Aux_material_4.pdf: Caption

Measurements of SF6 in 19 air samples from the Cape Grim Air Archive. In
the top panel, the dry-air SF6 mixing ratios are shown, in units of
picomole per mole (pmol mol-1), versus the air-sampling date. The red
symbols show the SF6 results from the GC/ECD measurements made at the
University of Heidelberg in 1995, while the blue symbols show the SF6
results from Medusa GC-MS measurements made at CSIRO Marine and
Atmospheric Research, Aspendale in 2007 (see main text). The bottom
panel shows the ratio (expressed as a percentage) of the difference
between the measurements made by the two laboratories. The mean offset
of 1.52% between the two sets of measurements undoubtedly reflects the
small difference between the two independently prepared SF6 calibration
scales.