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| Titel |
Emulating coupled atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6 – Part 1: Model description and calibration |
| VerfasserIn |
M. Meinshausen, S. C. B. Raper, T. M. L. Wigley |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 4 ; Nr. 11, no. 4 (2011-02-16), S.1417-1456 |
| Datensatznummer |
250009357
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| Publikation (Nr.) |
 copernicus.org/acp-11-1417-2011.pdf |
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| Zusammenfassung |
| Current scientific knowledge on the future response of the climate
system to human-induced perturbations is comprehensively captured by
various model intercomparison efforts. In the preparation of the
Fourth Assessment Report (AR4) of the Intergovernmental Panel on
Climate Change (IPCC), intercomparisons were organized for
atmosphere-ocean general circulation models (AOGCMs) and carbon
cycle models, named "CMIP3" and "C4MIP", respectively. Despite
their tremendous value for the scientific community and policy
makers alike, there are some difficulties in interpreting the
results. For example, radiative forcings were not standardized
across the various AOGCM integrations and carbon cycle runs, and, in
some models, key forcings were omitted. Furthermore, the AOGCM
analysis of plausible emissions pathways was restricted to only
three SRES scenarios. This study attempts to address these issues.
We present an updated version of MAGICC, the simple carbon
cycle-climate model used in past IPCC Assessment Reports with
enhanced representation of time-varying climate sensitivities,
carbon cycle feedbacks, aerosol forcings and ocean heat uptake
characteristics. This new version, MAGICC6, is successfully
calibrated against the higher complexity AOGCMs and carbon cycle
models. Parameterizations of MAGICC6 are provided. The mean of the
emulations presented here using MAGICC6 deviates from the mean AOGCM
responses by only 2.2% on average for the SRES scenarios. This
enhanced emulation skill in comparison to previous calibrations is
primarily due to: making a "like-with-like comparison" using
AOGCM-specific subsets of forcings; employing a new calibration
procedure; as well as the fact that the updated simple climate model
can now successfully emulate some of the climate-state dependent
effective climate sensitivities of AOGCMs. The diagnosed
effective climate sensitivity at the time of CO2 doubling for the
AOGCMs is on average 2.88 °C, about 0.33 °C cooler than the
mean of the reported slab ocean climate sensitivities. In the
companion paper (Part 2) of this study, we examine the combined
climate system and carbon cycle emulations for the complete range of
IPCC SRES emissions scenarios and the new RCP pathways. |
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