Evidence of changing concentrations of atmospheric CO2, N2O and CH4 from air bubbles in Antarctic ice

• Published in: Nature (London) 1986-03, Vol.320 (6059), p.248-250
• Main Authors: Pearman, G. I., Etheridge, D., de Silva, F., Fraser, P. J.
• Format: Article
• Language: English
• Subjects: Chemical composition and interactions. Ionic interactions and processes; Earth, ocean, space; Exact sciences and technology; External geophysics; Humanities and Social Sciences; letter; Meteorology; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/320248a0

Atmospheric carbon dioxide (CO 2 ) levels before the industrial revolution were ∼ 260–280 p.p.m.v. (parts per 10 6 by volume) as determined from studies of air trapped in ice 1,2 . We report here similar results, using Antarctic ice, for the CO 2 levels during the seventeenth and eighteenth centuries, which suggest an average concentration of 281 (standard deviation σ = 7) p.p.m.v. The data constrain the net release of biospheric carbon to the atmosphere over the past 200 yr, to ∼5 × 10 10 tonnes of carbon, mostly during 1850–1900. Measurements of two other ‘greenhouse’ gases, methane (CH 4 ) and nitrous oxide (N 2 O), show increases of about 90 and 8% respectively since 1600. This CH 4 increase is similar to the recently reported 3–6 doubling over the same period, and the N 2 O increase, the first direct evidence of historical changes in N 2 O, is consistent with releases due to expanding anthropogenic combustion processes 7 .