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). Smoothed line through the ice core data (75 year smoothing spline). From Figure 2. Mean Air Age CH4 Mixing Years Before (year A.D.) Ratio (ppb) 2000 A.D. 1010 667.1 990 1015 668.7 985 1020 670.3 980 1025 671.8 975 1030 673.1 970 1035 674.4 965 1040 675.4 960 1045 676.3 955 1050 676.9 950 1055 677.3 945 1060 677.5 940 1065 677.5 935 1070 677.5 930 1075 677.4 925 1080 677.3 920 1085 677.2 915 1090 677.2 910 1095 677.4 905 1100 677.7 900 1105 678.2 895 1110 678.9 890 1115 679.7 885 1120 680.6 880 1125 681.6 875 1130 682.5 870 1135 683.5 865 1140 684.4 860 1145 685.2 855 1150 685.9 850 1155 686.5 845 1160 686.9 840 1165 687.0 835 1170 687.0 830 1175 686.8 825 1180 686.4 820 1185 685.6 815 1190 684.7 810 1195 683.4 805 1200 681.8 800 1205 679.9 795 1210 677.8 790 1215 675.6 785 1220 673.3 780 1225 671.0 775 1230 668.7 770 1235 666.6 765 1240 664.7 760 1245 663.1 755 1250 661.9 750 1255 661.1 745 1260 660.6 740 1265 660.4 735 1270 660.5 730 1275 660.9 725 1280 661.5 720 1285 662.3 715 1290 663.2 710 1295 664.3 705 1300 665.5 700 1305 666.7 695 1310 667.9 690 1315 669.1 685 1320 670.3 680 1325 671.4 675 1330 672.5 670 1335 673.3 665 1340 674.1 660 1345 674.7 655 1350 675.3 650 1355 675.8 645 1360 676.2 640 1365 676.5 635 1370 676.8 630 1375 677.1 625 1380 677.3 620 1385 677.6 615 1390 677.8 610 1395 678.1 605 1400 678.4 600 1405 678.6 595 1410 678.8 590 1415 679.0 585 1420 679.1 580 1425 679.1 575 1430 679.1 570 1435 678.9 565 1440 678.6 560 1445 678.2 555 1450 677.7 550 1455 677.1 545 1460 676.7 540 1465 676.7 535 1470 677.4 530 1475 678.8 525 1480 680.7 520 1485 683.0 515 1490 685.5 510 1495 688.2 505 1500 690.8 500 1505 693.1 495 1510 695.3 490 1515 697.1 485 1520 698.7 480 1525 699.9 475 1530 700.8 470 1535 701.3 465 1540 701.2 460 1545 700.5 455 1550 698.9 450 1555 696.4 445 1560 693.2 440 1565 689.5 435 1570 685.5 430 1575 681.5 425 1580 677.7 420 1585 674.3 415 1590 671.7 410 1595 670.1 405 1600 669.5 400 1605 669.7 395 1610 670.6 390 1615 671.8 385 1620 673.2 380 1625 674.4 375 1630 675.4 370 1635 676.2 365 1640 677.0 360 1645 677.9 355 1650 678.9 350 1655 680.2 345 1660 681.6 340 1665 682.8 335 1670 683.7 330 1675 684.2 325 1680 683.9 320 1685 682.9 315 1690 681.2 310 1695 679.4 305 1700 677.8 300 1705 676.5 295 1710 675.7 290 1715 675.5 285 1720 676.1 280 1725 677.5 275 1730 679.8 270 1735 682.8 265 1740 686.2 260 1745 689.9 255 1750 693.7 250 1755 697.4 245 1760 700.9 240 1765 704.2 235 1770 707.4 230 1775 710.4 225 1780 713.4 220 1785 716.4 215 1790 719.5 210 1795 722.9 205 1800 726.8 200 1805 731.0 195 1810 735.4 190 1815 740.0 185 1820 744.7 180 1825 749.4 175 1830 753.9 170 1835 758.5 165 1840 763.2 160 1845 768.4 155 1850 774.1 150 1855 780.3 145 1860 787.2 140 1865 794.6 135 1870 802.4 130 1875 810.5 125 1880 818.9 120 1885 827.9 115 1890 838.3 110 1895 850.6 105 1900 865.4 100 1905 882.8 95 1910 903.1 90 1915 925.7 85 1920 950.2 80 1925 975.6 75 1930 1001.0 70 1935 1026.4 65 1940 1052.6 60 1945 1081.3 55 1950 1115.7 50 1955 1158.7 45 1960 1211.1 40 1965 1272.1 35 1970 1339.8 30 1975 1410.7 25 1980 1482.2 20 Global mixing ratios calculated over the last 1000 years from Antarctic and Greenland measurements. Smoothing spline fit with 75 year cut off (Table 2, part 1, Etheridge et al., 1998) Also appears in IPCC WGI TAR Chapter 4 Figure 1 and Summary for Policymakers Figures 2 and 11, and as Figure 14-17 IN Chemistry of the Upper and Lower Atmosphere by Barbara J Finlayson-Pitts and James N. Pitts Jr. Academic Press, 2000. Mean Air Age CH4 Mixing Years Before (year A.D.) Ratio (ppb) 2000 A.D. 1010 676.0 990 1020 679.2 980 1030 682.0 970 1040 684.3 960 1050 685.8 950 1060 686.4 940 1070 686.4 930 1080 687.0 920 1090 688.5 910 1100 690.4 900 1110 692.7 890 1120 695.3 880 1130 698.4 870 1140 701.5 860 1150 704.3 850 1160 706.8 840 1170 707.4 830 1180 706.3 820 1190 704.5 810 1200 701.9 800 1210 698.6 790 1220 694.3 780 1230 690.0 770 1240 686.0 760 1250 682.8 750 1260 680.6 740 1270 679.1 730 1280 678.3 720 1290 679.3 710 1300 680.9 700 1310 682.6 690 1320 684.2 680 1330 685.8 670 1340 686.9 660 1350 687.8 650 1360 688.5 640 1370 689.0 630 1380 689.4 620 1390 689.5 610 1400 689.7 600 1410 689.8 590 1420 689.9 580 1430 689.7 570 1440 689.2 560 1450 688.5 550 1460 687.7 540 1470 689.3 530 1480 693.4 520 1490 698.4 510 1500 703.8 500 1510 708.6 490 1520 712.3 480 1530 715.1 470 1540 716.9 460 1550 716.9 450 1560 713.7 440 1570 707.4 430 1580 700.9 420 1590 695.6 410 1600 692.7 400 1610 691.9 390 1620 692.0 380 1630 691.8 370 1640 691.3 360 1650 691.5 350 1660 693.7 340 1670 695.5 330 1680 696.1 320 1690 694.9 310 1700 693.3 300 1710 692.5 290 1720 693.2 280 1730 696.1 270 1740 702.3 260 1750 710.2 250 1760 717.8 240 1770 725.0 230 1780 730.7 220 1790 734.9 210 1800 741.6 200 1810 750.8 190 1820 760.3 180 1830 769.8 170 1840 779.4 160 1850 791.6 150 1860 805.6 140 1870 821.0 130 1880 837.1 120 1890 856.6 110 Smoothing from here down has 12.5 year cut-off (Table 2 part 2 Etheridge et al., 1998) 1900 879.4 100 1902 887.9 98 1904 896.5 96 1906 905.3 94 1908 914.4 92 1910 924.0 90 1912 933.9 88 1914 944.3 86 1916 955.1 84 1918 966.4 82 1920 978.1 80 1922 989.9 78 1924 1001.8 76 1926 1013.6 74 1928 1025.0 72 1930 1036.2 70 1932 1047.2 68 1934 1058.0 66 1936 1068.7 64 1938 1078.9 62 1940 1088.9 60 1942 1099.0 58 1944 1109.4 56 1946 1120.6 54 1948 1133.2 52 1950 1147.5 50 1952 1163.8 48 1954 1182.1 46 1956 1202.4 44 1958 1224.2 42 1960 1247.5 40 1962 1272.2 38 1964 1298.4 36 1966 1326.0 34 1968 1355.3 32 1970 1386.0 30 1972 1417.5 28 1974 1449.3 26 1976 1481.5 24 1978 1514.0 22 1980 1547.1 20 1982 1580.9 18 1984 1614.2 16 1986 1644.9 14 1988 1671.6 12 1990 1694.3 10 1992 1714.0 8