AOSC Seminar by Dr. Michael Mann, 9/16/2021
Dr. Michael Mann
Title: Climate Change and Extreme Summer Weather Events
In addition to well-established direct physical linkages between a warming planet and extreme summer weather events such as floods, droughts, heat waves and wildfires are more tenuous but potentially profound linkages tied to altered characteristics of the Northern Hemisphere jet stream and associated wave disturbances. Some of the most significant extreme summer weather events in recent years have been associated with high-amplitude quasi-stationary Rossby waves with zonal wavenumbers 6-8 tied to the phenomenon of Quasi-Resonant Amplification (QRA). Current state-of-the-art (CMIP5) climate models are unable to adequately resolve this mechanism owing to substantial errors in the models in the curvature of the zonal velocity field which is a key quantity controlling the associated wave disturbances. A reliable fingerprint for the occurrence of QRA can, however, be defined in terms of the zonally-averaged surface temperature field. Examining climate observations and historical (CMIP5) climate model simulations, we have demonstrated consistent evidence for an increasing trend in QRA events over the past half century tied to anthropogenic warming. Examining CMIP5 model projections we find that QRA-related extreme weather events are likely to increase by ~50% this century under business-as-usual carbon emissions, but there is considerable variation among climate models, and a reduction in mid-latitude aerosol loading could actually lead to Arctic de-amplification this century, ameliorating potential further increases in persistent extreme weather events. Given the uncertainties, substantial further increases in these events cannot however be ruled out.
Dr. Michael E. Mann is Distinguished Professor of Atmospheric Science at Penn State, with joint appointments in the Department of Geosciences and the Earth and Environmental Systems Institute (EESI). He is also director of the Penn State Earth System Science Center (ESSC). Dr. Mann was a Lead Author on the Observed Climate Variability and Change chapter of the Intergovernmental Panel on Climate Change (IPCC) Third Scientific Assessment Report in 2001 and was organizing committee chair for the National Academy of Sciences Frontiers of Science in 2003. He has received a number of honors and awards including NOAA's outstanding publication award in 2002 and selection by Scientific American as one of the fifty leading visionaries in science and technology in 2002. He contributed, with other IPCC authors, to the award of the 2007 Nobel Peace Prize. Dr. Mann is author of more than 200 peer-reviewed and edited publications, numerous op-eds and commentaries, and five books.
Contact: Ning Zeng
Pre-seminar refreshment: N/A
Seminar: 3:30-4:30pm, Zoom
Meet-the-Speaker: 4:30-5:00pm, Zoom [For AOSC Students only]