Princeton AOS program
Abstract: CO2 forcing, defined as the change in outgoing thermal radiation due to a perturbation in CO2 concentration, is fundamental to contemporary climate change. Complex radiation codes calculate this forcing with great accuracy, but basic features of CO2 forcing remain enigmatic. For instance, we lack simple explanations for what sets the overall magnitude of CO2 forcing, its dependence on mean climate, its logarithmic scaling, and its spatial pattern (in which CO2 forcing varies from strong positive values in the tropics to zero or even negative values near the poles). This talk will develop a simple yet quantitative model for CO2 forcing which explains these features, and which we validate with state-of-the-art radiative transfer calculations. A central inference from the simple model is that CO2 forcing depends on the surface-stratosphere temperature contrast, which explains the spatial pattern of CO2 forcing as well as its dependence on mean climate state.
Biography: Nadir Jeevanjee studies the physics of clouds, radiation, and climate, using a hierarchy of approaches ranging from pencil-and-paper theory to comprehensive computer simulations. He is currently an Associate Research Scholar in the Princeton AOS program, and received a PhD in Physics from UC Berkeley in 2016. Before turning to climate science he studied mathematical physics for many years, during which he authored the textbook An Introduction to Tensors and Group Theory for Physicists.