I promised a few folks (@[email protected] @[email protected]) over on this thread an effort post about stratospheric aerosol injection today. My doctorate is in philosophy, but I did my PhD work on the foundations of climate modeling and complex systems theory, and I ended up in a climate lab for two years as a postdoc, where I worked explicitly on this proposal. Long story short, we should not be doing it. Here’s what it is, how it works, and why I think it’s a bad idea.
There’s a ton to say here, so I’m going to just start with a kind of general overview of the proposal and why it worries me. Folks can ask questions if they want to, and I can go into more technical detail or give references on any part of it that folks are interested in. I’ll try to get to any serious comments eventually, but I do have a job and shit. OK, here we go.
Very large volcanic eruptions release a truly mind-boggling amount of volcanic shit into the atmosphere, including compounds known as sulfate aerosols. Sulfate aerosols are small droplets of sulfur-based chemicals that aren’t quite liquid and aren’t quite gaseous. When they get into the upper atmosphere, they can block significant amounts of incoming solar energy, preventing it from getting down to the Earth’s surface where it would otherwise get stuck thanks to the greenhouse effect. This has a major cooling effect: the last big volcanic eruption, 1991’s Mt. Pinatubo, reduced incoming sunlight by 10% and decreased global temperatures by about 0.5 degrees C for two years.
If we wanted to, we could intentionally release similar aerosols into the atmosphere (probably either with high-altitude balloons or literally shooting them into the stratosphere with specialized guns; they need to get way too high up for planes to disperse them). High atmospheric winds would rapidly spread aerosols released near the equator to cover the globe, and with enough aerosols, we could potentially cool the planet off enough to cancel out a quadrupling of GHG concentrations. If successful, such a plan could prevent sea level rises, save the glaciers, and prevent many other extreme weather events that we anticipate would accompany drastic temperature increases. The total cost is projected to be something like $50 billion per year, which is just absolutely insanely cheap by the standards of effective global environmental policy–it’s something on the order of 1% the cost of totally retooling the global economy away from fossil fuels.
OK, so what’s the catch? Well for one thing, global temperature increases aren’t the only consequences of climate change (that’s why we call it “climate change” instead of “global warming”). CO2 in the atmosphere turns to carbolic acid in the oceans, endangering marine life and disrupting ecosystems on land and at sea; aerosol injection (like all SRM plans) would have no effect on ocean acidification. Plus, all that sulfur in the upper atmosphere would start eating away at the ozone layer again, potentially undoing all the progress we’ve made toward closing the ozone hole (remember that?) since banning CFCs two decades ago. Perhaps most worryingly of all, decreased sunlight plus a stronger greenhouse effect would wreak havoc on the water cycle across the globe by decreasing evaporation and changing rainfall patterns. In the years after Pinatubo blew, worldwide rainfall dropped to more than three standard deviations below normal. That’s a gigantic decrease: to use an (imperfect) analogy, a difference of three standard deviations in adult male height in the United States is the difference between someone who is five feet and eight inches tall and someone who is six and a half feet tall. The years after Pinatubo’s eruption saw droughts over much of the world, many of them severe. Moreover, the drought wasn’t equitably distributed: traditionally dry places (like the middle east) tended to get a lot of precipitation immediately after Pinatubo, while traditionally wet places (like SE Asia and the Amazon basin) got much, much less. Both of these are very bad. And that eruption, remember, only cooled the planet by 0.5 degrees: the effect on rainfall is expected to increase with greater aerosol concentrations, and this plan would call for enough to cool the planet by 4 degrees C or more. The effect on agriculture the world over could very well be catastrophic–arguably just as bad (or worse) than the damage done by warming alone.
We may reach a point where the benefits outweigh the costs–particularly if we continue not reducing our GHG emissions–but who’s to say where that point lies? There’s no way to target this plan by region: either we do it to the whole globe, or we don’t do it at all.
Are we comfortable asking farmers on another continent to sacrifice their livelihoods for the sake of other nations’ unwillingness to reduce CO2 emissions? Should we be comfortable with that? Who even is “we” here?
How much agreement among nations is enough to take this plunge? If the citizens of every nation but one decide that the sacrifice is worth it, would we be justified in starting the program even over that single nation’s protests? What if it’s two nations objecting? What if it’s just under half? These are not idle questions–not mere hypotheticals of the type that concern few but moral philosophers inside the seminar room–but real decisions we could be facing before the century’s out, and I’m very worried that we are in no way ready to handle them. Considering the difficulty we have making tough decisions inside individual nations, I can’t even imagine how we’d even begin to deliberate about this as a species.
But the really scary thing about aerosol injection–the thing that really keeps people who work on this up at night–is just how easy it really is, and how difficult to stop it would be once the compound was released. If a Peter Thiel or an Elon Musk (or an Exxon-Mobil) decided to initiate a program like this, it would be almost impossible to stop them if they managed to get started; we’d just have to wait for the aerosols to fall out of the atmosphere, a process that could take years even after the emissions ceased. The same goes for a single nation that decides such a program is in its national interest and elects to go it alone, full speed ahead and damn the torpedoes–or, in this case, damn the rainfall. Would we go to war to stop this from happening? Would we go to war to make this happen, should we decide it’s in our national interest? Either way, the implications are deeply troubling.
Because the residence time–the amount of time a compound hangs around in the atmosphere before it decays or precipitates out–of aerosols is so much shorter than that of greenhouse gases (sulfur dioxide has a residence time on the order of months, as opposed to decades or centuries for most greenhouse gases), once we start this program there’s really no turning around. We’re almost certain that it would reduce the temperature, but then we’ve got a tiger by the tail: either we keep pumping more compounds into the atmosphere forever, or we stop. If we stop, the aerosols–which, remember, are not gasses but rather small droplets of liquid–fall out of the atmosphere entirely within a year or two. Suddenly, all that warming that they’ve been masking is back, only instead of seeing 4+ degrees warming spread over a century, we see it spread over 24-36 months. It’s impossible to overstate how catastrophic that would be, both for human civilization and ecosystems. It would leave the world with no adaptation time. That means we need to keep this technology running with nearly 100% uptime for an indefinite period into the future, or end up worse off than we would have been if we’d just done nothing. Because it’s so cheap and easy to start, it would be really simple for a billionaire (or single nation) to just start doing this in secret without the world noticing until the temperature reduction signal became detectable by the scientific community at large. At that point, we’re locked in and the single-actor geoengineer has effectively taken the world hostage. This fucking sucks for obvious reasons.
There’s more to say here (for instance, there’s some evidence that change to precipitation patterns is at least partially a function of release location, and so who gets impacted in what way depends in part on how and where the injection is performed), but I feel like this is enough of a start. I can dive into more technical detail if people want.
To buy us time to rapidly decarbonise rightThe threat of termination shock seems like all the reason you’d ever need to not want to do this. It would be like handing a nation or group of nations a whole new style of nuke, except this one has a dead man’s switch and can’t be decommissioned.
Everyone else would be participating at that point, because they have a vested interest in keeping it going, even if its against their own will.
Sounds like the plot of a dystopian Sci fi novel, especially if you get a couple generations removed from the decision to flip the switch.
it would be like handing a nation or group of nations a whole new style of nuke
Or some guy! Or an oil company!
“Just keep buying my shitty cars and building the Mars colony and no one gets hurt!”On an unrelated note, are you still working in the same space now or have you moved on to something else post-postdoc?
I quit “real” academia. I teach this stuff at a university-attached high school for super smart kids now.
Gotcha, thanks for sharing!
Aside from drastically changing patterns of precipitation, I could only imagine screening 10% of the sunlight reaching the surface would have a negative impact on photosynthesis, with impacts both on natural environments and industrial agriculture.
It wouldn’t need to be that much. A change of 1-2% in planetary albedo would likely be enough for the foreseeable future.
Photosynthesis is horrendously inefficient - on the order of 1-2%. A lot of what plants do is to mitigate the effects of intercepting more energy than they can handle. This isn’t to say that solar dimming wouldn’t have an effect, but it would be completely masked by changes to the water cycle.
Yeah, this is correct. You’d need to dim things a lot more than what’s possible with aerosol injection like this before photosynthesis failure would start to be the dominant problem.
If we stop, the aerosols–which, remember, are not gasses but rather small droplets of liquid–fall out of the atmosphere entirely within a year or two.
What effects might the aerosols themselves have as they fall out of the atmosphere? Even if everything is nominal, I can’t imagine tons and tons of sulfuric compounds raining down on the planet every year wouldn’t cause new problems.
Acid rains mostly.
Depends a bit on what compound we end up using. Sulfur dioxide is the one that gets the most attention in the literature because it’s the easiest to make and work with (sulfur is the 5th most abundant element on Earth), but it’s also an especially risky one. Not all of the aerosols would precipitate out–some would break down in the stratosphere, and many of the decomposition byproducts of sulfur dioxide are really bad for the ozone layer, so that problem might crop back up again. There’s some risk that the precipitation itself might lead to a resurgence of acid rain, though that part probably wouldn’t be too bad given the quantities and elevation. Sulfur dioxide was a major driver of acid rain in the 20th century, but that was largely because it was being injected into the low troposphere as a result of industry and coal combustion. This would be an injection of much smaller quantities at much higher elevations, so that element of the risk is probably low. There are also other candidate compounds that aren’t nearly as risky in that respect (generally calcium-based), though those are much less well-studied. Again, though, there’s a lot of uncertainty here which is bad for things like this.
If a Peter Thiel or an Elon Musk (or an Exxon-Mobil) decided to initiate a program like this, it would be almost impossible to stop them if they managed to get started; we’d just have to wait for the aerosols to fall out of the atmosphere, a process that could take years even after the emissions ceased. The same goes for a single nation that decides such a program is in its national interest and elects to go it alone, full speed ahead and damn the torpedoes–or, in this case, damn the rainfall. Would we go to war to stop this from happening? Would we go to war to make this happen, should we decide it’s in our national interest? Either way, the implications are deeply troubling.
Because the residence time–the amount of time a compound hangs around in the atmosphere before it decays or precipitates out–of aerosols is so much shorter than that of greenhouse gases (sulfur dioxide has a residence time on the order of months, as opposed to decades or centuries for most greenhouse gases), once we start this program there’s really no turning around. We’re almost certain that it would reduce the temperature, but then we’ve got a tiger by the tail: either we keep pumping more compounds into the atmosphere forever, or we stop. If we stop, the aerosols–which, remember, are not gasses but rather small droplets of liquid–fall out of the atmosphere entirely within a year or two. Suddenly, all that warming that they’ve been masking is back, only instead of seeing 4+ degrees warming spread over a century, we see it spread over 24-36 months. It’s impossible to overstate how catastrophic that would be, both for human civilization and ecosystems. It would leave the world with no adaptation time. That means we need to keep this technology running with nearly 100% uptime for an indefinite period into the future, or end up worse off than we would have been if we’d just done nothing.
Those vampires would absolutely crave a worldwide captive market like that. They’re so alienated and insulated from consequences that they wouldn’t even notice the damage or care about it until it was far, far too late.
I think between this angle, the potential to put pressure on increasingly “uppity” parts of the Global South (and China), the ability it would lend us to kick the can down the road while still looking like we’re doing “serious climate change policy,” and the absurdly low price, it’s pretty much a guarantee that this is going to happen.
But the really scary thing about aerosol injection–the thing that really keeps people who work on this up at night–is just how easy it really is, and how difficult to stop it would be once the compound was released. If a Peter Thiel or an Elon Musk (or an Exxon-Mobil) decided to initiate a program like this,
“How to Blow Up a
PipelineStratospheric Aerosol Injection Guns”Random serious question from the cheap seats, don’t feel you need to answer.
For this type of project, come across any research on what the effects could/would be for wavelengths of light not visible to the human eye?
I occasionally wonder how the chemicals that could do this would affect birds/bugs (lots of species can see parts of the light spectrum that we can’t see right?), maybe reptiles, and I know plants (trees come to mind) use more of the light spectrum than we humans typically notice.
That’s an interesting question. My educated guess is that it shouldn’t have much of an impact, because the intervention is on albedo–the reflectivity of the atmosphere to incoming radiation, which is concentrated around the visible spectrum and UV–and even there, it’s not much. We’re talking about an adjustment of only a few (low single-digits) percent of the overall planetary albedo, which would be undetectable to human eyes and shouldn’t be terribly hard on anything else either. It would be a very, very slight dimming of the light that makes it down to the surface; we’re talking a few watts per square meter. It probably wouldn’t meaningfully impact photosynthesis or vision. I don’t know if that question has ever been explored in detail, though. I’ll look into it.
The total cost is projected to be something like $50 billion per year, which is just absolutely insanely cheap by the standards of effective global environmental policy–it’s something on the order of 1% the cost of totally retooling the global economy away from fossil fuels.
we need to keep this technology running with nearly 100% uptime for an indefinite period into the future
So what you’re saying that capitalism is 100% gonna try and use this climate wunderwaffen and do0m us all. Like not even joking. This is what will happen. It’s “cheap”. It’s a last minute “solution”. It requires missiles and explosions to deliver, aka subsidizing the MIC to deliver it around the world.
It’s been good run folks.
This is why I’ll be shocked if we don’t try it in the next 15 or 20 years.
Are there any geo-engineering alternatives that aren’t horrifying?
Chopping up calcium silicate rocks and spreading them around, cheap and efficient, kinda slow but
This is interesting but I’m skeptical that mining and grinding that much silicate material would pay for itself in carbon terms. Mining and grinding are very energy intensive
Is it? rock crusher machine can work from solar/wind, its not ideal intermittent process, but it works (as opposed to steel/chemistry, where you would need 24/7), and electro-mechanical thingies don’t use that much energy anyways. Eyeballey (real word)-wise explosives maybe displace similar amount of air to the rocks blown up, which, considering density difference, is trivial amount.
Transportation would obviously suck a lot of carbon profit, so it should be used locally
If someone could figure out a way to make carbon capture and sequestration work at scale, it would actually be a great part of a meaningful climate policy portfolio and likely would have no significant side effects. We can do it now (and the Earth does it naturally as part of the carbon cycle), but we haven’t figured out a way to do it at levels that would be sufficient to fix the problem on the time scales that are relevant yet. Direct air capture is probably a pipe dream for thermodynamic reasons (removing and sequestering a gas with a concentration of ~450 parts per million is really hard and energy intensive), but something like enhanced weathering could work.
The scale we’d need to run it at would basically look like the fossil fuel industry run in reverse, though: we’d need that level of mining, processing, distribution, and collection of some candidate mineral (calcium carbonate or the like), which is also energy intensive. If we seized every fossil fuel company, forced them to start using all of their infrastructure for this, and also forcibly converted all (or nearly all) global energy production to renewable, that might work. That’s pretty much my preferred policy portfolio, but it ain’t gonna happen.
Excellent effortpost.
At that point, we’re locked in and the single-actor geoengineer has effectively taken the world hostage.
I was against it until you said this. Sorry planet, my childhood dreams of being an evil supervillain finally have a path forward.
(great post thanks)
Thank you so much for this. This is truly a well written post. Bloody hell I didn’t think termination shock was gonna be that potentially bad
10/10 summary, i completely agree
Are we comfortable asking farmers on another continent to sacrifice their livelihoods for the sake of other nations’ unwillingness to reduce CO2 emissions? Should we be comfortable with that? Who even is “we” here?
Would we go to war to stop this from happening? Would we go to war to make this happen, should we decide it’s in our national interest? Either way, the implications are deeply troubling.
I truthfully believe this is part of a kind of hybrid warfare against China by the US and if the modeling shows it will devastate them while hurting the US significantly less then they’ll go ahead with it. The resulting famines and other issues are ripe for exploiting to overthrow the CPC or at the very least seriously injure their aspirations for surpassing the US and hobble them and set them back by a decade or more. The US is also the one most likely to believe that China won’t use nukes to prevent this kind of a plan and to be willing to gamble even if they’re unsure as it has a chance of ensuring another century of hegemony in their minds. Climate change in general I believe has largely been allowed to continue not just because of capitalist interests but because the models show the US will be among the most resilient to it, it represents an incredibly powerful form of hybrid warfare to wage on and destabilize the rest of humanity to allow US hegemony to continue. Your mentioning that a single actor could do this also worries me. The US would love the plausible deniability angle of using a US corporation to do this and when China threatens them they claim “wasn’t us, hey you can’t nuke us for the actions of one of our companies without our knowledge”.
Suddenly, all that warming that they’ve been masking is back, only instead of seeing 4+ degrees warming spread over a century, we see it spread over 24-36 months.
I assume as do many others you mean if this were started and continued for decades, those at the end of that line would have no choice. Not that if this were started and allowed to run for say 6 years that we couldn’t stop it and we’d only reap the normal amount of warming we’d have gotten anyways (not 4 degrees C over that limited span) though which could still be bad as the change in temperatures would be harmful to various ecosystems I’d imagine and the stress of going from warm to cool to even warmer again could be devastating to a lot of things.
we’d only reap the normal amount of warming we’d have gotten anyways (not 4 degrees C over that limited span) though which could still be bad as the change in temperatures would be harmful to various ecosystems I’d imagine and the stress of going from warm to cool to even warmer again could be devastating to a lot of things.
Right! By starting this, we immediately create a warming deficit. Even if it’s only something like 2°C, getting that much warming in 18 months would be incredibly destabilizing. We actually have no idea what the impacts would be, which is terrifying. The longer it goes on, though, the worse the snap back looks. One of my colleagues compares it to starting a heroin regimen.
I had the same thought a while ago about how we as a species could become “addicted” to this kind of solution, leading us to darken the sky more and more over time to compensate for never ending emissions. Fucking bleak to realize Operation Dark Storm from the Animatrix will probably be our actual future
There’s an upper limit to how much we can do this, at least with this method. Above a certain concentration (probably an offset of around 8°C), the aerosol particles will start sticking together into macroscopic droplets and just precipitating out. It’s not the kind of thing we could just do forever to offset arbitrarily high amounts of warming, which is either good or worrying depending on your perspective.
With particulates we’ll never get to complete darkness, but if we’re maxing out our artificial cooling capacity, we might become desperate enough to start putting actual sunshades into orbit.
Thank you for this fascinating writeup!
Because it’s so cheap and easy to start, it would be really simple for a billionaire (or single nation) to just start doing this in secret without the world noticing until the temperature reduction signal became detectable by the scientific community at large. At that point, we’re locked in and the single-actor geoengineer has effectively taken the world hostage. This fucking sucks for obvious reasons.
This part kind of confused me though. Wouldn’t we only be locked in after decades of aerosol dispersal had accumulated a substantial warming debt?
Even then, I didn’t really understand how you’d be locked in after years - wouldn’t you just inject less sulfate aerosols next year, and slowly reduce the amount until you’re no longer injecting anything?
When we start the injection, we immediately create a warming deficit of however much we’ve reduced the temperature by. Even if that’s only 2°C to start with, that much warming in 18 months has the potential to be incredibly destabilizing to weather and ecosystems–possibly more so than just sitting at a +2°C anomaly. We don’t really know what the impacts would be, because it’s totally unprecedented. My prediction is that the longer it goes on, the worse the snapback will be, even if the warming debt isn’t substantially larger. The more adapted things are to one equilibrium, the more violent and disruptive the transition to a new one will be.
I see, that makes sense!
