Much of the ozone trends can be att

Much of the ozone trends can be attributed to precursor emissions. Other contributions come from the decline of stratospheric ozone and from changes in stratospheric ozone intrusions (Grewe, 2007). NOx precursor emissions from road traffic saw a large increase in the 1970s and 1980s, but later decreased due to the wide-spread implementation of catalytic converters (Uherek et al., 2010).