Guest Speaker: Robert Pincus (Columbia)
Title: The Kodachrome revolution- the roots of a colder stratosphere, more rain, and cloud feedbacks with increasing CO2
Abstract: The combination of deep understanding of the physics controlling the flow of radiation though the atmosphere, increasingly detailed characterization of atmospheric state, and rapidly-expanding computational capabilities, has enabled ever-more-accurate calculations of radiation balance over the last decades. These computations underlie many of our expectations about the future including stratospheric cooling in response to increasing CO2 levels and more precipitation from a warming atmosphere… but they don’t tell us why these phenomena emerge. I will describe how the three key idealizations underlying the Kodachrome revolution – of spectroscopy, of radiative transfer, and of constraints imposed by the condensability of water vapor – are driving rapid progress in understanding of a wide range of behavior. I’ll show how the enormous spectral variation of absorption by water vapor and carbon dioxide are responsible a) for the cooling of the stratosphere and the resulting increase in top-of-atmosphere imbalance as CO2 concentrations are increased; b) for the increased precipitation that occurs as the atmosphere warms; and c) for the surprising influence of water vapor and carbon dioxide on the radiation budget in fully cloudy skies.