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Comment by deciplex | Hacker News Reader

> they only stay suspended for 10 years or so

And then what happens? Earnest question.

And then we have to do it again, and again, and again; once you grab that tiger's tail, there is no letting go. In the meantime, sense of urgency abated, we would most likely keep on burning fossil fuels and putting more CO2 into the atmosphere, locking ourselves further into the loop.

It is a terrible idea which will almost certainly happen.

Entropy is inexorable and must always be resisted. Humans need to drink water and eat food, again, and again, and again. Unimaginable amounts of time, effort, and resources are spent every day maintaining civilization. If we build out solar panels, we will have to replace them in 20 years. There is no free lunch.

We don't know how bad the climate will be at 800 ppm. 300 millions years ago, during the Carboniferous era, there were vast forests and very high CO2 levels, around 1000 to 5000 ppm. If the Earth gets too hot we will simply do stratospheric aerosol injection. If climate change turns out to be overhyped, then we get the CO2 fertilization boost for free, win-win.

Regardless, the real solution is next level energy production from advanced fission, deep geothermal, and ultimately fusion power. With a vast surplus of energy we could do wildly impractical things like filter sea water for gold, and of course extract extremely diffuse gases from the atmosphere. Renewable energies are very low energy density, and more akin to farming from a physics perspective. They make sense in certain situations, but are not reliable for powering an advanced industrial civilization.

I also suspect people's intuitions are out of perspective in terms of time scales. It seems likely AGI will arise within the next 20 years. Climate change is nothing compared to the singularity and rise of superintelligence.

Back to the ground in rainfall I guess.

Yeah that's kind of what I was getting at: the implications of all these aerosols falling to earth later, and getting into everything.

Calcium carbonate aerosols are proposed as a good alternative to sulfur dioxide since they are basic and do not react with ozone. Calcium carbonate is used an additive to soils to reduce acidity and is used by organisms to construct bone tissues. Furthermore, these aerosols would be extremely diffuse. It's estimated that we'd need 5 million tons of sulfur dioxide per year to reduce temperatures by 1 degree centrigrade. Assuming we need 10 million tons of calcium carbonate that eventually descends to the Earth, that would come out to be 0.0196g per square meter. Effectively negligible, and may even be beneficial for areas that have slightly acidic rains.

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