Important new research led by NOAA scientists, “Irreversible climate change because of carbon dioxide emissions,” finds:
…the climate change that is taking place because of increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop…. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450-600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the ”dust bowl” era and inexorable sea level rise.
I guess this is what President Obama meant when he warned today of “irreversible catastrophe” from climate change. The NOAA press release is here. An excellent video interview of the lead author is here.
The Proceedings of the National Academies of Science paper gives the lie to the notion that it is a moral choice not to do everything humanly possible to prevent this tragedy, a lie to the notion that we can “adapt” to climate change, unless by “adapt” you mean “force the next 50 generations to endure endless misery because we were too damn greedy to give up 0.1% of our GDP each year” (see, for instance, McKinsey: Stabilizing at 450 ppm has a net cost near zero or the 2007 IPCC report).
The most important finding concerns the irreversible precipitation changes we will be forcing on the next 50 generations in the U.S. Southwest, Southeast Asia, Eastern South America, Western Australia, Southern Europe, Southern Africa, and northern Africa (see also US Geological Survey stunner: SW faces “permanent drying” by 2050 and links below)
Here is the key figure (click to enlarge)
Figure: Best estimate of expected irreversible dry-season precipitation changes, as a function of the peak carbon dioxide concentration during the 21st century. The quasi-equilibrium CO2 concentrations shown correspond to 40% remaining in the long term as discussed in the text. The yellow box indicates the range of precipitation change observed during typical major regional droughts such as the ”dust bowl” in North America [except, of course, this Dust Bowl lasts 1000 years, not 10 to 20, which is what some people might call a desert (see Australia faces the "permanent dry" -- as do we)].
On our current emissions path, we are headed toward 1000 ppm by century’s end, as a close reading of the IPCC report makes clear (see my 2008 recent Nature online article). That would put essentially every at risk region into conditions worse than the Dust Bowl for a long, long, long time. Clearly we must peak no higher than 450 ppm.