Settled science update from Gavin Schmidt: "relatively little is understood about the reasons for the observed warmth" of the mid-Pliocene

Pubs.GISS: Lunt et al. 2012: On the causes of mid-Pliocene warmth and polar amplification

Lunt, D.J., A.M. Haywood, G.A. Schmidt, U. Salzmann, P.J. Valdes, H.J. Dowsett, and C.A. Loptson, 2012: On the causes of mid-Pliocene warmth and polar amplification. Earth Planet. Sci. Lett., 321-322, 128-138, doi:10.1016/j.epsl.2011.12.042.

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.