Persistent anticyclonic conditions and climate change exacerbated the exceptional 2022 European-Mediterranean drought

Abstract

A prolonged drought affected Western Europe and the Mediterranean region in 2022 producing large socio-ecological impacts. The role of anthropogenic climate change (ACC) in exacerbating this drought has been often invoked in the public debate, but the link between atmospheric circulation and ACC has not received much attention so far. Here we address this question by applying the method of circulation analogs, which allows us to identify atmospheric patterns in the period 1836-2021 very similar to those occurred in 2022. By comparing the circulation analogs when global warming was absent (1836-1915) with those occurred recently (1942-2021), and by excluding interannual and interdecadal variability as possible drivers, we identify the contribution of ACC. The 2022 drought was associated with a persistent anticyclonic anomaly over Western Europe. Circulation analogs of this atmospheric pattern in 1941-2021 feature 500 hPa geopotential height anomalies larger in both extent and magnitude, and higher temperatures at the surface, relative to those in 1836-1915. Both factors exacerbated the drought, by increasing the area affected and enhancing soil drying through evapotranspiration. While the occurrence of the atmospheric circulation associated with the 2022 drought has not become more frequent in recent decades, the influence of the Atlantic Multidecadal oscillation cannot be ruled-out.

A Global Assessment of Heatwaves Since 1850 in Different Observational and Model Data Sets

“…The bias is especially large in the Southern Hemisphere (Figures S1 and S2 in Supporting Information S1) where uncertainties in the 20CRv3 reanalysis and the EUSTACE data set are also very pronounced due to limited observations (Rayner et al, 2020;Slivinski et al, 2021). Faranda et al (2023) show that 20CRv3 can be used to analyze drought events over Western Europe caused by stationary heights suggesting that the reanalysis is suitable to analyze heatwaves over this area caused by similar processes which is consistent with our findings. Land-surface processes are also very important, especially for shorter duration heatwaves (Domeisen et al, 2022).…”

European Summer Synoptic Circulations and Their Observed 2022 and Projected Influence on Hot Extremes and Dry Spells

“…However, the observed HDs and DDs anomalies are not fully explained by the anomalous occurrence of CTs. The exceptional S22 resulted from a combination of the synoptic‐scale CTs influence and thermodynamical factors exacerbating the extremes, like very low soil moisture enhancing the land surface Bowen ratio and associated diabatic warming and, more likely than not, the growing signal of the unequivocal anthropogenic global warming (Faranda, Pascale, & Bulut, 2023; Lee et al., 2023; Schumacher et al., 2022). By applying a simple decomposition, we distinguished how the CTs (i.e., BC ) versus other (i.e., WC , mostly thermodynamical) effects contributed to the anomalous occurrence of HDs and DDs during S22.…”

“…Over Europe, many of these effects are already ongoing, for example, the expansion of dry conditions (meteorological droughts) in many regions since the late 1980s (Bešťáková et al., 2023), an increasing number of hot days combined with warmer summer conditions (Marvel et al., 2019), and an intensification of heatwaves (Rousi et al., 2022). As we start facing circulation changes in response to increasing CO 2 concentrations and non‐uniform global warming, their contribution to recent and future extremes remains a matter of debate (Belleflamme et al., 2015; de Vries et al., 2022; Faranda, Pascale, & Bulut, 2023; Räisänen, 2019; Terray, 2023).…”

“…The extreme summer of 2022 (S22) was characterized by strong, persistent and widespread mid‐tropospheric anticyclonic anomalies over western Europe. This atmospheric circulation helped to exacerbate the drought by increasing its area of influence and by enhancing soil drying due to evapotranspiration (Faranda, Pascale, & Bulut, 2023). Atmospheric circulation plays a crucial role in the occurrence, extent and intensity of weather extremes (Coumou et al., 2015; Rogers et al., 2022).…”

Maximal reachable temperatures for Western Europe in current climate

“…Here we make use of the flow analogues attribution methodology proposed by [55] and adapted from [53] (see also [59,60]). The idea of the method is to compare the expectation of a variable of interest X in the counterfactual world (F = 0) and in the factual world (F = 1), conditional on the large scale circulation C(ζ) of the observed event ζ:…”