If You Thought This Summer’s Heat Waves Were Bad, a New Study Has Some Disturbing News About Dangerous Heat

Yves here. The message with the coming increases in heat is “No way out” for way too many. And even though the focus here is on humans, punishing heat can’t be good for farm animals or wildlife.

By David Battisti, Professor of Atmospheric Sciences, University of Washington. Originally published at The Conversation

As global temperatures rise, people in the tropics, including places like India and Africa’s Sahel region, will likely face dangerously hot conditions almost daily by the end of the century – even as the world reduces its greenhouse gas emissions, a new study shows.

The mid-latitudes, including the U.S., will also face increasing risks. There, the number of dangerously hot days, marked by temperatures and humidity high enough to cause heat exhaustion, is projected to double by the 2050s and continue to rise.

In the study, scientists looked at population growth, economic development patterns, energy choices and climate models to project how heat index levels – the combination of heat and humidity – will change over time. We asked University of Washington atmospheric scientist David Battisti, a co-author of the study, published Aug. 25, 2022, to explain the findings and what they mean for humans around the world.

What does the new study tell us about heat waves in the future, and importantly the impact on people?

There are two sources of uncertainty when it comes to future temperature. One is how much carbon dioxide humans are going to emit – that depends on things like population, energy choices and how much the economy grows. The other is how much warming those greenhouse gas emissions will cause.

In both, scientists have a really good sense of the likelihood of various scenarios. For this study, we combined those estimates to get a likelihood in the future of having dangerous and life-threatening temperatures.

We looked at what these “dangerously high” and “extremely dangerous” levels on the heat index would mean for daily life in both the tropics and in the mid-latitudes.

“Dangerous” in this case refers to the likelihood of heat exhaustion. Heat exhaustion won’t kill you if you’re able to stop and slow down – it’s characterized by fatigue, nausea, a slowed heartbeat, possibly fainting. But you really can’t work under these conditions.

The heat index indicates when a person is likely to reach that threshold. The National Weather Service defines “dangerous” as a heat index of 103 F (39.4 C), and “extremely dangerous” as 125 F (51.7 C). If a person gets to “extremely dangerous” temperatures, that can lead to heat stroke. At that level, you have a few hours to get medical attention to cool your body down, or you die.

Signs of heat illness. elenabs via Getty Images

“Extremely dangerous” heat index conditions are almost unheard of today. They happen in a few locations near the Gulf of Oman, for example, for maybe a few days in a decade.

But the odds of the number of “dangerous” days are increasing as the planet warms. We’ll likely have about the same weather variability as today, but it’s all happening on top of a higher average temperature. So, the likelihood of extremely hot conditions increases.

What does your study show for each region?

In the mid-latitudes by 2050, we’ll see the number of dangerous heat days double in the most likely future scenario – even under modest greenhouse gas emissions that would meet the Paris climate agreement target of keeping warming under 2 C (3.6 F).

In the Southeastern U.S., the most likely scenario is that people will experience a month or two of dangerous heat days every year. The same is likely in parts of China, where some regions have been sweating through a summer 2022 heat wave for over two straight months.

We found that by the end of the century, most places in the mid-latitudes will see a three- to tenfold increase in the number of dangerous days.

In the tropics, such as parts of India, the heat index right now can exceed the dangerous level for a few weeks a year. It’s been like that for the past 20 to 30 years. By 2050, those conditions are likely to occur over several months each year, we found. And by the end of the century, many places will see those conditions most of the year.

What that means in practice is if you’re a rich country like the U.S., most people can afford or find air conditioning. But if you’re in the tropics, where about half the world’s population lives and poverty is higher, the heat is a more serious problem for a good part of the year. And a large percentage of people there work outside in agriculture.

The average number of days with dangerous heat index levels in 1979-1998 and the study’s median projections for 2050 and 2100. Zeppetello, Raftery & Battisti, 2022

As we get toward the end of the century, we’ll start exceeding “extremely dangerous” conditions in several places, primarily in the tropics.

Northern India could see over a month per year in extremely dangerous conditions. Africa’s Sahel region, where poverty is widespread, could see a few weeks of extremely dangerous conditions per year.

Can humans adapt to what sounds like a dystopian future?

If you’re a rich country, you can build cooling facilities and generate electricity to run air conditioners – hopefully they won’t be powered with fossil fuels, which would further warm the planet.

If you’re a developing country, a very large fraction of people work outdoors in agriculture to earn money to buy food. There, if you think about it, there aren’t a lot of options.

Migrant workers in the U.S. also face more difficult conditions. A farm might be able to provide cooling facilities, but farmers’ margins are pretty small and migrant workers are often paid by volume, so when they aren’t picking, they aren’t paid.

Eventually, conditions will get to the point that more workers are overheating and dying.

The heat will be a problem for crops, too. We expect most of the major grains to be less productive in the future because of heat stress. In the mid-latitudes right now, we’re close to optimal temperatures for growing grains. But as temperatures increase, grain yield goes down. In the tropics, that could be anywhere between a 10% to 15% reduction per degree Celsius increase. That’s a pretty big hit.

What can be done to avoid these risks?

Part of our work in this study was determining the odds that the world will actually meet the Paris agreement. We found that to be around 0.1%. Basically, it’s not going to happen.

By the end of the century, we found the most likely scenario is that the planet will see 5.4 F (3 C) of warming globally compared to pre-industrial times. Land warms faster than ocean, so that translates to about a 7 F (3.9 C) increase for places where we live, work and play – and you can get a sense of the future.

The faster renewable energy comes online and fossil fuel use is shut down, the better the chances of avoiding that.

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  1. Parker Dooley

    Interestingly, AC can be provided without an electricity driven compressor (which is the major power consumer). Might need a small electric pump, or possibly a Stirling engine to circulate fluid:

    Absorption cooling

    Of course, this requires a heat differential to work, as does any heat engine. This could be created by concentrated sunlight. Could work when the grid goes down.

    1. Synoia

      Better to mist with water. Evaporation of water cools the air, without machinery or added mechanical heat.

      1. Parker Dooley

        Doesn’t work in a high humidity environment. Water will not evaporate under those conditions. That is exactly the reason why sweating does not provide cooling in high humidity/high heat situations. In those conditions, misting will provide no cooling unless the water is already cooled below body temperature.

  2. Doc

    The part I feel no one is talking about is how can reduce our energy use. Everyone (MSM) talks about how renewables will never be able to replace fossil fuel. Maybe it doesn’t need to at 1:1 ratio. Why can’t we talk about using less? Building in a way that is naturally cooling? Moving to local production of goods that we NEED, rather than plastic crap and fast fashion? We need more than just an energy shift. We need to change how we consume and consume less.

    1. tom baxter

      Well interestingly enough, that’s something we have been doing, just not in the way the eco-warriors intended. There was a massive power-down over the corona virus period, and now with the European war sanctions, another big leg down in consumption. Wars are usually very energy intensive but this one is just using old weapons stocks so the cost is negligible.

      Whether we think these events were random or not is irrelevant, the net effect is factories all over the globe are shutting down, consumer miles driven falling, and the high energy prices are drastically effecting the amount of heating/cooling people apply to living spaces. Like I said, it’s not the solution the average consumer wanted but it is reducing our energy consumption.

      From the article “Will Europe Go Down to Defeat Before Ukraine?”

      …Now that European leaders are returning from summer holidays, it appears only now to be dawning on them that Europe is entering a severe and almost certainly protracted economic crisis.

      Mind you, they were worried enough in late July to Do Something in the form of agreeing to 15% voluntary energy use cuts starting August 1…

  3. Jason Boxman

    This is also essentially a map of mass migration destinations. Much of Europe and Scandinavia are looking pretty good right now. Maybe parts of Canada as well. Much of the United States looks to be finished. Perhaps eventually we’ll have swaths of the United States that are simply abandoned by the administrative state, much like New Orleans was during Katrina.

    Fun times.

  4. Dave in Austin

    Alarmist and suspect but not necessarily wrong. According to the chart, from now to 2100 almost all of Europe will avoid extremely hot days. And the US west coat will also avoid that fate. The models have not been reading the newspapers.

    No mention of the winners, places like Russia and Canada.

    And the assumption that “migrant workers” (shorthand for underpaid people doing work the locals will not do at the prevailing wage) will still exist in 2100 is suspect. At the rate automation is taking hold, the solar-powered field workers are coming, a real disaster for some places.

    In south Asia the monsoon rains have been heavy but not unprecedented. The results vary. India and Bengladesh are doing OK; Pakistan is overwhelmed. To understand why look at the local Pakistani newspaper Dawn’s article on the birth rates. Look back to the 2004 birthrates and you will know how many people are turning 18 and being force to live in flood-prone areas and farm ever more marginal formerly forested land. Bangladesh used to be the “No hope” local basket case. No longer. Look at the chart. Demographics are destiny.

    1. Anthony G Stegman

      In a capitalist world humans are both sources of labor and sources of consumers. Capitalists require both in ever increasing numbers. Long term reductions in human populations will result in increases in tales of woe in the Wall Street Journal, the various business publications, economists of all stripes, politicians, and corporate CEOs. Both Japan and China are expected to experience population declines due to changing demographics. This is considered bad news for both nations. India on the other hand is expected to experience increases in population. This is considered good news for India. As for the US it is expected that immigration will more than offset declining birth rates, so the US will be in good shape. At least the capitalists will be in good shape.

  5. The Rev Kev

    The worse of it is that it seems that those countries most badly effected are also those that are population dense, especially India. Will it work out that some regions will be uninhabitable? The quick and easy answer is air-conditioning like has been applied to other countries but in a world of energy depletion, this may not be an option.

  6. Rip Van Winkle

    Keeping cool – In the 1960s/1970s the Chicago Fire Department by order of The Late Mayor Daley (Daley I) built several small new swimming pools for the communities adjacent to the fire houses, typically supervised by the firefighters. The one I went to was at 50th & Union. CFD would open up fire hydrants with ‘fine spray caps” as sprinklers on the street usually next to parks which did not have pools. Again, firefighters supervising. It was a treat to talk with them and see the hook and ladder trucks up close, usually at CPD Boyce Park at Root Street and Lowe, right by the main Stockyards Gate on Halsted. CPS Tilden High School on 48th and Union would open their vast indoor pool to the community in the evenings, too. The only places I recall having air conditioning at that time were grocery stores and the neighborhood corner gin mills.

  7. mrsyk

    “The mid-latitudes, including the U.S., will also face increasing risks. There, the number of dangerously hot days, marked by temperatures and humidity high enough to cause heat exhaustion, is projected to double by the 2050s and continue to rise.”
    Hard to take this article seriously with an opener using this scale (Come 2050 it could get dangerously warm!). We will be damn lucky to see 2030, let alone the 50’s if we can’t get a handle on methane emissions, particularly from the Arctic Ocean floor.

  8. Synoia

    As s child I lived in the Tropics without Air Conditioning.

    We rose early and we’re at school at 8sm. School ended at Noon, we had lunch and then rested or sleipt until about 3:30 pm. Supper at 7pm, bed at 10 pm,

    Culturally this schedule appears impossible in the US, with it’s very rigid work culture and long commutes.

  9. Susan the Other

    I’d just say that this analysis of 6 degrees F by 2050 is leaving out what a planet this hot will do to plants and animals. If it will harm agricultural crops it will certainly harm all the natural vegetation leading to desertification all over the planet. It will kill off sensitive marine animals like whales who have adapted to cold water. If it kills off the rainforests, the regular flora, seaweed forests, etc. we will risk running out of oxygen. That will be fun.

  10. John Moffett

    The planet will adapt over time, even if it takes hundreds of thousands of years, but people don’t have that kind of time. Earth has gone from a near complete freeze-over to complete melting of the polar ice caps, and animal life has suffered greatly in the short term with each shift. What humans are doing is going to have its most severe impacts on human civilization, with plenty of additional pain for animal life at all latitudes. But it can’t be sustained and it won’t be. The question is whether people will change their behavior and policies now voluntarily, or later involuntarily. Doing it now in a controlled and thoughtful way will give the best potential outcomes, but that would mean the people in charge would have to change their behavior and policies drastically. Right now they are more worried about keeping gas prices down so people don’t complain, and that is just going to prolong the pain and suffering. Capitalism is good at concentrating wealth, but very poor at adapting to the messes that it creates while doing so.

  11. Ignacio

    A physician told me that during the different stages of heat shock the moment you stop feeling thirsty and needing drinking water you are already in danger zone.

  12. Ben

    As a mining engineer where heat stroke underground can be a quick acting and serious problem, one thing not mentioned is humidity which is critical. Assuming enough water and in serious conditions salt, the human body is quite efficient in dealing with heat through evaporation of sweat. Even a light breeze can make a difference.

    1. Synoia

      True, but does not work well if the air is near saturation, which is the case in the non desert tropics.

      Such cooling depends on non saturated air.

  13. Anthony G Stegman

    I don’t like the use of the term “renewable”. If human populations continue to grow no form of energy is renewable. None. As a society we need to stop kidding ourselves that there are magic bullets out there in the absence of reductions (not merely replacement level reproduction) in human populations. As global societies continue to dither and maintain the status quo the situation is growing more and more dire. Will we wake up from our lethargy in time to forestall utter disaster? Things don’t look encouraging.

  14. Peter

    I really wish people would STOP talking about 2050. I may make some people think there is plenty of time. DROP the 50 and change it to 2030. If we do not wake up and address this as any climate-ending event needs to be, we are in serious trouble. People do not realize the number of problems that will come at the same time – heat, draught, followed by crop failures, animals that we need that not many people know – bees, beavers, wolves they all keep the system in balance. There are many more but there is one WE CANNOT forget – STOP the media and ad companies helping fossil fuels companies – they are enemies of the people and war criminals
    in the WAR (not the game) of addressing Climate Change. Lastly it is unlikely that our capitalist company, and there little pathetic trolls in our congress from doing anything except moving forward – NOW.

  15. Millie Watkins

    Quick Question- NZ shows no colouring in any of the 3 progressed maps. Is that because they will never face increased heat or because (as usual) they are left off the global map? Dearth of Data on NZ is our biggest problem :)

  16. Bat Stevens

    I have a feeling the answer to your question is the same answer to the question: why are so many billionaires building bunkers in NZ?

  17. thoughtful person

    Heat is a big issue. A number of comments point out that this is ths tip of the ice berg. Population continues to grow. Crop failures will increase with the predicted conditions.

    What if there was organization that studied the many interlocking variables of human civilization and project some scenarios?

    The IPCC seems to have a severely limited (and biased) formula – only releasing what there is 99% agreement on. It’s like seeing only ultra violet. What about the rest of the visible spectrum?

    The Limits to Growth Study of the early 70s was a good effort at that time. Perhaps these are professors and departments of environmental studies that have followed up. I don’t see a lot of follow-up myself.

    Just as we now know Exxon was studying (and ignoring) CO2 and climate change in the 70s or 80s, I’m sure there are think tanks looking at the trends into the future. I suspect we don’t hear much because the outcomes for most (a die off) would lead to rebellion.

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