Northern Hemisphere warming hotspots linked to intensified tripole wind anomaly patterns

Spatially heterogeneous surface warming across continents is strongly governed by atmospheric circulation changes. Although long-term trends in upper-level atmospheric circulation have been identified, their contribution to regional warming hotspots remains unclear. In this paper, we use dynamical adjustment analysis to decompose the dynamical and thermodynamic components of long-term warming in observations and climate models. Our findings show that the observational warming is accelerating in eastern Europe, northwestern China, eastern Siberia, and western North America. While climate models broadly reproduce total warming trends in these hotspot regions, part of this agreement arises for the wrong reasons. In particular, model ensembles underestimate dynamics-induced warming in eastern Europe, northwestern China and eastern Siberia, but compensate for this with an overestimation of the thermodynamic component of warming. Conversely, climate models more accurately reproduce the dynamics-induced warming in western North America. To disentangle the underlying dynamical regime, we then adopt a complex network approach and identify a north-south-oriented tripole wind anomaly pattern characterised by westerly–easterly–westerly zonal wind anomalies surrounding heat extremes. Variability in this tripole pattern explains up to 70% of the dynamics-induced interannual temperature variability and at least 50% of its long-term warming trend in hotspot regions. Climate models further project that the dynamics-induced warming over western North America will double by the end of the 21st century in response to an amplified tripole wind anomaly pattern. Our findings highlight the need to incorporate upper-level wind-field dynamics in regional surface temperature projections, particularly given the projected intensification of the tripole pattern under global warming.