On the causes of mid-Pliocene warmth and polar amplification

Earth and Planetary Science Letters
By: , and 



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.
Publication type Article
Publication Subtype Journal Article
Title On the causes of mid-Pliocene warmth and polar amplification
Series title Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2011.12.042
Volume 321-322
Year Published 2012
Language English
Publisher Elsevier
Contributing office(s) Eastern Geology and Paleoclimate Science Center
Description 11 p.
First page 128
Last page 138
Additional Online Files (Y/N) N
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