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,” say

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-17-3879-2017.pdf https://acp.copernicus.org/articles/17/3879/2017/acp-17-3879...