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Warmer Mediterranean temperatures do not decrease snowy cold spell intensity over Italy

Abstract : Cold spells are compound extreme events associated to drops of air temperatures and heavy snowfalls. The mechanisms that link those events to global climate change are still debated. We focus on winter cold spells over Italy, reconstructing 32 major events in the past 60 years from documentary sources. We show that the frequency and intensity of cold spells have not decreased in recent years, which can be deemed paradoxical in a warming climate. We explore this paradox by performing ensembles of climate simulations in fixed emission scenarios changing boundary conditions (such sea-surface temperature, SST). We find that anthropogenic emissions enhance features linked to the intensity of simulated cold spells. Our results show that the response of extreme cold weather events to climate change is not purely thermodynamical nor linked to the global average temperature increase, but crucially depends on modifications of the atmospheric circulation at mid-latitudes. This explains how Mediterranean areas like southern Italy are likely to witness more intense and frequent snowfall events with warmer SSTs. 11
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https://hal.archives-ouvertes.fr/hal-02367559
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Submitted on : Monday, November 18, 2019 - 9:34:43 AM
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Miriam D'errico, Pascal Yiou, Cesare Nardini, Frank Lunkeit, Davide Faranda. Warmer Mediterranean temperatures do not decrease snowy cold spell intensity over Italy. 2019. ⟨hal-02367559⟩

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