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| Titel |
Does Antarctic glaciation cool the world? |
| VerfasserIn |
A. Goldner, M. Huber, R. Caballero |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 9, no. 1 ; Nr. 9, no. 1 (2013-01-24), S.173-189 |
| Datensatznummer |
250017431
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| Publikation (Nr.) |
 copernicus.org/cp-9-173-2013.pdf |
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| Zusammenfassung |
In this study, we compare the simulated climatic impact of adding an
Antarctic ice sheet (AIS) to the "greenhouse world" of the Eocene and
removing the AIS from the modern world. The modern global mean surface
temperature anomaly (ΔT) induced by Antarctic Glaciation depends on
the background CO2 levels and ranges from −1.22 to −0.18 K. The
Eocene ΔT is nearly constant at ~−0.25 K. We
calculate an climate sensitivity parameter S[Antarctica] which
we define as ΔT divided by the change in effective radiative forcing
(ΔQAntarctica) which includes some fast feedbacks imposed
by prescribing the glacial properties of Antarctica.
The main difference between the modern and Eocene responses is that a
negative cloud feedback warms much of the Earth's surface as a large AIS is
introduced in the Eocene, whereas this cloud feedback is weakly positive and
acts in combination with positive sea-ice feedbacks to enhance cooling
introduced by adding an ice sheet in the modern. Because of the importance of
cloud feedbacks in determining the final temperature sensitivity of the AIS,
our results are likely to be model dependent. Nevertheless, these model
results suggest that the effective radiative forcing and feedbacks induced by
the AIS did not significantly decrease global mean surface temperature across
the Eocene–Oligocene transition (EOT −34.1 to 33.6 Ma) and that other
factors like declining atmospheric CO2 are more important for cooling
across the EOT. The results illustrate that the efficacy of AIS forcing in
the Eocene is not necessarily close to one and is likely to be model and
state dependent. This implies that using EOT paleoclimate proxy data by
itself to estimate climate sensitivity for future climate prediction requires
climate models and consequently these estimates will have large uncertainty,
largely due to uncertainties in modelling low clouds. |
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