Derivation of a series of annual values for CO2 The series for CO2 concentrations is generated from the file ftp://ftp.ngdc.noaa.gov/paleo/icecore/antarctica/law/law_co2.txt Historical CO2 record from the Law Dome DE08, DE08-2, and DSS ice cores D.M. Etheridge, L.P. Steele, R.L. Langenfelds, R.J. Francey, Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia; J.-M. Barnola, Laboratoire of Glaciologie et Geophysique de l'Environnement, Saint Martin d'Heres-Cedex, France; V.I. Morgan, Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania, Australia We use the 20 Year Smoothed series which covers the years 1832-1978 The value for 1970 (324.8 ppm) is in very good agreement with the SRES value for this year (325 ppm) A series CO2_for_fit.dat is assembled with this series up to 1970 and IPCC values for 1980, 1990, 2000 The series is then imported in xmgrace using Data | Import | ASCII Then it is interpolated to annual resolution from 1850-2000 using Data| Transformations | Interpolation/splines | Method: Cubic spline, Sampling: Linear mesh, Start at: 1850 Stop at: 2000 Length: 151 The resulting series is then written to file CO2_fit_1973.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 result in a wrong value.