Emerging near-surface extratropical circulation changes due to climate change: a weather typing based global analysis

Abstract This study examines how large-scale near-surface circulation is projected to evolve under anthropogenic forcing throughout the 21st century. Using a multi-model ensemble of 41 state-of-the-art Global Climate Models high emissions scenarios, we analyze changes in Weather Type (WT) frequencies, based on Sea-Level Pressure (SLP), as a function of global warming and estimate their Time of Emergence (ToE) from historical variability. Significant and robust trends are identified across key climatic regions, including shifts in anticyclonic types in subtropical high-pressure belts and the Mediterranean, westerly and cyclonic types in the Subantarctic, and unclassified types in the Mediterranean. While most robust signals emerge by the late 21st century, some changes in the Mediterranean are already emerging in the present decade. Overall, results reveal significant circulation changes in the coming decades, affecting dominant near-surface circulation modes globally. A comprehensive dataset of 6-hourly WT projections (2006/15-2100) over mid-latitudes is publicly available as part of this study.