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The European Project for Ice Coring in Antarctica Dome C icecore enables us to extend existing records of atmospheric methane(CH4) and nitrous oxide (N2O) back to 650,000 years before thepresent. A combined record of CH4 measured along the Dome Cand the Vostok ice cores demonstrates, within the resolutionof our measurements, that preindustrial concentrations overAntarctica have not exceeded 773 ± 15 ppbv (parts perbillion by volume) during the past 650,000 years. Before 420,000years ago, when interglacials were cooler, maximum CH4 concentrationswere only about 600 ppbv, similar to lower Holocene values.In contrast, the N2O record shows maximum concentrations of278 ± 7 ppbv, slightly higher than early Holocene values.
1 Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. 2 Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE, CNRS-UJF), CNRS, 54 Rue Molières, 38402 St. Martin d'Hères, Grenoble, France. 3 Institut Pierre Simon Laplace/Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS 1572, CE Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France.
Present address: Scripps Institution of Oceanography, Universityof California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093–0244,USA.
Present address: Institute of Arctic and Alpine Research, Universityof Colorado at Boulder, 450 UCB Boulder, Colorado 80309–0450,USA.
* To whom correspondence should be addressed: stocker{at}climate.unibe.ch
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Present address: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093–0244, USA. 
Present address: Institute of Arctic and Alpine Research, University of Colorado at Boulder, 450 UCB Boulder, Colorado 80309–0450, USA. 
