Abstract
Abstract. The Earth System Model Evaluation Tool (ESMValTool), a community diagnostics and performance metrics tool for evaluation and analysis of Earth system models (ESMs), is designed to facilitate a more comprehensive and rapid comparison of single or multiple models participating in the Coupled Model Intercomparison Project (CMIP). The ESM results can be compared against observations or reanalysis data as well as against other models including predecessor versions of the same model. The updated and extended version (v2.0) of the ESMValTool includes several new analysis scripts such as large-scale diagnostics for evaluation of ESMs as well as diagnostics for extreme events, regional model and impact evaluation. In this paper, the newly implemented climate metrics such as effective climate sensitivity (ECS) and transient climate response (TCR) as well as emergent constraints for various climate-relevant feedbacks and diagnostics for future projections from ESMs are described and illustrated with examples using results from the well-established model ensemble CMIP5. The emergent constraints implemented include constraints on ECS, snow-albedo effect, climate–carbon cycle feedback, hydrologic cycle intensification, future Indian summer monsoon precipitation and year of disappearance of summer Arctic sea ice. The diagnostics included in ESMValTool v2.0 to analyze future climate projections from ESMs further include analysis scripts to reproduce selected figures of chapter 12 of the Intergovernmental Panel on Climate Change's (IPCC) Fifth Assessment Report (AR5) and various multi-model statistics.
Highlights
Climate models are important tools to improve our understanding of the key processes in present-day climate and to project future climate change under different plausible scenarios
As part of a series of four articles describing the new features and diagnostics of the Earth System Model Evaluation Tool v2.0, this paper focuses on the newly included diagnostics for emergent constraints and for analysis of future projections from Earth system models (ESMs) as well as multi-model products (Sect. 3.1) and the two new climate metrics: effective climate sensitivity (ECS) and transient climate response (TCR) (Sect. 3.2)
The open-source release of ESMValTool (v2.0) that accompanies this paper is intended to work with CMIP5 and CMIP6 model output, but the tool is compatible with any arbitrary model output, provided that it is in CFcompliant (CF: Climate and Forecast; http://cfconventions. org/, last access: 18 June 2020) NetCDF format and that the variables and metadata are following the CMOR (Climate Model Output Rewriter; https://pcmdi.github. io/cmor-site/media/pdf/cmor_users_guide.pdf, last access: 18 June 2020) tables and definitions
Summary
Climate models are important tools to improve our understanding of the key processes in present-day climate and to project future climate change under different plausible scenarios. The increasing complexity of the models is needed to represent key feedbacks that affect climate change but is likely to increase the spread of climate projections across the multi-model ensemble (Eyring et al, 2019) This poses a challenge for evaluation and analysis of the model results that requires efficient tools able to handle the increasing number of variables, processes and the increasing data volume. A. Lauer et al.: Earth System Model Evaluation Tool (ESMValTool) v2.0 ferent ESM components, providing well-documented source code and scientific background of implemented diagnostics and metrics and allowing for traceability and reproducibility of results (provenance). Lauer et al.: Earth System Model Evaluation Tool (ESMValTool) v2.0 ferent ESM components, providing well-documented source code and scientific background of implemented diagnostics and metrics and allowing for traceability and reproducibility of results (provenance) This has been made possible by a lively and growing development community continuously improving the tool supported by multiple national and European projects. The aim of this paper is to document and illustrate how these newly added ESMValTool “recipes”, i.e., configuration files defining input, preprocessing, diagnostics and run-time options of the ESMValTool, can be used for model evaluation and analysis
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