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| Titel |
The CSIRO Mk3L climate system model version 1.0 – Part 2: Response to external forcings |
| VerfasserIn |
S. J. Phipps, L. D. Rotstayn, H. B. Gordon, J. L. Roberts, A. C. Hirst, W. F. Budd |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 5, no. 3 ; Nr. 5, no. 3 (2012-05-14), S.649-682 |
| Datensatznummer |
250002611
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| Publikation (Nr.) |
 copernicus.org/gmd-5-649-2012.pdf |
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| Zusammenfassung |
The CSIRO Mk3L climate system model is a coupled general circulation
model, designed primarily for millennial-scale climate simulation
and palaeoclimate research. Mk3L includes components which describe
the atmosphere, ocean, sea ice and land surface, and combines
computational efficiency with a stable and realistic control
climatology. It is freely available to the research community. This
paper evaluates the response of the model to external forcings which
correspond to past and future changes in the climate system.
A simulation of the mid-Holocene climate is performed, in which
changes in the seasonal and meridional distribution of incoming
solar radiation are imposed. Mk3L correctly simulates increased
summer temperatures at northern mid-latitudes and cooling in the
tropics. However, it is unable to capture some of the regional-scale
features of the mid-Holocene climate, with the precipitation over
Northern Africa being deficient. The model simulates a reduction of
between 7 and 15% in the amplitude of El Niño-Southern
Oscillation, a smaller decrease than that implied by the
palaeoclimate record. However, the realism of the simulated ENSO is
limited by the model's relatively coarse spatial resolution.
Transient simulations of the late Holocene climate are then
performed. The evolving distribution of insolation is imposed, and
an acceleration technique is applied and assessed. The model
successfully captures the temperature changes in each hemisphere and
the upward trend in ENSO variability. However, the lack of a dynamic
vegetation scheme does not allow it to simulate an abrupt
desertification of the Sahara.
To assess the response of Mk3L to other forcings, transient
simulations of the last millennium are performed. Changes in solar
irradiance, atmospheric greenhouse gas concentrations and volcanic
emissions are applied to the model. The model is again broadly
successful at simulating larger-scale changes in the climate
system. Both the magnitude and the spatial pattern of the simulated
20th century warming are consistent with observations. However, the
model underestimates the magnitude of the relative warmth associated
with the Mediaeval Climate Anomaly.
Finally, three transient simulations are performed, in which the
atmospheric CO2 concentration is stabilised at two, three
and four times the pre-industrial value. All three simulations
exhibit ongoing surface warming, reduced sea ice cover, and
a reduction in the rate of North Atlantic Deep Water formation
followed by its gradual recovery. Antarctic Bottom Water formation
ceases, with the shutdown being permanent for a trebling and
quadrupling of the CO2 concentration. The transient and
equilibrium climate sensitivities of the model are determined. The
short-term transient response to a doubling of the CO2
concentration at 1% per year is a warming of 1.59 ± 0.08 K,
while the long-term equilibrium response is a warming of at least
3.85 ± 0.02 K. |
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