Abstract
High resolution climate information is critical for the vulnerability, impacts, adaptation, and climate services communities (VIACS). Coordinated ensembles generated by initiatives like CORDEX provide consistent and comparable information for the present and future over all land areas of the globe. This manuscript focuses on the European CORDEX initiative (hereafter EURO-CORDEX), and its coordinated effort to build regional climate ensembles for the years to come. In its first phase, EURO-CORDEX produced a rich ensemble of regional climate simulations under different representative concentration pathway scenarios. The EURO-CORDEX dataset is openly available and was fed into the Regional Atlas of 6th IPCC Assessment Report. However, this ensemble suffered from several shortcomings, which the community seeks to address in the next phase of production. Chief among these is the oft cited criticism that the selection of GCMs that provide input to the regional climate models was not rigorous and that the resulting ensemble represents an “ensemble of opportunity”. The present paper provides a description of how the community has addressed these shortcomings. We present a comprehensive, flexible and traceable evaluation framework and toolkit for assessing the suitability of GCMs for downscaling, using EURO-CORDEX as an example. Its value lies in its explicit recognition of subjectivity and mechanisms implemented to transparently track decision making. Further, the utility of the framework extends well beyond pre-downscaling decisions to also include post-downscaling investigations performed by the VIACS communities and beyond, to include researchers investigating such topics as model biases, future constraints and exploring future storylines.
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