Addressing the Grand Challenge of regional sea level change prediction

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Sea level change is one of the most widely known and potentially serious consequences of climate change due to emissions of greenhouse gases. It concerns both the public and policymakers, because of its adverse impact on the populations and ecosystems of coastal and low-lying areas. This impact is expected to increase for centuries to come.Sea water expands as it warms in a process known as thermal expansion. Thermal expansion due to changes in the amount of heat entering the ocean is the largest contributor to sea level rise projected for the 21st century. Regional sea level is also affected by changes in precipitation, evaporation and winds over the ocean because, along with heating, these affect ocean density and currents. The contraction of glaciers and ice sheets expected in a warming climate is another important contributor to projected global and regional sea level change, but it is a different scientific subject which we do not propose to address directly here.Computer climate models disagree in their projections of sea level change. This means that we are not able to make precise predictions of sea level rise on average over the globe. Moreover, while all models predict that some regions will experience a larger rise than average and others a smaller rise than average, they do not agree on these geographical patterns. A large part of the uncertainty is related to the different behaviour of the various models in response to the changing effects of heat, water and winds. They behave differently because different assumptions have been made in their formulations, reflecting a lack of precise knowledge.This project aims to study these uncertainties, by detailed analysis, using new techniques, of how the ocean models respond to particular inputs, and by comparison with theory and observations. Our aim is thus to reduce the range of the projections. Any such reduction is potentially of large societal and economic benefit; for example, planning decisions need to be made concerning coastal infrastructure that may last for decades and cost billions of pounds.