Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 1 2 2005 10.5194/cpd-1-155-2005 http://www.clim-past-discuss.net/1/155/2005/ http://www.clim-past-discuss.net/1/155/2005/cpd-1-155-2005.html http://www.clim-past-discuss.net/1/155/2005/cpd-1-155-2005.pdf 155 168 2005-09-22 Summer temperature trend over the past two millennia using air content in Himalayan ice S. Hou J. Chappellaz J. Jouzel P. C. Chu V. Masson-Delmotte D. Qin D. Raynaud P. A. Mayewski V. Y. Lipenkov S. Kang Laboratoire de Glaciologie et Geophysique de l’Environnement (CNRS-UJF), 54 rue Molière, Domaine Universitaire, BP 96, 38 402 St Martin d’Hères Cedex, France IPSL-Laboratoire des Sciences du Climat et de l’Environnement (CEA-CNRS), Bâtiment 701, CE Saclay, Annexe Orme des Merisiers, 91 191 Gif-sur-Yvette, France Laboratory of Cryosphere and Environment, Chinese Academy of Sciences, 260 Donggang West Road, 730000 Lanzhou, China Naval Ocean-Atmosphere Prediction Laboratory, Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943, USA Climate Change Institute (CCI), University of Maine, Orono, ME 04469, USA Arctic and Antarctic Research Institute, Beringa Street 38, 199397, St. Petersburg, Russia Two Himalayan ice cores display a factor-two decreasing trend of air content over the past two millennia, in contrast to the relatively stable values in Greenland and Antarctica ice cores over the same period. Because the air content can be related with the relative frequency and intensity of melt phenomena, its variations along the Himalayan ice cores provide an indication of summer temperature trend. Our reconstruction point toward an unprecedented warming trend in the 20th century but does not depict the usual trends associated with "Medieval Warm Period" (MWP), or "Little Ice Age" (LIA).