As Scientists Have Long Predicted, Warming Is Making Heatwaves More Deadly

By Dana Nuccitelli, an environmental scientist, writer, and author of ‘Climatology versus Pseudoscience,’ published in 2015. Originally published at Yale Climate Connections.

In its 2001 Third Assessment Report, the Intergovernmental Panel on Climate Change (IPCC) foresaw that global warming would lead to increasingly deadly heatwaves. “More hot days and heatwaves are very likely over nearly all land areas,” the world’s top climate scientists warned. “These increases are projected to be largest mainly in areas where soil moisture decreases occur.”

 “The greatest increases in thermal stress are forecast for mid- to high-latitude (temperate) cities, especially in populations with non-adapted architecture and limited air conditioning,” they wrote at the time. “A number of U.S. cities would experience, on average, several hundred extra deaths each summer.”

Sound prescient? And familiar?  All too much so.

Twenty years later, it seems as though these climate scientists were gazing into a crystal ball rather than computer monitors. At the end of June 2021, the normally temperate Pacific Northwest experienced a record-shattering heatwave. The village of Lytton, in British Columbia,  set a new all-time Canadian temperature record of 49.6 degrees Celsius (121.3 degrees Fahrenheit) and was largely destroyed by a wildfire soon thereafter. Quillayute in the northwest corner of Washington, shattered its previous high temperature record by a full 11°F.

At least 800 deaths have so far been attributed to the extreme heat, and experts say they expect the final mortality tally to be considerably higher. Because of the region’s historically temperate weather, many homes lack air conditioning; residents were enveloped by temperatures well in excess of 100°F.

University of British Columbia marine biologist Christopher Harley estimates that the heatwave also caused over a billion marine wildlife deaths, as shells of dead mussels and clams coated rocks along the Pacific seashore.

Climate Change Made the Heatwave More Deadly

Contributing to the World Weather Attribution project, 27 scientists worked around the clock for a week immediately after this extreme event to determine the role played by climate change. The team used published peer-reviewed methods, comparing numerous model simulations of two scenarios: the “world as it was” when the event occurred, and a counterfactual “world that might have been” had humans not altered Earth’s climate by burning fossil fuels over the past 150 years.

The results are striking. The authors concluded that a heat event so extreme was “virtually impossible without human-caused climate change.” While it’s difficult to quantify the rarity of such unprecedented weather, their best estimate was that it was a 1-in-1,000-year event. Without human-caused climate change, such an extreme event would be at least 150 times rarer, and the heatwave was about 3.6°F hotter than it would have been naturally.

But continued climate change will make these extreme events much more common. If global warming breaches the Paris Climate Agreement guardrail of 2°C (3.6°F) above pre-industrial temperatures (compared to today’s 1.2°C, or 2.2°F higher), the scientists estimate that an event like this “would occur roughly every 5 to 10 years.” As study co-author Dim Coumou of the Potsdam Institute for Climate Impact Research suggested, “we may have crossed a threshold in the climate system where a small amount of additional global warming causes a faster rise in extreme temperatures.”

Heatwave Climate Connections

In fact, a 2020 analysis by Columbia University climate scientists James Hansen and Makiko Sato found that what was considered extreme Northern Hemisphere summer heat in the 1950s to 1980s is about 200 times more likely to occur today as a result of shifting temperature patterns.

But one question the new attribution study’s authors were unable to answer involves whether the June 2021 event was simply a case of “really bad luck” – just a natural extreme heatwave amplified by global warming – or whether climate change has loaded the dice in favor of this type of extreme heatwave in other ways.

For example, higher temperatures also draw more moisture out of the soil and vegetation and into the atmosphere, thus tending to exacerbate droughts. The region between southern British Columbia and California has been anomalously dry this year, with below-normal soil moisture since the beginning of April 2021 as a result of low precipitation. With less soil moisture available to evaporate, there is more heatwave energy available to raise air temperatures, as the 2001 IPCC report alluded to.

In short, it’s possible that climate change will worsen droughts in western North America, which will in turn worsen heatwaves.

Another possible factor involves a slowing jet stream resulting from  human-caused changes in the Arctic. The June heatwave was characterized by an atmospheric heat dome trapped by an omega blocking pattern, so-called because the shape of the jet stream current resembles the Greek symbol Ω. Authors of a 2018 study in Science Advances concluded that climate change is making these sorts of jet stream patterns occur more frequently in the Northern Hemisphere summer. But in the June 2021 event, the rapid attribution study concluded that – unlike the record temperatures on the ground – the jet stream circulation pattern was not particularly exceptional.

Those researchers were able to rule out a common suspect often posited by those described as climate deniers – ocean cycles. The El Niño cycle was in a neutral phase leading up to the heatwave, and the authors concluded “it had no influence on the occurrence of the heatwave.” Another ocean cycle called the Pacific Decadal Oscillation was found to “slightly favor cooler conditions for this region” at the time.

What Makes Extreme Heat Especially Deadly?

The combination of rising heat and humidity is especially dangerous, as Texas A&M climate scientist Andrew Dessler explained in a Twitter thread. The human body generates heat, and at temperatures above around 82°F, the surrounding air no longer carries away enough heat to keep the body cool. The remaining options to avoid a dangerously overheating body involve air flow across the skin (for example from wind or a fan) or evaporating sweat. And as climate change draws more moisture from the soil into the atmosphere, thus increasing humidity, sweating offers less relief. At 100% relative humidity, the body can’t evaporate any sweat (hence ‘dry heat’ is less uncomfortable because of the body’s ability to cool itself by sweating).

Scientists combine measurements of heat and humidity through what are known as ‘wet bulb’ temperatures. Prolonged wet bulb values close to body temperature (98°F) are not survivable. A 2020 study in Science Advances found that areas near the equator like the Persian Gulf and portions of Central America, India, and Southeast Asia are already very close to this survivability limit, and that the limit will be regularly exceeded if global warming approaches 2.5°C (4.5°F) above pre-industrial temperatures, rendering these regions potentially uninhabitable.

“Our results provide a strong warning: Our rapidly warming climate is bringing us into uncharted territory that has significant consequences for health, well-being, and livelihoods,” the authors of the new attribution study concluded. “Greenhouse gas mitigation goals should take into account the increasing risks associated with unprecedented climate conditions if warming would be allowed to continue.”

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  1. Eustachedesaintpierre

    Nothing as extreme as the Canadian example here in the British Isles, but the heatwave here in Northern Ireland broke all previous records over 3 consecutive days finally reaching 31.3 C with around 56% humidity. Although I am older now I have experienced 39 C in Italy which I managed much better.

    As for ocean currents we are apparently dependant here on the Gulf stream keeping our climate from turning into the equivalent of Canada’s as we share the same latitude.

  2. Petter

    A super duper summer here where I live in Norway. Day after day of sun with temperatures in the upper 20’s but according to NRK, the national broadcaster (from a week or so ago) the finest weather was to be found in far northern Norway, possibly breaking the record of three years ago. I rememberer three years ago – drought and wildfires in the Arctic. Large areas of south central Norway are close to drought conditions now, with, my go to weather app showing the wildfire danger at orange level. We’ve already had a small fire along a train line in the forest north of Oslo, probably started by a spark from a train. Thankfully the weather is changing and and Yr shows some days of rain starting tomorrow night. It’s been really dry, not 2018 dry but very dry and this is not normal.
    Here is a link to the possible new record temperatures in the Arctic region. Not a single sentence in the article voicing concern about these extreme temperatures.

  3. The Rev Kev

    Perhaps I am showing a reader bias here but several years ago when they were showing & talking about the latest disaster in some poor country and the underlying cause was due to climate change, I seemed to pick up on a message in those stories. And that message was that even if climate change was a real thing after all, that it would really only effect countries in the third world. We in our more advanced countries would not really be experiencing these sorts of disasters but it did not matter if we did as we were more developed and could actually cope. If you asked me to prove this idea of mine, I can’t. It was one of these between-the-lines sort of thing so it may have just been me thinking this message was there.

    1. Eustachedesaintpierre

      A bit like Covid in a way, as in all of those nasty 3rd World diseases & famines, they should stay where they belong, in places where they serve as occasional short attention span stories for the MSM. The West puts me in mind of a group of affluent people who fall apart after the initial state of denial, in a kind of ” How can this happen to us ? ” as if they are immune to such things & are in constant expectation of a perpetual continuance of their normal.

      Other people get cancer, become disabled, use foodbanks, die in RTA’s etc.

      Things change, as Don Ameche once said.

      1. Tom Bradford

        But the more things change, the more they stay the same as the current crop of third-rate politicians ignore what they can’t cope with in the hope it will go away, hiding under the blankets of their delusions of grandeur and exceptionalism like eight-year-olds waiting to be rescued by their mothers. And we let them.

        1. Beli Tsari

          They don’t WANT it to go away. They want to monitize each and every crisis, by delaying ANY effective, pragmatic response until we’re sufficiently terrorized into Catastrophe Capitalism’s ONLY trope: It’s simply too late, only our tech Oligarch’s carbon sequestration, geo-engineering, GE monoculture & of course, bailing-out fission, “bridge” fuels… can save us?

          1. Christopher Horne

            I wonder whether all the hype about living (and mining) on
            the moon is a bit of a trojan horse on the part of certain
            wealthy industrialists. If you can survive (and thrive)
            on a place with no atmosphere with advanced technology,
            it would be childsplay to do the same thing on Earth,
            regardless of any climate conditions.

            1. BeliTsari

              Lot’s of folks noticed Bloomberg’s buying-up blogs, as Gates, Bezos, Musk, etc. had before 2018; to greenwash ridiculously unnecessary bio-mass, bridge-fuel & pretty terrifying sci-fi geoengineering scams, right as renewables, efficient, smart, regenerative equities bounced back dragging NASDAQ up out of yet another crash (of course, lots of these companies are East Asian, now? And our oilgarchy’s Biden- boondoggle billionaires were busy trying to destroy ANYTHING Mr Market was buying up, that would finally kill off slick-water fracking, “clean” coal, decrepit fission reactors, GE monoculture/ CAFO agribusiness & suburban consumerism?



  4. Louis Fyne

    To mitigate a 1.5 degree C rise, the IPCC also recommended in its 2018 report that the world massively increase its output of fission energy (its “middle of the road scenario” advocates increasing fission by 500% from 2010’s base). Section c.2.

    The solutions are there (increased fission, wind and decreased consumption, see the trans-oceanic supply chain), but the political-cultural will to push those changes isn’t.

    Everyone (but bird lovers and Martha’s Vineyard beachfront homeowners) are onboard with wind.

    Fission = NO, decreased consumption = no, intercontinental tarifffs = heck-no as inflation would further jolt higher as it’ll take years for the supply chain of tube chains and widgets to migrate away from their current centers of production back to the North America and Europe.

    1. Samuel Conner

      > intercontinental tarifffs = heck-no

      I’m pretty poorly informed about climate change mitigation policies, but I think the ocean haulage contribution to CO2 might be, in principle, significantly reduced with conversion of the carrier fleet to, or replacement of it with, wind-based propulsion. There was an intriguing article about this linked at NC some years ago; it was about a wheat shipper who continued to use wind-powered ships well into the 20th century, decades after most ocean transport had converted to coal- or oil-fired steam.

      Can’t find the article, but here is a recent item on wind-powered cargo haulage

      1. Jokerstein

        Try and dig out a copy of “The Last Grain Race” by Eric Newby. He describes this trade. It wasn’t just Gustav Erikson, who he sailed for. There were almost a score of barques which went out to South Australia in ballast to bring back the grain harvest.

        Great read – Newby is an excellent writer – and the details are fascinating.

      2. drumlin woodchuckles

        It would be simpler to ban Free Trade and destroy and abolish the International Free Trade System.
        Regions should re-autarkify and cross-ocean shipping should be hard-limited as deeply as possible.
        ( I don’t think zero ocean shipping will be possible, but it should be treated as the “ideal goal”).

    2. Larry Y

      I’ve had some past conversations about the Y2K issue (and the upcoming Unix 2038), and the mentality of some people completely baffles me. A lot of time, effort, and money was spent to prevent a problem – but since the problem didn’t happen, it was all “hype” or worse.

      COVID feels similar. Localized overwhelmed hospitals, morgues filling up, funeral workers exhausted, crematories running around the clock and overheating… none of this registers. Neither do concepts such as exponential growth and public health.

      Climate change is like that too. The signs are here, but substantive collective action hurts profits, livelihoods, lifestyles…

      1. drumlin woodchuckles

        Co-ordinated collective action is hard. Its even harder against the opposition of the Ruling Oligarchic Tyrannocracy.

        Merely-additive collective action around the edges might be easier. Suppose America divides neatly into two populations, the global warming reality accepters versus the global warming deniers.
        If each group is 150 million people, perhaps the 150 million global warming reality accepters can take 150 million separate sets of lifestyle actions designed to reduce their 150 million separate sets of matter and energy footprints.

        If all 150 million global warming reality accepters were to do that, and see eachother do that, they might then go on to form a political culture and a political movements for conquering the government and forcing it to address the problem at a co-ordinated collective level. Maybe it wouldn’t work. But maybe it can be tried, just to see.

        Meanwhile, those who accept reality should try to help themselves and eachother survive the Big Heat Rising as best as they/we can. In jurisdictions where realists are a functional monopoly-majority, they can try forcing co-ordinated collective response through those levels of government they can conquer and exclude the global warming deniers from any power in or power over.

        And what of the global warming deniers who do everything they can to make the problem worse?
        We should withhold survival information and assistance from them as best we can. Let Darwin take them.

    3. tegnost

      increased fission, wind and decreased consumption

      Well they are doing everything they can to keep wages down, so there’s some consumption alleviation there…just looking for bright spots…/s

    4. Felix_47

      Carbon tax? Gas Tax to make McMansion living away from the underclasses unaffordable. Here in Europe we can do everything on a bike. Of course, we are seeing more and more McMansions and SUVs. People want to get away from the cities because of fear…..mostly women…..of the new arrivals who tend to settle in cities. Somehow we seem to be copying the worst of America. Politicians on both sides of the Atlantic are clueless and are doing essentially nothing. China seems to be leading the way.

      1. drumlin woodchuckles

        Eventually the ChinaGov will have enough of this dithering and delay, and will begin its own program of geo-engineering. The easiest thing they could do would be to try enshrouding the earth in a high-atmosphere layer of sunlight-reflective sulfuric acid droplets, for a man-made Pinatubo effect, if you will.

        And can anyone blame them?

        ” As we starve and freeze and die beneath a silver-yellow sky.”

    5. drumlin woodchuckles

      I suspect bird lovers are more on board with wind power than Martha’s Vineyard beachfront homeowners are.

      Bird lovers would just like to see the several hundred foot tall phased arrays of birdie blenders kept out of certain key birds-of-prey migration routes. Or maybe even just switched off for the couple of months per year that the birds-of-prey are migrating through those key route choke points.

  5. Telee

    The dangers of climate change have been apparent for decades yet it’s trajectory has not been meaningfully slowed down for decades. Good science supported by Exxon was done in the late 1970’s and early 80’s but then the findings were suppressed by the oil companies. They have bought off enough politicians to be climate deniers and we elected a climate denier to the presidency. When republican Senator Inhofe brought a snowball into the senate to “prove” that climate change was not real and that was enough to convince many many Americans that climate change was to be ignored and that is largely what our policy has been. The overall dynamic is that the wealth supremacists have captured the government and nothing can be done without their approval. One example, is Obama’s ACA which guaranteed that the health insurers and pharmaceutical companies would not experience any loss in their income flow. Another is how the use of lead in gasoline was used for 70 years when ethanol could have been used in its place but couldn’t generate the profits of tetraethyl lead. Now it is looking like the Biden administration is looking for solution to climate change which will not affect the bottom line of the fossil fuel industry. There solution involves the unproven technology of carbon capture. This scenario goes on and on in this society with no relief. This can’t end well.

    1. Sue inSoCal

      Telee, quite a good read you have on the situation, in many ways. Carbon capture is unrealistic, imho. But lobbyists rule and have for quite some time. I agree that there is no happy ending.

      I’m beginning to believe that we are never going to get out of this mess without enforced use of masks and other relatively simplistic measures. But then we’ll get the usual screeds of “they’re taking away my freedom!” Well, in my opinion, that happened after 9/11. Just keep giving away your data under the guise of, ahem, “personalized advertising”.

      1. Christopher Horne

        Herein lies the difference between ‘liberty’ and ‘freedom’.
        Freedom means there are no rules. Liberty means that a citizen
        accepts certain rules promulgated by a higher authority.
        When a Navy ship docks in a foreign port, for example,
        the sailors hear over the loudspeaker, “Liberty Call, now, Liberty Call.”
        Hearing ‘Freedom Call” would mean that the sailors had no obligation
        to obeys commands to return to the ship.
        Freedom is effectively anarchy (ask any trumpy), whereas liberty
        means that you agree to certain restrictions and obligations, such
        as a jury duty summons or to pay taxes. Savvy?

    2. drumlin woodchuckles

      i voted for the climate denier, because the alternative was permitting Hillary Clinton to become President.
      And she posed an unacceptable risk of thermonuclear exchange with Russia.

      Granted, a thermonuclear exchange with Russia would have de-warmed the global for several years at least, but at an unacceptably high cost.

      And when you consider that the MDS-DemParty Industrial Complex tilted the Republican Primary Pinball Machine to produce a Trump Nomination, on the theory that Trump would be the easiest Republican for Hillary to defeat, we should accept the fact that Trump was DemParty Boss Hillary’s gift to the nation and to the world.

      1. drumlin woodchuckles

        In ” MDS-DemParty etc.”, I meant “MSM”. As in . . . MSM-DemParty Industrial Complex.

  6. Parker Dooley

    The first chapter of Kim Stanley Robinson’s latest novel “The Ministry for the Future” describes what happens when the wet bulb temp exceeds the survivable limit and the power goes out in a large city (in India). A truly horrifying scenario.

  7. Arizona Slim

    Slim checking in from Tucson, where it has been raining for four days. Yup, you read that right. Four straight days of rain in our desert city.

    It’s officially the wettest monsoon to date through July 25th. Link:

    Don’t have the foggiest idea if our current weather has anything to do with climate change, but I do know that my cistern is officially filled to the brim. Got 1,500 gallons of delicious rainwater for the fruit trees and the garden beds.

    1. c

      Just a normal ‘monsoon’ coming up from Mexico…. on steroids.
      The monsoon in India is said to very bad as well. Refugees, anyone?

  8. David in Santa Cruz

    When Jon Stewart intoned, “We live in hard times, not End Times,” he was wrong.

    There’s a reason why Our Billionaire Overlords are hoarding everything in sight as if it were the End of Days.

    It is…

    1. Christopher Horne

      Come now, friend, these things happen. Spanish flu, the Great Plague…
      Humans are resilient. At the end of the Great Plague, so many wealthy
      people had died that the disease served as a great distributor of money.
      You thing socialism is hated by the rich? They at least have ample
      power to challenge that political ideology. Against plagues, they are
      our equals if it comes to the level of ‘end times’.

      1. David in Santa Cruz

        Pestilence is one thing my friend, but human history is also replete with another driver of redistributive collapse: war.

        When Climate Change makes vast swaths of the planet uninhabitable, Our Billionaire Overlords will meet scarcity with rationing as well as hoarding. The displacement of billions will inevitably create conflict over access to resources necessary to life itself.

        Eight billion human beings isn’t the only world-historical game-changer that we face. So is the ability to wage war with thermonuclear weapons. Even a “limited” exchange of thermonuclear devices is likely to create a nuclear winter that could wipe-out life as we know it. There is no historical precedent for a nuclear winter, other than an asteroid collision, but it is likely to be unlike any plague in recorded history.

        Our Billionaire Overlords will convince themselves that they can survive a nuclear winter that kills-off the rest of us. Science says that they are probably wrong, but ignoring science is the fundamental hubris of our age…

      2. drumlin woodchuckles

        As long as rats and roaches can survive, so can people. Because rats and roaches are edible and people can eat the rats and roaches. I’m not saying we would enjoy it. I don’t think I would enjoy it.
        But it could be done.

        Before we get to that point, we will be fighting with squirrels in the park over stray nuts.

  9. BeliTsari

    All through the last three crashes, those of us investing in efficient, renewable, regenerative & sustainable equities watched PV, storage, smart grid, water, resilient eco-ag and “small” local, innovative, competetive companies recover as investors who’d shunned these “alternatives” woke up (Bush, Obama, Trump… it hardly mattered. Obama pushed “all of the above,” “clean coal,” “bridge fuel” Energy In Depth LIES more than anybody, since Albright, Hillary & Kerry (Biden’s in simply to CRUSH Mr Market’s move to pragmatic renewables) there’s a special place in HELL for DNC™ LLC. Look at all these GREAT stocks, AFTER January 2021. All plateaued and many dropped.

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