Historical CH4 mixing ratios from Law Dome (Antarctica) and Summit (Greenland) ice cores. Source: D.M. Etheridge L.P. Steele R.J. Francey R.L. Langenfelds Historical CH4 record from DE08, DE08-2 and DSS ice cores (Antarctica). Mean Air Age CH4 Mixing Mean Ice Ice Age Years before (year A.D) Ratio (ppb) Depth (m) (year A.D.) sample no. 2000 A.D. 1008 666.0 534.2 948 DSS 038 992 1048 677.8 523.4 988 DSS 040 952 1098 676.4 505.9 1038 DSS 042 902 1148 685.9 488.3 1088 DSS 043 852 1198 683.7 467.7 1138 DSS 036 802 1248 660.9 447.2 1188 DSS 039 752 1329 672.9 414.0 1269 DSS 034 671 1389 676.3 387.1 1329 DSS 024 611 1389 678.9 387.2 1329 DSS 026 611 1448 681.5 360.6 1388 DSS 022 552 1467 671.4 351.2 1407 DSS 044 533 1501 693.0 336.7 1441 DSS 023 499 1529 698.9 323.7 1469 DSS 035 471 1549 704.3 313.9 1489 DSS 018 451 1572 684.8 302.0 1512 DSS 032 428 1591 665.4 293.2 1531 DSS 021 409 1606 667.7 285.2 1546 DSS 012 394 1622 679.4 276.3 1562 DSS 045 378 1649 674.6 263.4 1589 DSS 013 351 1681 692.0 245.6 1621 DSS 020 319 1694 676.1 238.0 1634 DSS 011 306 1722 671.9 223.0 1662 DSS 019 278 1749 692.9 207.6 1689 DSS 025 251 1751 696.9 206.5 1691 DSS 014 249 1762 703.1 200.5 1702 DSS 031 238 1779 714.4 190.9 1719 DSS 017 221 1796 716.9 181.3 1736 DSS 016 204 1798 728.5 180.0 1738 DSS 015 202 1827 755.8 163.5 1767 DSS 010 173 1834 756.3 242.8 1802 DE08-2 006 166 1842 766.9 228.7 1810 DE08 222 158 1847 763.7 151.6 1787 DSS 009 153 1852 785.5 218.0 1820 DE08 200 148 1856 775.9 214.1 1824 DE08 234 144 1863 789.9 206.1 1831 DE08 232 137 1871 811.9 197.5 1839 DE08 228 129 1879 822.3 190.2 1847 DE08 255 121 1884 828.5 184.3 1852 DE08 229 116 1888 833.6 179.5 1856 DE08 252 112 1893 836.8 122.8 1833 DSS 030 107 1894 852.3 174.4 1862 DE08 241 106 1900 862.4 167.9 1868 DE08 230 100 1901 868.4 116.9 1841 DSS 007 99 1907 891.0 114.3 1847 DSS 033 93 1907 885.3 160.6 1875 DE08 253 93 1907 887.8 160.8 1875 DE08 254 93 1914 921.6 153.0 1882 DE08 239 86 1917 929.9 149.9 1885 DE08 233 83 1926 989.0 138.8 1894 DE08 231 74 1926 991.1 138.8 1894 DE08 237 74 1928 997.0 100.3 1868 DSS 008 72 1931 1006.4 99.7 1871 DSS 041 69 1934 1023.2 130.3 1902 DE08 238 66 1936 1045.2 135.7 1904 DE08-2 011 64 1938 1053.0 94.1 1878 DSS 027 62 1940 1059.9 121.9 1908 DE08 240 60 1941 1055.7 92.7 1881 DSS 037 59 1941 1062.2 121.8 1909 DE08 243 59 1942 1069.1 128.8 1910 DE08-2 007 58 1944 1082.5 90.5 1884 DSS 052 56 1946 1081.8 115.7 1914 DE08 227 54 1950 1103.7 86.2 1890 DSS 029 50 1950 1102.9 120.2 1918 DE08-2 009 50 1955 1143.5 104.3 1923 DE08 236 45 1955 1140.0 104.4 1923 DE08 201 45 1955 1145.3 104.6 1923 DE08 208 45 1956 1164.3 81.8 1896 DSS 001 44 1956 1171.8 81.8 1896 DSS 003 44 1956 1183.8 81.8 1896 DSS 002 44 1957 1179.5 81.4 1897 DSS 047 43 1957 1186.4 81.4 1897 DSS 048 43 1961 1218.5 78.0 1901 DSS 004 39 1964 1258.7 92.7 1932 DE08 214 36 1964 1248.6 92.8 1932 DE08 215 36 1964 1273.3 93.0 1932 DE08 212 36 1964 1260.6 93.2 1932 DE08 213 36 1965 1261.3 92.0 1933 DE08 203 35 1967 1285.2 89.0 1935 DE08 226 33 1967 1278.4 89.2 1935 DE08 225 33 1967 1288.5 74.0 1907 DSS 049 33 1970 1351.7 84.0 1938 DE08 235 30 1971 1357.2 83.1 1939 DE08 205 29 1972 1380.3 92.2 1940 DE08-2 016 28 1972 1379.9 91.6 1940 DE08-2 015 28 1973 1385.8 90.6 1941 DE08-2 005 27 1974 1421.5 70.4 1914 DSS 050 26 1975 1420.4 88.0 1943 DE08-2 002 25 1977 1458.1 85.1 1945 DE08-2 003 23 1980 1479.7 81.1 1948 DE08-2 008 20 1980 1479.3 81.2 1948 DE08-2 012 20 Greenland Ice Core Results. From Figure 3. Mean Air Age CH4 Mixing Ice Age Years Before (year A.D.) Ratio (ppb) Depth (m) (year A.D.) Sample ID 2000 A.D. 1075 701.2 272.1 871 Eurocore 4 925 1121 720.7 261.2 917 Eurocore 4 879 1165 743.1 252.3 971 Eurocore 4 835 1209 734.4 242.9 1015 Eurocore 4 791 1281 706.4 227.9 1080 Eurocore 4 719 1376 710.1 208.9 1177 Eurocore 3 624 1464 706.3 188.4 1262 Eurocore 3 536 1512 732.0 178.4 1308 Eurocore 3 488 1556 750.2 168.7 1351 Eurocore 3 444 1648 712.6 148.9 1442 Eurocore 2 352 1733 724.2 129.1 1527 Eurocore 2 267 1775 759.6 119.2 1572 Eurocore 2 225 1797 761.8 118.7 1602 GISP2 203 1800 766.8 118.0 1605 GISP2 200 1807 774.0 116.6 1612 GISP2 193 1842 808.8 104.1 1639 Eurocore 1 158 1885 875.3 94.2 1681 Eurocore 1 115 CH4 in archive tanks from Cape Grim Station, Tasmania, deseasonalised.From Figure 5. Mean Air Age CH4 Mixing Years Before (year A.D.) Ratio (ppb) 2000 A.D. 1978.3 1468.3 22 1979.1 1490.9 21 1980.7 1507.7 19 1984.4 1572.9 16 1986.1 1594.6 14 1986.1 1593.2 14 1986.9 1603.5 13 1987.0 1603.5 13 1987.0 1602.3 13 1987.2 1608.5 13 1987.4 1617.2 13 1988.5 1620.9 12 1989.4 1635.0 11 1989.9 1636.3 10 1990.3 1641.7 10 1990.4 1641.5 10 1990.9 1646.6 9 1990.9 1645.7 9 1990.9 1645.5 9 1990.9 1646.2 9 1990.9 1645.4 9 1990.9 1644.2 9 1990.9 1645.6 9 1990.9 1645.1 9 1991.0 1645.2 9 1991.5 1658.7 9 1991.5 1655.5 9 1992.0 1665.8 8 1992.1 1665.9 8 1992.2 1665.8 8 1992.3 1667.1 8 1992.7 1667.9 7 1992.7 1667.1 7 1993.2 1666.7 7 1993.4 1669.7 7 1993.6 1671.4 6 1993.8 1671.1 6 1994.0 1668.8 6 1994.1 1669.2 6 1994.2 1670.1 6 1994.3 1670.4 6 1994.3 1669.3 6 1994.4 1675.5 6 1994.9 1677.7 5 1994.9 1677.2 5 1995.1 1680.4 5 1995.1 1679.7 5 1995.2 1681.9 5 1995.3 1681.2 5 1995.4 1681.2 5 1995.5 1678.6 4 1995.6 1677.6 4 1995.6 1677.9 4 1995.6 1678.8 4 1995.7 1680.5 4 1995.8 1682.8 4 1995.9 1683.6 4 1995.9 1684.0 4 CH4 in firn air samples from DE08-2. From Figures 1 and 5. Mean Air Age CH4 Mixing Years Before (year A.D.) Ratio (ppb) Depth (m) 2000 A.D. 1978.2 1460.9 85 22 1981.5 1498.7 80 19 1981.5 1497.3 80 19 1984.2 1563.9 75 16 1984.2 1562.6 75 16 1985.5 1593.2 70 15 1985.5 1589.6 70 15 1986.1 1601.5 65 14 1986.7 1603.0 60 13 1987.2 1608.6 55 13 1987.2 1607.8 55 13 1988.7 1626.5 40 11 1988.7 1625.0 40 11 1989.6 1641.8 30 10 1989.6 1639.4 30 10 1990.5 1650.5 20 9 1991.0 1655.3 15 9 1991.4 1659.0 10 9 1991.4 1656.3 10 9 1993.1 1654.1 0 7 1993.1 1652.5 0 7