Why do we need multiple methods for extreme event attribution?

Over the past 20 years, extreme event attribution has developed rapidly, providing a wide range of methods to attribute weather events – from unconditioned probabilistic to strongly conditioned storyline approaches. Advancing the field now requires combining results from multiple methods, allowing more robust conclusions drawn from various lines of evidence. Yet, doing so remains challenging. I will outline various methods currently used highlighting the benefits and disadvantages of each.

I will then present the ‘new kid on the block’: ReBASE. ReBASE (Reanalysis Based Attribution and Storylines of Extremes) is a collaborative project led jointly by the University of Edinburgh and the University of Reading. 

We use a novel data driven reanalysis based approach to examine real-world weather translated into different climates. We produce a reanalysis product of the current decade. Then, by altering the sea surface temperature, sea-ice concentrations, and forcings, we create storylines of how the weather could play out in both warmer and colder climates. These storylines can be used to attribute impacts and assess amplification of extreme weather events in a warmer climate. We can also provide counterfactuals of past events, translated to the present day climate.

This approach allows a global perspective on extreme events and their impacts - the same experiments produce global factual and counterfactual reconstructions of every day in the chosen periods. The data will be made openly available to allow anyone to explore their own choice of extreme event anywhere in the globe. Counterfactuals will also be developed for future warmer climate conditions to understand how extreme events and their impacts will change, and help inform adaptation decisions.