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| Titel |
Reconstruction of a continuous high-resolution CO2 record over the past 20 million years |
| VerfasserIn |
R. S. W. Wal, B. Boer, L. J. Lourens, P. Köhler, R. Bintanja |
| 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 ; 7, no. 4 ; Nr. 7, no. 4 (2011-12-21), S.1459-1469 |
| Datensatznummer |
250004700
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| Publikation (Nr.) |
 copernicus.org/cp-7-1459-2011.pdf |
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| Zusammenfassung |
| The gradual cooling of the climate during the Cenozoic has generally been
attributed to a decrease in CO2 concentration in the atmosphere. The
lack of transient climate models and, in particular, the lack of
high-resolution proxy records of CO2, beyond the ice-core record
prohibit, however, a full understanding of, for example, the inception of the
Northern Hemisphere glaciation and mid-Pleistocene transition. Here we
elaborate on an inverse modelling technique to reconstruct a continuous
CO2 series over the past 20 million year (Myr), by decomposing the
global deep-sea benthic δ18O record into a mutually consistent
temperature and sea level record, using a set of 1-D models of the major
Northern and Southern Hemisphere ice sheets. We subsequently compared the
modelled temperature record with ice core and proxy-derived CO2 data to
create a continuous CO2 reconstruction over the past 20 Myr. Results
show a gradual decline from 450 ppmv around 15 Myr ago to 225 ppmv for mean
conditions of the glacial-interglacial cycles of the last 1 Myr, coinciding
with a gradual cooling of the global surface temperature of 10 K. Between 13
to 3 Myr ago there is no long-term sea level variation caused by ice-volume
changes. We find no evidence of change in the long-term relation between
temperature change and CO2, other than the effect following the
saturation of the absorption bands for CO2. The reconstructed CO2
record shows that the Northern Hemisphere glaciation starts once the
long-term average CO2 concentration drops below 265 ppmv after a period
of strong decrease in CO2. Finally, only a small long-term decline of
23 ppmv is found during the mid-Pleistocene transition, constraining
theories on this major transition in the climate system. The approach is not
accurate enough to revise current ideas about climate sensitivity. |
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