CHANGES IN THE GLOBAL CONCENTRATION OF TROPOSPHERIC OZONE DUE TO HUMAN ACTIVITIES

THERE is evidence from records of ground-level measurements1-6 that the average tropospheric concentration of ozone in the Northern Hemisphere has increased. In particular, the comparison of recent observations with those made at the Montsouris laboratory in Paris between 1876 and 19105,6, suggests that the surface concentration of ozone at mid to high latitudes has more than doubled in the past 100 years. This has potential implications for a wide range of environmental issues both because of the direct effects of elevated concentrations of ozone on man and ecosystems7,8 and because ozone is a radiatively active gas which could contribute significantly to global warming if its concentration were to increase9-12. We have used a global tropospheric model to simulate the chemistry of the pre-industrial atmosphere and that of the present day. The model results for surface ozone concentrations in the pre-industrial atmosphere agree well with the Montsouris data, and the calculated concentrations for the present day agree with recent observations of a wide range of chemical species. Estimates of the future growth in emissions of nitrogen oxides (NOx) (ref. 13) have been used to make similar calculations for the year 2020. On the basis of these estimates, the global tropospheric concentration of ozone will continue to increase at a rate faster than during the past 100 years. The potential for further increases in tropospheric ozone needs to be taken into account when assessing the impact of air pollution emissions and the adequacy of measures to control them. © 1990 Nature Publishing Group.