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Ice core sample measurements give atmospheric CO2 content during the past 40,000 yr
Recent measurements1,2 on ice samples from Camp Century (Greenland, 77°10'N, 61°08'W), Byrd Station (Antarctica, 80°01'S, 110°31'W) and Dome C (74°40'S, 125°10'E) suggest that during the late part of the last glaciation the atmospheric CO2 concentration was significantly lower than during the Holocene. Further investigation of this natural increase of the atmospheric CO2 concentration in the past should aid our understanding of the climatic implications of the man-made CO2 increase since the beginning of industrialization3. Here we report new and precise measurements of the CO2 concentration of the air occluded in bubbles of ice samples from Camp Century and Byrd Station, using a new dry extraction technique. The extracted gases were analysed with an IR-laser spectrometer (IRLS). Samples from 22 different depths were analysed from each core. The samples are distributed over a depth interval corresponding approximately to the past 40,000 yr. In addition results for ice samples from selected depth horizons from a colder region (North Central, Greenland 74°37'N, 39°36'W) and from a warmer region (Dye-3, Greenland 65°11'N, 43°50'W) are given. Based on these results we estimate the trend of the atmospheric CO2 concentration during the past 40,000 yr.