Human influence on recent trends in extratropical low-level wind speed

Trends in atmospheric circulation have begun to emerge in recent decades. Summertime mean circulation trends aloft have been attributed to human influence, but discrepancies exist for wintertime. For low-level extreme winds, it remains unclear to what extent human activities have influenced recent trends and whether models can capture them. Here, we compare satellite-era trends in extratropical low-level mean and extreme (>90th percentile) winds in reanalyses and climate model simulations. In summer, Southern Hemisphere midlatitude winds have strengthened, driven by greenhouse gases and stratospheric ozone forcings. Wind stilling over Europe in summer is dominated by aerosol forcing. In winter, models cannot capture the strengthening over the Southern Hemisphere and the weakening over the subtropical North Pacific and Europe. These discrepancies, particularly in the Pacific, are reduced but still exist when observed sea surface temperatures are prescribed. Our results highlight human influence on summertime low-level extreme winds and reveal regional wintertime discrepancies.