Is flood risk increasing? Exploring the relationships between atmospheric circulation, extreme rainfall and flooding

There is now a broad scientific consensus that the global climate is changing in ways that are likely to have a large impact on our society and the natural environment over the coming decades. Global warming, and its impact on extreme weather events, may have a profound influence on the way we live in the future. Recent extreme weather events, such as the unusual number of hurricanes in the US 2005 hurricane season, the unprecedented flooding in central Europe in summer 2002, the tragic loss of life in the European heatwave the following summer, or the severity of flooding in the UK during autumn 2000, have been said to be a possible impact of global warming by the media. This has made us focus our attention on the possible impacts of future climate change on our society. However, how can we predict how future global warming may change the frequency and intensity of extreme weather events and their impacts if we do not understand how current local scale climatic variability is governed by the larger-scale atmosphere and how these processes may change in the future? This fellowship will examine these and other fundamental research questions through collaboration with international experts in the US at the National Center for Atmospheric Research, Europe and through links with the Centre for Ecology and Hydrology and the Environment Agency in the UK. This fellowship will examine the links between large-scale atmospheric circulation patterns, local scale extreme rainfall and their impact on flooding using the UK as a test-bed. The recent government-funded Foresight project suggests that flooding costs the UK £2.2 billion annually; £800 million on flood defence and £1.4 billion average damage. This may rise to somewhere from £2 to £27 billion by the 2080s, depending on how we manage greenhouse gas emissions in the future. Whilst changes through time in UK flooding are reasonably well characterised, changes in the spatial extent and severity of flooding are not. Additionally, we do not understand the atmospheric mechanisms that cause severe rainfall events and thus flooding, how these may be currently changing and how these may further change under global warming. The UK is an ideal location for this study as it has a wealth of hydrological, climatological and meteorological data, and the study will concentrate firstly on an understanding of the climatic processes that contribute to flood risk UK-wide. It will then use two case studies, the river Ouse in Yorkshire and the river Eden in Cumbria, to look at the more detailed response to climate variability within a river catchment using a hydrological modelling framework. Although the study has a UK focus, the results will be applicable to other parts of the world, through an understanding of the processes that combine to cause flooding. Finally, using this new understanding of the complex atmospheric processes that cause extreme rainfall events and flooding, I will develop a method to investigate the impacts of future climate change on the risk of flooding in the UK. This methodology will be developed using the latest regional and global climate model outputs and will contribute to the development of a new probabilistic framework for climate change impacts in Europe and new tools that can be used by managers to design flood defence systems that are robust to the impacts of climate change. These will be necessary for the future management of flood risk in UK catchments under climate change; as indicated by the UK government's Department for Environment, Food and Rural Affairs (DEFRA) recent report 'Making Space for Water'.