Summary/Abstract
Between October of 2023 and March of 2024, the United Kingdom and Ireland experienced a series of damaging storms. In this event study, the authors use peer-reviewed methods to assess the extent to which human-induced climate change and the North Atlantic Oscillation influenced the average storm severity during this period.
The authors separately assess changes in storm severity, storm-related precipitation, and accumulated precipitation in the region over the 2023-2024 storm season. The study concludes that, in today’s climate with 1.2C of warming as compared to pre-industrial temperatures, stormy days with winds as intense as in the 2023/24 season are expected to occur about every 4 years, equivalently severe storm-driven precipitation is expected to occur once every five years, and equivalent seasonal precipitation is expected to occur about once every 20 years.
Observations suggest that the average precipitation on stormy days has become 30% more intense as compared to a 1.2C cooler pre-industrial climate, and the authors’ modelling indicates an average precipitation increase of 20% due to human-induced climate change. In total, this finding suggests that storm-driven precipitation equivalent to the 2023-2024 season has become ten times more likely than in pre-industrial climate conditions, and that seasonal precipitation at 2023-2024 levels has become at least four times more likely due to human-induced climate change. However, in contrast to other climate models, the authors’ analysis also shows that human-induced climate change is contributing to a negative trend in storminess over the United Kingdom and Ireland, and that the average Storm Severity Index (measuring wind speed and area affected by high winds) in the region is likely to decrease due to human-induced climate change.