The 2023 Vilhelm Bjerknes Medal is awarded to Christoph Schär for pioneering research on extreme weather, based on his skills in atmospheric dynamical theory and numerical modeling, that have enabled regional climate models to couple with complex topography.
Christoph Schär is an outstanding atmospheric physicist and dynamicist, a world leader in numerical climate modeling, and an expert in the scientific understanding of extreme weather and climate events. In his thirty years at ETH Zürich, Christoph Schär’s research has made foundational contributions to mountain meteorology, regional climate change, numerical methods, computational science, hydrological extremes, and geophysical fluid dynamics.
Christoph Schär was among the first to tackle the important problem of how precipitation extremes vary with climate. His 2001 paper with Christoph Frei established a methodology for distinguishing trends from noise in extreme events using short climate records, and he has continued to provide a strong scientific influence in climate trend detection, especially of precipitation extremes. This information is of particular importance since floods are a leading cause of mortality and damage from natural disasters worldwide. His 2004 landmark paper on the European summer heat wave of 2003 has become a classic. Christoph showed that the rather spectacular heat wave that affected western Europe in 2003 was more easily explained by assuming that the range of variability in temperatures also increases as the climate warms, and he then showed that temperature variance does increase in future climate projections using global climate models. This paper changed the way many of us think about, and how the community prepares for, heatwaves, such as those decimating much of the northern hemisphere in 2022.
In recent years Schär has been pushing the boundaries of climate modelling by descending to the kilometer-scale resolution in global models. This capability was made possible by large-scale increases in computational power through innovative code migration to graphics processing units. He spearheaded this pioneering research by teaming up with the Swiss Centre of Scientific Calculation, which has produced the first global climate baseline simulations at this scale. His continuing efforts to assess the performance of regional climate models with respect to precipitation processes have provided the scientific metrics for model development.
Christoph Schär‘s work changed the landscape of atmospheric science for many of us and has advanced, not only theoretical meteorology and climate science, but also enabled progress in the operational realm of weather prediction.