NASA’s James Hansen and Makiko Sato have a new draft paper that brings potential climate tipping points into more focus and the results are incredibly important. They examine some differences between two recent geologic times, the Eemian and the Pliocene, and today. During the Eemian, sea levels were 15-20 feet higher than today. During the Pliocene, sea levels were 82 feet higher than today. If we maintain our business-as-usual (BAU) greenhouse emissions path, the authors state that multi-meter sea level rise within this century becomes “almost dead certain” because of nonlinear responses to that forcing. To be clear, that means that future temperature increases will not be equal for the same amount of future emissions. Instead, future emissions will cause a radical and unreversable jump in global temperatures, which will lead to radical jumps in sea level rise. We won’t have a 1″ per year increase in sea level. The difference year after year will be greater and greater as the climate system attempts to find a new stable region.
I want to point out that Hansen and Sato use extremely strong language for climate scientists. Will it be strong enough to generate the political will necessary to take us off that path?