In order to work out the timing of these processes in more detail, one must consider where CO 2 goes after it leaves our smokestacks and exhaust pipes. Some of it will be taken up by soils and organisms but most of it will dissolve into the oceans, with between two thirds and half of our emissions perhaps going into solution during the next millennium or so (Inman 2008, Eby et al. 2009). In many computer simulations, maximum ocean acidification lasts 2000 years or more, depending on the amount of CO 2 we emit in the near future. Marine species living in the polar regions and deep sea basins and trenches will be the most rapidly and severely impacted because the solubility of such gases is greatest in cold waters. But after the seas have absorbed as much CO 2 as they can, roughly a fifth of our fossil carbon emissions will still be left adrift in the air (Tyrell et al. 2007, Inman 2008).

The next stage of the cleanup will proceed more slowly. As atmospheric CO 2 dissolves into raindrops, the carbonic acid that it produces will react with calcite and other carbonate minerals in rocks and sediments. Over thousands of years, those geochemical weathering processes will transfer many of the formerly airborne carbon atoms into groundwater and runoff, finally delivering them to the oceans in the form of dissolved bicarbonate and carbonate ions. Meanwhile, carbonate-rich deposits on the sea floor will experience similar reactions with overlying seawater as the oceans become more acidified. This slow addition of acid-buffering substances to marine ecosystems will act much like an antacid pill that allows the seas to consume more CO 2 from the overlying atmosphere. These processes are generally expected to dominate the long-term recovery for 5,000 years or so.