I read your post and the comments from Robert Stone with great interest. I am a retired physicist and worked in research and with particle accelerators at a National Lab all my life. I was always very interested in environmental issues and climate science. Presently I still chair an international panel on sustainability within the International Committee for Future Accelerators, itself a working group of IUPAP.
I agree with you that making extreme weather events an existential issue for humanity is counterproductive. For one it is simply not true and, although the human tragedies are real, there are also major economic activities triggered by these events. What is much more concerning to me are the heat waves that are occurring more often and are more extreme. They will have the effect of making large areas of the tropics uninhabitable for warm-blooded creatures such as us. Air conditioning can fix this for the wealthy as is presently the case in the US South West and for the rich folks in the Middle East, but not for the vast majority of the people that live in the potentially affected areas. I think heat waves are a bigger threat than sea level rise over the next few decades.
The danger of increased heat in the tropics is central to the impact of increased CO2 concentration. I am always puzzled by the fact the pretty much all climate modeling ends in 2100 as if we shouldn’t care about the lives of our grandchildren and great grandchildren. A well known but rarely discussed fact is that the energy budget of our earth is not in balance. The imbalance has been rising and now about 1 Watt more energy per second and square meter comes in as goes out, all because of the increasing level of CO2 concentration, the main and only long-term greenhouse gas. Jim Hanson et al in their recent article “Global warming in the pipeline” model that it will take well over a hundred years for the earth’s energy budget to get into balance if the present level of CO2 concentration is maintained. In reality it is continuing to go up and the earth will not be in balance for a much longer time.
To determine the state of the earth when it is in balance at the present CO2 level Hansen and also Emily Judd et al in “A 485-million-year history of Earth’s surface temperature” look back in time to when equilibrium conditions existed with a certain level of CO2 concentration. In her paper Judd makes a very good case that the CO2 concentration is the sole determinant of the surface temperature. Fig 4B shows the historically determined relation between CO2 concentration and Global Mean Surface Temperature under equilibrium conditions. For our present level of CO2 of about 430 ppm the temperature rise over pre-industrial is about 5 degrees Celsius. This temperature last existed about 10 million years ago, there was no ice on Greenland and the sea level was about 7 m higher. Granted that this reality is a few hundred years from now and back 10 million year ago there was life on earth. So, it will be a livable earth, just not where most of the people live today. A few hundred years is a very short time to adapt to this massive climate change. I believe this is the main challenge for humanity.
Thanks for your note. I'm familiar with these issues. Heat waves will definitely get hotter in the coming decades. But we are a long way off from wetbulb temperatures that people were obsessing about a few years ago and it is harder to get there in the tropics than a lot of people think because the periods when it is hottest are generally the dry season when it is not as humid. Once we get to the climate and sea levels several hundred years from now I think its all basically science fiction. Think about how profoundly human societies and the human experience have transformed over the last 200 years and then consider what human civilization might look like in 2300 or 2400. We really have no idea. I look out my window every morning at the San Francisco Bay, which we have filled a third of over the last 100 years and I don't have a lot of existential angst over the possibility that that land might be reclaimed over the next 100 or 200 years. In fact it gives me a lot of confidence that human settlements will adapt quite well over multicentury timescales to 7M of sea level rise or whatever it ends up being. Hanson's estimates should also remind us that if his projections of climate sensitivity and warming are correct, there is enormous climate change already baked into the human future. Those projections are contested by a lot of other climate scientists but if they are correct, then even quite radical mitigation efforts won't avoid 7M of sea level rise and 5C of warming.
Thank you for your quick response. I appreciate the opportunity to discuss the impacts of vastly increased atmospheric CO2 concentrations. I do think that it is useful and maybe critical to consider the challenges that are posed to humanity by a much hotter earth 200 to 300 years from now, especially as you point out, and I agree, that it might be “baked into the human future”. Even if we were to miraculously stop emitting CO2 the CO2 concentration would go down for while but then settle around 350 ppm when there is an equilibrium with the CO2 in the oceans. Further reduction would take thousands of years. (Susan Solomon et al. “Irreversible climate change due to carbon dioxide emissions”, PNAS)
I am also a little skeptical that there are purely technological solutions: carbon sequestration beyond the natural processes at the necessary scale is extremely energy intensive and needing carbon-neutral energy sources that are desperately needed to replace fossil energy, and geo-engineering is also an extremely large effort that needs to be maintained indefinitely.
This leaves us with mitigation and adaption. Again, the heat is the issue. Sea level rise can be mitigated or one can just move inland. But the heat will require massive migration towards to poles as animals have done several times during “hot house” periods of the Earth’s history, except that in the past this evolved over many millennia. Now it is occurring over maybe 200 years. One could argue that this migration to the north has begun and it already is causing many conflicts. The growing nationalism around the world doesn’t bode well for avoiding escalating major conflicts. On the other hand it seems that it would be feasible to prepare for the migration by encouraging and supporting it and by realizing that immigration is the true live-blood of many nations. This is what could actually. make Russia a super-power, not by invading other countries. The UN would be the obvious organization to advance this effort. You might say that I must be dreaming, but, as you said, a lot of things can happen in 200 years.
Thanks again for your reply. I agree that heat is the more important impact vs a lot of other things that people talk about. Assuming 3C warming wet bulb conditions are very rare even in theory. When you factor in the fact that the hot season in tropical regions and the humid season don't occur at the same time, even more so. But all else equal, heat will take a greater toll than today (and cold a lesser toll). Of course, a world where everyone is relatively rich and has access to modern energy is one that will be able to adapt to a lot of that. And obviously, once you get out into the 22nd century the deep uncertainties about human societies are arguably far greater than the climate uncertainties.
Fair enough, assuming your estimates are correct and no unexpected tipping points occur.
But my central questions remain unanswered: what level of CO2ppm are you predicting at 2100 that lead you to this conclusion (IPCC suggests we maybe at around 650ppm)? Are your conclusions born out by the historical record that temperature increases are likely be limited to 3 degrees with that level of CO2ppm, given all the potential feedback loops we know about and those that may be unforeseen? We’re looking at CO2 levels that have been unseen on this planet in over a million years. We did that. And we did it in less than 200 years. If this is a manageable problem, as you argue, then please point me concrete evidence for it in the historical record. In what era were CO2 levels this high in which temperatures and sea levels were such that it could still sustain our existing human civilization? Or are you arguing that the relationship between CO2 and temperature are unproven?
Pretty much the entirety of human civilization has unfolded during a period of temperature and CO2 levels that were theretofore unprecedented during the evolutionary history of modern humans. The Holocene was/is not unusually stable, it was unusually WARM in the history of evolutionarily modern humans.
Not wanting to get into an extended debate with you here, Ted, but your comment here about the Holocene is factually incorrect. Your conclusions are downstream of this error. I hope there’s room in the ecomodernist community for disagreement on this matter. Because based on my understanding of the underlying science and historical record, I profoundly disagree.
Yes the Halocene has been unusually stable. Humans evolved and thrived by being adaptable to cold, not extreme heat. Humans have never experienced a world with more than 400ppm CO2 nor a world very much warmer than today. Projections of temperature rise in the next 100 years are wildly uncertain but your estimate of us being able to hold it at 3 degrees above pre-industrial levels is at the very optimistic end of the spectrum of possible outcomes.
I think the argument about our current adaptability to extreme weather is a red herring. I don’t argue with the facts. Sure, better forecasting and better infrastructure have reduced mortality. Great. But to extrapolate from that to conclude that CO2 levels of 600 or 700ppm in the next century (a real possibility) are not potentially catastrophic seems illogical. We’re heading into completely uncharted territory.
As for geo engineering, I think it will be essential. I’m all for it. We need to remove CO2. Fusion may allow us to do it at scale.
Finally, just because climate alarmists are often wrong and utterly hysterical (they are) does not necessarily mean that we have nothing to worry about.
Respectfully Robert, the main difference in the Holocene was that it was the first significant interglacial period experienced by modern humans. It was warmer and less of the land mass was covered by ice. This is not a controversial view. "Stability" whatever that actually means, was not the key factor in the development of agriculture or complex human societies. Humans did not "thrive" in the cold paleolithic era, they mostly struggled. Only with the warm Holocene did humans become a thriving and ecologically dominant species. Erle Ellis recently pushed back on this. But his push back was against environmental determinism in either direction. He argues that there were plenty of places on Earth where humans could have developed agriculture at scale prior to the Holocene - that the deterministic claims about the Holocene, whether grounded in stability or warmth, are just wrong and contradicted by all sorts of evidence.
Your claim about projected warming over the next 100 years is also out of date. 3C is now at the pessimistic end of possible outcomes. Again this is not controversial. The range of likely warming is now between 2 and 3C, with most scenarios coming in below 2.5C. See for instance https://iopscience.iop.org/article/10.1088/1748-9326/ac4ebf
I would still welcome any literature you want to send along demonstrating that the Holocene was more stable or that humans have experienced warmer epochs prior to the Holocene.
We’re talking at cross purposes or misunderstanding each other. Agree Halocene was stable. My earlier point was that our adaptability evolved by surviving (not thriving) in a cold environment. Our evolutionary adaptability is predisposed to surviving extreme cold more than extreme heat. It’s what made us human. We have clearly thrived in a the warmer and stable era of the Halocene. No argument there.
I’m glad to see Pielke’s assessment about 2100, though what 3 degrees above pre-industrial levels actually feels like is debatable. Assuming he’s right I stand corrected on that point. But history does not stop in 2100. And CO2 does not suddenly return to 250ppm the moment we stop burning fossil fuels (a common misconception among greens - and almost everyone).
If you can persuade me that we can double or even triple atmospheric CO2 concentrations to levels not seen in all of human history and not really worry about the consequences then I’ll buy you a nice bottle of Scotch.
I would be interested to know where you are getting this cold adaptation thing Robert. Humans mostly evolved in warmer equatorial and tropical climates. Humans have adapted to a very large range of terrestrial climates and all evidence suggests that our adaptation to climate variability continues to improve. Even in our anthropogenically warmed climate, 5 times more people die annually from cold extremes than hot extremes. And rising CO2 concentrations, unprecedented in human history are thus far associated with improving human well being and better adaptation to climate extremes. All of which points to a warmer climate being better for humans.
It is true that humans have never lived on a planet with 600 ppm CO2 concentrations. But they had also never lived on a planet with 350 or 400 ppm. No, the human future doesn't end in 2100. But that is true of many things besides whatever additional warming the world experiences after 2100. At some point, we are speaking of world that we can't possibly imagine, anymore than a New Yorker in, say, 1700, could conceivably have imagined the world and the human experience today. So it seems to me that the burden of evidence here would be on those who say this will be catastrophic for humans. Otherwise the position just becomes unfalsifiable precautionary hand waving.
By contrast, there are lots of far more prosaic and proximate reasons to support clean energy innovation, economic growth, infrastructure development, and adaptation to climatic extremes whether or not they are influenced at all by anthropogenic warming that don't require us to figure out the likelihood of the world ending in 2400 in a climate apocalypse if we don't build a bunch of nuclear power plants in the coming decades.
I agree with most of what you wrote but there are two other criticisms of the current orthodoxy I would offer, not limited to the catastrophist version, ways in which the cost of climate change is being overestimated:
1. Positive effects are ignored or minimized. The one effect of increased CO2 concentration on food supplies of which we can be certain, on the basis of extensive experimental evidence, is carbon fertilization. Exact numbers are uncertain but doubling CO2 concentration can be expected to increase the yield of C3 plants, most important crops other than maize, by about 20% and reduce water requirements for all crops. Human land use is currently limited by cold, not heat, as you can see by comparing a temperature map of the globe to a population density map. A 3°C increase in global temperature shifts temperature contours towards the poles, increasing the amount of land in the northern hemisphere warm enough for human use by (my estimate) something close to the area of the US. Warming increases mortality from heat, decreases it from cold. A series of Lancet articles found mortality from suboptimal temperatures much larger than from temperatures above optimal. The authors project an increase in net mortality from at least rapid warming — but also find the net effect of temperature change so far to be reduced mortality: https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00081-4/fulltext.
2. People discuss long tail risks from warming but not from preventing warming. The obvious one is the end of the current interglacial. That does not seem likely — indeed there is some evidence that it is being prevented by anthropogenic warming from much earlier due to the invention of agriculture — but a symmetric calculation of low probability high cost outcomes should include it. I expect with a little effort one could come up with other examples.
I am an academic economist with a doctorate in physics and have been blogging on these subjects for a long time. If curious you can find much I have written, including support for details of paragraph 1 above, at http://www.daviddfriedman.com/Sorted_Posts.html#Climate
Thank you for your comment David. I agree with both points. The literature is very focused on calculating the costs and risks of warming without giving commensurate consideration to potential benefits. Hadn't considered the tail risks of preventing warming but its at the very least an interesting thought experiment. I'll check out your other writing.
This is all well and good but I'm surprised you didn't address what seems to me the key metric: the rising global CO2ppm as measured on Mauna Loa (our best long term global benchmark). We have effectively doubled the concentration of CO2 in the atmosphere over pre-industrial levels (they continue to rise). The historical evidence from the study of ice cores shows a pretty clear correlation between CO2 concentrations and planetary temperature and sea levels. In less than 200 years CO2ppm have risen to levels not seen in over 800,000 years. It's reasonable to conclude that such a dramatic change in the chemical composition of the atmosphere in such a short period of time stands a good chance of triggering an equally dramatic impact on global temperature and sea levels, as has happened in the past and appears to be starting to happen in our lifetime. Are you suggesting that this time will be different? Or are you saying that the time horizon for any of this to have a negative impact on human civilization is so long that it won't matter? Or do you accept that dramatic change is coming but that we'll find a way to adapt? If so, I'd like to hear those argument and to see the data that backs it up. I agree with you that the catastrophism you decry is misleading and that the weather related metrics presented by climate activists are highly exaggerated and designed to achieve a political end. I'm with you there. But your argument that today's weather events are manageable fails to persuade me that this will continue to be the case and that some sort of a catastrophe isn't looming, possibly within a time frame that matters (a vague concept to be sure). I'm remain concerned given all that what we know. I'm even more concerned about all that we undoubtedly don't know.
There are three questions here that are worth unpacking. 1. How much temperature change and resulting impact on climatic phenomena should we expect. 2. Over what time frame. 3. What is the capacity of human society to adapt to that amount of change over that timeframe. Our best estimate of 1 is less than 3C by the end of the century, of which about half has already occurred. So for purposes of 2, the answer through 2100 is that human societies should expect to see about as much warming over the rest of this century as they experiences over the last century. And then we come to 3, which is do we think that increasingly wealthy and technologically advanced human societies will be more or less resilient to about as much climate change over the rest of this century as poorer and less advanced human societies were over the last century. And I would suggest that everything we know about growing climate resilience and the very wide range of climatic conditions in which humans are now able to thrive across the planet suggests that humans will be more, not less resilient to the changing climate over the rest of this century than they were over the course of the last century.
I read your post and the comments from Robert Stone with great interest. I am a retired physicist and worked in research and with particle accelerators at a National Lab all my life. I was always very interested in environmental issues and climate science. Presently I still chair an international panel on sustainability within the International Committee for Future Accelerators, itself a working group of IUPAP.
I agree with you that making extreme weather events an existential issue for humanity is counterproductive. For one it is simply not true and, although the human tragedies are real, there are also major economic activities triggered by these events. What is much more concerning to me are the heat waves that are occurring more often and are more extreme. They will have the effect of making large areas of the tropics uninhabitable for warm-blooded creatures such as us. Air conditioning can fix this for the wealthy as is presently the case in the US South West and for the rich folks in the Middle East, but not for the vast majority of the people that live in the potentially affected areas. I think heat waves are a bigger threat than sea level rise over the next few decades.
The danger of increased heat in the tropics is central to the impact of increased CO2 concentration. I am always puzzled by the fact the pretty much all climate modeling ends in 2100 as if we shouldn’t care about the lives of our grandchildren and great grandchildren. A well known but rarely discussed fact is that the energy budget of our earth is not in balance. The imbalance has been rising and now about 1 Watt more energy per second and square meter comes in as goes out, all because of the increasing level of CO2 concentration, the main and only long-term greenhouse gas. Jim Hanson et al in their recent article “Global warming in the pipeline” model that it will take well over a hundred years for the earth’s energy budget to get into balance if the present level of CO2 concentration is maintained. In reality it is continuing to go up and the earth will not be in balance for a much longer time.
To determine the state of the earth when it is in balance at the present CO2 level Hansen and also Emily Judd et al in “A 485-million-year history of Earth’s surface temperature” look back in time to when equilibrium conditions existed with a certain level of CO2 concentration. In her paper Judd makes a very good case that the CO2 concentration is the sole determinant of the surface temperature. Fig 4B shows the historically determined relation between CO2 concentration and Global Mean Surface Temperature under equilibrium conditions. For our present level of CO2 of about 430 ppm the temperature rise over pre-industrial is about 5 degrees Celsius. This temperature last existed about 10 million years ago, there was no ice on Greenland and the sea level was about 7 m higher. Granted that this reality is a few hundred years from now and back 10 million year ago there was life on earth. So, it will be a livable earth, just not where most of the people live today. A few hundred years is a very short time to adapt to this massive climate change. I believe this is the main challenge for humanity.
Thanks for your note. I'm familiar with these issues. Heat waves will definitely get hotter in the coming decades. But we are a long way off from wetbulb temperatures that people were obsessing about a few years ago and it is harder to get there in the tropics than a lot of people think because the periods when it is hottest are generally the dry season when it is not as humid. Once we get to the climate and sea levels several hundred years from now I think its all basically science fiction. Think about how profoundly human societies and the human experience have transformed over the last 200 years and then consider what human civilization might look like in 2300 or 2400. We really have no idea. I look out my window every morning at the San Francisco Bay, which we have filled a third of over the last 100 years and I don't have a lot of existential angst over the possibility that that land might be reclaimed over the next 100 or 200 years. In fact it gives me a lot of confidence that human settlements will adapt quite well over multicentury timescales to 7M of sea level rise or whatever it ends up being. Hanson's estimates should also remind us that if his projections of climate sensitivity and warming are correct, there is enormous climate change already baked into the human future. Those projections are contested by a lot of other climate scientists but if they are correct, then even quite radical mitigation efforts won't avoid 7M of sea level rise and 5C of warming.
Thank you for your quick response. I appreciate the opportunity to discuss the impacts of vastly increased atmospheric CO2 concentrations. I do think that it is useful and maybe critical to consider the challenges that are posed to humanity by a much hotter earth 200 to 300 years from now, especially as you point out, and I agree, that it might be “baked into the human future”. Even if we were to miraculously stop emitting CO2 the CO2 concentration would go down for while but then settle around 350 ppm when there is an equilibrium with the CO2 in the oceans. Further reduction would take thousands of years. (Susan Solomon et al. “Irreversible climate change due to carbon dioxide emissions”, PNAS)
I am also a little skeptical that there are purely technological solutions: carbon sequestration beyond the natural processes at the necessary scale is extremely energy intensive and needing carbon-neutral energy sources that are desperately needed to replace fossil energy, and geo-engineering is also an extremely large effort that needs to be maintained indefinitely.
This leaves us with mitigation and adaption. Again, the heat is the issue. Sea level rise can be mitigated or one can just move inland. But the heat will require massive migration towards to poles as animals have done several times during “hot house” periods of the Earth’s history, except that in the past this evolved over many millennia. Now it is occurring over maybe 200 years. One could argue that this migration to the north has begun and it already is causing many conflicts. The growing nationalism around the world doesn’t bode well for avoiding escalating major conflicts. On the other hand it seems that it would be feasible to prepare for the migration by encouraging and supporting it and by realizing that immigration is the true live-blood of many nations. This is what could actually. make Russia a super-power, not by invading other countries. The UN would be the obvious organization to advance this effort. You might say that I must be dreaming, but, as you said, a lot of things can happen in 200 years.
Thanks again for your reply. I agree that heat is the more important impact vs a lot of other things that people talk about. Assuming 3C warming wet bulb conditions are very rare even in theory. When you factor in the fact that the hot season in tropical regions and the humid season don't occur at the same time, even more so. But all else equal, heat will take a greater toll than today (and cold a lesser toll). Of course, a world where everyone is relatively rich and has access to modern energy is one that will be able to adapt to a lot of that. And obviously, once you get out into the 22nd century the deep uncertainties about human societies are arguably far greater than the climate uncertainties.
Fair enough, assuming your estimates are correct and no unexpected tipping points occur.
But my central questions remain unanswered: what level of CO2ppm are you predicting at 2100 that lead you to this conclusion (IPCC suggests we maybe at around 650ppm)? Are your conclusions born out by the historical record that temperature increases are likely be limited to 3 degrees with that level of CO2ppm, given all the potential feedback loops we know about and those that may be unforeseen? We’re looking at CO2 levels that have been unseen on this planet in over a million years. We did that. And we did it in less than 200 years. If this is a manageable problem, as you argue, then please point me concrete evidence for it in the historical record. In what era were CO2 levels this high in which temperatures and sea levels were such that it could still sustain our existing human civilization? Or are you arguing that the relationship between CO2 and temperature are unproven?
Pretty much the entirety of human civilization has unfolded during a period of temperature and CO2 levels that were theretofore unprecedented during the evolutionary history of modern humans. The Holocene was/is not unusually stable, it was unusually WARM in the history of evolutionarily modern humans.
Not wanting to get into an extended debate with you here, Ted, but your comment here about the Holocene is factually incorrect. Your conclusions are downstream of this error. I hope there’s room in the ecomodernist community for disagreement on this matter. Because based on my understanding of the underlying science and historical record, I profoundly disagree.
If you want to point me to factual evidence that the Holocene was more stable or that humans have experienced warmer epochs prior to the Holocene I’d love to see it but I’ve written at some length on the subject and am pretty sure what I’ve said here is accurate. https://thebreakthrough.org/journal/no-20-spring-2024/yes-we-should-try-to-control-the-weather
Yes the Halocene has been unusually stable. Humans evolved and thrived by being adaptable to cold, not extreme heat. Humans have never experienced a world with more than 400ppm CO2 nor a world very much warmer than today. Projections of temperature rise in the next 100 years are wildly uncertain but your estimate of us being able to hold it at 3 degrees above pre-industrial levels is at the very optimistic end of the spectrum of possible outcomes.
I think the argument about our current adaptability to extreme weather is a red herring. I don’t argue with the facts. Sure, better forecasting and better infrastructure have reduced mortality. Great. But to extrapolate from that to conclude that CO2 levels of 600 or 700ppm in the next century (a real possibility) are not potentially catastrophic seems illogical. We’re heading into completely uncharted territory.
As for geo engineering, I think it will be essential. I’m all for it. We need to remove CO2. Fusion may allow us to do it at scale.
Finally, just because climate alarmists are often wrong and utterly hysterical (they are) does not necessarily mean that we have nothing to worry about.
Respectfully Robert, the main difference in the Holocene was that it was the first significant interglacial period experienced by modern humans. It was warmer and less of the land mass was covered by ice. This is not a controversial view. "Stability" whatever that actually means, was not the key factor in the development of agriculture or complex human societies. Humans did not "thrive" in the cold paleolithic era, they mostly struggled. Only with the warm Holocene did humans become a thriving and ecologically dominant species. Erle Ellis recently pushed back on this. But his push back was against environmental determinism in either direction. He argues that there were plenty of places on Earth where humans could have developed agriculture at scale prior to the Holocene - that the deterministic claims about the Holocene, whether grounded in stability or warmth, are just wrong and contradicted by all sorts of evidence.
Your claim about projected warming over the next 100 years is also out of date. 3C is now at the pessimistic end of possible outcomes. Again this is not controversial. The range of likely warming is now between 2 and 3C, with most scenarios coming in below 2.5C. See for instance https://iopscience.iop.org/article/10.1088/1748-9326/ac4ebf
I would still welcome any literature you want to send along demonstrating that the Holocene was more stable or that humans have experienced warmer epochs prior to the Holocene.
We’re talking at cross purposes or misunderstanding each other. Agree Halocene was stable. My earlier point was that our adaptability evolved by surviving (not thriving) in a cold environment. Our evolutionary adaptability is predisposed to surviving extreme cold more than extreme heat. It’s what made us human. We have clearly thrived in a the warmer and stable era of the Halocene. No argument there.
I’m glad to see Pielke’s assessment about 2100, though what 3 degrees above pre-industrial levels actually feels like is debatable. Assuming he’s right I stand corrected on that point. But history does not stop in 2100. And CO2 does not suddenly return to 250ppm the moment we stop burning fossil fuels (a common misconception among greens - and almost everyone).
If you can persuade me that we can double or even triple atmospheric CO2 concentrations to levels not seen in all of human history and not really worry about the consequences then I’ll buy you a nice bottle of Scotch.
I would be interested to know where you are getting this cold adaptation thing Robert. Humans mostly evolved in warmer equatorial and tropical climates. Humans have adapted to a very large range of terrestrial climates and all evidence suggests that our adaptation to climate variability continues to improve. Even in our anthropogenically warmed climate, 5 times more people die annually from cold extremes than hot extremes. And rising CO2 concentrations, unprecedented in human history are thus far associated with improving human well being and better adaptation to climate extremes. All of which points to a warmer climate being better for humans.
It is true that humans have never lived on a planet with 600 ppm CO2 concentrations. But they had also never lived on a planet with 350 or 400 ppm. No, the human future doesn't end in 2100. But that is true of many things besides whatever additional warming the world experiences after 2100. At some point, we are speaking of world that we can't possibly imagine, anymore than a New Yorker in, say, 1700, could conceivably have imagined the world and the human experience today. So it seems to me that the burden of evidence here would be on those who say this will be catastrophic for humans. Otherwise the position just becomes unfalsifiable precautionary hand waving.
By contrast, there are lots of far more prosaic and proximate reasons to support clean energy innovation, economic growth, infrastructure development, and adaptation to climatic extremes whether or not they are influenced at all by anthropogenic warming that don't require us to figure out the likelihood of the world ending in 2400 in a climate apocalypse if we don't build a bunch of nuclear power plants in the coming decades.
I agree with most of what you wrote but there are two other criticisms of the current orthodoxy I would offer, not limited to the catastrophist version, ways in which the cost of climate change is being overestimated:
1. Positive effects are ignored or minimized. The one effect of increased CO2 concentration on food supplies of which we can be certain, on the basis of extensive experimental evidence, is carbon fertilization. Exact numbers are uncertain but doubling CO2 concentration can be expected to increase the yield of C3 plants, most important crops other than maize, by about 20% and reduce water requirements for all crops. Human land use is currently limited by cold, not heat, as you can see by comparing a temperature map of the globe to a population density map. A 3°C increase in global temperature shifts temperature contours towards the poles, increasing the amount of land in the northern hemisphere warm enough for human use by (my estimate) something close to the area of the US. Warming increases mortality from heat, decreases it from cold. A series of Lancet articles found mortality from suboptimal temperatures much larger than from temperatures above optimal. The authors project an increase in net mortality from at least rapid warming — but also find the net effect of temperature change so far to be reduced mortality: https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00081-4/fulltext.
2. People discuss long tail risks from warming but not from preventing warming. The obvious one is the end of the current interglacial. That does not seem likely — indeed there is some evidence that it is being prevented by anthropogenic warming from much earlier due to the invention of agriculture — but a symmetric calculation of low probability high cost outcomes should include it. I expect with a little effort one could come up with other examples.
I am an academic economist with a doctorate in physics and have been blogging on these subjects for a long time. If curious you can find much I have written, including support for details of paragraph 1 above, at http://www.daviddfriedman.com/Sorted_Posts.html#Climate
Thank you for your comment David. I agree with both points. The literature is very focused on calculating the costs and risks of warming without giving commensurate consideration to potential benefits. Hadn't considered the tail risks of preventing warming but its at the very least an interesting thought experiment. I'll check out your other writing.
This is all well and good but I'm surprised you didn't address what seems to me the key metric: the rising global CO2ppm as measured on Mauna Loa (our best long term global benchmark). We have effectively doubled the concentration of CO2 in the atmosphere over pre-industrial levels (they continue to rise). The historical evidence from the study of ice cores shows a pretty clear correlation between CO2 concentrations and planetary temperature and sea levels. In less than 200 years CO2ppm have risen to levels not seen in over 800,000 years. It's reasonable to conclude that such a dramatic change in the chemical composition of the atmosphere in such a short period of time stands a good chance of triggering an equally dramatic impact on global temperature and sea levels, as has happened in the past and appears to be starting to happen in our lifetime. Are you suggesting that this time will be different? Or are you saying that the time horizon for any of this to have a negative impact on human civilization is so long that it won't matter? Or do you accept that dramatic change is coming but that we'll find a way to adapt? If so, I'd like to hear those argument and to see the data that backs it up. I agree with you that the catastrophism you decry is misleading and that the weather related metrics presented by climate activists are highly exaggerated and designed to achieve a political end. I'm with you there. But your argument that today's weather events are manageable fails to persuade me that this will continue to be the case and that some sort of a catastrophe isn't looming, possibly within a time frame that matters (a vague concept to be sure). I'm remain concerned given all that what we know. I'm even more concerned about all that we undoubtedly don't know.
There are three questions here that are worth unpacking. 1. How much temperature change and resulting impact on climatic phenomena should we expect. 2. Over what time frame. 3. What is the capacity of human society to adapt to that amount of change over that timeframe. Our best estimate of 1 is less than 3C by the end of the century, of which about half has already occurred. So for purposes of 2, the answer through 2100 is that human societies should expect to see about as much warming over the rest of this century as they experiences over the last century. And then we come to 3, which is do we think that increasingly wealthy and technologically advanced human societies will be more or less resilient to about as much climate change over the rest of this century as poorer and less advanced human societies were over the last century. And I would suggest that everything we know about growing climate resilience and the very wide range of climatic conditions in which humans are now able to thrive across the planet suggests that humans will be more, not less resilient to the changing climate over the rest of this century than they were over the course of the last century.