Drivers of Trends in Northern Hemisphere Cold Spell Characteristics Over 1980–2025

This study quantifies trends in winter cold spell (CS) frequency, intensity, persistence and spatial extent across the Northern Hemisphere (NH) over 1980–2025. Cold spells are identified using a tracking methodology applied to daily near-surface temperature anomalies from reanalysis. To separate the trends associated with mean local temperature rise from other (residual) trends, tracking is also applied to detrended temperature anomalies. Across the NH, cold spells have become less frequent (−19.3 ± 4.2 days d⁢e⁢c⁢a⁢d⁢e−1), with 15% of this reduction related to residual effects. The cumulative annual CS area has decreased by 43.5 ± 9.7% of the NH spatial extent per decade. Cold spells have become less intense, with the NH average 5th percentile near-surface temperature increasing by 0.309 ± 0.052 K d⁢e⁢c⁢a⁢d⁢e−1. The persistence of cold spells has decreased in northern North America and in southern Europe. Northern North America is the only region where effects not related to background mean warming significantly contribute to the trends.