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. For low-level extreme winds, the extent of human influence and climate model fidelity remains unclear. Here, we compare satellite-era trends in extratropical low-level mean and extreme (>90th percentile) winds defined using daily distribution in reanalyses and climate model simulations. In summer, Southern Hemisphere midlatitude winds have strengthened, driven by greenhouse gas and stratospheric ozone forcings. The summertime European wind stilling trend is dominated by aerosol and greenhouse gas forcings. In winter, models cannot capture the strengthening over the Southern Hemisphere and the weakening over Europe and the subtropical North Pacific. These discrepancies, particularly in the Pacific, are reduced but persist when observed sea surface temperatures are prescribed and affect the low-level baroclinicity. Our results highlight human influence on summertime low-level extreme wind trends and reveal regional wintertime discrepancies.