On the causes of mid-Pliocene warmth and polar amplification

Daniel J. Lunt*, Alan M. Haywood, Gavin A. Schmidt, Ulrich Salzmann, Paul J. Valdes, Harry J. Dowsett, Claire A. Loptson

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

78 Citations (Scopus)


The mid-Pliocene (~3 to 3.3Ma ago), is a period of sustained global warmth in comparison to the late Quaternary (0 to ~1Ma 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 CO 2, 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 CO 2. 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 CO 2 and orographic changes, to derive uncertainty ranges for the various contributing processes. © 2012 Elsevier B.V.

Translated title of the contributionOn the causes of mid-Pliocene warmth and polar amplification
Original languageEnglish
Pages (from-to)128-138
Number of pages11
JournalEarth and Planetary Science Letters
Publication statusPublished - 1 Mar 2012


  • Mid-Pliocene
  • Paleoclimate modelling
  • Polar amplification


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