Soil moisture and temperature thresholds drive 53% of accelerated extreme heat rise in Central Europe

Researchers report in Science Advances that nonlinear interactions between atmospheric circulation, soil moisture and temperature amplify the most extreme heat waves in midlatitude humid regions science.orgScience Advancesscience.orgOpen source ↗. The most extreme temperatures are rising faster than moderate ones, and the authors set out to identify the physical mechanism behind this acceleration. Using an interpretable analysis framework, they quantified critical thresholds in temperature and soil moisture, beyond which heat extremes are strongly amplified.

According to the study, this behavior is evident across 30% of midlatitude humid areas and contributes to a 10% increase in the magnitude of individual heat waves. In these regions, 15% of the accelerated rise in extreme temperatures is attributable to the growing probability of crossing the thresholds. In Central Europe, a heat wave hotspot, the share is 53%.

The authors also find that biases in CMIP6 projections of extreme heat come from an underestimation of these nonlinear processes, which is further driven by a lagged soil moisture response during heat waves. After statistical correction of the projections, they estimate that the gap between the most extreme and moderate temperatures could be 4.2 ± 0.16 times greater than currently projected in midlatitude humid regions by the end of the 21st century.