Derivation of a series of annual values for CH4 The series for methane CH4 concentrations is generated from the file ftp://ftp.ngdc.noaa.gov/paleo/icecore/antarctica/law/law_ch4.txt NAME OF DATA SET: Ice Core, Firn Air and Archived Air Atmospheric Methane Concentration Data. LAST UPDATE: 6/2002 (Original receipt by WDC Paleo). CONTRIBUTORS: D.M. Etheridge, L.P. Steele, R.J. Francey, and R.L. Langenfelds Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia. IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2002-039 SUGGESTED DATA CITATION: Etheridge, D.M., et al., 2002, Ice Core, Firn Air and Archived Air Atmospheric Methane Concentration Data, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2002-039. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Etheridge, D. M., Steele, L. P., Francey, R. J., and Langenfelds, R. L., 1998, Atmospheric methane between 1000 A.D. and present: Evidence of anthropogenic emissions and climatic variability J. Geophys. Res. Vol. 103, No. D13, p. 15,979 (98JD00923) In this dataset we use the 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 appear in IPCC WGI TAR Chapter 4 Figure 1 and Summary for Policymakers Figures 2 and 11. This series covers the years 1010-1890 with 10 year sampling interval and 1900-1992 with smoothing with 12.5 year cut-off (Table 2 part 2 Etheridge et al., 1998) The series is then imported in xmgrace using Data | Import | ASCII .The value for 2000 (1760) from the IPCC report is added to this series Then it is interpolated to annual resolution from 1973-2000 using Data| Transformations | Interpolation/splines | Method: Cubic spline, Sampling: Linear mesh, Start at: 1850 Stop at: 2000 Length: 151. This series is pasted with the interpolated series 1970-2000 using Data | Dataset operations| Join resulting in a series of 201 values The resulting series is then written to file CH4_fit.dat using Data| Export | ASCII | Format: %12.2f To make sure that it is clear that the series represent annual mean (that is central values) for the year in question 0.49 is added to the year before writing the series. This has been chosen so that a rounding of the year when writing it in integer form will not round the year to the upper integer.