This compensating increase in the o

This compensating increase in the other sectors is due to the non-linearities in NOx chemistry. When road traffic emissions are turned off, the total ozone production decreases slightly. This leads to a little less ozone, but ozone production per NOx molecule (¼production efficiency) does increase, which is in agreement with earlier findings (Lin et al., 1988; Ehhalt and Rohrer, 1994; Grooß et al., 1998). This 2.5 DU increase due to higher production efficiency largely offsets the substantial 3.1 DU from road traffic emissions. Overall, the ozone change amounts to 0.6 DU only - the same small value that the perturbation method “falsely” attributesto road traffic alone.
Therefore the perturbation method is well suited to estimate the total ozone change of an alternative emission scenario, but it lacks the possibility of interpreting the results, since compensating effects may conceal a more detailed interpretation