R 134a first appeared in the early 1990s as a replacement for dichlorodifluoromethane (R-12), which has ozone depleting properties. 1,1,1,2-Tetrafluoroethane has been atmospherically modeled for its impact on depleting ozone and as a contributor to global warming. Research suggests that over the past 10 years the concentration of 1,1,1,2-tetrafluoroethane has increased significantly in the Earth's atmosphere, with a recent study revealing a doubling in atmospheric concentration between 2001 and 2004. It has insignificant ozone depletion potential (ozone layer), significant global warming potential (100-yr GWP = 1430) and negligible acidification potential (acid rain).