of Upstate New York.
Degraded air quality reached the Boston and New York City areas on Tuesday night and is expected to linger through Thursday. The smoke reaches as far north as Maine, having dimmed the morning light in New Hampshire, and could spread as far south as Washington, D.C. over the next 24 hours.
Though the smoke is staying largely to the north over the middle part of the country, forecasts show it could dip into downtown Chicago on Thursday as well.
Wednesday and early Thursday will be the worst days for the eastern U.S., per the current outlook. A cold front should help push the worst of the smoke out of the region as we head into the weekend.
So far it appears that much of the smoke has remained high enough in the atmosphere that while you’ll be able to see and likely smell it, it might not cause extreme air quality problems on the ground. As of Wednesday afternoon, New York City was recording some of the worst air on the East Coast, with an air quality index of around 160 — bad enough to trigger an “unhealthy” alert for the general public and to rank fifth-worst among major cities worldwide. The rest of the region still mostly showed orange readings designed to alert sensitive groups such as older adults, people with respiratory conditions, and pregnant women, or more moderate yellow ratings.
Conditions could still change, though. Heat, pressure, and winds can drive smoke down to ground level, where it becomes a threat to public health. In fact, the Fox Forecast Center’s models indicate that particulate matter concentrations around the Great Lakes and Northeast could be on par with the 2023 East Coast smoke event, during which New York had the world’s worst air quality, although The New York Times reports that “even the most severe forecasts” this week should not approach that level.
The best thing to do is to continue monitoring your local air quality. If you want help navigating what those readings mean, my colleague Emily Pontecorvo has written a great explainer.
For many on the East Coast, the orange skies are a flashback to the 2023 smoke event. While eerie and apocalyptic, the smoke also gives us an excuse to talk about Mie theory.
Air molecules are much smaller than the wavelength of light. When white light from the sun enters the atmosphere, nitrogen and oxygen scatter the short, higher-frequency blue light in multiple directions. This is known as Rayleigh scattering, and is also the answer to, “Why is the sky blue?” Under normal conditions, wherever you look in the sky, blue light is headed toward your eye.
Smoke particles, while small enough to enter our lungs when inhaled, are larger than air molecules — about the same size as light wavelengths. Because these particles are larger, they also scatter light more democratically, including the lower-frequency, longer reds and oranges. This is called Mie scattering. When sunlight passes through smoke, the reds, oranges, yellows, and blues are all mixed together as they reach our eyes, appearing as a hazy gray or white.
You might expect thicker smoke to result in a darker gray, then. But smoke also contains organic compounds from burned plants called brown carbon, plus soot, both of which absorb visible light. Brown carbon, in particular, prefers light at the shorter end of the spectrum, absorbing about three-quarters of the total light at blue wavelengths in smoke plumes, compared to about half at red wavelengths. That means that when the smoke thickens, the blue light doesn’t reach our eyes nearly as well, and the sky takes on an orange appearance.
One of the dangers of the current smoke event is that it coincides with high temperatures across the Central U.S. and New England. Both conditions together — high heat and smoke — can lead to some confusion over how to respond.
The best strategy is to keep your windows closed. But while it might feel safe side, wildfire smoke can still degrade indoor air quality. “If you have a fresh air intake on your air conditioning system, I would shut that off so that you’re recirculating just your purified air inside your house,” Allen, the firefighter, told me.
You can also install activated carbon exterior filters on attic and crawl space vents and run a purifier with a HEPA filter. (If you bought an air purifier during the last smoke event, consider this your reminder to replace your filter.) “Then I would avoid going outside or exercising outside if there’s smoke in the air,” Allen added. “When the particles are arriving to you from a great distance from the wildfire, they are the smaller particles that can get in your lungs. So not to create undue fear, but there’s definitely stuff in that air that you don’t want to breathe.”
Deciding what counts as a heat death is more difficult than it sounds.
Just last month, a heat wave killed an estimated 2,700 people in France. Think about that for a second: 2,700 people. That’s equivalent to the mortality of two Hurricane Katrinas or 10 Hurricane Sandys. In France, where there were roughly 970 murders in 2024, the heat wave killed more people in two weeks than almost three years’ worth of homicides.
But unlike floods, hurricanes, tornadoes, or murders, heat doesn’t leave behind much of a crime scene. Although heat kills people in obvious, direct ways like heat stroke, it also puts enormous strain on our hearts and kidneys as our bodies work to keep our internal temperature at 98.6 degrees Fahrenheit. Heart attacks spike during heat waves because vasodilation diverts blood to the skin’s surface to cool it down, in the process lowering blood pressure and forcing the heart to work harder and faster to circulate oxygen. Deaths from renal diseases also jump during periods of high temperatures due to severe dehydration and restricted blood flow to the kidneys.
“Let’s say you have two people with underlying heart disease; somebody has a heart attack versus somebody has a heart attack because it’s too hot,” Kristie Ebi, an epidemiologist at the University of Washington and an expert on heat-related mortality, explained to me. “Will the second one be recorded as a heat death or will it just be recorded as a heart attack? Frankly, when both go into the emergency department, the number one goal is to save a life — it’s not necessarily to record whether it was because of temperature.”
But if physicians don’t code the second heart attack as a heat death— a procedure designed for insurance and billing rather than getting to the root of underlying environmental conditions — then the headline number of heat wave-related deaths will almost certainly be an undercount. In Washington during the 2021 heat dome, for example, the state health department initially reported that 129 people died from the temperatures. But later analyses compared the overall number of people who died that week in the state to the average number of people who died during the same week from 2013-2019 and concluded that there were 485 “additional” deaths compared to what would have been expected during normal early summer conditions.
Those 485 deaths are called “excess deaths,” and the number offers a broader picture of who actually dies from a heat wave. The tally captures not only those heart attacks that are coded by physicians and medical examiners as caused by the heat, but also the ones the state may have overlooked or discounted. Air pollution deaths, homicides, drownings, and accidents, for example — all of which also spike in relation to heat waves — show up. As one epidemiologist explained it to the Seattle-area NPR affiliate KUOW, a boating death might count as an excess heat death, too, because while “not directly attributable to heat in the sense of heat stroke … it arguably is attributable to heat in the sense that had it not been hot, they would not have gone out.”
Excess death analyses are also methodical in what they don’t count. “After a heat wave, there’s a deficit in the number of deaths, which means that the heat wave brought forward deaths that would have occurred anyway,” Ebi told me. The analyses also take those into account to model only the “true” excess events. This, at least, is relatively simple in scope: The advantage of heat waves for mortality accounting is that they don’t have the long tails associated with hurricanes and other weather-related tragedies. “Deaths occur over a few days of a heat wave, and then it’s over,” Ebi added.
But the calculation, while relatively straightforward, has its critics, too. “The limitation of that approach is that it doesn’t actually quantitatively attribute that excess mortality to the heat,” Christopher Callahan, a climate scientist and assistant professor at Indiana University Bloomington, told me. Take the boating accident example: Maybe if it’d been a regular summer day, the enthusiast still would have taken his pontoon out and had all those beers. Maybe during the heat wave it was also smoky, and that caused some of the excess deaths. There’s also the possibility that the baseline number of deaths already includes some baked-in heat-related deaths, obscuring the cumulative total.
A third approach, favored by academics — and recently employed by Callahan to estimate the 2,700 heat-related deaths in France last month — involves using long-term data on both temperatures and mortality for a given location and then fitting a statistical model that relates the two. This method has the advantage of generating a U-shaped relationship that shows how mortality rates change once temperatures exceed a certain threshold (or drop below it, in the case of cold-weather-related deaths, hence the “U”). Like an excess death analysis, this method “has the benefit of, again, not having to rely on individual diagnoses,” Callahan said. “It has the drawback that there is no one right statistical model. Different people have different philosophies about how to fit those models.”
The other drawback is that creating such a model and subjecting it to the rigor of peer review is time-consuming — by the time you’re able to publish a death toll, the news cycle has probably moved on. Callahan got lucky: He had already created such a model for France to study the 2003 heat wave, which killed an estimated 15,000 in the country in a couple of weeks. The model relies on a historical understanding of the relationship between temperature and mortality in France — “not a crazy assumption, but an assumption,” he admitted to me — and he published the findings in Carbon Brief earlier this month. (Callahan also estimated that 20,000 people died continent-wide in Europe during the June 2026 heat wave — a number that circulated widely, but that he told me he’s now working to revise downward.)
Notably, the number Callahan arrived at for France does not represent “real” people or “real” deaths, at least as linked to death certificates. There are no biographical or even demographic numbers attached to it. (That said, you can create models of the same U-shaped relationship for anything: temperature and age, income, race.) More mind-bending, though, is that because of this, Callahan’s model can also be used to predict. Had there been a way to know the exact temperatures before the European heat wave, he could have told you how many people would likely die before they actually did.
In the case of France, the simple excess death count put the toll at 2,025, though officials say they expect the number to rise. While Callahan’s number and the official tally from France differ by what seemed to me to be a lot — 675 deaths — Callahan told me he’s actually encouraged by how close his model came to the government’s empirical count, given that the two use completely different methodologies.
After all, heat death counts can vary by orders of magnitude, including within a single government. Before 2020, the Centers for Disease Control and Prevention reported that only about 700 Americans died each year from heat, relying primarily on physician diagnostic codes. After moving in recent years to better incorporate underlying and contributing causes of death, the CDC adjusted its estimate upward to about 2,000 heat-related deaths per year in the United States. Still, the government’s numbers remain extremely conservative; independent researchers studying heat mortality say the figure is likely closer to 12,000.
But even more holistic heat-related mortality numbers have their critics. For example, models don’t work as well for many lower-income countries, where mortality may be reported monthly, thereby making day- or week-level heat attribution impossible.
Granularity presents its own set of problems. Excess deaths and modeling analyses both have to define the first “heat day” of an event. You can do that by setting a fixed threshold — say, anything above 90 degrees Fahrenheit counts as “high heat” — but Ebi told me there is little value in analyses or policies that take that approach. That’s because heat is contextual: “My standard joke is, if we had the temperatures here in Seattle that they have in Phoenix, we basically all die, because we don’t have the infrastructure and we’re not acclimatized,” she said.
A slightly better metric might be a relative threshold — say, temperatures above the 95th percentile of historical temperatures for a specific location count as “extreme heat.” The problem there, though, is that it may need to be stratified further by vulnerable populations that feel the effects much sooner, like adults over the age of 65, pregnant women, outdoor workers, or people with certain medical conditions. While that approach might seem overly complicated, parts of Asia already use nuanced thresholds to warn older adults to take precautions. “It’s going to be more challenging to communicate, I grant you that,” Ebi told me of such an approach — much less to try to model. “But it’s also going to be more useful.”
Even so, a larger problem remains: The multiple systems for calculating heat deaths are honed to address different questions, which makes them impossible to compare. The Federation of American Scientists has pushed for the CDC to upgrade and standardize its heat-mortality tracking. “We’ve thought about if it’s possible to ever set a goal of bringing heat-related deaths down by 50%, or something like that,” Grace Wickerson, the senior manager of climate and health at FAS, told me. “But we don’t even have a baseline number or a way to say, ‘This is the starting point for this goal or strategy.’”
Wickerson also suggested, though, that there might be things we lose in trying to nail down the most correct heat-related mortality number. “I’m almost a bit weary of the pursuit of large numbers,” she said. “At least to me, what feels more important is why people are suffering and dying, what types of people they are, and what stories, messages, and stakeholders we need to engage and target to actually build meaningful policy strategies.”
Despite being deeply engrossed in the calculations, Callahan stressed that he wants readers to have a similar takeaway from his own research. Improved “healthcare access and access to cooling, shade, and shelter” — or in the case of heat-related mortality from climate change, “reducing greenhouse gas emissions” — lead to fewer heat deaths, meaning the vast majority are preventable.
“The relationship between environmental conditions and a person’s mortality is not fixed or necessary,” he told me. “It can be stopped.”