Future equivalent of 2010 Russian heatwave intensified by weakening soil moisture constraints

The 2010 heatwave in eastern Europe and Russia ranks among the hottest events ever recorded in the region1,2. The excessive summer warmth was related to an anomalously widespread and intense quasi-stationary anticyclonic circulation anomaly over western Russia, reinforced by depletion of spring soil moisture1,3,4,5. At present, high soil moisture levels and strong surface evaporation generally tend to cap maximum summer temperatures6,7,8, but these constraints may weaken under future warming9,10. Here, we use a data assimilation technique in which future climate model simulations are nudged to realistically represent the persistence and strength of the 2010 blocked atmospheric flow. In the future, synoptically driven extreme warming under favourable large-scale atmospheric conditions will no longer be suppressed by abundant soil moisture, leading to a disproportional intensification of future heatwaves. This implies that future mid-latitude heatwaves analogous to the 2010 event will become even more extreme than previously thought, with temperature extremes increasing by 8.4 °C over western Russia. Thus, the socioeconomic impacts of future heatwaves will probably be amplified beyond current estimates

Amplification of mega-heatwaves through heat torrents fuelled by upwind drought

Mega-heatwaves are among the deadliest natural disasters in midlatitudes. During such events, the atmospheric circulation is typically governed by persistent anticyclones, enabling cloud-free conditions and advection of hot air. Dry soils in heatwave regions are also known to further contribute to the escalation of air temperatures. However, while local land–atmosphere feedbacks are well studied, the same does not apply to the influence of upwind areas, from where heat is advected. Here we investigate reanalysis data using a Lagrangian heat-tracking model to unravel the role of upwind land–atmosphere feedbacks during the two European mega-heatwaves of this century: the events in 2003 and 2010. Our analysis indicates that advected sensible heat can come in torrents, suddenly and intensely, leading to abrupt increases in air temperatures that further strengthen local land–atmosphere feedbacks via soil desiccation. During both mega-heatwaves, about 30% of the advected sensible heat was caused by the drought upwind. Since subtropical droughts are projected to aggravate during this century, in light of our results, this may be accompanied by consequent intensification of midlatitude mega-heatwaves. We therefore recommend considering not only local, but also upwind land cover and land-use management in the design of adaptation strategies against compound drought–heatwave events.<br/

Vegetation feedbacks during drought exacerbate ozone air pollution extremes in Europe

Reducing surface ozone to meet the European Union\u2019s target for human health has proven challenging despite stringent controls on ozone precursor emissions over recent decades. The most extreme ozone pollution episodes are linked to heatwaves and droughts, which are increasing in frequency and intensity over Europe, with severe impacts on natural and human systems. Here, we use observations and Earth system model simulations for the period 1960\u20132018 to show that ecosystem\u2013atmosphere interactions, especially reduced ozone removal by water-stressed vegetation, exacerbate ozone air pollution over Europe. These vegetation feedbacks worsen peak ozone episodes during European mega-droughts, such as the 2003 event, offsetting much of the air quality improvements gained from regional emissions controls. As the frequency of hot and dry summers is expected to increase over the coming decades, this climate penalty could be severe and therefore needs to be considered when designing clean air policy in the European Union