Hemispheric divergent trends in winter temperature drop days

As global temperatures rise, widespread warming and fewer cold extremes are generally observed. However, using the metric “temperature drop days”, we identify hemispheric divergent trends in winter cold weather over the past four decades. North America experiences increasing temperature drop days, whereas Europe sees a decline, forming a “Cold North America–Warm Europe” pattern. These opposing trends are linked to atmospheric circulation changes: a weakened but asymmetric tropospheric polar vort