Simmered to the Edge of the World

When denier ideologues make the transition to accepting the reality of anthropogenic global warming, one of the arguments they start to use tends to go something along the following lines: “Sure, the polar bears might get screwed over, but otherwise things will be just great. Crop yields will increase and northerners will get to have their own sun-drenched beaches”. You wish. New research* indicates that beyond temperature rises of 7C, “zones of uninhabitability” will begin to overspread much of the world (“An adaptability limit to climate change due to heat stress” by Sherwood & Huber 2010). Not a Mediterranean world, more like Mad Max in Waterworld.

Of late climate models have been leaning to the upper range of the IPCC’s projections for global warming, e.g. the median forecast from a recent MIT study gives a rise of 5C by 2100 (with a 10% chance it will exceed 7C). According to the Sherwood paper, “peak heat stress” (quantified by the wet-bulb temperature) never climbs above 31C across today’s climes, which is safely below the body’s normal temperature of 37C. But with a global temperature rise of 7C possible by as early as the late 21st century – even without accounting for predictable tripwires such as accelerated release of Siberian and Arctic methane – some regions of the world will be subjected to peak wet-bulb temperatures of 35C, inducing “hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible“. With a global temperature rise of 11-12C, a belt of uninhabitability will come to encompass the bulk of today’s densely populated areas.

Let that sink in. Forget the rainforest collapses, the icecap disintegrations, the plummeting crop yields as the increased CO2 fertilization effect is cancelled out by heat stress… during the long summers, the bulk of continental interiors below the Arctic Circle will become PHYSICALLY UNINHABITABLE for humans. Cities from Atlanta to Madrid to New Delhi will become ghost towns in the desert, crumbling relics to the long-dead gods of the industrial age.

“Periods of net heat storage can be endured, though only for a few hours… and with ample time needed for recovery”, but since “adjacent night time minima of [wet-bulb temperatures] are typically within 2-3C of the daytime peak, and adjacent daily maxima are typically within 1C”, conditions would prove intolerable “if the peak wet-bulb temperature exceeded, by more than 1-2C, the highest value that could be sustained for at least a full day”. Thus, even healthy individuals cannot sustain heat stress levels of above 35C for prolonged periods, because the skin must be at least 2-3C cooler than the body temperature, whose normal level is 37C. If the wet-bulb temperature rises to 38C, for instance, then the result will be a rise in body temperature to above 40C and death from hyperthermia.

Which areas will be effected? Just look at the maps below (click to enlarge, source).


[Map of max rates of global heat stress during 1999-2008. Graph represents incidences of various temperatures during this period at 60S-60N – Black is average temperature, Blue is max temperature, Red is max wet-bulb temperature. Note how maximum wet-bulb temperature takes a nose-dive after 30C, such that there are practically no instances of this measure exceeding 32C (in practice this means that today no areas are blocked off to human habitation because of excessive heat stress levels).]


[Same as above, except this time it’s a high-CO2 world model in which global average temperatures are 12C higher than today. The white and purple areas are completely uninhabitable, while the yellow areas are only marginally habitable at best. Note how much of Siberia experiences a higher max wet-bulb temperature than today’s tropics!]

For a preview of things to come, look no further than the 20,000 Parisians who died in the 2003 European heatwave**. True, most most were elderly folks with no air conditioning or climate control. But these things require a lot of energy. With dammed reservoirs drying up throughout Europe and hydrocarbon supplies peaking by 2030-50, a reliable electricity supply should not be expected (least of all during heatwaves). As the authors put it, “the power requirements of air conditioning would soar; it would surely remain unaffordable for billions in the third world and for protection of most livestock; it would not help the biosphere or protect outside workers; it would regularly imprison people in their homes; and power failures would become life threatening”. Not only people will begin to die away. So will plants and animals – indeed, the main catalyst for migration may become failed harvests and famine. Entire nations will have to pack up their bags and move north towards the peoples-teeming Mediterranean shores of the Arctic Ocean.

Finally, the authors point out that even these dark conclusions may be too optimistic, since “our limit applies to a person out of the sun, in gale-force winds, doused with water, wearing no clothing, and not working” (i.e. quite a lot of leeway for enhancing chances of survival!). In other words, it is quite possible that only polar, sub-polar, and mountainous areas will remain comfortably habitable (at least by the new standards).

One more thing I’d like to note is that the map seems to indicate that at least along coastlines, the moderating effects of the oceans will keep those areas livable. That is highly significant… even with the loss of continental interiors, some tropical and mid-latitude nations may continue eking out a bare bones sustenance existence by intensive use of permaculture, organic farming, and hydroponics (the oceans will be too acidic to support fisheries). But don’t forget about sea level rise and the ocean anoxic event.

Waves slowly lap on the quiet shore, slow-motion waves with the consistency of gelatin. Most of the shoreline is encrusted with rotting organic matter, silk-like swathes of bacterial slick now putrefying under the blazing sun… [W]e look out on the surface of the great sea itself, and as far as the eye can see there is a mirrored flatness, an ocean without whitecaps. Yet that is not the biggest surprise. From shore to the horizon, there is but an unending purple color — a vast, flat, oily purple. No fish break its surface, no birds or any other kind of flying creatures dip down looking for food. The purple color comes from vast concentrations of floating bacteria, for the oceans of Earth have all become covered with a hundred-foot thick veneer of purple and green bacterial soup. …There is one final surprise. We look upward, to the sky. … We are under a pale green sky, and it has the smell of death and poison. We have gone to Nevada of 200 million years ago only to arrive under the transparent atmospheric glass of a greenhouse extinction event, and it is poison, heat and mass death that are found in this greenhouse.

* Back in November 2009, the article abstract was put online. Published in March 2010 (access from scribd) and made its way into MSM this May (e.g. see Telegraph story).

** Incidentally, I happened to be in Paris during the 2003 heatwave. Overall, it was a pleasant visit, though the heat and multiple cold showers every day stand out in my memory.

Anatoly Karlin is a transhumanist interested in psychometrics, life extension, UBI, crypto/network states, X risks, and ushering in the Biosingularity.


Inventor of Idiot’s Limbo, the Katechon Hypothesis, and Elite Human Capital.


Apart from writing booksreviewstravel writing, and sundry blogging, I Tweet at @powerfultakes and run a Substack newsletter.


  1. AK, you are simplifying things, and dangerously so.

    Lets start with Wet Bulb temperature. Wet bulb temp. is influenced by much more than heat – humidity and air pressure have as large an influence on wet bulb as do shifts in Celsius. Problem is, climate change (particularly at the 7+ level) will change both of those things world over. But even if this study included long term projections of air pressure and humidity, it would still be incredibly wanting in accuracy. We don’t know what the world is going to look like past 3+ C. Will the Amazon be a great desert? The Iberian peninsula a rain forest? The Pacific an ocean of cyclones, the Atlantic an ocean bereft of them? We don’t know. There is no comprehensive assessment of what the world would look like when temperatures are 4+ higher than they are now, much less 7+. And even our century long predictions using lower temperature shifts are but rough approximations which cannot provide us with anything but the broadest of generalities.

    Let us be honest with ourselves. Region specific and comprehensive models that go out further than 30 years are guesses in the dark. There are too many variables, and the models cannot account for the unknown changes in them all. In the future rests critical transition points for almost every part of the biosphere: the size, number, density, or duration of deserts, rain forests, agricultural lands, algal blooms, glaciers, snow pack, ice sheets, cyclones, plankton populations, river levels, air pressure, monsoon cycles, and a thousand other parts of our Earth that possess the potential to throw the system one way or another. As it is scientists are arguing furiously over each and every one of these things and cannot provide anything less than a broad range of estimations for each … and this is without taking into account the changes all the other variables will have on each other!

    To imagine we know what the world will be like in a century is lunacy or arrogance. Once the temperature starts to shift in earnest we really won’t be able to do anything but guess.

    Which is to say that the map shown in this post, along with references to specific uninhabitable cities and regions, is ridiculous.

    Furthermore, you are peddling the extremes of extremes as if they are the mean. Can you name one climate scientists who would stake their reputation on the claim that we will have 7 degrees of warming by the end of the century? Much less 12 C? The temperature shift being discussed here are a matter of centuries.

    Finally – the one bit that strikes me as most odd is how far this seems to deviate from the current fossil record and paleoclimate data. The Paleocene and Eocene were much hotter than today, and there is a clear Mammalian fossil record for both of these periods. If what this study says is true, how could these mammals have survived?

    The same criticism works for an ocean anoxic event. The Earth has had much higher temperatures since the last (possible) event happened 300 MYA. Bringing it up is blatant scare mongering.

    • TG, I don’t claim any expertise in CC, so I can’t judge to what extent this model by Sherwood & Huber is valid. However, I do think it’s useful to help make it known, if for nothing else but to demonstrate that 1) the higher projections related to GW will lead to a drastically different world and 2) said new world is likely to bring major disruptions to most populations, possibly up to and including making parts of the world physically uninhabitable.

      I acknowledge your point that there are major disputes over regional prospects, but there is general agreement that climate feedback loops are mostly positive (accelerate GW) and that a warmed world is going to be both hotter and more humid. Given a large enough warming, the appearance of “zones of uninhabitability” (given the information we have on the body’s limits to heat stress) over the sub-polar lowland interiors is almost intuitively obvious.

      Can you name one climate scientists who would stake their reputation on the claim that we will have 7 degrees of warming by the end of the century? Much less 12 C?

      The 7C rise is not much beyond the top of the IPCC’s worse-case scenario (6.1C), so I think it would be OK to take it is a feasible worst-case scenario for 2100 (cue the recent work on long tails in climatology). The 11-12C rise was cited as feasible by 2300 in the paper.

      If what this study says is true, how could these mammals have survived?

      Adaptation and dwarfism, I suppose. Lots more didn’t make it, and today’s global warming processes are likely happening much faster than previous mass extinctions.

      • Adaptation and dwarfism, I suppose. Lots more didn’t make it, and today’s global warming processes are likely happening much faster than previous mass extinctions.

        Perhaps, but again, the fossil record presents problems. Geologists, Paleontologists, and other folks interested in Earth’s ancient past divide the Paleocene (65-55 MYA) and the Eocene (55-35 MYA) at the point of the Paleocene-Eocene Thermal Maximum, a period of about 10,000 years where the temperature jumped some 12 degrees. However, the maximum is only part of the reason this point is chosen. It is also the beginning of the so-called Eocene Explosion, where mammal lineage diversity quite literally exploded. It was in the Eocene most modern mammalian orders – ugilates, rodents, carnivora, primates, whales, bats, ect. – evolved. This all happened during a period much warmer than today. (And this general warm trend lasted tens of millions of years – even though the planet as a whole and the polar regions in particular cooled down during the period, the tropic regions – which were extensive – were rather stable and hot).

        So we know that the last there was a major upward climb in the climate it was a period where mammals not only survived, but thrived.. It is quite likely that if the event did not happen (and the low level extinction event that accompanied it) mammals never would have become Earth’s ruling class. But the event did happen and we are forced to come to terms with the evidence it left us.

        It is quite possible that ancient mammals were similar to the camels and gazelles living in the Arabian peninsula (highest wet-bulb temperature on Earth, BTW) had the ability to allow their body temperature to swing wildly with outside conditions (in the case of the gazelle, their body temp. can undergo 10-degree shifts!). But if so, why is this incredibly useful evolutionary adaptation not to be found in most all mammals today? We are all descendants of the Eocene; with the exception of marsupials, almost every single major Mammalian order evolved during this era. (And the marsupials still survived it.) It is not plausible that none of their descendants did not retain the adaptation.

        This issue really has more questions than answers.

        Which could be said about climate science as a whole. We know, as you state, that the climate will warm and the great majority of feedback effects will increase, not decrease, this warming. But that is about it. We are stuck on the planetary scale. Anything below that is a crap shoot in the dark.

        The reason is easy enough to see. Lets take an easy example: desertification in Northern Africa. For simplicity’s sake, let us imagine that the only variable that affects desertification in Northern Africa is temperature. As temperature increases so do the deserts. But as deserts in Africa increase, so do the size and frequency of Atlantic dust storms. Scientists are not too sure on this, but they suspect that these dust storms have an adverse effect on Atlantic coral populations and increase the likelihood for tropical storm events in the North Atlantic. Setting aside the coral populations for a moment, we know that an increase in tropical storms and hurricanes could potentially change humidity and precipitation levels in North America and the Caribbean, provide a tipping point for swamp and coral ecosystems ravaged by these storms, and change the pattern of human use of the land concerned. Just to take the last one of those, a change in agricultural use of land near the coasts could result in a decrease in the fertilizer that gets into the sea, thus reducing the number of algal blooms and making coast ecosystems a bit more stable. Or perhaps it will lead to more direct human control and management of the coasts, swamplands, and everglades. Or perhaps it will lead to an intensification of industrial or agricultural activity inland, which in turn could…

        And you get the point. Something that seems very simple – dust storms – can have massive ripple effects across the entire system. And not just one ripple, but dozens. Notice too that I used the words “could”, “Potentially”, and “possibly” – and this for good reason. Much of what we have is speculative. We do not possess a spare planet on which we can test our hypotheses against Ho. We know that sandstorms change Atlantic storm patters, but we do not know to what extent. And even if we did have a precise knowledge of the relationship between dust storms and hurricanes, we would still be in trouble, because we do not have one solid temperature prediction to rely on, but a whole range of possible temperatures. And this trickles down across the entire system – just as there are a range of temperatures that might change dust levels, so there are a range of ways anyone temperature could change dust levels, and so there are a range of possible responses that could occur in the Atlantic storm systems (as well as the other things sandstorms might affect), and so too is there a complete range of responses to the various range of responses of the Atlantic storms, and so on and so forth until you get to regions and ecosystems far removed from the original input.

        So the question is this: how many of those modeling future Amazon deforestation rates or water levels in the American southwest take dust storms over the Atlantic ocean into account when they create their models? Even better, how many modelers model not only Atlantic dust storms, but the complete range of possible increases in Atlantic dust storms? And the complete range of responses that could occur for each of these possible increases? How many account for all the possible dust storm scenarios, all of the potential scenarios which could occur because of these, and the possible scenarios emerging from other changes that temperature changes might prompt- say, rising sea levels or monsoon intensity?

        The task is impossible. The number of scenarios is beyond our ability to compute. The Earth is the greatest complex system humankind has yet found. It is Extremeistan. We know that things will change, but we cannot adequately model them on anything but the most general of scales.

        This is, incidentally, the reason Mark Lynas and co. book’s are so fanciful. There really is not a better word for it – the paintings they provide of a world on fire are fantasies, bits and pieces of potential possibilities they have chosen to sound particularly frightening. Will climate change be as scary as they say it will be? Probably. But will it be scary the way they say it will be? I remain skeptical.

        Which is to say that the map shown in this post, along with references to specific uninhabitable cities and regions, is ridiculous.


        Which could be said about climate science as a whole.

        • Disregard that last sentence, it creeped in on accident.

          I might also mention that this is a very strong reason not to even think about geoengineering – we cannot predict the consequences of our actions. Humanity has truly dug itself into a hole.

          Of course, we have always been in this hole, haven’t we? It is only now that we are smart enough to have figured this out.

  2. “The Earth has had much higher temperatures since the last (possible) event happened 300 MYA.”

    How many of those events had close to 7 billion people exploiting every inch of the planet’s carrying capacity (phantom and otherwise)? How bad do things have to get before you become concerned? As long as at least a handful of breeding pairs of homo sapiens remain, then don’t worry, be happy?

    • This misses the point. I do not claim that climate change is desirable. What I have stated is that the likelihood of the ocean suffering from an anoxic event because of AGW is next to nil. If the projected levels of heat would lead to such an event, it would have happened dozens of times throughout the last 300 MYA, and this simply hasn’t happened. The number of people on the Earth and the resources they are using is a nonfactor.

      Alas, I am going to have to let you guys have at me for a couple of days. Have at me, and when I’m settled down again I might be able to venture a response. ^_~

  3. georgesdelatour says

    I recommend you follow the climate work of James Annan. He’s done some excellent work on climate sensitivity.

    Here are his thoughts on the MIT study:

    Here are some other relevant blog posts. This:

    And this:

    And this:

  4. Paint me sceptical says

    “Of late climate models… the median forecast from a recent MIT study gives a rise of 5C by 2100

    Are there people who actually take this seriously? How dumb does one have to be to think that scientists can predict climate 90 years into the future while they are having a great deal of difficulty correctly predicting the weather 3 days ahead?

    • @Paint me sceptical:

      Let me introduce you to NASA’s brief explanation of the difference between weather and climate.

      Or to rejoinder: I don’t know a single weather man who can’t predict a region’s climate 3 days ahead. Do you?

      • Paint me sceptical says

        Your own link contradicts what you claim: “The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere “behaves” over relatively long periods of time.”

        So weather is just short-term climate. And since the scientists can’t predict the climate over a short term they can’t predict it over a long term. Period. It’s really that simple, stop deluding yourself.

        • Weather and climate are a matter of particulars and averages. Almost all predictions, absent those made in extremistan, are more accurate in the aggregate. This is a basic rule of statistics,acknowledged by all who practice that craft.

          Think of flipping a coin, if you will. Take one out of your pocket and flip it six times. Lets say 5 of the 6 are heads – an occurrence which is not unusual, as anybody who who has flipped a coin multiple times knows. However, on the face of it, it seems that the laws of probability (or our knowledge of them) are awry. The coin should land heads 50% of the time and land tails 50% of the time? What happened?

          The laws are not wrong, and neither is the probability count. The problem is that with such a small sample size local variance will skew the results. Six tosses is simply not enough to make a general statement about the behavior of the coin in question. More often that not randomness will set a pattern contrary to the true probability of the two results. But as you increase the number of observations – in this case, the number of times you flip your coin – you will find that the two results will get closer and closer to their true probabilities.

          As with coins, so with climate. On the short term weather is quite unpredictable. Randomness gets in the way of broader generalizations. It makes no more sense to reject the accuracy of climate projections on the basis of our inability to predict seven days of weather than it does to reject our probability projections for coins on the basis of our inability to predict the results of seven tosses.

          Climate is more complex than a coin, of course – but our predictions are quite a bit more general as well. Climate projections almost always deal with a range of numbers, not one crisp percentage point.

          All of this withstanding, our ability to predict the climate is not half bad. While we cannot predict the exact amount of rain any one location in the world will receive on a given day, we can predict with some accuracy the amount of rain a place will get in a month, and the likelihood that a certain amount will fall on any one day in that time. Likewise, we can generally predict when the snowfall of an area will have melted away, an estimation of the number of tornadoes a region is going to experience in this or that month, and the average humidity of a region during its summer and winter peaks.

          Or in short: It is not quite a simple as you make it out to be.

  5. I suspect that in order for me to acquire an informed opinion on whether or not the recent polar (it’s hardly global) warming has been anthropogenic, I’d have to spend years immersing myself in that field. I haven’t done that. In the absence of a truly informed opinion, I, like a lot of people, simply have a vague feeling of skepticism. There are obvious political and financial interests on both sides of this controversy. More than enough incentives to try to fool people into thinking that the scientific debate is settled.

    Anatoly, I would be interested in your take on this series of graphs:

    If you consider them misleading, why? I’d be willing to listen. Taken by themselves they imply that there is nothing unusual about the recent temperature increase.

    One of the smartest people I’ve ever known told me a few years ago that he had looked at the climate models used by global warming enthusiasts. He thought that they were very flawed, saying that there are too many variables, too many unknowns in the system for any long-term predictions to be made or for causation to be established. He described the models as assumptions piled on top of assumptions.

    While I’m ignorant of the details, this made intuitive sense to me. The atmosphere, besides being vast, is affected by an unknown, but obviously very large number of factors – how can anyone be sure about what will happen to it in 50 years? If someone invented a method to reliably predict the weather even 2 or 3 months in advance, he’d quickly become a billionaire, and yet there are people getting government pay who say that they know what the average temperature is going to be in 2100?

    • 1. Sorry but I think the argument that there are “political and financial interests on both sides of this controversy” is grossly disbalanced. The stakes for the hydrocarbons companies (trillions of dollars) are far higher than for climate scientists or renewable energy commercial interests (millions of dollars and billions of dollars, respectively). Not to mention that it is politically far easier to support the status quo than advocate for the economically painful change of energy transition to lower EROEI sources.

      2. Re-your link. Said temperature graphs, assuming they are accurately sourced (I don’t have the time or will to check), 1) only cover Greenland, one region of the world; taking another region, say the nearby Arctic, will yield vastly different results; taking the world as a whole, global temperatures have been rising at a fast clip since the 1970’s, and 2) is actually a strawman: contrary to what the author wants to imply, no-one denies there are natural climatic fluctuations and transitions based on the particularls of the Earth’s orbit and the level of solar irradiation. However, the main warmist argument is that the levels of atmospheric CO2 are now so high (and there’s no doubt that humans put them up there) – they were last seen during the Plicene 3mn years ago, a time when Greenland was deglaciated and sea levels 25 meters higher – that in coming years it is this anthropogenic greenhouse effect that will become the main driver of climate change.

      3. “He described the models as assumptions piled on top of assumptions.” Well, most models are. But the assumptions are valid, as far as these things go – things like albedo, heat transfers between bodies, etc, are well-established physical principles. (Interesting, telltale tidbit: the Norwegian chemist Arrhenius, 100 years ago, worked out that a doubling of global CO2 levels leads to a temperature rise of 5-6C; well in line with IPCC forecasts, using just pencil and paper and a lot of patience). Plus, the models are corroborated by the paleoclimatic evidence (at least in the most general sense that such a severe change in CO2 levels should lead to very substantial rises in temperature).

      4. There’s a very big difference between climate and weather. See TG’s reply.

  6. Regarding political and financial interests:

    Western media is pretty uncritical of AGW theories. What is Western media’s attitude to Saudi Arabia, Gulf states, Iran, Putin’s Russia? These are some of the biggest oil and gas exporters. Within the US high finance and media guys despise oilmen. There’s a deep cultural divide there. Politics is a series of conflicts among elites, and a lot of the elites, I would say most of the elites in the West, not only aren’t making money from oil and gas, but are hostile to those other elites, foreign and domestic, who do make money from oil and gas. So there IS, I believe, some motivation in high circles to hurt the oil business. That doesn’t necessarily mean that AGW research is politically tainted (it may or may not be – I don’t know), but it’s something to keep in mind.