Latest update: May 2006
 =======================

   1. All AGAGE data (except N2O, CH4, CHCl3, CO and H2) have been 
      calibrated to the Scripps Institution of Oceanography's SIO-2005
      scale since May 2006. The factors (SIO-2005/SIO-1998) for measured 
      species are following,

       Species   factor (SIO-2005/SIO-1998)
      ========   ==========================
       CFC-11,     0.9945
       CFC-12,     1.000
       CH3CCl3,    0.9957
       CCl4,       1.000
       CFC-113,    1.0042

   2. The N2O and CHCl3 are still in SIO-1998 scale. Please see Prinn
      et al., (2000) paper for detail description of SIO-1998 scale.

   3. The CH4 data are originally in the CSIR-94 scale (Steele et al.,
      Baseline Atmospheric Program Australia 1994-95, Francey et al.,
      eds., Bureau of Meteorology and CSIRO-DAR, Melbourne, pp. 107-110,
      1996). In current update, the CSIRO CH4 standard is multiplied by
      1.0119 to converted to the Tohoku University standard, which is
      developed by T. Nakazawa and co-workers at Tohoku University,
      Sendai, Japan,  in collaboration with the Nippon Sanso company
      (Aoki et al., 1992).

   4. Descriptions of calibration scales of CO and H2 can be found in 
      two separarte documents "COcalibration.doc" and "H2calibration.doc", 
      respectively.


Reference:

 1. Prinn et al., A history of chemically and radiatively important
    gases in air deduced from ALE/GAGE/AGAGE, J. Geophys. Res.,
    Vol. 105, No. D14, p17,751-17,792, 2000.