Air samples collected at Mauna Loa, USA.(19N,155W) SIL ID # Identification Number used at the Stable Isotope Lab, University of Washington. Date Date that this sample was collected. CH4-SIL Methane concentration (ppm) determined manometrically at SIL with precision of ± 2%, see Quay et al. (1). CH4-CMDL Methane concentration (ppm) determined by gas chromatography by NOAA/CMDL laboratory with precsion of ±0.2%, see Dlugokencky et al. (2). Del 13C Measured 13C/12C in per mil (0/00) units, where del 13C(0/00) ={[(13C/12C)sample/(13C/12C)standard - 1]*1000} and the standard is VPDB, see Quay et al. (1). Del 13C (0/00) corrected for standard drift, see Quay et al. (1). SIL ID # Date CH4-SIL CH4-CMDL Del 13C TTLM0014 20-JAN-88 1.58 1.671 -47.26 TTLM0016 20-APR-88 1.71 1.694 -47.40 TTLM0017 6-MAY-88 1.70 1.673 -47.55 TTLM0018 8-JUN-88 1.73 1.702 -47.39 TTLM0019 22-JUN-88 1.69 1.671 -47.44 TTLM0020 6-JUL-88 1.69 1.670 -47.34 TTLM0023 25-JUL-88 1.71 -47.27 TTLM0022 27-JUL-88 1.66 1.669 -47.33 TTLM0024 19-AUG-88 1.70 1.666 -47.27 TTLM0025 29-AUG-88 1.75 -47.47 TTLM0027 2-SEP-88 1.67 1.660 -47.39 TTLM0026 9-SEP-88 1.83 1.685 -47.46 TTLM0028 5-OCT-88 1.68 1.666 -47.36 TTLM0030 19-OCT-88 1.67 1.670 -47.36 TTLM0029 4-NOV-88 1.69 1.677 -47.37 TTLM0031 18-NOV-88 1.71 1.698 -47.48 TTLM0032 29-NOV-88 1.70 1.690 -47.51 TTLM0034 28-DEC-88 1.71 1.704 -47.38 TTLM0035 25-JAN-89 1.69 1.680 -47.21 TTLM0036 1-FEB-89 1.74 1.706 -47.41 TTLM0037 8-FEB-89 1.70 1.684 -47.12 TTLM0039 22-FEB-89 1.68 1.693 -47.39 TTLM0038 10-MAR-89 1.69 1.691 -47.43 TTLM0040 22-MAR-89 1.71 1.694 -47.46 TTLM0042 5-APR-89 1.69 1.698 -47.30 TTLM0041 19-APR-89 1.70 1.699 -47.45 TTLM0043 3-MAY-89 1.67 1.681 -47.43 TTLM0044 17-MAY-89 1.72 1.710 -47.36 TTLM0045 2-JUN-89 1.64 1.697 -47.35 TTLM0046 14-JUN-89 1.70 -47.32 TTLM0047 7-JUL-89 1.80 1.685 -47.39 TTLM0048 19-JUL-89 1.69 -47.33 TTLM0049 9-AUG-89 1.70 -47.36 TTLM0051 6-SEP-89 1.72 -47.40 TTLM0052 20-SEP-89 1.72 -47.47 TTLM0053 11-OCT-89 1.72 -47.56 TTLM0054 25-OCT-89 1.70 -47.55 TTLM0055 8-NOV-89 1.73 -47.53 TTLM0056 29-NOV-89 1.72 1.694 -47.38 TTLM0057 13-DEC-89 1.73 1.708 -47.50 TTLM0061A 10-JAN-90 1.71 1.720 -47.54 TTLM0059 10-JAN-90 1.75 1.720 -47.36 TTLM0060 24-JAN-90 1.72 1.700 -47.34 TTLM0061 7-FEB-90 1.76 1.748 -47.50 TTLM0064 9-MAR-90 1.74 -47.05 TTLM0063 16-MAR-90 1.75 1.740 -47.33 TTLM0066 13-APR-90 1.72 1.700 -47.34 TTLM0067 27-APR-90 1.74 1.712 -47.32 TTLM0068 9-MAY-90 1.73 1.720 -47.37 TTLM0069 25-MAY-90 1.75 1.714 -47.22 TTLM0070 8-JUN-90 1.73 1.688 -47.28 TTLM0071 22-JUN-90 1.71 1.698 -47.42 TTLM0072 2-JUL-90 1.70 1.688 -47.29 TTLM0073 25-JUL-90 1.69 1.690 -47.16 TTLM0074 8-AUG-90 1.69 1.690 -47.36 TTLM0075 22-AUG-90 1.70 1.707 -47.30 TTLM0076 5-SEP-90 1.70 1.707 -47.38 TTLM0077 14-SEP-90 1.69 1.691 -47.47 TTLM0078 5-OCT-90 1.70 1.716 -47.38 TTLM0079 7-NOV-90 1.73 1.724 -47.45 TTLM0080 30-NOV-90 1.71 1.699 -47.44 TTLM0081 2-JAN-91 1.71 1.708 -47.57 TTLM0082 16-JAN-91 1.71 1.708 -47.41 TTLM0083 30-JAN-91 1.72 1.713 -47.46 TTLM0084 15-FEB-91 1.74 1.713 -47.51 TTLM0085 1-MAR-91 1.69 1.695 -47.44 TTLM0086 20-MAR-91 1.69 -47.50 TTLM0087 20-MAR-91 1.71 -47.40 TTLM0091 15-MAY-91 1.70 1.722 -47.30 TTLM0092 29-MAY-91 1.71 1.699 -47.53 TTLM0093 14-JUN-91 1.71 1.705 -47.24 TTLM0096 2-AUG-91 1.71 -47.42 TTLM0100 16-OCT-91 1.70 1.711 -47.29 TTLM0102 24-JAN-92 1.75 1.738 -47.41 TTLM0110 3-JUN-92 1.79 1.726 -47.25 TTLM0108 17-JUN-92 1.75 1.715 -47.29 TTLM0106 1-JUL-92 1.73 1.710 -47.29 TTLM0107 5-AUG-92 1.75 1.717 -47.47 TTLM0111 2-SEP-92 1.73 1.724 -47.41 TTLM0115 18-SEP-92 1.78 1.734 -47.36 TTLM0113 30-SEP-92 1.75 1.745 -47.44 TTLM0114 4-DEC-92 1.75 1.729 -47.39 TTLM0116 16-DEC-92 1.70 -47.33 TTLM0118 30-DEC-92 1.76 1.734 -47.44 TTLM0120 29-JAN-93 1.77 1.717 -47.44 TTLM0119 19-FEB-93 1.74 1.721 -47.39 TTLM0121 05-MAR-93 1.79 1.741 -47.42 TTLM0123 13-MAR-93 1.76 1.733 -47.34 TTLM0122 14-APR-93 1.72 1.732 -47.34 TTLM0124 5-MAY-93 1.74 1.721 -47.21 TTLM0125 28-MAY-93 1.76 1.740 -47.43 TTLM0126 23-JUN-93 1.75 1.739 -47.20 TTLM0129 28-JUL-93 1.81 1.736 -47.39 TTLM0127 25-AUG-93 1.75 1.711 -47.21 TTLM0128 17-SEP-93 1.71 1.711 -47.51 TTLM0130 8-OCT-93 1.77 1.731 -47.38 TTLM0131 17-NOV-93 1.80 1.749 -47.33 TTLM0134 8-DEC-93 1.82 1.743 -47.39 TTLM0133 29-DEC-93 1.76 1.742 -47.32 TTLM0135 19-JAN-94 1.78 1.764 -47.36 TTLM0137 2-FEB-94 1.75 -47.38 TTLMO136 23-FEB-94 1.72 1.727 -47.34 TTLM0138 16-MAR-94 1.76 1.758 -47.17 TTLM0140 20-APR-94 1.75 1.740 -47.26 TTLM0141 27-MAY-94 1.76 1.734 -47.21 TTLM0143 22-JUN-94 1.73 1.720 -47.26 TTLM0142 26-AUG-94 1.75 1.718 -47.02 TTLM0144 21-SEP-94 1.74 1.718 -47.10 TTLM0145 7-OCT-94 1.76 -47.35 TTLM0148 30-NOV-94 1.77 1.744 -47.45 TTLM0149 14-DEC-94 1.81 1.759 -47.40 TTLM0154 22-FEB-95 1.75 1.726 -47.33 TTLM0152 10-MAR-95 1.77 1.744 -47.22 TTLM0153 22-MAR-95 1.77 1.737 -47.27 TTLMO157 17-MAY-95 1.77 1.754 -47.13 TTLM0158 7-JUN-95 1.77 1.750 -47.12 TTLM0160 12-JUL-95 1.78 1.737 -47.36 TTLM0161 26-JUL-95 1.73 1.722 -47.23 TTLM0163 23-AUG-95 1.77 -47.24 TTLMO162 31-AUG-95 1.75 1.720 -47.21 TTLM0166 8-SEP-95 1.74 -47.26 TTLM0165 6-OCT-95 1.78 1.756 -47.31 TTLM0166 8-SEP-95 -47.26 TTLM0168 29-NOV-95 1.76 1.756 -47.35 TTLM0169 15-DEC-95 1.75 1.744 -47.31 TTLM0170 12-JAN-96 1.78 1.763 -47.31 TTLM0171 24-JAN-96 1.76 1.754 -47.40 TTLM0172 21-FEB-96 1.77 1.753 -47.46 TTLM0173 6-MAR-96 1.77 1.754 -47.18 TTLM0174 7-FEB-96 1.75 1.718 -47.13 TTLM0175 29-MAR-96 1.76 -47.35 TTLM0176 17-APR-96 1.80 1.740 -47.19 TTLM0178 1-MAY-96 1.83 -47.15 (1) Quay, P.D., J. Stutsman, D. Wilbur, A. Snover, E. Dlugokenky and T. Brown, (submitted), Isotopic Composition of Atmospheric Methane, Global Biogeochemical Cycles. (2) DLUGOKENCKY, E.J., K.A. MASARIE, P.M. LANG, P.P. TANS, L.P. Steele, and E.G. Nisbet. A dramatic decrease in the growth rate of atmospheric methane in the northern hemisphere during 1992. Geophysical Research Letters 20(1):45-48 (1994).