Do we underestimate today's risk of climate extremes?
Dr. Erich M. Fischer
Institute for Atmospheric and Climate Science
ETH Zurich, Switzerland
Stakeholders express a strong need for reliable information on changes in climate extremes in the recent past and coming decades as a basis for adaptation strategies. Quantifying reliable hazard return periods, an important factor in the risk equation, is vital but remains challenging because extremes are very rare by definition and occur irregularly due to internal climate variability. Likewise, it is particularly challenging to detect potential local and regional changes in both observations and models. Since observational series are often short, there is a substantial risk of identifying spurious trends, or missing a climate change signal hidden by large variability. Based on a large initial condition ensemble, I demonstrate that the latter may lead to too high return period estimates for hot and heavy precipitation extremes in today’s climate. This implies a potential serious underestimation of present-day probabilities of temperature and precipitation extremes. Since the hazard probability is an important factor in the risk equation, we may regionally substantially underestimate the risk of temperature and precipitation extremes of the coming decades and not be well prepared for the events possible today and in the coming decades.
Erich Fischer is a senior scientist and lecturer at ETH Zurich, Switzerland. He acts as a lead author in the IPCC AR6 and is a co-lead in the WCRP Grand Challenge on Weather and Climate Extremes. In 2007 he completed his PhD at the Institute for Atmospheric and Climate Science at ETH Zurich. He then worked as a Postdoc at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado and as a visiting scientist at the University of Reading, UK before moving back to ETH Zurich.