Heat Wave 2040

Some things deserve repeating.

One of those things, which happened to come up in conversation recently, is that climate change has its most profound effect on extreme events. Climate change is a change in the probability function (the odds for each possible outcome) of weather, and when you look at probability functions you find that if they change in the way we expect them to, it can increase (or decrease) the chance of extremes by a surprising amount.


Zagreb-Gric, Croatia, is smack-dab in the middle of one of the fastest-warming regions of Europe. It has already warmed by about 3°C (5.4°F) since the year 1880 (here are annual averages of temperature anomaly):

The local warming is especially pronounced since around 1980. It’s entirely possible that by the year 2040, this region will have heated up to 4°C (7.2°F) above its pre-2000 average.

What might be the consequences?

Let’s talk about the daily high temperature during the month of July. We can get a decent picture of its climate — or at least, what it used to be — by taking all the high temperatures on July days prior to the year 2000, and making a histogram:

Zagreb can get pretty hot during July, but not extremely so. I’ve delineated three regions: temperatures as high as 30°C (86°F), which I call “hot” days, with those reaching 35°C (95°F) being “VERY hot” and days peaking at 40°C (104°F) and above are “WICKED hot.” About 20% of July days in Zagreb reach “hot” status, while “WICKED hot” has only happened once in nearly 140 years of record-keeping.

Here’s an idea of what we’ll see, if the average increases by 4°C (7.2°F):

Roughly 60% of July days will be hot days, three times as likely as they were before 2000. VERY hot (dangerously so) will be ten times as likely on a July day as it was. And “WICKED hot” temperatures will happen fifty times as often as they used to. When temperatures of 40°C (104°F) go from “once in a century” to “every other year,” there are consequences.

Heat waves are bound to come in the future, and they’re bound to be worse than the people of Zagreb have seen before. They will bring sickness and death, failure of critical infrastructure (like the electric grid) from the stress of high temperatures and high demand, and a host of other surprises we’re probably not going to be happy about.

Temperature is just one aspect of weather, and when it or any other changes its odds, the events we notice (and usually, suffer the most damage from) are those that used to be so rare we didn’t even worry about them, but become common enough that you can’t get through life without seeing them many times. When Houston suffers a once-in-500-years flood, people notice. When that happens three years in a row, smart people conclude that the odds of what used to be a once-in-500-years flood are no longer once in 500 years.

Unfortunately, such damaging extremes come and they go. We rejoice to be rid of them, when the flood waters recede or a cool evening finally arrives, but in the midst of our rejoicing for relief and all the work to recover from the damage, how soon we lose sight of the root cause. So far, we have neither worked to restrain how bad the future will get, nor prepared for the changes we know we can’t avoid.


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43 responses to “Heat Wave 2040

  1. Reblogged this on jpratt27 and commented:
    Stop Adani

  2. Hello. If you apply your analysis to the hottest regions on earth (middle eastern and equatorial regions), how long until such regions become uninhabitable due to extreme, un-survivable heat waves?

  3. Seems about right, sadly. Well-said.

  4. This analysis assumes the distribution of temperatures is constant with the warning only affecting the mean. It’s there evidence to support that assumption, or could the distribution be wider with warning?

    • Tamino has looked at this previously and found that the 2nd moment of the temperature distribution looks about the same. That may be true, or it may be that you need more data until the change in 2nd moment is evident. However, info to date supports the width staying roughly constant.

  5. So far, we have neither worked to restrain how bad the future will get, nor prepared for the changes we know we can’t avoid.

    So true, sadly. So true.

  6. Excellent summary of what we all have to look forward to!

  7. One adjustment to those super-high temps is adequate building: white and/or double roofs, thermal insulation, high thermal inertia buffers (water tanks), that can release heat during the night. So , air conditioning can be reduced or made unnecessary. For the rest, take photovoltaics – no grid breakdown. This is not only good for resilience but for emissions karma as well. And not only in Zagreb, but anywhere. A Dollar (respectively Euro) spent for those measures hurts upfront a little, but pays off after a while.
    Consciousness has to be built, by example, that it can be done.

    • Michael Sweet

      The problem with having a solution of white buildings with double roofs is that then all current buildings will be obsolete. In locations where they did not need air conditioners they have to retrofit them. What does it cost to Install a double roof on an existing home?

      Additonally, the plants in the area will be severely affected. Even grown trees that are able to withstand occasional 36 or 37C can be killed by 42 or 43C. And drought will likely also be stressing trees more. It takes a long time to grow new forrests. And by the time the new trees are grown the climate has changed again. Texas lost over 300 million trees in the 2011 drought. In the Brazos vally 10% of tree cover died in this singel event.

      • “What does it cost to Install a double roof on an existing home?”

        Well, quite a lot, but not a prohibitive amount. It depends very much on the building. Maybe £100 for a tin shack, £few thousand for typical houses. Many buildings in Europe are very poor indeed from a buildings efficiency point of view, for either hot or cold weather. It is reasonable to already describe them as obsolete. They have been heavily optimised for build cost over running cost, often because the builders are not the users, because people are shortsighted, and because a lot of them were built decades or centuries ago, considering only a much lower level of comfort and building technology.

        A massive program of refurb (or replacement) is needed anyway, of which installing much better insulated (or double) roofs, is just a small part.

  8. The principal impact of high temperatures is limiting the time that people can spend outdoors, and limiting the time people can work outdoors.

    Even in the northern tier of the United States, it is expected that with +3C warming by 2100, there will be weeks people cannot work or spend time outdoors. What this will do to the local economies and tourism is hard to estimate.

    Of course, in other places, where people do not have A/C, this means they need to move. In places that do have A/C, this means an additional wallop to the electrical grid.

    Two of the reasons we installed heat pumps in our home were (a) most of our annual electrical was for A/C, and (b), with warming, the heat pumps will be vastly cheaper and more efficient than oil, which is what they replaced.

  9. How much did Zagreb warm in each month? I’m more familiar with higher latitudes, where winter warms more.

  10. Let Eli quote a comment at Rabett Run, oh about nine years ago:

    It’s the creeping statistical hints between the lines of this paper that really bother me. Long before or even if we never see broad areas permanently enter a existentially threatening torrid regime, what about excursions? For instance, Pakistan this year has seen record temperatures approaching 54 degrees C in places where many people live, fortunately with lower humidity and only for handful of days but what about when/if such aberrations extend to a handful of weeks and are accompanied by inexorably increasing humidity? The resulting disaster would cause migrations. The worst-case scenario in Sherwood and Huber would not have to happen before we effectively lose major swathes of territory for year-round habitability.

    http://rabett.blogspot.com/2010/06/death-doom-and-disaster-coming-soon-to.html?showComment=1277263766931#c7358513299246960015

    • I’m pretty sure that that comment was one of mine Brere Eli: that was during my mock-Monckton phase and I didn’t always remember to sign my posts.

      I am suitably chagrined at not having properly left my bunny pellets at the end – and also at the grammatical oversights…

  11. Chris O'Neill

    Heat wave 2019: http://www.bom.gov.au/climate/dwo/201901/html/IDCJDW3033.201901.shtml
    This is only the 5th day this hot (42.6℃) this early in Summer in 160 years in Melbourne. The previous days were in 1868, 1876, 1898 and 2005. http://web.archive.org/web/20100122134226/http://www.earthsci.unimelb.edu.au/~blair/extremes/melbourne.html http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=122&p_display_type=dailyDataFile&p_startYear=2005&p_c=-1481636871&p_stn_num=086071

    The 20th century never had days this hot this early in Summer in Melbourne.

  12. John, there have been some papers out that you might find interesting (and I find terrifying), e.g.
    – Sherwood and Huber: An adaptability limit to climate change due to heat stress. PNAS (Open Access) https://doi.org/10.1073/pnas.0913352107
    – Im, Pal and Eltahir: Deadly heat waves projected in the densely populated agricultural regions of South Asia. Science Advances (Open Access), https://doi.org/10.1126/sciadv.1603322
    – Pal and Eltahir: Deadly heat waves projected in the densely populated agricultural regions of South Asia. Nature Climate Change, https://doi.org/10.1038/nclimate2833

    The key threshold seems to be a wet bulb temperature of 35°C. Pal and Eltahir conclude, “that extremes of wet-bulb temperature in the region around the Arabian Gulf are likely to approach and exceed this critical threshold [towards the end of this century] under the business-as-usual scenario”. Similary for the Ganges and Indus river basins in Im, Pal, Eltahir.

  13. A largely pointless article as it gives no historical data. Warm periods have come and gone over the past couple of hundred thousand years. Still waiting to see any firm evidence that anything man does or doesn’t do in the future will make more than three percent difference.

    [Response: Hmmm… “Gish gallop”? Amusing?]

    • A largely pointless comment because in this context it doesn’t matter whether climate change is anthropogenic or not: the climate is changing and we have to adapt our cities and our lifestyles.

    • Which studies did you read when you were looking for this firm evidence?

    • Invest everything you’ve got on the sure line and enjoy the show!

    • Apparently every article needs to answer every question for ‘Steve.’

      I’d consider that unrealistic, but hey, what do I know.

    • 3 percent on the Kelvin scale? Looks more like drive-by stupid to me.

    • Also–“three percent” of *what*, exactly?

      Mean terrestrial surface temperature is something like 288K. So 3 percent of *that* would be 8.64 K (or C, for that matter). Given that the ‘sort of safe’ limit has conventionally been considered 2 C, and that opinion is coming around to the idea that really, 1.5 C would be quite a bit safer, one can see that 8.64 C would be pretty disastrous.

      For instance, apply an 8.64 C shift of the mean to the Zagreb graph above, and you’ll find Zagreb would start to see 50 C days. And basically, every July would see average daily highs well above 25 C–almost none below 20. The mean daily high for the month would be above 35 C, or “wicked hot.”

      Apply that to large chunks of the Middle East and southern Asia, and there would be killer heatwaves with mortality rates among the unsheltered approaching 100%.

  14. Is this a weather station within Zagreb? If not, one can also add on an urban heat island effect that will knock the temperatures up by another degree or two. We have spent so much time trying to rid ourselves of the false idea that the temperature record is from UHI only that we forget that temperature changes within urban areas are real and are added to the CO2 forced change.

    • Yes, it is. However, one should be very careful to connect changes in temperatures with UHI. For example, National meteorological service of Slovenia did a great effort of providing homogenized datasets for various station across the country, There are two stations in the vicintiy (35 km distance) of Zagreb, and both are rural stations and homogenized data set for station Gornji Lenart showed a trend of 0.061 C/year from 1979 to 2011 and 0.0446 from 1981 to 2011 for July average temperatures. Which looks close to the rise of average July temperature in Zagreb in same period.

  15. @Steve,

    Let’s say you are correct on

    Warm periods have come and gone over the past couple of hundred thousand years.

    Given that civilization has developed only at the very end of that 200,000-300,000 years, I’d suggest that, on the adaptation side, there would be little difference in how the world should rejigger things and spend from the case of human-caused climate change.

    And on

    Still waiting to see any firm evidence that anything man does or doesn’t do in the future will make more than three percent difference.

    that’s very specific. So, accordingly, there must be some reasoning and calculation behind it, no? Let’s see it! Or are you just pulling that out of your a__?

  16. Massive crop failures will occur before 4C as plant-respiration is exceeded (and drought / deluge goes nuts). This seems to be one of the most overlooked facts of all. It’s absolutely possible that starvation will encompass vast swaths of the globe before we think about infrastructure failures on a wide scale due to rising temps.

    Don’t forget the other critical issue that is overlooked too – 95% of American sea ports will be totally unusable due to sea level rise by then, so this mean many other sea ports around the world will also be unusable. Global shipping will shut down and/or be greatly diminished affecting both economies and availability in a huge way.

    So then, whatever food is still being produced in plant-tolerable temperatures (elsewhere), will be hotly contested (pun intended), limited in supply (highly affected by temperatures and pollination variations due to rising temps) and extremely difficult to transport (and insanely expensive). Wealthy countries
    will eat, and you know what that means for the non-wealthy.

    Higher temperatures ultimately mean massive starvation, no matter what. It’s the giant elephant that everyone tries to ignore.

    • The Chinese are not ignoring this elephant – do people not wonder why they are quietly and determinedly expanding across Eurasia, the Pacific, and into Africa?

      They know what’s coming.

  17. “Warm periods have come and gone over the past couple of hundred thousand years.”

    Last I knew, over the past couple of hundred thousand years the median human population was less than 10 million. Decreasing the amount of habitable land due to extreme climate changes still left plenty of room for them (and the rate of change gave them plenty of time to migrate). At seven billion and counting, that is no longer true. Also, the infrastructure (caves and huts) was much easier to abandon and replace.

    I apologize for pointing out the obvious ways that the situation is different now, but I think conditions now are what we should be considering.

    • Ah! But your concern, Jim, isn’t for inspecting individual sand grains from the inside of the pile.

    • @JimV,

      Apart from the collapse of agriculture mentioned by @JR above, people continue to be myopically focussed upon what direct effects from CO2-induced warming are upon people. Climate change is but the latest — and, arguably, most important — insult to the biosphere by humankind. The warning has been made time and time over, and primarily ignored, but even without warming, the biosphere is under such assault that it’s services which support human life are collapsing. These are subtle, and the ramifications of this are not understood. (No doubt, the luckwarmer-like attitude is to demand proof of catastrophe before caring.) But the effect is to affect that ecological notion called carrying capacity for humankind. From an ecologist’s perspective, the only reason we have been able to have billions of humans on Earth is because of fossil fuels. But the destruction of habitat never-ending expansion wreaks its own havoc upon how biology works, and that system is not in equilibrium at the moment.

      In addition to impacting sources of protein from oceans, these biological services also keep microbial populations and pests in balance. Without the services, it isn’t difficult to imagine that interacting with the natural world could be a much greater risk.

      In connection with this, E. O. Wilson in his new book, Half Earth suggests that it is inevitable that as standards of living rise, human population will level off and begin to shrink, all on its own. He also suggests that to restore the biological services upon which we depend, a full half of the planet’s land and oceans need to be set aside as protected reserve, and these reserves need to be contiguous and varied.

      The idea that a loss of a single Earth system has effects which can be contained is a rookie mistake in ecology. But we collectively do worse, pretending that, apart from aesthetics, it doesn’t matter if the natural world is there or not.

      • But we collectively do worse, pretending that, apart from aesthetics, it doesn’t matter if the natural world is there or not.

        I’m reading Herman Daly & John Cobb’s “For The Common Good” , which points out that it has been a tenet of classical economic theory that natural capital can be infinitely substituted by man-made capital (and, for that matter, that natural capital has been conceptualized mostly as nothing more than real estate.) That has provided a pervasive cognitive bias affecting primarily the educated among us, and not least business and political leaders.

        Combine that with a persistent tendency for more and more people to live lives almost entirely isolated from most natural processes and phenomena, and the ‘pretense’ you note should perhaps not surprise us too much.

      • @Doc Snow,

        There is also a long lasting and increasingly pervasive practice of political leaders, policymakers, and businesspeople to downplay risks by appealing to selective information. I have seen this firsthand, and I heard about it at a meeting of the Environmental Business Council of New England (EBCNE) where NOAA’s Ellen Mecray, Regional Climate Services Director, mentioned that, while NOAA updates their rainfall predictions based upon historical information every (I think if I recall properly) 5 years or so, states and municipalities remained using 1960s and 1970s projections.

        In the case I am familiar, in Massachusetts, there is a Commonwealth document which prescribes how stormwater management should be planned, and uses an illustration from a 1960s rain projection from NWS to work an example. In a local building project, when I challenged an engineer at a civil and environmental engineering firm why they used such a low number for 24 hour rainfall, he claimed that the Commonwealth specified it, referring to this document. I checked it out, and they did not specify it, but the number is frozen in time and is being used for this purpose. This is entirely speculation on my part, but I can imagine an engineering firm being preferentially selected for contracts if their designs and solutions low-balled, say, stormwater management in order to keep costs low.

        Now, of course, if you look at the schedules for our town from NOAA, you’ll see that there’s a 2% chance per annum of 8 inches of rain in 24 hours. This has no climate model in it: It’s just an up-to-date projection based upon weather and data.

        Apparently, the way policymakers and administrators are playing this is either in total denial, or betting that, when it happens, they can play it as a once-in-a-very-blue-moon horrific event, act-of-Flying-Spaghetti-Monster-style, and thereby deflect the blame.

        I don’t think I’m being paranoid here. There was a flooding event in Westwoo in 2002 or 2003 before I lived here that caused some property loss. The Town, by public outcry, convened a committee, which held hearings, wrote a report, and then, when the public had gone on to other concerns, effectively mothballed the report. I know: I have a copy.

        This is how present risks are being “managed”. Don’t know what people would do/will do with climate risks.

      • Ecoquant, you sound like Jeff H, in that your points are well made…

        And a +1 for your reference to EO’s Half Earth.

        On the issue of collapsing ecosystems/services, we are in for a rude awakening over the next decade and beyond. There will be tears…

      • ecoquant, your points are indeed well-made. That up-close detail on ‘risk management’ as practiced is quite disturbing.

  18. John Brookes

    “The local warming is especially pronounced since around 1980. It’s entirely possible that by the year 2040, this region will have heated up to 4°C (7.2°F) above its pre-2000 average.”
    Isn’t it unlikely that a place that has had more than its share of rapid local warming will continue to do so? Regression to the mean and all that. I’m more worried about Perth Western Australia, where we have had quite a few mild summers lately (and this one, touch wood, seems like another). The thought that one year soon we’ll break loose and have a stinker of a summer fills me with dread.

    • Chris O'Neill

      “a stinker of a summer ”

      Try Tennant Creek:

      December: http://www.bom.gov.au/climate/dwo/201812/html/IDCJDW8045.201812.shtml

      January: http://www.bom.gov.au/climate/dwo/201901/html/IDCJDW8045.201901.shtml

      I’m sure they’re looking forward to a day that stays below 40 ℃.

    • @John Brookes,

      While there is bound to be some local fluctuation, regression to the mean technically only works when the mean is constant. If the mean itself is a function of an exogenous quantity, and depending upon how strong the dependence is, this won’t happen.

      In other words, while regression to the mean might be working, the mean itself itself stationary.

      • John Brookes

        I think you miss the point. When you find a local trend that is clearly at odds with the global trend, it is unwise to extrapolate that local trend, as it is likely to gradually come into line with the global trend. If I was a gambler, I’d put money on it. Just as I’d put money on the world this decade being hotter than the last and cooler than the next.

      • @John Brookes,

        That’s clear if the local trend is of opposite sign to the general, but what if it has the same sign? How much different does it need to be to be “at odds with the global trend”?

        The precise value of a sample average depends on the details of the sample and hence varies from sample to sample generated by the very same process. If the process is stationary, such averages converge with growing sample size and become independent of the details of the chosen sample. Only then do they represent a system property rather than a sample property. The issue of this paper is how slow such convergence can be;i.e., how far an average over a finite time window can be off the asymptotic limit. We do this specifically inview of the common practice to use a 30 year time window to quantify climate.

        From M. Massah, H. Kantz, “Confidence intervals for time averages in the presence of long-range correlations, a case study on Earthsurface temperature anomalies”, Geophysical Research Letters (2016), 43, 9243–9249.

        They don’t mention the Politis and Romano stationary bootstrap which is another way of assessing long run variability.

  19. I’ve been absent from the climate blogosphere a lot lately, and I deliberately returned tonight to ask tamino to revisit his old posts on exactly this issue – the future consequences of currently locked-in climate change. I was pleased to see this posting, and I hope that there are more to come, not only on the subject of more extreme events, but how these will affect us and other species physiologically and ecologically, and how it will affect societies economically.

    We need to start to understand what’s coming, because without doing so we cannot attempt to properly and effectively minimise the approaching damage, or to prepare for that to which we’ve already committed the planet. I’ve really enjoyed seeing Tamino collaborate with climatologists over the last few years, and I hope that he can reach out to some climate-focuessed ecophysiologists to explore what we should expect over the coming decades and centuries…