The first part of the Intergovernmental Panel on Climate Change’s Fifth Assessment Report (AR5) has been out for a couple of weeks. Looking at the physical science, AR5 covers the full range of how greenhouse gases are changing the face of our planet.
One area that is getting more attention this time around is the ocean. As you can see here, for instance, as carbon dioxide has continued to be taken up in the ocean in recent decades, its relative acidity has increased. (As pH decreases, acidity increases.) AR5 reports that, over the long haul, “The pH of ocean surface water has decreased by 0.1 since the beginning of the industrial era, corresponding to a 26% increase in hydrogen ion concentration.”
There is a lot more from AR5’s section on the ocean. Aside from sea-level rise, the increases in mass, and changes in ocean currents, we’re also seeing huge, seemingly inexorable increases in temperature. The ocean is, quite literally, taking heat. “Ocean warming dominates the global energy change inventory. Warming of the ocean accounts for about 93% of the increase in Earth’s energy inventory between 1971 and 2010 with warming of the upper (0–700 m) ocean accounting for about 64%of the total.” Warmer water also diminishes dissolved oxygen making it much harder, on top of the other stresses, for marine fauna to breathe.
So the growing concentration of greenhouse gases in the climate system has been driving both changes in chemistry and warming in the ocean. These were eloquently described by Elizabeth Kolbert going back several years to her seminal article, The Darkening Sea. See also this succinct look at the impact of carbon dioxide on ocean life from Ensia.
Where does this all lead? No very good place. A recent review by the scientist and climate activist Tim Flannery of a book on jellyfish and the future of the ocean identifies an array of devastating harms that we humans have been visiting upon our blue ocean planet, among those described here and in AR5. Flannery quotes the author: “But I think I underestimated how severely we have damaged our oceans and their inhabitants. I now think that we have pushed them too far, past some mysterious tipping point that came and went without fanfare, with no red circle on the calendar and without us knowing the precise moment it all became irreversible. I now sincerely believe that it is only a matter of time before the oceans as we know them and need them to be become very different places indeed.” So sad. So unnecessary.
NRDC has a good summary of the important points from AR5 about the ocean here at their blog, Switchboard. For more on ocean acidification, see this video from them.