More than half of the world's population lives in urban areas, a figure that rises to 75% for European residents. Due to ongoing global anthropogenic changes, such as climate change and urbanisation, city dwellers are facing increasing pressure and adverse weather and climate effects. In order to adapt to these challenges and build resilient cities, urban planners, stakeholders and decision-makers need high-resolution climate information tailored to their needs (e.g. in terms of spatial resolution, time horizon or impact indicators). Today, most of the climate information produced at the local level comes from regional climate models (RCMs) that are used to refine global climate projections made by global climate models (GCMs) (e.g. CORDEX, Coordinated Regional Climate Downscaling Experiment). One of the problems is that, historically, most regional climate models did not represent cities in great detail due to their still too coarse horizontal resolution (on the order of tens of kilometres) and because they did not activate the physical parameterisations dedicated to urban areas. Thanks to improvements in computing resources, a new generation of high-resolution (a few kilometres) regional climate models (known as convection-permitting regional climate models, or CPMs) has been developed over the last decade. These models enable more complex areas to be studied thanks to their increased resolution, such as mountainous areas, coastlines and cities.
As part of the CIRCE project, we are using the largest ensemble of high-resolution regional climate simulations produced as part of the CORDEX Flagship Pilot Study on convective phenomena (FPS-Convection) of the World Climate Research Programme (WCRP). These simulations have been widely used to study the added value of the new generation of models compared to their predecessors in representing extreme events such as heavy precipitation or heat waves, but they are being used here for the first time to study the urban climate of European cities.
The project is structured around two main areas, with a particular focus on evaluating the different types of models, the uncertainties associated with each type of configuration, and the second part focusing on the expected effects of these choices on climate impact projections.
