HOW LONG IS A MILLENIA SERIES

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. Meanwhile, carbonate-rich deposits on the sea floor will experience similar reactions with overlying seawater as the oceans become more acidified. 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. 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. The next stage of the cleanup will proceed more slowly. 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. 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. 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. 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. 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. Ocean acidification will peak shortly after atmospheric CO 2 concentrations do, threatening marine species that have acid-soluble carbonate shells or skeletons, including corals, shellfish, and crustaceans (Figure 1). For example, as CO 2 dissolves into the oceans, it combines with water to form carbonic acid, which alters the chemistry of seawater and makes limestone, chalk, and other carbonate-rich substances more likely to dissolve.

HOW LONG IS A MILLENIA SERIES

This, in turn, will cause a series of linked environmental responses in which other currently rising trends reverse one by one in a 'climate whiplash' phase that follows the lead of our carbon emissions. As a result, CO 2 concentrations in the atmosphere will also eventually peak and then decline. The first stage of this process will occur when the rate at which we burn coal, oil, and natural gas levels off and then declines, either because we switch to alternative energy sources soon, or because we run out of affordable fossil fuels later. Greenhouse gas concentrations and global temperatures will not increase indefinitely - today's carbon dioxide buildup and warming trend must eventually top out and then reverse as the atmosphere gradually recovers.

How long is a millenia