Science Source
Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn
- Analyzes the air enclosed in three ice cores from Law Dome, Antarctica to produce a record of atmospheric CO2 mixing ratios from 1006 A.D. to 1978 A.D.
- States that the enclosed air has unparalleled age resolution and extends into recent decades, overlapping with the record from direct atmospheric measurements for up to 20 years, because of the high rate of snow accumulation at the ice core sites
- Finds that preindustrial CO2 mixing ratios were in the range 275–284 ppm, with the lower levels during 1550–1800 A.D., probably as a result of colder global climate
- Asserts that natural CO2 variations of this magnitude make it inappropriate to refer to a single preindustrial CO2 level
- Results show that major CO2 growth occurred over the industrial period except during 1935–1945 A.D. when CO2 mixing ratios stabilized or decreased slightly, probably as a result of natural variations of the carbon cycle on a decadal timescale
