1Earth and Atmospheric Sciences Department, Purdue University, West Lafayette, Indiana, USA
2Department of Meteorology and Bert Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
Received: 19 Dec 2010 – Published in Clim. Past Discuss.: 18 Jan 2011
Abstract. The early Eocene "equable climate problem", i.e. warm extratropical annual mean and above-freezing winter temperatures evidenced by proxy records, has remained as one of the great unsolved problems in paleoclimate. Recent progress in modeling and in paleoclimate proxy development provides an opportunity to revisit this problem to ascertain if the current generation of models can reproduce the past climate features without extensive modification. Here we have compiled early Eocene terrestrial temperature data and compared with climate model results using a consistent and rigorous methodology. We test the hypothesis that equable climates can be explained simply as a response to increased greenhouse gas forcing within the framework of the atmospheric component of the Community Climate System Model (version 3), a climate model in common use for predicting future climate change. We find that, with suitably large radiative forcing, the model and data are in general agreement for annual mean and cold month mean temperatures, and that the pattern of high latitude amplification recorded by proxies can be largely, but not perfectly, reproduced.
Revised: 15 May 2011 – Accepted: 17 May 2011 – Published: 16 Jun 2011
Huber, M. and Caballero, R.: The early Eocene equable climate problem revisited, Clim. Past, 7, 603-633, doi:10.5194/cp-7-603-2011, 2011.