> And CO2 remains in the atmosphere for 100-200 years after emitted. My understanding is that methane is lighter than air, and circulates in the atmosphere unt

> And CO2 remains in the atmosphere for 100-200 years after emitted. My understanding is that methane is lighter than air, and circulates in the atmosphere until it breaks down (~12 years). CO2 is heavier than air, and readily dissolves itself in ocean water. In the pre-industrial era the oceans emitted carbon dioxide, to keep the plants on land alive. My earlier comment had a reference to estimates of how much CO2 is absorbed by the ocean: https://news.ycombinator.com/item?id=20002823 https://news.ycombinator.com/item?id=20002823 Searching now, the officially-sanctioned estimates are that 30-40% of human CO2 emissions are rapidly captured by the ocean. If we instantly stopped all CO2 emissions, I think most of the excess atmospheric CO2 would be captured by the plants and the ocean over just a few years.