On the causes of mid-Pliocene warmth and polar amplification

Lunt, Daniel, Haywood, Alan, Schmidt, Gavin, Salzmann, Ulrich, Valdes, Paul, Dowsett, Harry and Loptson, Claire (2012) On the causes of mid-Pliocene warmth and polar amplification. Earth and Planetary Science Letters, 321-32. pp. 128-138. ISSN 0012-821X

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Abstract

The mid-Pliocene (~ 3 to 3.3 Ma ago), is a period of sustained global warmth in comparison to the late Quaternary (0 to ~ 1 Ma ago), and has potential to inform predictions of long-term future climate change. However, given that several processes potentially contributed, relatively little is understood about the reasons for the observed warmth, or the associated polar amplification. Here, using a modelling approach and a novel factorisation method, we assess the relative contributions to mid-Pliocene warmth from: elevated CO2, lowered orography, and vegetation and ice sheet changes. The results show that on a global scale, the largest contributor to mid-Pliocene warmth is elevated CO2. However, in terms of polar amplification, changes to ice sheets contribute significantly in the Southern Hemisphere, and orographic changes contribute significantly in the Northern Hemisphere. We also carry out an energy balance analysis which indicates that that on a global scale, surface albedo and atmospheric emmissivity changes dominate over cloud changes. We investigate the sensitivity of our results to uncertainties in the prescribed CO2 and orographic changes, to derive uncertainty ranges for the various contributing processes.

Item Type:	Article
Uncontrolled Keywords:	mid-Pliocene, polar amplification, paleoclimate modelling
Subjects:	F800 Physical and Terrestrial Geographical and Environmental Sciences F900 Others in Physical Sciences
Department:	Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User:	Ellen Cole
Date Deposited:	20 Dec 2012 15:06
Last Modified:	13 Oct 2019 00:32
URI:	http://nrl.northumbria.ac.uk/id/eprint/10652

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