Future global tropospheric ozone changes and impact on European air quality

A global chemistry climate model is used in conjunction with a regional chemistry-transport model dedicated to air quality studies to investigate the impact of anthropogenic emission changes, under several scenarios, on western European summertime surface O₃ levels in 2030. The implementation of presently decided emission control legislation in the individual countries worldwide leads to a geographically heterogeneous impact on summertime surface O₃ levels over Europe. A decrease of the averaged O₃ mixing ratio reaching -3 ppbv is predicted in southern areas whereas an increase reaching up 4 ppbv is calculated in northwestern Europe. The benefit of European emission control measures is found to be significantly counterbalanced by increasing global O₃ levels and subsequent long range transport since both are of the same magnitude (up to 4 ppbv) but opposite in sign. However, the net effect of both global and European emission changes is a significant decrease of O₃ extreme episodes during summertime.