Collaborative Research Centre 1502 DETECT: 'Regional Climate Change: Disentangling the Role of Land Use and Water Management'
Authors: Siegismund Frank , Kusche Jürgen 
Published: March 2024

Several continental regions on Earth are getting wetter, while others are drying out not only in terms of precipitation but also measured by the increase or decrease in surface water, water stored in the soils, the plant root zone, and in groundwater. Drying and wetting as seen in terrestrial, space-geodetic and remote sensing data are generally ascribed to combined effects of global warming due to greenhouse gas forcing, natural variability, and anthropogenic modification of the water cycle. Existing climate models that account for these effects fail to explain observed patterns of hydrological change sufficiently. Contrary to common beliefs, observations also do not support a simple dry-gets-dryer and wet-gets-wetter logic. Instead, the observed trends, e.g. in precipitation, soil moisture, water storage, or flood discharge, differ considerably from a simplified logic.The CRC 1502 DETECT, a collaborative research centre of the Universities of Bonn and G&#246;ttingen, the Geomar, the Research Centre J&#252;lich and the German National Meteorological Service DWD, has been established by the German Research Foundation DFG with the objective of closing this gap of understanding. To better comprehend the origin of these patterns, DETECT &#160;is developing a regional coupled modeling framework further that explains past observations as realistically as possible, accounts for potential drivers of change that may have been understudied in the past, and that can predict future changes. Our modelling framework is based on the TerrSysMP platform (i.e. the coupling of ICON/COSMO, CLM and ParFlow with/without data assimilation) and it ingests various conventional and new satellite and terrestrial data sets.By applying this modelling framework to both historical and IPCC-type simulations, DETECT will test the hypothesis that humans &#8211; through several decades of land use change, and intensified water use and management &#8211; have caused persistent modifications in the coupled land and atmospheric water and energy cycles. It is hypothesized that (1) these human-induced modifications contribute considerably, compared to greenhouse gas (GHG) forcing and natural variability, to the observed trends in water storage at the regional scale, (2) land management and land and water use changes have modified the regional atmospheric circulation and related water transports and (3) these changes in the spatial patterns of the water balance have created and magnified imbalances that lead to excessive drying or wetting in more remote regions.We test this hypothesis for the Euro-CORDEX region. In later phases, we evaluate the transferability of our approach for regions with different environmental conditions. We will develop evidence-based sustainability criteria for land and water use activities. The presentation will provide an overview on the central hypotheses and objectives of our research programme, the study logic and common approach, as well as anticipated results and contributions to the community. After two years, we highlight some first &#160;findings.