AGAGE measurements of pollution events at Trinidad Head (near Eureka) in Northern California have been used to infer decreases of the emissions of CFC-11, CFC-12, CFC-113 and methyl chloroform from 1996 to 2003. It is shown that polluted air masses which reach Trinidad Head have traveled over the major cities in California, Washington and Oregon. As a result emission rates of these gases from California and Washington/Oregon have been estimated. The emissions of all these gases in the US West Coast region decreased from 1998 to 1999 by a factor of two or more, but the emissions of all four gases in 1999-2002 are calculated to have remained fairly constant at 0.016, 0.048, 0.002, and 0.006 kg/person/yr respectively. The emissions per person from California in 1996-1998, are calculated to have been factors of up to 2.2 less than the reported emissions at the same time from the New Jersey area. The methyl chloroform estimates in 1999-2000 are in agreement with the methyl chloroform emission per person averages for the USA estimated by the United Nations Environment Programme (UNEP). If the Trinidad Head and the New Jersey estimates are assumed to be representative of the USA, we estimate methyl chloroform emissions from the USA of 18 Gg/yr in 1996 to 1998 and 2.2 Gg/yr in 2001-2002. In addition we estimate average emissions of CH4, N2O and chloroform from the US West Coast region, in 1996 to 2002, of 44, 3.7 and 0.07 kg/person/year respectively.
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Article: Halocarbon emissions estimated from Advanced Global Atmospheric Gases Experiment measured pollution events at Trinidad Head, California. J. Li, D. M. Cunnold, H. Wang, R.F. Weiss, B.R. Miller, C. Harth, P. Salameh, and J.M. Harris (2005). Journal of Geophysical Research: Atmospheres 110: D14308 (doi:10.1029/2004JD005739).