Halocarbon Emissions from the United States and Mexico and Their Global Warming Potential

We use recent aircraft measurements of a comprehensive suite of anthropogenic halocarbons, carbon monoxide (CO), and related tracers to place new constraints on North American halocarbon emissions and quantify their global warming potential. Emissions continue for many compounds restricted under the Montreal Protocol, and we show that halocarbons make up an important fraction of the total greenhouse gas source for both countries: our best estimate is 9% (uncertainty range 6-12%) and 32% (21-52%) of equivalent CO₂ emissions for the U.S. and Mexico, respectively, on a 20 year time scale. Ongoing methylchloroform emissions are significant in the U.S. (2.8 Gg/y in 2004-2006), in contrast to bottom-up estimates (<0.05 Gg), with implications for tropospheric OH calculations. Mexican methylchloroform emissions are minor. For more details see Millet et al., 2009.