XAIDA Briefs
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.
DESPITE GLOBAL WARMING, COLD SPELLS SUCH AS WITNESSED IN THE 1980’s IN WESTERN EUROPE ARE STILL POSSIBLE
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.
EARLY 2022 HEAT WAVES IN EUROPE AND CLIMATE CHANGE
The summer of 2022 was pounded by a series of heat waves in Europe. The first, an outstanding early heat wave, took place in mid-June 2022 across Europe, mostly hitting Spain, France, but also other parts of Europe. The early character of the heat, in a crucial season for agriculture and ecosystems, is likely to have induced specific impacts on health and agriculture, which will need to be assessed. During the XAIDA Summer School in Trieste, students have studied the relation of this heatwave to climate change.
