Summary
The ACCESS 1-0 and ACCESS 1.3 now have a set of 3 historical ensemble members which include the late 20th Century and early 21st Century (2020) simulations. Recently we have just completed a new set of experiments designed to investigate the impact of the perturbation in ozone since 1960. In these experiments the ozone distribution was held at the 1960 values, but the remaining fields followed the historical change so the results are close to present day observations, so by comparing with the all forcing historical runs we can discern the effect of the ozone changes used in the CMIP5 simulations. Several other CMIP5 groups ran these NoOz experiments including the CSIRO Mk3.6 model, and this data has also been analysed and can be compared with the ACCESS results. However the Mk3.6 model was cheaper to run and was able to a 10 member ensemble with ACCESS 1.0 and 1.3 we only have 3 members as it is more expensive. We are still doing the ACCESS analysis, but we expect this ensemble will be large enough to pick up the large scale atmospheric response to the ozone perturbation in the model stratosphere and features like the southern annular mode changes but are less certain on whether the signal strength will allow us to detect more subtle regional changes at the surface and in the Southern Ocean. We intend investigate techniques to interpret the range of response in the ensemble members, and to diagnose differences and biases in the stratospheric dynamics in the ensemble members response to the ozone perturbation.
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