The relative roles of CO2 and palaeogeography in determining late Miocene climate: results from a terrestrial model–data comparison
- 1Bristol Research Initiative for the Dynamic Global Environment (BRIDGE), School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK
- 2School of the Built and Natural Environment, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
- 3School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
- 4British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG,UK
- 5Department of Geosciences and Geography, P.O. Box 64, 00014, University of Helsinki, Finland
- 6Biodiversity and Climate Research Centre LOEWE BiK-F, Senckenberganlage 25, 60325 Frankfurt am Main, Germany
Abstract. The late Miocene palaeorecord provides evidence for a warmer and wetter climate than that of today, and there is uncertainty in the palaeo-CO2 record of at least 200 ppm. We present results from fully coupled atmosphere-ocean-vegetation simulations for the late Miocene that examine the relative roles of palaeogeography (topography and ice sheet geometry) and CO2 concentration in the determination of late Miocene climate through comprehensive terrestrial model-data comparisons. Assuming that these data accurately reflect the late Miocene climate, and that the late Miocene palaeogeographic reconstruction used in the model is robust, then results indicate that:
1. Both palaeogeography and atmospheric CO2 contribute to the proxy-derived precipitation differences between the late Miocene and modern reference climates. However these contributions exibit synergy and so do not add linearly.
2. The vast majority of the proxy-derived temperature differences between the late Miocene and modern reference climates can only be accounted for if we assume a palaeo-CO2 concentration towards the higher end of the range of estimates.