I probably shouldn’t have cited the averages like I did here because it hides the seasonal extremes, also it’s really the variance that shows what society will need to contend with if this were to happen. This recent paper by van Westen published just a few weeks ago illustrates the differences in winter/summer temps as well as how “unusual” events will become more frequent. London for example, could face −40C winter weather. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL114611
Curious, how did you calculate your estimate of European population decline?
Thanks for clarifying. I still think the variation in the mean temperature is useful because they constrain the seasonal variation. Each season lasts for 0.25 years (= 1⁄4), so a season becoming e.g. 10 ºC cooler will make the year 2.50 ºC (= 0.25*10) cooler. Assuming the effect of AMOC’s collapse on Spring and Summer and is negligible, and that the effect on Autumn and Winter is similar, these would cool 2 (= 4⁄2) times as fast as I estimated above. So by 0.0600 (= 0.0300*2) to 0.400 ºC/year (= 0.200*2) in Western Europe, and up to 0.200 (= 0.100*2) to 1.33 ºC/year (= 0.667*2) in northern latitudes. I know you pointed out that the extremes matter, but I think the seasonal variations are still relevant. At least now, deaths from moderate cold are much larger than from extreme cold.
I did not calculate the probability of the European population decreasing by more than 10 %. I simply speculated it is lower than 0.01 %. For context, the deaths from non-optimal temperature as a fraction of the population in Europe in 2021 were 0.0416 %. The respective death rate across time is below. For the European population to become at least 10 % smaller, that death rate would have to become at least 240 (= 0.1/(4.16*10^-4)) times as large, which seems a lot considering how little is has varied across time.
Thanks for the explanation! I think I see what you’re saying now. I bet you’re right, deaths attributed to the change in temperature would likely remain low. I think most of the deaths would come from food shortages (as of the current data, a lot of land in Europe would no longer be arable) and that could affect a more significant portion of the population.
You are welcome! The deaths from non-optimal temperature plotted above are supposed to cover all causes of death, including from food shortages (although these might account for a much larger fraction of the deaths from non-optimal temperature for abrupt variations of temperature). There were 1.91 M deaths from non-optimal temperature in 2021, 53.1 (= 1.91*10^6/(36.0*10^3)) times the 36.0 k deaths from environmental heat and cold exposure. From Our World in Data (OWID):
Think about someone dying from extreme temperatures. You probably pictured someone passing out from heat stroke or dying from hypothermia.
But this is not how most people die from “heat”. They die from conditions such as cardiovascular or kidney disease, respiratory infections, or diabetes.
I probably shouldn’t have cited the averages like I did here because it hides the seasonal extremes, also it’s really the variance that shows what society will need to contend with if this were to happen. This recent paper by van Westen published just a few weeks ago illustrates the differences in winter/summer temps as well as how “unusual” events will become more frequent. London for example, could face −40C winter weather. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL114611
Curious, how did you calculate your estimate of European population decline?
Thanks for clarifying. I still think the variation in the mean temperature is useful because they constrain the seasonal variation. Each season lasts for 0.25 years (= 1⁄4), so a season becoming e.g. 10 ºC cooler will make the year 2.50 ºC (= 0.25*10) cooler. Assuming the effect of AMOC’s collapse on Spring and Summer and is negligible, and that the effect on Autumn and Winter is similar, these would cool 2 (= 4⁄2) times as fast as I estimated above. So by 0.0600 (= 0.0300*2) to 0.400 ºC/year (= 0.200*2) in Western Europe, and up to 0.200 (= 0.100*2) to 1.33 ºC/year (= 0.667*2) in northern latitudes. I know you pointed out that the extremes matter, but I think the seasonal variations are still relevant. At least now, deaths from moderate cold are much larger than from extreme cold.
I did not calculate the probability of the European population decreasing by more than 10 %. I simply speculated it is lower than 0.01 %. For context, the deaths from non-optimal temperature as a fraction of the population in Europe in 2021 were 0.0416 %. The respective death rate across time is below. For the European population to become at least 10 % smaller, that death rate would have to become at least 240 (= 0.1/(4.16*10^-4)) times as large, which seems a lot considering how little is has varied across time.
Thanks for the explanation! I think I see what you’re saying now. I bet you’re right, deaths attributed to the change in temperature would likely remain low. I think most of the deaths would come from food shortages (as of the current data, a lot of land in Europe would no longer be arable) and that could affect a more significant portion of the population.
You are welcome! The deaths from non-optimal temperature plotted above are supposed to cover all causes of death, including from food shortages (although these might account for a much larger fraction of the deaths from non-optimal temperature for abrupt variations of temperature). There were 1.91 M deaths from non-optimal temperature in 2021, 53.1 (= 1.91*10^6/(36.0*10^3)) times the 36.0 k deaths from environmental heat and cold exposure. From Our World in Data (OWID):