AGU: Abrupt climate change - the good, bad and ugly
The US Climate Change Science Program released its latest report at the AGU meeting today, taking a deeper look at several potential disaster scenarios that fall under the rubric of "abrupt climate change." The outlook is mixed, so we'll start with the good news, move through the bad and end with the ugly.
So. A rapid and massive methane release from sea floor or permafrost hydrates is unlikely this century, which is good news as methane is, pound-for-pound, a much more potent greenhouse gas than carbon dioxide. [Editor's note: see related story here.] Same story for the prospect of a halt to the ocean circulation (portrayed, rather loosely, by Hollywood) that pumps warm surface water into the north Atlantic, which in turn provides much of Europe with a surprisingly warm climate given its latitude.
The bad news is that global warming is likely to increase the chances of "severe and persistent" drought in the southwest United States (this report focuses on the US, though its implications are in many cases global). In fact, we may already be witnessing just this. Or not. Things like tree-rings tell us that such droughts have happened independent of human-induced global warming, so it's tough to pin down what's driving the current drought. But modelling suggests that global warming will only make the situation worse.
And now for the ugly: Sea-level rise this century is likely to "substantially exceed" the 0.18 - 0.58 meter projections released by the Intergovernmental Panel on Climate Change last year. In truth, this isn't a surprise. Even when the IPCC released its report, observations of ice-sheet loss on Greenland and Antarctica had already led many to the conclusion that the numbers were overly conservative, but the IPCC found its hands tied by the cutoff date for science that could be included in the assessment.
This report comes courtesy of the US Geological Survey, which took the lead in producing the document. As mentioned, it is one of many under a program that has a long and at-times-controversial history. For a little background (and a taste of the aforementioned controversy), check an earlier post on our Climate Feedback blog. WWF also put out a statement on the report today.
