Impacts on global ozone and climate from use and emission of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123)

Analyses of emissions, and consequent chlorine loading, show that projected use of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) will result in a virt ually indiscernible impact on stratospheric ozone. Parametric scenarios uph old this conclusion, even for extreme levels of emissions far exceeding tho se of current technologies and practices. Additional scenarios reaffirm the conclusion for continued use - beyond the scheduled phaseout date - as a r efrigerant in closed systems. By contrast, use of this compound offers uniq ue opportunities to reduce global warming. Moreover, time-dependent analyse s show that the minimal contribution to stratospheric chlorine from HCFC-12 3 emissions will not peak until more than a decade after the residual peaks of chlorine and bromine, from prior chlorofluorocarbon and halon releases, subside. While no single index exists to compare the relative demerits of ozone depletion and climate change, three conclusions are clear. First, rev ersal of the buildup of bromine and chlorine (i.e., healing of the `ozone l ayer') is underway and progressing on target, while sufficient practical re medies for global climate change are far more difficult. Second, the analys es show that phaseout of all chlorinated, and conceptually - but much less probably - all brominated, compounds of anthropogenic origin targets some c ompounds that provide environmental benefits. Most chlorinated and brominat ed compounds do warrant phaseout; the exceptions are those with very short atmospheric lifetimes, and consequent low ozone depletion potential (ODP), that also offer offsetting environmental benefits. And third, since new glo bal environmental concerns may, and probably will, be identified in the fut ure, a more scientific approach is needed to determine environmental accept ability or rejection.