Chappellaz et al, Nature 345,127-131 (1990) CH4 concentration Depth Gas age (PPBV) 2 Std. (m) Deviation 149.2 2569 668 46 173.1 3525 636 50 177.4 3701 595 44 228.7 5864 588 38 236.4 6197 574 52 266 7496 616 50 303.8 9195 667 39 321.2 10018 621 47 331.7 10537 477 24 342.1 11070 501 20 356 11827 662 31 365.6 12350 610 35 366.2 12385 642 30 381.7 13289 445 39 426.3 16242 395 45 443.5 17546 363 22 458.3 18752 349 46 471 19816 379 40 491.3 21532 348 34 506.4 22810 406 26 534.3 25172 384 33 544.7 26059 398 35 554.2 26870 415 38 585.8 29540 423 52 602.2 30902 432 60 617.6 32152 543 29 625.6 32796 522 45 642.1 34115 470 38 664.6 35892 484 45 694.6 38222 424 49 724.8 40525 441 45 748.3 42309 419 40 765.3 43598 402 51 788.2 45330 466 20 812 47123 504 40 834.8 48833 480 43 860.6 50755 514 38 885.3 52587 528 20 911.4 54574 442 44 937.3 56620 411 35 962.4 58665 414 38 986.3 60672 415 28 1011.3 62858 434 26 1037.5 65215 424 34 1062.2 67396 458 33 1087.2 69558 430 37 1112.6 71714 462 38 1137.7 73809 402 35 1162.1 75815 438 39 1186.5 77774 497 43 1209.7 79642 545 39 1237.2 81805 594 22 1261.2 83680 529 33 1289.2 85881 425 38 1309.2 87460 417 27 1338.2 89766 454 32 1363.7 91806 443 45 1387.2 93698 406 43 1413 95792 407 29 1442.8 98232 476 37 1451.4 98943 480 37 1463.3 99941 521 22 1476.1 101037 493 34 1505 103619 559 33 1526.2 105611 591 30 1532 106173 564 38 1542.1 107164 437 26 1557.4 108705 451 33 1582.8 111253 468 24 1614.8 114251 448 41 1627.7 115400 443 39 1637.7 116272 489 36 1669.5 118938 515 34 1694 120891 544 38 1716 122577 557 41 1736.8 124117 562 37 1770 126486 584 44 1789.2 127842 586 19 1834.7 131120 620 26 1852.3 132411 650 27 1857.4 132788 637 44 1869.4 133679 694 24 1875.5 134136 688 43 1883.3 134722 536 29 1903.6 136302 526 35 1932.1 138798 453 25 1954.6 141040 431 33 1969.9 142740 399 36 1980.2 143980 352 27 1987.4 144897 357 26 1994.7 145869 374 19 1998 146339 377 33 2005.9 147485 348 39 2009.4 148024 339 29 2016.4 149130 318 24 2030.9 151600 319 30 2042.5 153613 345 23 2063.7 157290 355 17