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.
A key factor driving major precipitation changes in Europe and worldwide is the level of global warming. This, in turn, depends not only on future greenhouse gas emissions but also on climate sensitivity, the equilibrium warming expected from a doubling of atmospheric CO2. Climate sensitivity has been a central research focus for decades. The latest IPCC report (AR6) provides a best estimate of 3 °C, but with a wide range of 2–5 °C. In the BUDGET project, we published a research paper in Science showing that climate models with climate sensitivity below 2.5 °C are inconsistent with satellite observations from CERES. CERES measures changes in reflected solar radiation and outgoing longwave radiation at the top of the atmosphere. Models with low climate sensitivity simulate only small changes in these energy fluxes and therefore fail to reproduce the much larger trends detected by CERES.
Atmospheric radiative cooling (dQ) is closely tied to latent heat release during precipitation, and changes in dQ provide insight into how Earth’s energy balance may affect future rainfall. This study analyzes dQ trends from 2001–2024 across satellite, reanalysis, and climate model datasets. The datasets show conflicting global mean trends: dQ reflects the balance of longwave and shortwave flux changes, which respond differently to natural and human forcing. While consistent trends across datasets would suggest a robust signal, our results highlight persistent uncertainties from observational inputs, assimilation methods, and model assumptions. As a result, both measurement and simulation of dQ, particularly the reliability of long-term trends, remain uncertain, calling for caution in interpretation.
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.
