Uncertainties in climate change projections covered by the ISIMIP and CORDEX model subsets from CMIP5
<p>Two international projects, ISIMIP (Inter-Sectoral Impact Model Intercomparison Project) and CORDEX (Coordinated Regional Climate Downscaling Experiment), have been established to assess the impacts of global climate change and improve our understanding of regional climate respectively. Mod...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-03-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://www.geosci-model-dev.net/13/859/2020/gmd-13-859-2020.pdf |
| Summary: | <p>Two international projects, ISIMIP (Inter-Sectoral Impact
Model Intercomparison Project) and CORDEX (Coordinated Regional Climate
Downscaling Experiment), have been established to assess the impacts of
global climate change and improve our understanding of regional climate
respectively. Model selection from the GCMs (general circulation models)
within CMIP5 (fifth phase of the Coupled Model Intercomparison Project) was
conducted using the different approaches for each project: one is a globally
consistent model subset used in ISIMIP and the other is a region-specific
model subset for each region of interest used in CORDEX. We evaluated the
ability to reproduce the regional climatological state by comparing the
subsets with the full set of CMIP5 multimodel ensemble. We also investigated
how well the subsets captured the uncertainty in the climate change
projected by the full set, to increase credibility for the
scientific outcomes from each project. The spreads of the biases and
Taylor's skill scores from the ISIMIP and CORDEX subsets are smaller than
that from the full set for the regional means of surface air temperature and
precipitation. However, the ISIMIP and CORDEX subsets show the larger spread
than high-performance models from the full set, despite using a small number
of models in ISIMIP and CORDEX. It was shown that better subsets exist that
would have smaller biases and/or higher scores than the current subset. The
ISIMIP subset captures the uncertainty range of the regional mean of
temperature change projections by the full set better than the CORDEX
subsets in 10 of 14 terrestrial regions worldwide. Compared with 10 000
randomly selected subset samples, the CORDEX subset shows low coverage of
the uncertainty for the temperature change projections in some regions, and
the ISIMIP subset shows high coverage in all regions. On the other hand, for the
precipitation change projections, the CORDEX subsets show lower coverage in
half of the regions than the randomly selected subsets, but tend to cover
the uncertainty wider than the ISIMIP subset. In the regions where CORDEX
used nine models or more, good coverage (<span class="inline-formula">>50</span> %) is evident for
the projections of both temperature and precipitation. The globally
consistent model subset used in ISIMIP could have difficulty in capturing
uncertainties in the regional precipitation change projections, whereas it
widely covers uncertainties in the temperature change projections. The
region-specific model subset, like CORDEX, can cover the uncertainties in
both temperature and precipitation changes well compared to the global
common subset, but a large number of models is needed. By changing the
number of models from the current ensemble members to at least nine members,
high coverage for both uncertainties can be also obtained in the other
regions, and this information would help model selection in the next
generations.</p> |
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| ISSN: | 1991-959X 1991-9603 |