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I'm no expert in this subject and I don't have any strong opinions on it. The point of this comment isn't to debate one side or the other. That said, your comm

I'm no expert in this subject and I don't have any strong opinions on it. The point of this comment isn't to debate one side or the other. That said, your comment stands out to me to be self-contradictory and unscientific (by way of being alarmist and not backing up an extraordinary claim ). > Unknown second order effects This sounds right. > Nearest real world success is continuous low volume maritime dispersal which has completely different dispersal dynamics than high-altitude bursts, and the continuous low volume maritime dispersal is non-viable Since I don't know a lot about this topic I'll take your word for it. > No way to undo it once done This doesn't sound quite right, my intuition says more likely "no known way to undo it once done". > If humans can’t perpetually release aerosols — and I mean perpetually, for the next millions of years — then the global climate “snaps back” violently within weeks Wait... So, to undo it all we have to do is stop doing it? Doesn't this contradict the statement right before it? > almost certainly eradicates all known life in the entire universe This statement makes me suspicious of the credibility of the rest. This is an extraordinary claim and I think deserves way more explanation if you want to convince anyone who doesn't already agree with you. It would be a lot easier to accept "decimates human civilization" than "eradicate all life on earth". Life is extremely resilient. How exactly would it eradicate all life on earth?

eimrine 9mo ago
Stopping spreading and undo the damage from spreading are not contradictable. Eradicating all life is not unscientific, you might be better at throwing real arguments of why you don't like this idea instead of boasting.
dmbche 9mo ago
Read on maritime SO2, it was stopped because it's second order effects were too negative (mostly acid rain if i recall right) The stuff about aerosols: The "plan" isn't that you dump a one time "treatment" of aerosols and then climate is reset. It's a continuous aerosol injection advitam aeternam to offset the warming - constant upkeep. About comments on destruction of all life: the biosphere is so conplex it's hard to even grasp the gist of it. Global temp affects every level of it. Were this "treatment" be a little too strong/maladjusted, it could very well cause runaway mass death. And we only have proof of life on earth - if we kill life on it, as far as we know, it's over for life itself. Can't be careful enough, and aerosol dispersal isn't that.
- metalman 9mo ago
  there is absolutly no possibility of injecting enough of anything into the atmosphere in such a way as the CO² cost of doing so dosn't cause more heating than the "airosol" reflects into space, which in itself is purely conjectural, there bieng, absolutly zero engineering paractice or experience to go from,.... well, not counting an unlimited supply of hubris
estearum 9mo ago
Wow gee wiz, it’s almost like my original comment was: go do some reading. Regarding the “no way to undo” and the “violent snap back”, we know the desire albedo effects dissipate and therefore require continuous maintenance. However, these aerosols also cause hard-to-reverse reactions to other things like damaging the ozone layer and causing rain pattern shifts. Yeah, most climate catastrophe scenarios are of the severity you describe. This one is not. The entire point of SAI is to “save up” damage to the environment. So over 100 years of SAI and then stopping, you will incur 100 years of atmospheric and temperature changes within a few months. And that’s only over a hundred years. If we depend on this and do it for a thousand years, now it’s a thousand years of damage applied in months. This is far, far, far faster than any biological system evolves. Sure maybe some microbes that can survive in a gigantic range of environments could survive, but no, probably no complex life forms would.
- FloorEgg 9mo ago
  > Wow gee wiz, it’s almost like my original comment was: go do some reading. My understanding is that the whole purpose of HN is to discuss interesting topics with intellectual curiosity. "Go do some reading" type statements aren't really conducive. What would be more appropriate is recommending specific sources, or just taking a moment to elaborate since the whole point is discussion. I appreciate your elaborations in this last comment. I don't appreciate the dismissive tone of your first line or your earlier comment. > Regarding the “no way to undo” and the “violent snap back”, we know the desire albedo effects dissipate and therefore require continuous maintenance. > However, these aerosols also cause hard-to-reverse reactions to other things like damaging the ozone layer and causing rain pattern shifts. This makes sense. I guess where the logic breaks down for me is the conflation between the time it would take us to recognize the second order effects and stop the process, the amount of violent snap back that would occur, and the time to reverse the second order effects. To be clear, I understand the risk you are pointing at and it is a significant risk, it still seems like you are exaggerating it. It's either we do this for thousands of years (in which case the second order effects must be minor to make it sustainable for that long), or we do it for a short time because second order effects aren't sustainable. It's the logical relationship between the reversibility, second order effects, and magnitude of snap back risks that isn't adding up for me. All this said, as I've engaged in this topic and thought more about it, my current stance is that we shouldn't be introducing new things into the climate to address the consequences of other changes we have made. A safer approach seems like economically sustainable ways to undo the root-cause damage we have done. (E.g. CO2 capture sounds better than novel aerosol injection). So I think we probably agree in principle, I just still find the comment I responded to originally alarmist and not very convincing.
counters 9mo ago
> Wait... So, to undo it all we have to do is stop doing it? Doesn't this contradict the statement right before it? It's not quite that simple. The intuition that you're subtly relying on is the idea that the response or effect of one of these geoengineering treatments is linear. But unfortunately, that's not something you can assume about a dynamical system. In reality, the climate system can undergo certain types of hysteresis where "undoing" the forcing doesn't revert the initial perturbation, because you're suddenly on a different response curve. Probably the most famous example of this in climate dynamics is the way that the ice-albedo effect sets up a hysteresis in the trajectory towards a "snowball Earth" scenario. Apologies for the lack of links/references; Wiki has decent write-ups on this, and it's typically covered in the first chapter of a climate dynamics textbook. The potential response to suddenly stopping a climate change mitigation strategy has a very well-popularized name: a "termination shock." In fact, Neal Stephenson used exactly this concept in his titular novel on the topic in 2021. As a climate scientist, my mental model to better understand the risk of termination shocks and unintended consequences boils down to how fast the response of the climate system is. Marine brightening is "less risky" because the meteorological response to these interventions is extremely fast; a cloud-precipitation system will respond on the order of minutes to hours, and unless the intervention continues unabated, it will clean the air quickly, limiting the repsonse. Stratospheric aerosol injection is more complicated, but we have a very good analogue - very large scale volcanic eruptions like Mt Pinatubo. The response to these sorts of events is measured more on the timescale of 2-5 years, although knock-on effects (such as a shift towards more diffuse solar radiation reaching the surface, which has significant effects on terrestrial and oceanic biogeochemistry) could very much persist longer than that - and don't "snap back" nearly as quickly. A continuous, Pinatubo-like intervention would compound and introduce coupled atmosphere/ocean responses that could decade years or longer to fully play out. And that's _in addition_ to the near immediate (1-2 year) response in global average temperature, which would bounce back to most of the pre-intervention level very quickly. These things are complex. There's a lot we don't know. But, there's also a lot we _do_ know. I would encourage anyone who does not have significant experience in climate dynamics to remain curious and avoid jumping to conclusions based on simple intuition; they're probably wrong.
- FloorEgg 9mo ago
tzs 9mo ago
It's the aerosol levels that "snap back" (although that takes months to a few years, not weeks). The effect that has on the climate depends on how much CO2 is in the atmosphere at the time. If during the time we were doing the aerosol program we've also continued increasing CO2, using increasing aerosol releases to prevent that from causing warming, then when we stop with the aerosol we get that deferred warming over a few years or less. We end up at the roughly the same place we would have been if we had not done the aerosols at all, except instead of getting from where we are now to them over several decades we get their over a few years. Let's say that is 3℃ above current average temperature. A 3℃ rise over 2 years is a lot harder to handle than a 3℃ rise over 30 years. Worse, if we started aerosols a lot of countries might decide that it is OK to keep increasing emission rates, so if we ever stop the aerosols were are looking at a rise to much higher than we would have had if we had not used aerosols.

eimrine 9mo ago

Stopping spreading and undo the damage from spreading are not contradictable. Eradicating all life is not unscientific, you might be better at throwing real arguments of why you don't like this idea instead of boasting.

dmbche 9mo ago

Read on maritime SO2, it was stopped because it's second order effects were too negative (mostly acid rain if i recall right) The stuff about aerosols: The "plan" isn't that you dump a one time "treatment" of aerosols and then climate is reset. It's a continuous aerosol injection advitam aeternam to offset the warming - constant upkeep. About comments on destruction of all life: the biosphere is so conplex it's hard to even grasp the gist of it. Global temp affects every level of it. Were this "treatment" be a little too strong/maladjusted, it could very well cause runaway mass death. And we only have proof of life on earth - if we kill life on it, as far as we know, it's over for life itself. Can't be careful enough, and aerosol dispersal isn't that.

metalman 9mo ago
there is absolutly no possibility of injecting enough of anything into the atmosphere in such a way as the CO² cost of doing so dosn't cause more heating than the "airosol" reflects into space, which in itself is purely conjectural, there bieng, absolutly zero engineering paractice or experience to go from,.... well, not counting an unlimited supply of hubris

estearum 9mo ago

Wow gee wiz, it’s almost like my original comment was: go do some reading. Regarding the “no way to undo” and the “violent snap back”, we know the desire albedo effects dissipate and therefore require continuous maintenance. However, these aerosols also cause hard-to-reverse reactions to other things like damaging the ozone layer and causing rain pattern shifts. Yeah, most climate catastrophe scenarios are of the severity you describe. This one is not. The entire point of SAI is to “save up” damage to the environment. So over 100 years of SAI and then stopping, you will incur 100 years of atmospheric and temperature changes within a few months. And that’s only over a hundred years. If we depend on this and do it for a thousand years, now it’s a thousand years of damage applied in months. This is far, far, far faster than any biological system evolves. Sure maybe some microbes that can survive in a gigantic range of environments could survive, but no, probably no complex life forms would.

FloorEgg 9mo ago
> Wow gee wiz, it’s almost like my original comment was: go do some reading. My understanding is that the whole purpose of HN is to discuss interesting topics with intellectual curiosity. "Go do some reading" type statements aren't really conducive. What would be more appropriate is recommending specific sources, or just taking a moment to elaborate since the whole point is discussion. I appreciate your elaborations in this last comment. I don't appreciate the dismissive tone of your first line or your earlier comment. > Regarding the “no way to undo” and the “violent snap back”, we know the desire albedo effects dissipate and therefore require continuous maintenance. > However, these aerosols also cause hard-to-reverse reactions to other things like damaging the ozone layer and causing rain pattern shifts. This makes sense. I guess where the logic breaks down for me is the conflation between the time it would take us to recognize the second order effects and stop the process, the amount of violent snap back that would occur, and the time to reverse the second order effects. To be clear, I understand the risk you are pointing at and it is a significant risk, it still seems like you are exaggerating it. It's either we do this for thousands of years (in which case the second order effects must be minor to make it sustainable for that long), or we do it for a short time because second order effects aren't sustainable. It's the logical relationship between the reversibility, second order effects, and magnitude of snap back risks that isn't adding up for me. All this said, as I've engaged in this topic and thought more about it, my current stance is that we shouldn't be introducing new things into the climate to address the consequences of other changes we have made. A safer approach seems like economically sustainable ways to undo the root-cause damage we have done. (E.g. CO2 capture sounds better than novel aerosol injection). So I think we probably agree in principle, I just still find the comment I responded to originally alarmist and not very convincing.

counters 9mo ago

> Wait... So, to undo it all we have to do is stop doing it? Doesn't this contradict the statement right before it? It's not quite that simple. The intuition that you're subtly relying on is the idea that the response or effect of one of these geoengineering treatments is linear. But unfortunately, that's not something you can assume about a dynamical system. In reality, the climate system can undergo certain types of hysteresis where "undoing" the forcing doesn't revert the initial perturbation, because you're suddenly on a different response curve. Probably the most famous example of this in climate dynamics is the way that the ice-albedo effect sets up a hysteresis in the trajectory towards a "snowball Earth" scenario. Apologies for the lack of links/references; Wiki has decent write-ups on this, and it's typically covered in the first chapter of a climate dynamics textbook. The potential response to suddenly stopping a climate change mitigation strategy has a very well-popularized name: a "termination shock." In fact, Neal Stephenson used exactly this concept in his titular novel on the topic in 2021. As a climate scientist, my mental model to better understand the risk of termination shocks and unintended consequences boils down to how fast the response of the climate system is. Marine brightening is "less risky" because the meteorological response to these interventions is extremely fast; a cloud-precipitation system will respond on the order of minutes to hours, and unless the intervention continues unabated, it will clean the air quickly, limiting the repsonse. Stratospheric aerosol injection is more complicated, but we have a very good analogue - very large scale volcanic eruptions like Mt Pinatubo. The response to these sorts of events is measured more on the timescale of 2-5 years, although knock-on effects (such as a shift towards more diffuse solar radiation reaching the surface, which has significant effects on terrestrial and oceanic biogeochemistry) could very much persist longer than that - and don't "snap back" nearly as quickly. A continuous, Pinatubo-like intervention would compound and introduce coupled atmosphere/ocean responses that could decade years or longer to fully play out. And that's _in addition_ to the near immediate (1-2 year) response in global average temperature, which would bounce back to most of the pre-intervention level very quickly. These things are complex. There's a lot we don't know. But, there's also a lot we _do_ know. I would encourage anyone who does not have significant experience in climate dynamics to remain curious and avoid jumping to conclusions based on simple intuition; they're probably wrong.

FloorEgg 9mo ago

tzs 9mo ago

It's the aerosol levels that "snap back" (although that takes months to a few years, not weeks). The effect that has on the climate depends on how much CO2 is in the atmosphere at the time. If during the time we were doing the aerosol program we've also continued increasing CO2, using increasing aerosol releases to prevent that from causing warming, then when we stop with the aerosol we get that deferred warming over a few years or less. We end up at the roughly the same place we would have been if we had not done the aerosols at all, except instead of getting from where we are now to them over several decades we get their over a few years. Let's say that is 3℃ above current average temperature. A 3℃ rise over 2 years is a lot harder to handle than a 3℃ rise over 30 years. Worse, if we started aerosols a lot of countries might decide that it is OK to keep increasing emission rates, so if we ever stop the aerosols were are looking at a rise to much higher than we would have had if we had not used aerosols.