Carbon dioxide level highest in 650,000 years

Refs: Spahni, R., J. Chappellaz, T.F. Stocker, L. Loulergue, G. Hausammann, K. Kawamura, J. Flückiger, J. Schwander, D. Raynaud, V. Masson-Delmotte, J. Jouzel, Atmospheric methane and nitrous oxide of the late Pleistocene from Antarctic ice cores, 310, Science, 1317-1321, 2005.
http://spot.colorado.edu/~flueckig/publications.html

Siegenthaler, U. T.F. Stocker, E. Monnin, D. Lüthi, J. Schwander, B. Stauffer, D. Raynaud, J.-M. Barnola, H. Fischer, V. Masson-Delmotte, J. Jouzel, 2005, Stable carbon cycle-climate relationship during the late Pleistocene. Science 310, 1313-1317.
http://www.climate.unibe.ch/~stocker/publications.html