Hacker News Reader

And doesn't produce acid rain, like sulfur does.

Acid rain resulted from the 30+ million tons of sulfur dioxide released into the lower atmosphere. To cut global warming in half, 25,000 tons of sulfur dioxide would be needed in the upper atmosphere. So, 3 orders of magnitude less SO2. Meaning, mitigating global warming with SO2 would not meaningfully increase acid rain.

Source: https://www.technologyreview.com/2013/02/08/84239/a-cheap-an...

That 25,000 tons figure sounds really controversial. Even the article mentions

> David [Keith] thinks it is going to be easy and cheap, and I don’t agree,” says Robock. He estimates that several million tons of sulfur would have to be injected into the atmosphere annually to offset doubled levels of carbon dioxide, but if the particles clump together, “it could be many times that.”

I found a review of sulfate injection geoengineering studies[0] published in 2017 and with a quick read I can't find any mentions under millions of tons annually.

[0] https://acp.copernicus.org/articles/17/3879/2017/acp-17-3879...

Fair enough. We really should be able to test this at some scale that we could know the order of magnitude required for efficacy. We are dangerously ignorant about the solution space.

Reply on news.ycombinator.com