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Comment by slimsag | Hacker News Reader

Are there ways this could be done with rapidly biodegradable materials, such that e.g. it would need to be continually done year after year or else the sky would return to the exact same state it was in before? Also, living in Arizona with 120F/49C summers, I sure wish someone could come up with some geography-wide sunshade!

I guess that will need to be after they stop growing the city forever, and stop paving the earth of my state with black asphalt and concrete, and stop giving all our groundwater to lettuce and alfalfa farming to be sent out of the state or country entirely.

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This is covered in the article, and comes with its own trade-offs:

> Sulfur disappears from the atmosphere quickly - it rains out after about a year. This means that once we’ve started SRM, it’s dangerous to suddenly stop. We need to keep spraying particles, all the time. If we suddenly stopped, the warming would spring back rapidly, causing a bad temperature shock. The correct way to stop is a gradual phase out.

Thank you for quoting it! For some reason the link won't load for me yet.

Sulphates have a cooling effect and drop out of the atmosphere. There was recently a push to remove the sulphate content in the fuel used for cargo ships from 3.5% to 0.5%, and as the sulphates dropped out of the upper atmosphere the water in the Atlantic warmed significantly. Turns out we had been unintentionally doing geoengineering that was counteracting some of the affects of climate change. The downside is that sulphates are deleterious to human health, causing asthma.

It's possible a sufficiently motivated billionaire or even a somewhat wealthy millionaire could independently finance a project to inject sulphates into the upper atmosphere in international waters and have a measurable impact on global warming, although people with respiratory issues might not be too happy.

Rains out as acid rain.

It says in the article it only lasts a year, so its an adjustable stop-gap.

Not sure if you consider sulphur biodegradable, but it will need to be done continually, or else the effect will disappear.

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