Regional climate change projections from NA-CORDEX and their relation to climate sensitivity
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Regional climate change projections from NA-CORDEX and their relation to climate sensitivity Melissa S. Bukovsky 1
& Linda O. Mearns
1
Received: 11 December 2019 / Accepted: 12 August 2020/ # The Author(s) 2020
Abstract
The climate sensitivity of global climate models (GCMs) strongly influences projected climate change due to increased atmospheric carbon dioxide. Reasonably, the climate sensitivity of a GCM may be expected to affect dynamically downscaled projections. However, there has been little examination of the effect of the climate sensitivity of GCMs on regional climate model (RCM) ensembles. Therefore, we present projections of temperature and precipitation from the ensemble of projections produced as a part of the North American branch of the international Coordinated Regional Downscaling Experiment (NA-CORDEX) in the context of their relationship to the climate sensitivity of their parent GCMs. NA-CORDEX simulations were produced at 50-km and 25-km resolutions with multiple RCMs which downscaled multiple GCMs that spanned nearly the full range of climate sensitivity available in the CMIP5 archive. We show that climate sensitivity is a very important source of spread in the NA-CORDEX ensemble, particularly for temperature. Temperature projections correlate with driving GCM climate sensitivity annually and seasonally across North America not only at a continental scale but also at a local-to-regional scale. Importantly, the spread in temperature projections would be reduced if only low, mid, or high climate sensitivity simulations were considered, or if only the ensemble mean were considered. Precipitation projections correlate with climate sensitivity, but only at a continental scale during the cold season, due to the increasing influence of other processes at finer scales. Additionally, it is shown that the RCMs do alter the projection space sampled by their driving GCMs. Keywords Projections . Climate sensitivity . Uncertainty . Regional climate modeling . North America . CORDEX
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10584-02002835-x) contains supplementary material, which is available to authorized users.
* Melissa S. Bukovsky [email protected]
1
National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307, USA
Climatic Change
1 Introduction This study aims to examine the ensemble of projections produced as a part of the North American branch of the international Coordinated Regional Downscaling Experiment (NACORDEX) in the context of their relationship to the climate sensitivity of the global climate models (GCMs) used as forcing for this regional climate model (RCM) ensemble. We present basic projections for the most commonly used variables, near-surface temperature and precipitation, for North America and 30 sub-regions. NA-CORDEX samples nearly the full range of climate sensitivity found in the Coupled Model Intercomparison Program Phase 5 (CMIP5) archive. Climate sensitivity, a measure of the global mean temperature
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