FUTURE-STORMS: Quantifying uncertainties and identifying drivers of future changes in weather extremes from convection-permitting model ensembles

点击翻译按钮获取中文摘要

Climate change is arguably the biggest challenge facing people this century, and changes to the intensity and frequency of climatic and hydrologic extremes will have large impacts on our communities. We use climate models to tell us about what weather in the future will be like and these computer models are based on fundamental physical laws and complicated mathematical equations which necessarily simplify real processes. One of the simplifications that really seems to matter is that of deep convection (imagine the type of processes that cause a thunderstorm). However, computers are so powerful now that we are able to produce models that work on smaller and smaller scales, and recently we have developed models which we call "convection-permitting" where we stop using these simplifications of deep convection. These "convection-permitting" models are not necessarily better at simulating mean rainfall or rainfall occurrence but they are much better at simulating heavy rainfall over short time periods (less than one day) which cause flooding, in particular flash-flood events. They are also better at simulating the increase in heavy rainfall with temperature rise that we can observe; therefore we are more confident in their projections of changes in heavy rainfall for the future.A few "convection-permitting" modelling experiments have now been run for different parts of the world but all of these have been over small regions, only the same size as the UK, or smaller. All of the experiments so far have concentrated on rainfall and none have examined how "convection-permitting" models might improve the simulation of other types of extreme weather such as hail, lightning or windstorms. In fact we know very little about how these types of extremes might change in the future. We also have no idea of the uncertainty in our experiments in terms of our predictions of future changes as we have only run one model simulation in each region - this is not useful for planning climate adaptation strategies where we really need to understand the uncertainties in our future predictions so we can plan for them. In FUTURE-STORMS we are running these "convection-permitting" models over a very large area (the whole of Europe) and we are comparing models from two different climate modelling teams at the UK Met Office and ETH Zurich in Switzerland. In addition to this we are now able to run a number of different climate models over the same region, which allows us to assess some of the uncertainties in future changes to heavy rainfall and other storm-related extreme weather. This will let us explore how heavy rainfall might change across Europe and what might be causing this. It will also allow us to look at whether these new models are able to simulate other types of extreme weather like hail, lightning and windstorms which have a huge impact on Europe, and how these might change in the future. Ultimately, we need better information on how extreme weather events might change in the future on which to make adaptation decisions and FUTURE-STORMS intends to provide this important advance, alongside translating this information into useful tools and metrics for use in climate change adaptation.