Earth System Model (ESM) evaluation is performed to assess the performance of a model either against predecessor versions, a wider set of other models or against observations. The evaluation of ESMs with observations is crucial for model improvements and an improved process understanding of the climate system. It is also a vital prerequisite for more trustworthy climate projections of the 21st century needed as basis for guidelines in climate policy.
The tasks at the DLR Institute of Atmospheric Physics include the development and application of methods for ESM evaluation and the development of new numerical tools to analyze large data sets.
The work aims at advancing ESM evaluation beyond the state-of-the-art by investing in routine benchmarking of physical and biogeochemical properties of ESMs, and a process-oriented evaluation. To support routine model evaluation, the Earth System Model Evaluation Tool (ESMValTool) is developed jointly with international partners. The ability to routinely evaluate complex ESMs with a wide range of diagnostics, performance metrics and observations will contribute to improve the quality of ESMs substantially on the long-term. Other research topics that are investigated are the identification of processes that are most important for climate projections (emergent constraints) and the predictability of decadal climate simulations.
As basis for the model evaluation, simulations with the global atmosphere-chemistry model EMAC (ECHAM/MESSy Atmospheric Chemistry) are used. To increase the robustness of the results and to put the DLR model results into the context of international research and other models, additional simulations from other ESMs are evaluated, in particular simulations submitted to the Coupled Model Intercomparison Project (CMIP) organized under the World Climate Research Programme WCRP). CMIP in its 6th phase is coordinated by DLR Institute of Atmospheric Physics with other partners and provides with its model archive and related scientific analyses a major contribution to the Intergovernmental Panel on Climate Change (IPCC) climate assessment reports.