Parts of the U.S. Government are closed. This site will not be updated; however NOAA websites and social media channels necessary to protect lives and property will be maintained. See www.weather.gov for critical weather information. To learn more, see www.commerce.gov.
Battle, M., M. Bender, T. Sowers, P. P. Tans, J. H. Butler, J. W. Elkins, J. T. Ellis, T. J. Conway, N. Zhang, P. M. Lang and A. D. Clarket, (1996), Atmospheric gas concentrations over the past century measured in air from firn at the South Pole, Nature, 383, 6597, 231-235, doi:10.1038/383231a0