Change search
ReferencesLink to record
Permanent link

Direct link
State-dependent climate sensitivity in past warm climates and its implications for future climate projections
Stockholm University, Faculty of Science, Department of Meteorology .
2013 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 110, no 35, 14162-14167 p.Article in journal (Refereed) Published
Abstract [en]

Projections of future climate depend critically on refined estimates of climate sensitivity. Recent progress in temperature proxies dramatically increases the magnitude of warming reconstructed from early Paleogene greenhouse climates and demands a close examination of the forcing and feedback mechanisms that maintained this warmth and the broad dynamic range that these paleoclimate records attest to. Here, we show that several complementary resolutions to these questions are possible in the context of model simulations using modern and early Paleogene configurations. We find that (i) changes in boundary conditions representative of slow Earth system feedbacks play an important role in maintaining elevated early Paleogene temperatures, (ii) radiative forcing by carbon dioxide deviates significantly from pure logarithmic behavior at concentrations relevant for simulation of the early Paleogene, and (iii) fast or Charney climate sensitivity in this model increases sharply as the climate warms. Thus, increased forcing and increased slow and fast sensitivity can all play a substantial role in maintaining early Paleogene warmth. This poses an equifinality problem: The same climate can be maintained by a different mix of these ingredients; however, at present, the mix cannot be constrained directly from climate proxy data. The implications of strongly state-dependent fast sensitivity reach far beyond the early Paleogene. The study of past warm climates may not narrow uncertainty in future climate projections in coming centuries because fast climate sensitivity may itself be state-dependent, but proxies and models are both consistent with significant increases in fast sensitivity with increasing temperature.

Place, publisher, year, edition, pages
2013. Vol. 110, no 35, 14162-14167 p.
Keyword [en]
superrotation, hyperthermal
National Category
Meteorology and Atmospheric Sciences
URN: urn:nbn:se:su:diva-94035DOI: 10.1073/pnas.1303365110ISI: 000323564600026OAI: diva2:651669


Available from: 2013-09-26 Created: 2013-09-24 Last updated: 2013-09-26Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Caballero, Rodrigo
By organisation
Department of Meteorology
In the same journal
Proceedings of the National Academy of Sciences of the United States of America
Meteorology and Atmospheric Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 105 hits
ReferencesLink to record
Permanent link

Direct link