17 Feb 2022
17 Feb 2022
Status: a revised version of this preprint is currently under review for the journal WCD.

A climate-change attribution retrospective of some impactful weather extremes of 2021

Davide Faranda1,2,3, Stella Bourdin1, Mireia Ginesta1, Meriem Krouma1, Gabriele Messori4,5, Robin Noyelle1, Flavio Pons1, and Pascal Yiou1 Davide Faranda et al.
  • 1Laboratoire des Sciences du Climat et de l’Environnement, UMR 8212 CEA-CNRS-UVSQ, Université Paris-Saclay, IPSL, 91191 Gif-sur-Yvette, France
  • 2London Mathematical Laboratory, 8 Margravine Gardens London, W6 8RH, UK
  • 3LMD/IPSL, Ecole Normale Superieure, PSL research University, Paris, France
  • 4Department of Earth Sciences and Centre of Natural Hazards and Disaster Science (CNDS), Uppsala University, Uppsala, Sweden
  • 5Department of Meteorology and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden

Abstract. The IPCC report AR6 indicates a general consensus that anthropogenic climate change is modifying frequency and intensity of class of extreme events such as cold spells, heatwaves, storms or floods. A different point of view is to investigate whether a specific extreme event would have been possible in the absence of climate change, or whether climate change may have affected its specific characteristics. Here, we address this question by performing an attribution of some major extreme events that occurred in 2021 over Europe and North America: the winter storm Filomena, the French Spring cold spell, the Westphalia Floods, the Mediterranean summer heatwave, the hurricane Ida, the Po Valley tornadoes outbreak, the medicane Apollo and the late autumn Scandinavian cold-spell. We focus on the role of the atmospheric circulation associated with the events and its likelihood in present (factual world) and past climate conditions (counterfactual world) – defined using the ERA5 dataset 1950 to present. We use an analogs-based methodology whose aim is to find the most similar sea-level pressure patterns to the target events in the factual and counterfactual worlds and compute significant shifts in probability, persistence, predictability and seasonality of the patterns. We also diagnose whether in the present climate the analogs of the studied events lead to warmer/cooler or dryer/wetter conditions than in the past. We find that most of the events are significantly modified in present climate with respect to the past, because of changes in position, persistence and seasonality of cyclonic/anticyclonic patterns. Two of the events, storm Filomena and Medicane Apollo, appears to be a black swan of the atmospheric circulation, with analogs of bad quality. Our approach, complementary to the statistical methods already available in the community, warns that the role of the atmospheric circulation should be taken into account when performing attribution studies.

Davide Faranda et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2022-9', Anonymous Referee #1, 31 Mar 2022
    • AC1: 'Reply on RC1', Davide Faranda, 26 Apr 2022
  • RC2: 'Comment on wcd-2022-9', Anonymous Referee #2, 02 Jun 2022

Davide Faranda et al.

Davide Faranda et al.


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Short summary
We analyse recent and impactful extreme events for the calendar year 2021. These events have produced widespread damage and casualties. It is a question of public interest to understand whether climate change have contributed to their occurrence or enhanced their intensity. Our approach, complementary to the statistical methods already available in the attribution community, underscore the importance of considering changes in the atmospheric circulation when performing attribution studies.