Publikationsdatum:
2009-07-13
Beschreibung:
The Palaeocene-Eocene Thermal Maximum (about 55 Myr ago) represents a possible analogue for the future and thus may provide insight into climate system sensitivity and feedbacks. The key feature of this event is the release of a large mass of 13 C-depleted carbon into the carbon reservoirs at the Earths surface, although the source remains an open issue. Concurrently, global surface temperatures rose by 5-9 C within a few thousand years. Here we use published palaeorecords of deep-sea carbonate dissolution and stable carbon isotope composition along with a carbon cycle model to constrain the initial carbon pulse to a magnitude of 3,000 Pg C or less, with an isotopic composition lighter than 50. As a result, atmospheric carbon dioxide concentrations increased during the main event by less than about 70% compared with pre-event levels. At accepted values for the climate sensitivity to a doubling of the atmospheric CO 2 concentration, this rise in CO 2 can explain only between 1 and 3.5 C of the warming inferred from proxy records. We conclude that in addition to direct CO 2 forcing, other processes and/or feedbacks that are hitherto unknown must have caused a substantial portion of the warming during the Palaeocene-Eocene Thermal Maximum. Once these processes have been identified, their potential effect on future climate change needs to be taken into account. © 2009 Macmillan Publishers Limited.
Print ISSN:
1752-0894
Digitale ISSN:
1752-0908
Thema:
Geologie und Paläontologie
