A large amount of work has taken place over a number of years to make measurements of chemicals and small particles, included land-derived dust, in both the global ocean and its overlying atmosphere. These chemicals and particles play important roles in determining the Earth's climate and the quality of the air we breathe. In addition, dust derived from the land surface is transported through the atmosphere and becomes distributed globally. Some of this land-derived dust deposits onto the oceans and provides a source of nutrients, particularly iron, which are vital to the livelihood of marine microscopic plants (plankton). We propose to work with the scientific community to bring such measurements together into large databases and to use them, along with the most up-to-date information on rates at which chemicals and particles exchange between the air and the sea, to make the best possible estimates of the amounts of materials exchanging between the ocean and the atmosphere. An improved understanding of the relative amounts of these compounds and particles and their exchange between the ocean and atmosphere will be particularly beneficial to scientists who are trying to model the Earth's climate and air quality. This information will also be useful for predicting future changes due to factors such as increased carbon dioxide in the atmosphere and its affect on ocean acidity, temperature and ocean mixing. The predictions from such models are important to policy makers in order to maximise the benefits and minimise the costs of mitigating and adapting to climate and other global changes.

Climate change presents a significant planning challenge for the Yangtze River Delta (YRD) Region, where urban build-up has given rise to what may be the largest concentration of adjacent metropolitan areas in the world. The YRD metropolitan region is centred at Shanghai, a mega city sitting on the south edge of the mouth of Yangtze River. YRD in general and Shanghai in particular face compound extreme flooding events caused by sea level rise, extreme rainstorms, astronomical high tides, storm surge, and upstream floods. To effectively mitigate the potential devastating consequences of such compound events in YRD will not only save human lives in the region but also contribute to sustainable development and social stability in China. This project will develop resilient adaptation measures to address future increasing flood risk under climate change and rapid socioeconomic development in YRD and Shanghai. We will quantify the compound flooding risks in the future based on the latest developments in climate and hydrodynamic modelling, and assess both direct (physical damage of buildings, assets and infrastructures, etc.) and indirect losses (economic losses along the input-output chain of the economy) caused by such compound events. We will then evaluate proposed mitigation and adaptation alternatives with a focus on Shanghai and visualize the sustainable solutions over the period of 2017-2100 based on the enhanced Robust Decision Making (RDM) method. In this proposed project, the UK team will lead two working packages (WPs) and contribute to other packages. The UK team will lead WP-1 on climate change scenarios because the Met Office is currently routinely running a numerical weather prediction (NWP) forecast model with 1.5-km horizontal resolution over the UK (the UKV model). Based on this advantage, the UK team will work with Chinese partners to develop climate change scenario based on a regional climate model so as to create very high resolution rainfall data in the YRD region. In addition, the UK team will also contribute to the estimation of the joint distribution of co-occurring extreme weather/climate events (WP2). The UK team will lead WP-4 on Indirect Impact Assessment because Prof Laixiang SUN and his collaborators have advanced a mixed input-output model with supply constraint to effectively estimate the indirect impact of extreme events on socioeconomic sectors. The UK team will also make significant contributions to WP-6 on Evaluation of Potential Solutions because the team has made the most important contribution to the design on combining the robust decision making (RDM) scheme and the dynamic adaptive policy pathways (DAPP) for this project. Both the overall missions of this proposed project and the contribution of the UK team to the project fit well with the EPSRC's theme on Living With Environmental Change. Our project has a well-specified emphasis on both the resource challenge and the infrastructure challenge under climate change, and shows a clear recognition of the important role that engineering and physical sciences can play in dealing with such challenges in the areas of Flood risk management, Water engineering, Coastal and waterway engineering, and Sustainable land management. In terms of modelling, we develop an integrated modelling framework to take into account the entire cascade of factors from the effect of climate change on storms and sea levels, to the physical and economic damages resulting from extreme events, allowing the robust determination of annual probability of damage states and a synthesized trade-off analysis of flood control pathways. This integrated, probabilistic analysis tool promotes the mission of EPSRC in modelling complexity using advanced mathematics and ICT.

The anthropogenic burning of fossil fuels is affecting the climate system via raised atmospheric CO2 concentrations. But are there aspects of the natural Earth system that, when forced by imposed climate change, have themselves a major impact on the carbon cycle? Such climate-carbon (C) cycle feedbacks might be positive - that is, they may cause a reduction in the current capability of natural systems to mitigate anthropogenic CO2 emissions, or may even force natural systems to become direct sources of CO2. Such positive feedbacks are a major cause for concern, and their initiation could be regarded as a climate 'tipping point'. It has been hypothesised that the Arctic land surface could be one such 'tipping point', whereby global warming is sufficient to induce soil C losses greater than any extra draw-down of C through enhanced tundra (shrub) and boreal forest growth in a warmer, CO2-enriched environment. In addition, a warmer climate will impact on the on the energy and water cycles, with less snow cover in Northern Latitudes reducing surface reflectivity and so inducing additional warming. In reality the energy, water and C cycles are all strongly linked and need to be modelled interactively to provide robust estimates of the future. Global Circulation Models (GCMs) are designed to emulate the climate system and the global carbon cycle, and in the process, provide pointers to potential 'tipping points' in the climate system. But their predictions for the Arctic region will only be as good as the hydrology, ecology and energy interactions depicted in the land surface model for that region. This project therefore has two aims - to provide much more physical realism in land surface models, and then to see how this enhancement impacts on modelled future climate. Does the Arctic region eventually enhance human-induced climate change by increasing future levels of atmospheric carbon dioxide? Modelling the land surface for the Arctic region is complicated. To get this correct, we will need to capture how the vegetation may grow and expand in a warmer environment, and how this might change soil C stocks. We also need to model how the snow interacts with vegetation - snow cover will change with climate, and will influence the energy inputs, the water cycle, the frozen ground and the vegetation distribution. For example, deeper snow will occur in areas of tall vegetation and thus vegetation structure influences not only the timing of snow melt but also the thermal regime as deeper snow actually insulates the soils. There is thus a knock-on effect on soil respiration and vegetation growth. This project will model all of these features, dynamically, such that the impact of future temperature and snowfall patterns on the Arctic ecosystems can be assessed. Extensive use will be made of existing observational datasets developed by the PIs and others over the last decade and, in particular the International Polar Year. This new knowledge of the Arctic land surface will be introduced within a pan-Arctic gridded modelling system. The local and regional behaviours will be integrated to determine net land-atmosphere CO2 fluxes. However, major future changes in land surface behaviour might have strong feedbacks on other aspects of the climate system e.g. surface temperatures and soil moisture. Hence, the last component of this project is to make coupled land-atmosphere simulations, thereby capturing all feedbacks. We will achieve this through our existing and on-going collaboration with the Hadley Centre (a world leading centre for modelling the climate system, who make predictions with their family of GCMs). This link will allow a final assessment to be made of whether the Arctic land-surface could pass an unwelcome climate 'tipping point', and thus feedback on existing warming, either locally through enhancing warming further or through the global C cycle.

North west Europe has a relatively mild climate in part because of heat pulled north through the Atlantic by the overturning. There is a risk that global warming will cause this circulation to rapidly decrease with consequences involving not only colder winters for Europe but also changes in sea level and precipitation. This project will carry out a risk assessment of rapid changes of the Atlantic overturning. We will use two models of the climate system, HADCM3, the Hadley Centre model used in the IPCC AR4, and CHIME, a global climate model developed at the National Oceanography Centre, Southampton. This has the same atmospheric model as HADCM3 but has a very different structure to the ocean component. Making use of the resources of climateprediction.net we will run a large ensemble of both models to assess the uncertainties in the system. We will then use modern Bayesian statistical techniques to combine model output, data and expert opinion in our risk assessment. An assessment of the utility of the data from the RAPID-WATCH arrays is an important aim of the project.

There is widespread concern about how climate is responding to the on going rise in atmospheric CO2 from carbon emissions and land use changes. In our view, the climate response can be divided into the following stages: 1. Past and on going increases in atmospheric CO2 are leading to a global warming of up to 0.6C over the last 50 years. The regional variability is though much larger than this global signal. 2. Continuing emissions are increasing atmospheric CO2 and driving a heat flux into the ocean, leading to ocean warming and steric sea level rise. The amount of warming is sensitive to the carbon emission scenario, as well as the rate of carbon uptake by the ocean and terrestrial system. 3. The regional distribution of warming and steric sea level rise is sensitive to how the ocean interior takes up heat, involving the transfer of surface properties into the thermocline and deep ocean. 4. After emissions cease, there will be a thermal adjustment of the lower atmosphere, and the net heat flux into the ocean will cease, and so ocean warming and steric sea level will eventually likewise cease. 5. As well as a thermal equilibrium being reached, the atmosphere and ocean approach a carbon equilibrium after emissions cease, on a timescale of perhaps several hundred years to a thousand years. At this equilibrium, the final atmospheric CO2 and the amount of climate warming is related to cumulative carbon emissions based on our idealised theory. The climate warming and steric sea level rise will be investigated using diagnostics of (i) present day temperature and salinity observations, allowing the steric sea level to be diagnosed; (ii) thought experiments with a range of ocean and climate models on timescales of centuries to several thousand years, designed to explore how the ocean warming spreads from the sea surface into the ocean interior, which ultimately determines the steric sea level rise; (iii) comparison with diagnostics of state of the art climate models, integrated for a century; (iv) comparison with idealised theory, relevant for when emissions cease; and (iv) finally a down scaling to provide bounds on the steric sea level response on a regional scale. This combination of the theory and Earth System models of intermediate complexity will allow a wide parameter space to be explored for a range of emission scenarios, much broader than that usually employed within IPCC assessments for the next 100 years. The study has the potential to provide accessible bounds for steric sea level rise, relevant for policy makers interested in different energy policies, and a link to end users is provided via the collaboration with the Hadley Centre.