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| Titel |
Past temperature reconstructions from deep ice cores: relevance for future climate change |
| VerfasserIn |
V. Masson-Delmotte, G. Dreyfus, P. Braconnot, S. Johnsen, J. Jouzel, M. Kageyama, A. Landais, M.-F. Loutre, J. Nouet, F. Parrenin, D. Raynaud, B. Stenni, E. Tuenter |
| 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 ; 2, no. 2 ; Nr. 2, no. 2 (2006-10-26), S.145-165 |
| Datensatznummer |
250000501
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| Publikation (Nr.) |
 copernicus.org/cp-2-145-2006.pdf |
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| Zusammenfassung |
Ice cores provide unique archives of past climate and environmental changes
based only on physical processes. Quantitative temperature reconstructions
are essential for the comparison between ice core records and climate
models. We give an overview of the methods that have been developed to reconstruct
past local temperatures from deep ice cores and highlight several points that are
relevant for future climate change.
We first analyse the long term fluctuations of temperature as depicted
in the long Antarctic record from EPICA Dome C. The long term imprint of
obliquity changes in the EPICA Dome C record is highlighted and compared to
simulations conducted with the ECBILT-CLIO intermediate complexity climate
model. We discuss the comparison between the current interglacial period and
the long interglacial corresponding to marine isotopic stage 11, ~400
kyr BP. Previous studies had focused on the role of precession and the
thresholds required to induce glacial inceptions. We suggest that, due to
the low eccentricity configuration of MIS 11 and the Holocene, the effect of
precession on the incoming solar radiation is damped and that changes in
obliquity must be taken into account. The EPICA Dome C alignment of
terminations I and VI published in 2004 corresponds to a phasing of the
obliquity signals. A conjunction of low obliquity and minimum northern
hemisphere summer insolation is not found in the next tens of thousand
years, supporting the idea of an unusually long interglacial ahead.
As a second point relevant for future climate change, we discuss the
magnitude and rate of change of past temperatures reconstructed from
Greenland (NorthGRIP) and Antarctic (Dome C) ice cores. Past episodes of
temperatures above the present-day values by up to 5°C are recorded at
both locations during the penultimate interglacial period. The rate of polar
warming simulated by coupled climate models forced by a CO2 increase of 1%
per year is compared to ice-core-based temperature reconstructions. In
Antarctica, the CO2-induced warming lies clearly beyond the natural
rhythm of temperature fluctuations. In Greenland, the CO2-induced
warming is as fast or faster than the most rapid temperature shifts of the
last ice age. The magnitude of polar temperature change in response to a
quadrupling of atmospheric CO2 is comparable to the magnitude of the
polar temperature change from the Last Glacial Maximum to present-day. When
forced by prescribed changes in ice sheet reconstructions and CO2
changes, climate models systematically underestimate the
glacial-interglacial polar temperature change. |
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