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***  Concentrations of N2O from the Law Dome (Summit, "BHD" Site)          ***
***  Ice Core(a)                                                           ***
***                                                                        ***
***  September 1994                                                        ***
***                                                                        *** 
***   Source: D.M. Etheridge                                               ***
***           G.I. Pearman                                                 ***
***           F. de Silva                                                  ***
***          Commonwealth Scientific and Industrial Research Organisation  ***
***          Aspendale, Victoria, Australia                                ***
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Mean      N20
date      Concentration
of        (ppbv)(b) 
air
enclosure
(yr A.D.)
1966  298.9
1966  322.9
1964  304.8
1964  305.3
1947  289.5
1937  301.4
1913  307.3
1912  296.2
1912  285.7
1901  309.0
1901  305.7
1890  290.7
1890  294.1
1878  287.3
1870  312.9
1865  296.6
1865  290.0
1860  284.5
1826  308.2
1808  301.1
1796  299.4
1735  281.7
1735  296.6
1735  302.6
1730  302.8
1729  272.2
1718  289.9
1718  281.8
1714  284.4
1712  296.7
1712  299.9
1702  283.9
1686  290.6
1662  284.1
1610  282.3
1606  284.5
1606  283.5
1602  329.8
1520  328.3
1520  303.2

(a) These atmospheric N2O concentrations derived from the Law Dome BHD ice core 
were published in Etheridge et al. (1988).
(b) In instances in which two or more values are presented for a single air age 
(e.g., two values are presented for the year 1966), the arithmetic mean was used 
for generating the graph. In addition, the data for years 1520 and 1602 were 
considered as outliers and not plotted.