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| Titel |
Global sensitivity analysis of the climate–vegetation system to astronomical forcing: an emulator-based approach |
| VerfasserIn |
N. Bounceur, M. Crucifix, R. D. Wilkinson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2190-4979
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| Digitales Dokument |
URL |
| Erschienen |
In: Earth System Dynamics ; 6, no. 1 ; Nr. 6, no. 1 (2015-05-04), S.205-224 |
| Datensatznummer |
250115421
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| Publikation (Nr.) |
 copernicus.org/esd-6-205-2015.pdf |
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| Zusammenfassung |
| A global sensitivity analysis is performed to describe the effects
of astronomical forcing on the climate–vegetation system simulated
by the model of intermediate complexity LOVECLIM in interglacial
conditions. The methodology relies on the estimation of sensitivity
measures, using a Gaussian process emulator as a fast surrogate of
the climate model, calibrated on a set of well-chosen experiments.
The outputs considered are the annual mean temperature and
precipitation and the growing degree days (GDD). The experiments
were run on two distinct land surface schemes to estimate the
importance of vegetation feedbacks on climate variance. This
analysis provides a spatial description of the variance due to the
factors and their combinations, in the form of "fingerprints"
obtained from the covariance indices. The results are broadly
consistent with the current under-standing of Earth's climate response
to the astronomical forcing. In particular, precession and obliquity
are found to contribute in LOVECLIM equally to GDD in the Northern
Hemisphere, and the effect of obliquity on the response of Southern
Hemisphere temperature dominates precession effects. Precession
dominates precipitation changes in subtropical areas. Compared to
standard approaches based on a small number of simulations, the
methodology presented here allows us to identify more systematically
regions susceptible to experiencing rapid climate change in response
to the smooth astronomical forcing change. In particular, we find
that using interactive vegetation significantly enhances the expected
rates of climate change, specifically in the Sahel (up to 50%
precipitation change in 1000 years) and in the Canadian Arctic
region (up to 3° in 1000 years). None of the tested
astronomical configurations were found to induce multiple steady
states, but, at low obliquity, we observed the development of an
oscillatory pattern that has already been reported in LOVECLIM.
Although the mathematics of the analysis are fairly straightforward,
the emulation approach still requires considerable care in its
implementation. We discuss the effect of the choice of length scales and
the type of emulator, and estimate uncertainties associated with
specific computational aspects, to conclude that the principal
component emulator is a good option for this kind of application. |
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