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Dr. Susan SolomonSenior Scientist, NOAA
Timescales and Processes in Climate Change: Transience, Persistence, Irreversibility, and the Surprising Roles of Different Greenhouse Gases
The severity of damaging human-induced climate change depends not only on the magnitude of the change but also on the potential for irreversibility. In this talk, it will be shown that the climate change that takes place due to 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. The warming due to non-CO2 greenhouse gases, although not irreversible, also persists notably longer than the anthropogenic changes in the greenhouse gas concentrations themselves. Dr. Solomon will explore why the persistence of warming depends not just on the decay of a given greenhouse gas concentration but also on climate system behavior, particularly the timescales of heat transfer linked to the ocean. For carbon dioxide and methane, nonlinear optical absorption effects also play a smaller but significant role in prolonging the warming. In effect, dampening factors that slow temperature increase during periods of increasing concentration also slow the loss of energy from the Earth’s climate system if radiative forcing is reduced. Approaches to climate change mitigation options through reduction of greenhouse gas or aerosol emissions therefore should not be expected to decrease climate change impacts as rapidly as the gas or aerosol lifetime, even for short-lived species; such actions can have their greatest effect if undertaken soon enough to avoid transfer of heat to the deep ocean.
Wednesday, 20 April, 3:30 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Auditorium (Rm. 1022)