Oxidant limitation on sulphate trends
In a paper by Paul Manktelow in GRL we have shown that the 12% change in global SO2 emissions between 1985 and 2000 resulted in only a 3% reduction in global sulphate. The reason is that SO2 oxidation is limited by oxidants in Europe (where emissions have fallen) but barely limited in Asia (where emissions have risen). So the reduction in SO2 emissions over Europe had much less impact on sulphate than expected.
Figure shows:(a) Anthropogenic SO2 emission inventory for 1985 and (b) absolute change in emission by 2000. Units =
mg (S)/m2/day. (c) Change in zonal mean emission of SO2 and (d) change in zonal mean production of sulfate through
in-cloud oxidation (solid line) and dry oxidation (dotted line). Units = Tg (S)/yr.
Notice how the decrease in SO2 emissions at 50N (~Europe/US) is much less than the increase at 30N (Asia), and yet the changes in sulphate largely compensate.
See pdf of the paper