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| Titel |
Investigating vegetation-climate feedbacks during the early Eocene |
| VerfasserIn |
C. A. Loptson, D. J. Lunt, J. E. Francis |
| 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 ; 10, no. 2 ; Nr. 10, no. 2 (2014-03-07), S.419-436 |
| Datensatznummer |
250116930
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| Publikation (Nr.) |
 copernicus.org/cp-10-419-2014.pdf |
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| Zusammenfassung |
Evidence suggests that the early Eocene was a time of extreme global warmth.
However, there are discrepancies between the
results of many previous modelling studies and the proxy data at high
latitudes, with models struggling to simulate the shallow temperature
gradients of this time period to the same extent as the proxies indicate.
Vegetation–climate feedbacks play an important role in the present day, but
are often neglected in these palaeoclimate modelling studies, and this may be a
contributing factor to resolving the model–data discrepancy.
Here we investigate these vegetation–climate feedbacks by carrying out
simulations of the early Eocene climate at 2 × and 4 ×
pre-industrial atmospheric CO2 with fixed vegetation (homogeneous shrubs
everywhere) and dynamic vegetation.
The results show that the simulations with dynamic vegetation are warmer in
the global annual mean than the simulations with fixed shrubs by
0.9 °C at 2 × and 1.8 °C at
4 ×. Consequently, the warming when CO2 is doubled from
2 × to 4 × is 1 °C higher (in the global
annual mean) with dynamic vegetation than with fixed shrubs. This corresponds
to an increase in climate sensitivity of 26%. This difference in warming
is enhanced at high latitudes, with temperatures increasing by over 50% in
some regions of Antarctica. In the Arctic, ice–albedo feedbacks are
responsible for the majority of this warming. On a global scale, energy
balance analysis shows that the enhanced warming with dynamic vegetation is
mainly associated with an increase in atmospheric water vapour but changes in
clouds also contribute to the temperature increase. It is likely that changes
in surface albedo due to changes in vegetation cover resulted in an initial
warming which triggered these water vapour feedbacks.
In conclusion, dynamic vegetation goes some way to resolving the discrepancy,
but our modelled temperatures cannot reach the same warmth as the data
suggest in the Arctic. This suggests that there are additional mechanisms,
not included in this modelling framework, behind the polar warmth or that the
proxies have been misinterpreted. |
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