Group seminar on 23. November, 14:15 CET
Fingerprinting Persistent Extreme Events and Assessing Their Response to Climate Change Using Large Deviation Theory
Valerio Lucarini
Extreme events provide relevant insights into the dynamics of climate and their understanding is key for mitigating the impact of climate variability and climate change. By applying large deviation theory to a state-of-the-art Earth system model, we define the climatology of persistent heatwaves and cold spells in key target geographical regions by estimating the rate functions for the surface temperature, and we assess the impact of increasing CO2 concentration on such persistent anomalies. Hence, we can better quantify the increasing hazard due to heatwaves in a warmer climate. Such rate functions are, in the range we have been able to explore, simply quadratic. Hence, we propose and test an approximate formula for the return times of large and persistent temperature fluctuations from easily accessible statistical properties. Furthermore, we showcase several high-impact events - like the 2010 summer Russian heatwave and winter Dzud in Mongolia, and the 2019 winter coldwave in North America are associated with atmospheric patterns that are exceptional compared to the typical ones but typical compared to the climatology of extremes. Some preliminary results are also presented for the 2021 Western North American heatwave. Their dynamics is encoded in the natural variability of the climate.
Ref:
V. M. Galfi and V. Lucarini, Fingerprinting Heatwaves and Cold Spells and Assessing Their Response to Climate Change Using Large Deviation Theory, Phys. Rev. Lett. 127, 058701 (2021)
V. M. Galfi, V. Lucarini, F. Ragone, and J. Wouters, Applications of large deviation theory in geophysical fluid dynamics and climate science. Riv. Nuovo Cim. 44, 291–363 (2021).