Extending the history of atmospheric CH 4 concentrations back to 650 kyr ago European Geosciences Union European Geosciences Union General Assembly 2005 Vienna, Austria, April 2005 R. Spahni 1, J. Chappellaz 2, G. Hausammann 1, L. Loulergue 2, T. F. Stocker 1, J. Jouzel 3 (1) Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland (2) Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE, CNRS-UJF), Grenoble, France (3) Laboratoire des Sciences du Climat et de l‘Environnement (UMR CEA-CNRS), CE Saclay, Gif-Sur-Yvette, France

A. Short introduction B. Available CH 4 records (Vostok, Dome C) C. New CH 4 measurements for MIS 12 to 16 and first interpretations Outlook

Reconstructing atmospheric CH 4 ice sample size: ~40g melt and refreeze technique for the extraction of the air analysis by gas chromatography reproducibility of ~10ppbv

EPICA Dome C & Vostok ice cores Delmotte et al. (2004) Petit et al. (1999) EPICA Community Members (2004)

EPICA Dome C & Vostok ice cores New data!

Climate shift

Measured CH 4 data

Missing Termination from MIS 14 to 13

Last Glacial Period MIS 3 Huber et al. (submitted 2004)

Oppo et al. (1998) McManus et al. (1999) Millennial Scale Variations

Conclusions for MIS 16 to 12 Consistent with the temperature proxy  D, mean CH 4 levels were lower during interglacials 15 and 13 than in the consecutive interglacials 11, 9, 7, 5 and 1. High correlation to Antarctic temperature on glacial- interglacial time scales the climatic transition from MIS 14 to 13 is saw tooth shaped instead of showing a clear termination Thank you for your attention rapid CH 4 increases are observed  millennial scale variations similar to the Last Glacial Period seem to be a robust feature of our climate system