Constraining future precipitation changes in Europe and the Arctic from historical observations of the atmospheric energy budget

BUDGET will increase our understanding of the causes of why climate models have such large differences in future Arctic rainfall and summer precipitation in northern Europe. This is done by analyzing the atmospheric energy budget, which consists of atmospheric radiation cooling and heating as well as sensible heat from the surface to the atmosphere. Recent work has focused on analysing the local atmospheric energy budget over Europe during June, July and August in model, reanalysis and satellite datasets with the aim to identify causes of differences in precipitation in model simulations. During the 1980-2023 period we find variation in the spatial pattern, sign and magnitude of the mean trend in precipitation in 15 CMIP6 models, along with variation in the spatial patten and magnitude of atmospheric radiative cooling, sensible heat flux and dry static energy. These discrepancies are also evident in reanalysis datasets, demonstrating that these products might differ as much as models with respect to atmospheric energy budget terms. Over both southern and northern Europe, a strong positive trend in dry static energy appears to be the main driver of wettening in several models, whilst a negative trend in atmospheric longwave radiative cooling and increase in sensible heat correlate with a decrease in precipitation over central-eastern Europe. Further work is being carried out to determine the reliability of reanalysis datasets and the robustness of the linear trends. In a previous study, we found that on a global scale in the climate models the reduction in sensible heat, which causes an increase in precipitation, is as large as the global precipitation change over the industrial period. This finding is reinforced by the latest climate model calculations featured in the most recent IPCC report within BUDGET. However, a compelling contrast emerges when these climate models are compared with data obtained from satellites and re-analyses. In contradiction to the models, these observational datasets indicate a global-scale increase in sensible heat, leading to a decline in precipitation. These findings call into question how well we understand global precipitation changes.

The hydrological cycle closely links the atmosphere, hydrosphere, biosphere and cryosphere on various timescales. Precipitation changes, including extreme precipitation changes, are likely to become one of the most important consequences of our changing climate over the coming decades. Precipitation is strongly linked to the energy budget in the atmosphere since the surface latent heat flux is a direct heat source for the atmosphere when water vapour condenses. BUDGET will apply the constraint of the atmospheric energy budget to improve quantification of future precipitation changes in Northern Europe and the Arctic by using the observed trends. BUDGET utilizes thereby the satellite era advancement and available satellite data to quantify trends in the atmospheric energy budget components. Re-analysis will complement the satellite data. We will apply this new scientific knowledge to weight climate model performance and thus constrain future regional precipitation changes. BUDGET will quantify causes of diversity in model simulated regional precipitation changes. We will quantify whether model discrepancies of historical and future precipitation changes are linked to different climate drivers, such as greenhouse gases and aerosols, or host model differences. BUDGET will investigate whether the constraints on the atmospheric energy budget have implications for changes in extreme precipitation. A main aim in BUDGET is to understand the physical processes causing model diversity using four different climate models allowing for the possibility of future model improvements.