Long-term wetting and drying conditions predicted by global climate models are (often) confirmed by satellite gravimetry

Global coupled climate models are important for predicting future climate conditions. Due to sometimes large and often systematic model uncertainties, it is crucial to evaluate the outcome of model experiments against independent observations. Changes in the distribution and availability of terrestrial water storage (TWS), which can be measured by the satellite gravimetry missions GRACE and GRACE-FO, represent an important part of the climate system. However, the use of satellite gravity data for the evaluation of coupled climate models has only very recently become feasible. Challenges arise from large model differences with respect to land water storage-related variables, from conceptual discrepancies between modeled and observed TWS, from the still rather short time series of satellite data, and from a limited spatial resolution and sensitivity of the observations.

This presentation will highlight the latest results achieved from our ongoing research on climate model evaluation based on the analysis of an ensemble of models taking part in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We will focus on long-term wetting and drying conditions in TWS, by deriving hot spot regions of common trends in GRACE/-FO observations and regions of large model consensus. In the discussion of the agreement/disagreement between observed and modeled trends we will consider uncertainties arising from dominant inter-annual variations in the short GRACE/-FO observation time span and from the necessary separation of the integral gravity signal (e.g.by subtraction of a GIA model)