A new reanalysis-based approach is proposed to examine how reconstructions of extreme weather events differ in warmer or cooler counter-factual worlds. This approach offers a novel way to develop plausible storylines for changes in some types of extreme event that other methods may not be suitable for. Here, we re-run the 20th Century Reanalysis (20CRv3) system to produce improved and plausible reconstructions of certain historical extreme weather events by adding newly rescued pressure observations. We then translate these events into a warmer world by increasing the SSTs used as reanalysis boundary conditions and assimilating the same pressure observations. This approach represents the same extreme weather patterns but in a warmer world with physically consistent changes to the atmospheric state. As proof-of-concept, we apply this approach to a severe windstorm that occurred in February 1903. This event, known as Storm Ulysses, produced stronger winds than any other more recent event for parts of the UK. The translated reconstruction produces even higher wind speeds and increased rainfall, suggesting that this storm would be more damaging if it occurred today rather than 121 years ago. We expand this proof-of-concept to examine a wider range of historical extreme weather events in multiple regions.
Talk by Ed Hawkins, University of Reading
Moderation: Chloe Brimicombe