[yrral]

Has anyone looked into the theory that SO2 is an "anti-greenhouse" gas and that much of the greenhouse effects of CO2 have been negated by SO2. Essentially SO2 particles stay in the air for a long time and reflects a large spectrum of light so it fails to be absorbed by land or sea/converted to infrared (infrared is primarily what the CO2 reflects).

Recently (since 2010ish but moreso since 2020 in shipping) there has been a global effort to reduce SO2 emissions (eg by installing scrubbers) which has caused the CO2 increase over the last 150 years to actually "take effect" since the SO2 is no longer negating the effects.

I stumbled upon this theory recently and it sounds compelling but am curious if better informed people could shine a light about this.

https://twitter.com/hankgreen/status/1687535525169930241

https://twitter.com/LeonSimons8/status/1688145475289931776

https://www.weforum.org/agenda/2023/07/sea-surface-temperatu...

[BillFranklin]

Yeah it's mentioned in Stephen Hawking's last book: https://en.m.wikipedia.org/wiki/Stratospheric_aerosol_inject...

“The Intergovernmental Panel on Climate Change concludes that it is the most-researched solar geoengineering method, with high agreement that it could limit warming to below 1.5 °C”

There’s a risk it’d affect the ozone layer. But Paul Crutzen, who won the Nobel Prize for his ozone research in 95, said the sulfur plan is “the only option available to rapidly reduce temp rises and counteract other climactic effects”.

We’d also need to add shockingly little SO2 to the stratosphere. We currently emit 200m tons per year (25% is humans, rest is volcanos and other natural sources). We’d need to add an extra 100k per year.

Edit: I think one of the Microsoft co-founders was looking into it, the problems of proving it would work were political - not engineering-related.

[bee_rider]

It always strikes me as odd that the geoengineering experiment that got us into the predicament (dumping boatloads of CO2 into the atmosphere), the politics were so much easier.

[trescenzi]

I've generally come to the belief that it's related to how humans think about cause and effect.

Dumping boatloads of CO2 into the atmosphere is second order from the actual goal of producing electricity so most people just can't/don't/won't think about it.

In this case we'd be intentionally dumping SO2 so people are capable of thinking "wow that's not moral" or whatever issue they might have with it.

[dingnuts]

I think the biggest concern with something like releasing SO2 as a geoengineering project, which needs, quoting someone else in the thread "very little" to be released to have a big effect, the concern is over-correction or unforeseen effects caused by an insufficient understanding of the system as a whole.

Don't want to accidentally start an ice age by trying to prevent a hothouse planet from forming :P

[lamontcg]

And we want to stop releasing CO2. We don't want to wind up charging onwards to 1,000 ppm CO2 just because we released enough SO2 to compensate for the climate change.

[darkmarmot]

Especially since human brains suffer significant cognitive effects above 1,000ppm.

[blooalien]

"SnowPiercer" here we come...

[animal_spirits]

The current predicament we are in was not produced by a deliberate attempt at global geoengineering. It was a global economic project with a byproduct of climate change.

[ClumsyPilot]

It does not matter if someone screwed up my life on purpose or by accident, I am still harmed

[ortusdux]

I'd say that we need to discover a source of energy that produces SO2 as a byproduct, but given our species' track record we would probably trigger an ice-age in a few decades.

[bee_rider]

Hah!

Or maybe if some billionaire could figure out a way for their space-tourism project to “accidentally” produce SO2, then we’d give them the moral mulligan.

[NikkiA]

SO₂ was a byproduct of coal power stations, we started scrubbing it because it was the cause of acid rain.

[aoeusnth1]

100k or 100M?

200M + 100k = 200.1M, and I doubt the 200M figure had 4 significant figures.

[mercurywells]

It'd be a smaller amount that gets injected into the stratosphere, as opposed to what we normally release into the troposphere. A quick skim of the wikipedia link seems to suggest 5M tons in total, not sure what the annualized basis would be.

[NoMoreNicksLeft]

That's a tiny amount, relatively. But is that "just a little more" or is it "just a little more, but in a really inconvenient and difficult to reach altitude"?

What kind of infrastructure would be required to put it where it needs to go?

[BillFranklin]

You would need a few pipes the width of garden hoses constantly flowing, suspended by helium balloons, near the Arctic where the stratosphere is 1km closer.

[theK]

I think putting any amount of tons of matter into stratospheric altitude is a hard challenge.

Especially if we consider the fact that you would be putting upwards of 200t[0] of CO2 into roughly the same altitude Only to deliver maybe 5 tons of sulfur.

[0]: https://www.theguardian.com/science/2021/jul/19/billionaires...

[nine_k]

But we don't need to do that excessively fast. How about a stratospheric balloon? Balloons reach 30-40 km for weather observation purposes.

[brucethemoose2]

https://newatlas.com/environment/sai-polar-refreezing/

> To achieve a 2 °C result, the plan would inject 6.7 teragrams (6.7 billion kg/14.8 billion lb) of sulfur dioxide per year into each pole, calling for an eye-watering total of 13.4 teragrams (29.5 billion lb) of material annually.

>The study goes on to look at logistics, finding that existing aircraft can't carry enough payload to a sufficient height to get the job done... To hit the cooling target, this project would need 125 purpose-built SAIL-43Ks, flying a total of 1,458 missions per day during the four-month injection period at each pole. These planes would take off, climb for 30 minutes, vent their entire load of sulfur dioxide within two minutes, then come back down over the following 30 minutes, and spend the next hour loading up again and refueling for the next mission.

> All sulfur oxides are nasty to breathe in, harming the lungs and causing asthma and bronchitis if inhaled regularly... It notes that the effects of teragrams of sulfur dioxide and the associated acid rain deposits are risky both to humans and to the wider ecosystem, requiring lots more research. And it expects some stratospheric heating as well.

So yeah, we could. It would be expensive (but not $trillions), and the environmental effects would be horrific.

And yet its still being proposed, because that's how desperate we are.

[anigbrowl]

13.4 teragrams (29.5 billion lb)

Why can't people use normal units. If you absolutely must use imperial units then at least use tons.

[BurningFrog]

Delivering the SO2 directly to the stratosphere needs some new tech to be developed.

Assuming that's done, the environmental side effects should be negligible, as I understand it. The stratosphere is pretty isolated from the atmosphere we live in, and the SO2 breaks down there over 1-2 years.

[brucethemoose2]

> sulfur dioxide tends to rise high into the stratosphere, where it combines with water molecules to create sulfuric acid particles, and remains for up to three years

> the way that sulfuric acid eventually leaves the atmosphere is by combining into larger and larger droplets that eventually become heavy enough to fall down to earth as acid rain

[BurningFrog]

My understanding is that sulfuric acid in the stratosphere is mostly broken down by sunlight, and the acid rain contribution from there is minimal.

But I couldn't quickly find any supporting facts, so this is just me saying "I think I read that somewhere".

[CorrectHorseBat]

Break down into what and where else than down would it go?

[brucethemoose2]

Yeah... Its sulfer dioxide. I am no chemist, but I don't see a safe way that can come down.

[BurningFrog]

Don't know, sorry.

Maybe the main factor is that the SO2 stays up there for 1-2 years, which gives a lot of cooling "bang" for the acid rain "buck".

[danbruc]

Airplanes fly in the lower stratosphere.

[boppo1]

Hey look, it’s the plot of The Matrix, except without the antagonist!

[JoshTko]

Probably make more sense to launch from ground. No reason to lift entire plane into the air. The launch stations can be placed in relatively remote locationst to minimize human or natural habitat impact. Possibly place launch locaitons close to So2 mining location to limit transport Co2.

[brucethemoose2]

The original paper says:

> For the sort of globally effective SAI deployment in the tropics and sub-tropics envisioned in (Smith and Wagner 2018) and (Smith 2020), a deployment altitude of 20 km is commonly assumed in order to remain well above the tropopause, which can often appear as high as 17 km in the tropics. Injection of large masses of aerosols at 20 km is not judged to be feasible with existing aircraft, requiring the development of new lofting platforms designed for this mission as envisioned

Ground deployment is not extensively discussed, but perhaps the referenced papers discuss the necessity of high altitude more.

[SketchySeaBeast]

What does a "launch" location for SO2 look like from the ground? Is there any guarantee it would get as high as we'd like, especially given that SO2 is heavier than air?

[mmanfrin]

I feel if we get to the point where we have to do that, humanity will just give up.

[blooalien]

Kinda feels like entirely too large a percentage of humanity already gave up entirely too long ago, and now it's rather too late for many of 'em to change their minds. Isn't that why we'd rather let our "leaders" geoengineer some more screw-ups upon our environment rather than actively work toward the changes we know will actually improve the situation? (eg; "fast track" our societal transitions globally toward more "planet-friendly" everything that we can? Just all-around "cleaner" modes of living? Better for the planet, and for humanity.)

[brucethemoose2]

The effective window for this to stave off bad effects is very short.

...A decade before starting, maybe?

Thats the problem with climate change. The tipping points are so disconnected from the collective pain thresholds.

[gumby]

Yes, this has been studied quite a bit (but not "extensively"). I am (guardedly) a fan of managing the earth's albedo, but not on a global scale and especially not with a toxic compound like SO2. Some of the most important issues:

* It's not just SO2, but soot and other particulates that reflect sunlight, in particular IR.

* SO2 (and soot etc, for that matter) have other side effects; its not that they were eliminated for no reason. And the point of any ecological activity (not just climate intervention) is to make the environment more supportive to human life and ativity. Stratospheric SO2 advocates tend to dismiss these issues.

* solar radiation adjustment has other consequences (on agriculture, for example). In the case of SO2 the frequencies reflected by SO2 are not all ones we want to do without -- we need some UV to get through.

* Stratospheric SO2 injection (AKA "SAI") is hard to switch off, so if we are unhappy with the results (widespread reduction in agriculture, if that's what happens) we would be waiting years, possibly decades, to get things back on track.

Solar radiation can also be managed at a more local level in the troposphere through marine cloud brightening for example, and can be done with more benign chemicals than SO2 (e.g. water), and can be switched on and off quite rapidly (days). It will use more energy and activity, but also provide greater control (in some locations on the water you may not want increased shade because of microscopic marine life).

Note I am working on removal of ambient greenhouse gas (CH4) and so am quite sensitive to the safety and consequences of intervention.

[vondur]

I wonder if there's a way to keep the SO2 localized to a geographic area? The best bang for the buck should be over the arctic to help with the ice loss and less reflectivity due to that.

[gumby]

I talked about localized marine cloud brightening, but why would you choose something toxic like SO2? There’s a reason why the first emissions trading market was one that controlled SO2 emissions: acid rain.

In the case of the arctic there are non-atmospheric (i.e. surface) interventions being investigated as well to change the local albedo. In fact the best way to brighten the arctic (and glaciers) is to reduce particulate emissions — and it’s happening!

[akira2501]

> Has anyone looked into the theory that SO2 is an "anti-greenhouse" gas

Yes.. there is an entire section in the IPCC report dedicated to this. This is also the reason they believe there is a "missing volcanic eruption," as it would explain data anomalies in their back projections. Make of that what you will.

https://en.wikipedia.org/wiki/1808_mystery_eruption

[gdubs]

Yes, James Hansen. His page [1] has links to his newsletter posts, but here's a recent example that looks into the shipping emissions reductions and the role they may be playing:

http://www.columbia.edu/~jeh1/mailings/2023/FlyingBlind.14Se...

1: http://www.columbia.edu/~jeh1/mailings/

[RandallBrown]

Neal Stephenson wrote a whole novel exploring this theory.

It's called Termination Shock.

[digging]

FWIW, I found this book to be an extremely disappointing introduction to Neal Stephenson and an extremely disappointing exploration of Sulfur-based geoengineering. The actual geoengineering is just a vehicle for a semi-political thriller IMO.

[tommoor]

It's not a great book, but the fact that a single billionaire could decide to change the climate with a relatively small amount of SO2 was news to me until I read this!

[RandallBrown]

I felt exactly the same way. It seemed like he thought "If Elon Musk tried to stop global warming, what would happen?" and then just sorta fleshed it out an released it during his spare pandemic time.

[imglorp]

Maybe SO2 is what the Venusians tried.

https://arxiv.org/abs/2108.08393

[spacephysics]

Contrarian opinion, but given the models have been poor at predicting the catastrophes that they typically claim, I’m hesitant to support atmospheric engineering to try and cool the planet.

Let’s not kid ourselves, global cooling is FAR worse than global warming. Ice ages are no joke.

The risk/reward bet here is that we put jussst enough SO2 to drop by X degrees. I’m just not confident enough in our computational capacity to account for all the variables that could produce unintended consequences.

Tangential, but we can’t even figure out proper programs/legislation to improve education or reduce inner city poverty.

[deepsun]

> global cooling is FAR worse than global warming

As a person from a cold country I'm not so sure about that. It's much easier to dress up on a cold day than to cool down on a hot day. It's cheaper to warm up a house than to cool it down. There are way less diseases/viruses/insects in cold climates. Granted, the food is much harder to come by, though, unless it's maritime (cold waters are much more abundant with life than warm oceans).

And in case of global warning, if it ever gets too cold, we know what to do.

[darkmarmot]

As someone who went to school for this, no. Mammals evolved to survive colder conditions. Going hotter and with higher CO2 is not going to be awesome for our biology.

[leesec]

https://x.com/powerbottomdad1/status/1702142367900549454?s=2...

It's been all around twitter. Casey Handmer writes about it in depth, worth checking out.

[unglaublich]

https://en.wikipedia.org/wiki/Sulfur_dioxide#Impact_on_clima...

[tppiotrowski]

First heard about this on Nova probably 15 years ago

https://www.pbs.org/wgbh/nova/sun/

[deepsun]

Corals are screwed either way from acidification (aka bleaching): either from ocean warming, or from sulfuric acid rains.

[andruc]

This wouldn't do anything to reduce ocean acidification from CO2 absorption though, would it?

[bregma]

Sulphur dioxide. That's the thing that caused all the acid rain that was going to be the end of all life as we know it back in the 1980s when were still concerned about global cooling, right? The same thing that made it possible to practice the moon landings just downwind of Sudbury, Ontario because all vegetation was stripped by the fallout from the big stacks at the nickle smelters?

Yeah. Pump that shit into our atmosphere. What could possibly go wrong?

[darkmarmot]

It's a tiny fraction of what we already emit -- above the tropopause and, you know, weather? The primary concern is related to ozone damage.