Trace gas emissions from Melbourne, Australia, based on AGAGE observations at Cape Grim, Tasmania, 1995–2000

Atmospheric observations of ten atmospheric gases have been used to estimate total emissions of nine of these ten trace gases from Melbourne, Australia. The ten trace gases measured as part of the AGAGE program at the Cape Grim Baseline Air Pollution Station in Tasmania are: CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2FCClF2), methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), hydrogen (H2), chloroform (CHCl3), methyl chloroform (CH3CCl3) and carbon tetrachloride (CCl4). The process of estimating emissions involved first identifying pollution episodes in the Cape Grim record that were attributed to air masses that passed over the Melbourne region before travelling across Bass Strait to Cape Grim. Correlations between the trace species and an estimate of CO emissions from Melbourne were used to deduce the mass of the Melbourne emissions. Where possible, comparisons of these estimates have been made with estimates from established inventory techniques. In particular, comparisons have been made with Australia's National Greenhouse Gas Inventory. Results from this study showed emission estimates of CFC-12 and CFC-11 ranging from 30–52% and 30–55%, respectively, of the inventory estimates. These results may indicate a more rapid phase-out of these CFCs than industrial inventory models predicted. The emission estimates of CH4 ranged from 53% to 87% of inventory estimates over the years 1995–2000. Emission estimates of N2O exceed inventory estimates by more than 200% over the years 1995–2000.