[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.