Upgrade of the HadGEM3-A based attribution system to high resolution and a new validation framework for probabilistic event attribution

We present a substantial upgrade of the Met Office system for the probabilistic attribution of extreme weather and climate events with higher horizontal and vertical resolution (60 km mid-latitudes and 85 vertical levels), the latest Hadley Centre atmospheric and land model (ENDGame dynamics with GA6.0 science and JULES at GL6.0) as well as an updated forcings set. A new set of experiments designed for the evaluation and implementation of an operational attribution service are described which consist of pairs of multi-decadal stochastic physics ensembles continued on a season by season basis by large ensembles that are able to sample extreme atmospheric states possible in the recent past. Diagnostics from these experiments form the HadGEM3-A contribution to the international Climate of the 20th Century Plus (C20C+) project and were analysed under the European Climate and Weather Events: Interpretation and Attribution (EUCLEIA) event attribution project as well as contributing to the Climate Science for Service Partnership (CSSP)-China programme.