5 ms·

People continue to point out the (widely known) negative effects of global warming, but how are we so confident that the net effects will be long-term negative?

People continue to point out the (widely known) negative effects of global warming, but how are we so confident that the net effects will be long-term negative?[1] It seems to me an extremely complicated calculation which doesn't merit extreme certainty in either direction. Here are some of the positives of global warming: - Statistically, an order of magnitude more humans die from colder temperatures than from hotter ones (as discussed in this article). So hotter temperatures could easily lead to net lives saved, at least in this area. - Hotter temperatures and higher CO2 in northern/arctic areas will increase (net) crop yields substantially. Many areas which formerly weren't hospitable for certain types of crops will suddenly become so. This isn't so surprising since CO2 is an input to photosynthesis. - Global warming will free up northern trade routes and make potentially millions of square miles of land more habitable for humans. - The distribution of global temperature increases is expected to be tilted towards colder areas (that is: higher temperature increases in colder regions than in hotter regions). This means we get to experience the positive effects of global warming disproportionately to the negative effects. - Slight temperature increases might even hedge against long-term climate risk: we are technically still in an ice age, and there is long-term tail risk that we will recede back into a deeper one within a few millennia. So how do we know that stopping CO2 emissions won't make human climate long-term worse? - Even from an ecological standpoint: hotter climates will positively impact some species (including species which don't even exist yet!), while negatively impacting others. It seems to me a general rule of thumb that more life flourishes in hotter climates than colder ones. So why be so confident that the net effects of global warming will be long-term negative to animals, en totale? Of course, the negative effects of global warming (flooding, rising sea levels, etc) are well-known, so I omit them. My point is not that global warming is definitely a net positive; it's that it's not clear why there is so much confidence it's "definitely" a net negative. [1] Credit to David Friedman for helping point out many of these things.

afpx 5y ago
You make some great points. You actually have me wanting to fire up some turbines. Another possibly good societal optimization: backyard pooping. Good for the soil, saves on maintaining a sewage system, and the odds of getting sick from it are surprisingly low.
marcosdumay 5y ago
You mean the immediate effects on you civilization, that is extremely optimized for the current climate? Or the long term effects? Because the immediate (up to decades or even a couple of centuries long) effects will be overwhelming bad. There's just no chance we will end with a climate that is better than the one we optimized the hell for. There will be almost no positive effect on that horizon, that's how extreme optimization works. About the long (after a century or so) effects for humanity, I really doubt anybody knows them. Humanity will optimize itself for them, and make lemonades out of lemons anyway it can. For nature, it's still too short a timeframe for it to adapt, and global warming means a loss on diversity on a several millenia horizon; the same happens every time there is a large climate change. (About that new land for agriculture, plants need solar radiation, and that area has little of it. That's why it's frozen.)
- georgewsinger 5y ago
  > Because the immediate...effects will be overwhelming bad. There's just no chance we will end with a climate that is better than the one we optimized the hell for. There will be almost no positive effect on that horizon, that's how extreme optimization works. [Emphasis added] This just seems like dogma to me. Of course there will be both negative and positive effects. The question is: which is greater? Suppose I "optimize" my life for $60K/year income, but suddenly get a job which pays me $80K/year but with longer work hours and less interesting work. Question: Is my life definitely worse because my current optimization will be disrupted? The answer is that it's completely unclear. $20K more per year is good; less interesting work is bad. We need better models of what we're going to do with the money, and exactly how less interesting our work is going to be. W.r.t. to global warming: some of our existing "optimizations" will no longer be necessary, since life will just be easier in certain ways (e.g., more crops and ecnomic opportunities in the northern regions which currently make human living very hard). Some of our existing "optimizations" will fail, and need to be adjusted (e.g., areas where the sea line is expected to rise). The question is: why think "there's just no chance" (<- your words, not mine) that we're going to be net better off in the long-term?
jrlocke 5y ago
> Even from an ecological standpoint: hotter climates will positively impact some species (including species which don't even exist yet!), while negatively impacting others. The worry isn't that global warming will be bad for animals, you're right, there will be winners and losers, likely in comparable amounts. The worry is that it will be bad for biodiversity, a resource that is extremely slow to replenish (even taking into account these new opportunities). On the edges of the curve, some animals will be huge winners, and some will be huge losers. 10xing the populations of some species while others go extinct is only a net null on the very surface, it's still a huge loss diversity wise.
- georgewsinger 5y ago
  I agree with your point, but perhaps only when the timeline is short. From Nature:[1] > Researchers examined the number of known families of marine invertebrates, as well as sea-surface temperatures, over the course of 540 million years of Earth's history. They found that when temperatures were high, so was biodiversity. When temperatures fell, biodiversity also declined. This happens because global warming causes a marginal increase in tropical areas: > Tropical ecosystems are known to be Earth's most diverse, and the tropics would be expected to expand during warm eras. Of course, from a short-term timeline (say 100 years), the rate of species extinction from global warming will surely outpace the rate of species creation, since evolution has no time to act. [1]: https://www.nature.com/articles/nature.2012.11350 https://www.nature.com/articles/nature.2012.11350
  - OrbitRock 5y ago
    > Of course, from a short-term timeline (say 100 years), the rate of species extinction from global warming will surely outpace the rate of species creation, since evolution has no time to act. Which is really the only factor that matters here. A large quantity of things will likely go extinct before being able to adapt or migrate sufficiently to keep up with the changes. The re-development of biodiversity takes millions of years, and that’s basically irrelevant from the timescale of humanity.
kzrdude 5y ago
Changing equilibria is enormously stressful for the biosphere and for our "civosphere". Everything in the world would run along more smoothly if things didn't change so much(!). You could claim that we humans on earth are all equal and reasonable and it shouldn't be so hard to get along.. Except this breaks down in practice as soon as people want to move from where the climate got tougher and into the places where you said the crop yields will only get bigger. It gets ugly. Migration and turmoil.
- georgewsinger 5y ago
  It seems to me changing equilibria is precisely what allows the world to run more smoothly! Businesses coming and going, migrants moving from static societies to more prosperous ones, scientific revolutions overturning old ones, etc. I'm not saying that change doesn't cause any local instability, but the world very frequently net improves from change when its long-term benefits outweigh its short-term costs. It's not clear to me that several million square miles of land suddenly becoming more habitable wouldn't provide a better economic arrangement for the world 100 years from now, even when you net out the costs of people having to migrate to new areas.
tshaddox 5y ago
How do you calculate "net effects" when dealing with millions of people suffering in the near term? What does it take to balance that and end up with a net positive?
- georgewsinger 5y ago
  It's really hard; that's basically my point. But I think a good starting place is to model the expected effects on various populations of all of these various factors (increased floods, increased crop yields, etc). If the vast majority of these models are tilted overwhelmingly negative or positive, we can somewhat adjust our confidence levels. Of course, we'll never be able to be that confident when the time horizon stretches so long (100+ years) and the effect sizes are so small (e.g., sea levels are expected to rise by a lower amount on average than the existing low-tide to high-tide variance). But..that's also my point: it's not merited to be so extremely confident that the effects of global warming are going to be so negative (or positive) over 100+ years. People focus extremely hard on the negatives of global warming, don't focus much at all on the positives (my guess is most people living in urban areas aren't even aware there even exist any positives), and focus their debating efforts on the (as far as I can tell) long ago settled question of whether or not the climate warming is happening, or is caused by humans. My guess as to why this happens is that considering whether global warming could be a positive thing for the world conflicts with an anti-market bias that people in urban areas frequently share.
lkrubner 5y ago
Given long enough to adapt (perhaps a million years? Perhaps two million?) then there would be no negative effects to the current changes. The dangers are entirely to do with the speed of the current change. The increasing acidity of the oceans will, over the next two centuries, lead to a mass extinction in the oceans which could eventually have large effects on the gases that make up our atmosphere -- and here we need to concern ourselves with black swan events, which will remain unlikely, even 200 years from now, but which, if they were to occur, would lead to an extinction so broad that it would threaten human survival.
- georgewsinger 5y ago
  As pointed above, there is also human survival tail risk to stopping global warming. How are you so certain to know which tail risk is larger, or likelier?
  - BlueTemplar 5y ago
    Humans have already lived through several glaciations. But we weren't even around yet when the current ice age started 4M years ago.
  - lkrubner 5y ago
    I don't think you read what I wrote. I never mentioned global warming. If we continue at current rates of fossil fuel use for another 200 years, the acidification of the ocean will start to endanger phytoplankton, which makes much of the oxygen we breathe. The loss of phytoplankton drove the most serious mass extinction in the Earth's history: https://earthsky.org/earth/ocean-acidification-drove-earths-largest-mass-extinction/ https://earthsky.org/earth/ocean-acidification-drove-earths-... The article that started this thread on Hacker News suggested that the death rate goes up 10% in the winter, which gives some sense of what the tail risk is from cold weather. By contrast, the tail risk from the acidification of the oceans is something like the Permian/Triassic mass extinction. You ask "How are you so certain to know which tail risk is larger, or likelier?" We can be certain because one risk is many orders of magnitude worse than the other.

afpx 5y ago

You make some great points. You actually have me wanting to fire up some turbines. Another possibly good societal optimization: backyard pooping. Good for the soil, saves on maintaining a sewage system, and the odds of getting sick from it are surprisingly low.

marcosdumay 5y ago

You mean the immediate effects on you civilization, that is extremely optimized for the current climate? Or the long term effects? Because the immediate (up to decades or even a couple of centuries long) effects will be overwhelming bad. There's just no chance we will end with a climate that is better than the one we optimized the hell for. There will be almost no positive effect on that horizon, that's how extreme optimization works. About the long (after a century or so) effects for humanity, I really doubt anybody knows them. Humanity will optimize itself for them, and make lemonades out of lemons anyway it can. For nature, it's still too short a timeframe for it to adapt, and global warming means a loss on diversity on a several millenia horizon; the same happens every time there is a large climate change. (About that new land for agriculture, plants need solar radiation, and that area has little of it. That's why it's frozen.)

georgewsinger 5y ago
> Because the immediate...effects will be overwhelming bad. There's just no chance we will end with a climate that is better than the one we optimized the hell for. There will be almost no positive effect on that horizon, that's how extreme optimization works. [Emphasis added] This just seems like dogma to me. Of course there will be both negative and positive effects. The question is: which is greater? Suppose I "optimize" my life for $60K/year income, but suddenly get a job which pays me $80K/year but with longer work hours and less interesting work. Question: Is my life definitely worse because my current optimization will be disrupted? The answer is that it's completely unclear. $20K more per year is good; less interesting work is bad. We need better models of what we're going to do with the money, and exactly how less interesting our work is going to be. W.r.t. to global warming: some of our existing "optimizations" will no longer be necessary, since life will just be easier in certain ways (e.g., more crops and ecnomic opportunities in the northern regions which currently make human living very hard). Some of our existing "optimizations" will fail, and need to be adjusted (e.g., areas where the sea line is expected to rise). The question is: why think "there's just no chance" (<- your words, not mine) that we're going to be net better off in the long-term?

jrlocke 5y ago

> Even from an ecological standpoint: hotter climates will positively impact some species (including species which don't even exist yet!), while negatively impacting others. The worry isn't that global warming will be bad for animals, you're right, there will be winners and losers, likely in comparable amounts. The worry is that it will be bad for biodiversity, a resource that is extremely slow to replenish (even taking into account these new opportunities). On the edges of the curve, some animals will be huge winners, and some will be huge losers. 10xing the populations of some species while others go extinct is only a net null on the very surface, it's still a huge loss diversity wise.

georgewsinger 5y ago
I agree with your point, but perhaps only when the timeline is short. From Nature:[1] > Researchers examined the number of known families of marine invertebrates, as well as sea-surface temperatures, over the course of 540 million years of Earth's history. They found that when temperatures were high, so was biodiversity. When temperatures fell, biodiversity also declined. This happens because global warming causes a marginal increase in tropical areas: > Tropical ecosystems are known to be Earth's most diverse, and the tropics would be expected to expand during warm eras. Of course, from a short-term timeline (say 100 years), the rate of species extinction from global warming will surely outpace the rate of species creation, since evolution has no time to act. [1]: https://www.nature.com/articles/nature.2012.11350 https://www.nature.com/articles/nature.2012.11350
- OrbitRock 5y ago
  > Of course, from a short-term timeline (say 100 years), the rate of species extinction from global warming will surely outpace the rate of species creation, since evolution has no time to act. Which is really the only factor that matters here. A large quantity of things will likely go extinct before being able to adapt or migrate sufficiently to keep up with the changes. The re-development of biodiversity takes millions of years, and that’s basically irrelevant from the timescale of humanity.

kzrdude 5y ago

Changing equilibria is enormously stressful for the biosphere and for our "civosphere". Everything in the world would run along more smoothly if things didn't change so much(!). You could claim that we humans on earth are all equal and reasonable and it shouldn't be so hard to get along.. Except this breaks down in practice as soon as people want to move from where the climate got tougher and into the places where you said the crop yields will only get bigger. It gets ugly. Migration and turmoil.

georgewsinger 5y ago
It seems to me changing equilibria is precisely what allows the world to run more smoothly! Businesses coming and going, migrants moving from static societies to more prosperous ones, scientific revolutions overturning old ones, etc. I'm not saying that change doesn't cause any local instability, but the world very frequently net improves from change when its long-term benefits outweigh its short-term costs. It's not clear to me that several million square miles of land suddenly becoming more habitable wouldn't provide a better economic arrangement for the world 100 years from now, even when you net out the costs of people having to migrate to new areas.

tshaddox 5y ago

How do you calculate "net effects" when dealing with millions of people suffering in the near term? What does it take to balance that and end up with a net positive?

georgewsinger 5y ago
It's really hard; that's basically my point. But I think a good starting place is to model the expected effects on various populations of all of these various factors (increased floods, increased crop yields, etc). If the vast majority of these models are tilted overwhelmingly negative or positive, we can somewhat adjust our confidence levels. Of course, we'll never be able to be that confident when the time horizon stretches so long (100+ years) and the effect sizes are so small (e.g., sea levels are expected to rise by a lower amount on average than the existing low-tide to high-tide variance). But..that's also my point: it's not merited to be so extremely confident that the effects of global warming are going to be so negative (or positive) over 100+ years. People focus extremely hard on the negatives of global warming, don't focus much at all on the positives (my guess is most people living in urban areas aren't even aware there even exist any positives), and focus their debating efforts on the (as far as I can tell) long ago settled question of whether or not the climate warming is happening, or is caused by humans. My guess as to why this happens is that considering whether global warming could be a positive thing for the world conflicts with an anti-market bias that people in urban areas frequently share.

lkrubner 5y ago

Given long enough to adapt (perhaps a million years? Perhaps two million?) then there would be no negative effects to the current changes. The dangers are entirely to do with the speed of the current change. The increasing acidity of the oceans will, over the next two centuries, lead to a mass extinction in the oceans which could eventually have large effects on the gases that make up our atmosphere -- and here we need to concern ourselves with black swan events, which will remain unlikely, even 200 years from now, but which, if they were to occur, would lead to an extinction so broad that it would threaten human survival.

georgewsinger 5y ago
As pointed above, there is also human survival tail risk to stopping global warming. How are you so certain to know which tail risk is larger, or likelier?
- BlueTemplar 5y ago
  Humans have already lived through several glaciations. But we weren't even around yet when the current ice age started 4M years ago.
- lkrubner 5y ago
  I don't think you read what I wrote. I never mentioned global warming. If we continue at current rates of fossil fuel use for another 200 years, the acidification of the ocean will start to endanger phytoplankton, which makes much of the oxygen we breathe. The loss of phytoplankton drove the most serious mass extinction in the Earth's history: https://earthsky.org/earth/ocean-acidification-drove-earths-largest-mass-extinction/ https://earthsky.org/earth/ocean-acidification-drove-earths-... The article that started this thread on Hacker News suggested that the death rate goes up 10% in the winter, which gives some sense of what the tail risk is from cold weather. By contrast, the tail risk from the acidification of the oceans is something like the Permian/Triassic mass extinction. You ask "How are you so certain to know which tail risk is larger, or likelier?" We can be certain because one risk is many orders of magnitude worse than the other.