Summary/Abstract
During the first two weeks of September 2023 torrential rain fell in several countries across the Mediterranean, caused by low-pressure systems, notably storm “Daniel”, forming around a blocking high centered over the Netherlands. The devastating scale of impacts associated with the event is rendering it the deadliest and costliest storm over the Mediterranean and Africa, respectively, on record.
In this event study, the authors use collected data and use three multi-model ensembles from climate modelling experiments using very different framings: Sea Surface Temperature (SST) driven global circulation high resolution models, coupled global circulation models and regional climate models, as well as the single coupled model ensemble FLOR. To assess the role of climate change, the authors combined observation-based products and climate models and assess changes in the likelihood and intensity of a 1 in 10 year 4-day event over the larger region encompassing Greece, and the parts of Türkiye and Bulgaria that were impacted by flooding, as well as the 1 in 600 year 1-day maximum rainfall event over Libya.
For the large region including Greece and parts of Bulgaria and Türkiye, the authors find that human-induced climate change made an event as extreme as the one observed up to 10 times more likely and up to 40% more intense. An event as extreme as the one observed over Libya has become up to 50 times more likely and up to 50% more intense as compared to a 1.2C cooler climate. However, the uncertainties in these estimates are high, and encompass the possibility of no detectable change