How can we attribute weather extremes to climate change?

With climate change we see an increase in extreme weather events around the globe; occurrences of floods, heatwaves, and droughts. Within XAIDA, we aim to determine to what extent human induced climate change has altered the probability of occurrence and/or intensity of an extreme weather event, also known as attribution science. Several institutions work on attribution science, using different but complementary methodological frameworks. In this brief we explain the three main approaches used within XAIDA: unconditional probabilistic analysis, circulation analogues, and the storyline approach.

Paper: Attributing Venice Acqua Alta events to a changing climate and evaluating the efficacy of MoSE adaptation strategy

Read the paper: This research employs an innovative approach by utilizing analogues of atmospheric patterns to scrutinize four notable Acqua Alta events in the Venice lagoon, specifically those connected with intense Mediterranean cyclones that transpired in 1966, 2008, 2018, and 2019. The findings provide compelling evidence that modifications in atmospheric circulation, while not solely attributable to human activities, are undeniably linked to the increased severity of these events, thereby illuminating the vulnerability of Venice to the impacts of climate change. Furthermore, the study conducts a comprehensive assessment of the MoSE system, a crucial adaptation infrastructure designed to mitigate flooding in Venice, and underscores its effectiveness in protecting the city against events with historical analogues, particularly those akin to the catastrophic 1966 flood.


Life of the project – We are happy to announce that Dim COUMOU is now the Scientific Coordinator of the XAIDA Project, unanimously approved by the Consortium. Read more to know the context and the other changes in the XAIDA governance.

Paper: Heat Extremes in Western Europe warmed faster than simulated

Extract from the article, Figure 3.

Read the paper: Over the last 70 years, extreme heat in Western Europe has intensified with 3.4°C per degree global warming. A rate much larger than nearly anywhere else. Very few models capture the observed trend. None of them captures the large contribution from trends in atmospheric circulation.
The mismatch can be due to an underestimated circulation response to external forcing or underestimated unforced internal variability, or both. The former implies that heat extremes continue to intensify at an extreme rate, the latter that the trend continues but may slow down.


Located in València, Spain, the XAIDA’s Second General Assembly took place in October 2023.


ClimaMeter is a rapid framework for understanding extreme weather events in a changing climate based on looking at similar past weather situation (©ClimaMeter). The platform is a collaboration between 4 institutions (LSCE-IPSL, ICTP, INGV and Uppsala University), 2 EU funded projects (XAIDA and EDIPI) and a French CNRS funded project (CROIRE).



Extreme cold spells are still possible today in Western Europe, even with current warming trends.
The atmospheric circulation patterns that drive extreme low temperatures, e.g. as in January 1985, remain possible in current winters.
Under such conditions we anticipate that with current regional warming trends, temperatures would only be about 1.4°C warmer than in 1985, with potential impacts on the electricity grid, and health.
As an example, a circulation-induced 1985-like cold spell in today’s climate would likely stand at around -9°C over France for minimum temperatures, which would still be amongst the 5-10 coldest cold spells observed in the past five decades.

The “Medicanes” (Mediterranean Hurricanes) and climate change

Medicanes are Mediterranean cyclones whose characteristics resemble those of tropical cyclones. They are often associated with hurricane-force winds and heavy precipitation. With a frequency of 1-2 per year, it is a challenge to determine whether their frequency should increase or decrease in a warmer world. Their intensity is however projected to increase due to the warming projections for the Mediterranean sea, the main source of energy for medicanes.


Located in Sorbonne University, Paris France, the XAIDA’s First General Assembly took place from 12 to 14 October 2022, in a hybride format.