On the differences between two semi-empirical sea-level models for the last two millennia
M. Vermeer1, S. Rahmstorf2, A. Kemp3, and B. Horton41Department of Real Estate, Planning and Geoinformatics, School of Engineering, Aalto University, P.O. Box 11200, 00076 Aalto, Finland 2Potsdam Institute for Climate Impact Research, Telegrafenberg A62, 14473 Potsdam, Germany 3School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, USA 4Sea Level Research Laboratory, Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104, USA
Received: 24 Jul 2012 – Accepted for review: 25 Jul 2012 – Discussion started: 14 Aug 2012
Abstract. We compare hindcasts of global mean sea level over the past millennium obtained using two semi-empirical models linking temperature and sea-level rise. The models differ in that one of them includes a term for a very long-term sea-level rise component unfolding over many millennia. On short (century) time scales, both models give very similar results.
Proxy sea-level reconstructions from the northern (North Carolina) and southern (New Zealand and Tasmania) hemispheres are used to test the ability of both models to reproduce the longer-term sea-level evolution. In both comparisons the model including the second term produces a markedly better fit from 1000 AD to the present.
When both models are used for generating sea-level projections, they behave similarly out to 2100 AD. Further out, to 2300–2500 AD, the projections differ significantly, in no small part due to different values for the sea-level response time scale τ obtained. We conclude that careful model validation on long time scales is important before attempting multi-century projections.
Vermeer, M., Rahmstorf, S., Kemp, A., and Horton, B.: On the differences between two semi-empirical sea-level models for the last two millennia, Clim. Past Discuss., 8, 3551-3581, doi:10.5194/cpd-8-3551-2012, 2012.