"Ship-borne ozone measurements, performed by researchers of the Max Planck Institute for Chemistry and the German Weather Service over the Atlantic Ocean during the period 1977-2002, show that the ozone trends in the northern mid-latitudes are small. In contrast, remarkably large ozone trends occur at low latitudes and in the Southern Hemisphere, implying that the ozone smog problem has expanded far beyond the areas traditionally affected by photochemical air pollution in Europe and the USA (Science Express, 13 May, 2004).
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The article in Science is based on ozone measurements by the Max Planck Institute for Chemistry (Mainz) and the German Weather Service (Hohenpeißenberg and former Meteorological Observatory Hamburg), taken on ships sailing the Atlantic Ocean since 1977. The results confirm that in middle latitudes in the northern hemisphere the ozone concentrations are quite high, although the increases since about 1980 have not been very large. Remarkably and unexpectedly, however, in the subtropics, the tropics and the southern hemisphere, ozone increases since 1980 have been much larger. In some regions the ozone levels have even doubled in two decades. The area where the high ozone concentrations have been measured is mostly downwind of Africa, and the researchers have calculated that biomass burning and especially increasing energy use on this continent have contributed substantially to emissions of nitrogen oxides, thus catalyzing ozone formation. The implication is that increasing energy use worldwide causes large-scale ozone increases, thus reducing global air quality."
EDIT
http://www.sciencedaily.com/releases/2004/05/040517072915.htm