Atmospheric circulation compounds anthropogenic warming and impacts of climate extremes in Europe - PubMed (original) (raw)

Atmospheric circulation compounds anthropogenic warming and impacts of climate extremes in Europe

Davide Faranda et al. Proc Natl Acad Sci U S A. 2023.

Abstract

Diagnosing dynamical changes in the climate system, such as those in atmospheric circulation patterns, remains challenging. Here, we study 1950 to 2021 trends in the frequency of occurrence of atmospheric circulation patterns over the North Atlantic. Roughly 7% of atmospheric circulation patterns display significant occurrence trends, yet they have major impacts on surface climate. Increasingly frequent patterns drive heatwaves across Europe and enhanced wintertime storminess in the northern part of the continent. Over 91% of recent heatwave-related deaths and 33% of high-impact windstorms in Europe were concurrent with increasingly frequent atmospheric circulation patterns. While the trends identified are statistically significant, they are not necessarily anthropogenic. Atmospheric patterns which are becoming rarer correspond instead to wet, cool summer conditions over northern Europe and wet winter conditions over continental Europe. The combined effect of these circulation changes is that of a strong, dynamically driven year-round warming over most of the continent and large regional and seasonal changes in precipitation and surface wind.

Keywords: European heatwaves; European windstorms; atmospheric dynamics; climate change.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.

Fig. 1.

Sea-level pressure wintertime atmospheric circulation patterns with significant occurrence trends and associated surface anomalies: Composite anomalies of DJF sea-level pressure (A and B), 10-m horizontal wind speed (C and D), 2-m temperatures (E and F), and precipitation rates (G and H) for days with increasing (A, C, E, and G) or decreasing (B, D, F, and H) occurrence trends. In the composites (A_–_H), contours indicate regions with changes significant at the one-sided 5% level, computed with a bootstrap sample size of 500. Spatial averages of seasonal temperature anomalies (black) and precipitation rates (blue) during the days with increasing (I) or decreasing (J) occurrence trends and count of days displaying the corresponding occurrence trend (orange stems) during DJF. Solid lines represent linear trends of the spatial averages with the 95% confidence intervals of the two linear fits in each panel shown in the legends. The averages in (I) and (J) are computed on all European land points (

SI Appendix Fig. S3

).

Fig. 2.

Fig. 2.

Sea-level pressure summertime atmospheric circulation patterns with significant occurrence trends and associated surface anomalies: Composite anomalies of DJF sea-level pressure (A and B), 10-m horizontal wind speed (C and D), 2-m temperatures (E and F), and precipitation rates (G and H) for days with increasing (A, C, E, and G) or decreasing (B, D, F, and H) occurrence trends. In the composites (A − H), contours indicate regions with changes significant at the one-sided 5% level, computed with a bootstrap sample size of 500. Spatial averages of seasonal temperature anomalies (black) and precipitation rates (blue) during the days with increasing (I) or decreasing (J) occurrence trends and count of days displaying the corresponding occurrence trend (orange stems) during DJF. Solid lines represent linear trends of the spatial averages with the 95% confidence intervals of the two linear fits in each panel shown in the legends. The averages in (I) and (J) are computed on all European land points (

SI Appendix, Fig. S3

).

Fig. 3.

Fig. 3.

Impacts of changing atmospheric circulation patterns in terms of heatwave casualties and European Windstorms. (A) The size of the pie chart for each country shows the total number of heatwave excess deaths as recorded in the EM-DAT database for the whole year. The purple slices show the fraction of excess deaths associated with heatwaves showing an above-average frequency of circulation patterns with a positive occurrence trend. The yellow slices show the excess deaths associated with heatwaves that we excluded from our analysis (Methods). Finally, the blue slices show the corresponding fractions for heatwaves showing circulation patterns with no or negative occurrence trends. The shading on the geographical map shows the temperature anomalies (°C) during the 228 heatwave days retained for analysis. (B) The size of the pie chart for each country shows the total number of destructive windstorms in the storm database for the whole year (Methods). The purple slices show the fraction of windstorms showing an above-average frequency of circulation patterns with a positive occurrence trend. The blue slices show the corresponding fraction for windstorms showing analogs with no or negative occurrence trends. The shading on the geographical map shows the precipitation anomalies (mm day−1) during the 438 windstorm days retained for analysis.

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