Eastern Asian emissions of anthropogenic halocarbons deduced from aircraft concentration data

The Montreal Protocol restricts production of ozone‐depleting halocarbons worldwide. Enforcement of the protocol has relied mainly on annual government statistics of production and consumption of these compounds (bottom‐up approach). We show here that aircraft observations of halocarbon:CO enhancement ratios on regional to continental scales can be used to infer halocarbon emissions, providing independent verification of the bottom‐up approach. We apply this top‐down approach to aircraft observations of Asian outflow from the TRACE‐P mission over the western Pacific (March–April 2001) and derive emissions from eastern Asia (China, Japan, and Korea). We derive an eastern Asian carbon tetrachloride (CCl 4 ) source of 21.5 Gg yr −1 , several‐fold larger than previous estimates and amounting to ≃30% of the global budget for this gas. Our emission estimate for CFC‐11 from eastern Asia is 50% higher than inventories derived from manufacturing records. Our emission estimates for methyl chloroform (CH 3 CCl 3 ) and CFC‐12 are in agreement with existing inventories. For halon 1211 we find only a strong local source originating from the Shanghai area. Our emission estimates for the above gases result in a ≃40% increase in the ozone depletion potential (ODP) of Asian emissions relative to previous estimates, corresponding to a ≃10% global increase in ODP.