Trends and scenarios of ground-level ozone concentrations in Finland

This paper presents an overview of the changes in ground-level ozone and vegetation exposure occurring in Finland, both as observed in the recent decade, and as estimated for the period 1900 to 2100. A trend analysis of ozone and total nitrate concentrations is carried out for the 1989-2001 period. Future and past concentrations are modelled based on chemistry-transport model simulations, the SIZES (Special Report on Emissions Scenarios) scenarios of the Intergovernmental Panel on Climate Change and emission inventories. Measured summertime ozone shows no decreasing trend despite reported precursor emission reductions. In central Finland, AOT40 (accumulated exposure over a threshold of 40 ppb) over April-September is presently about 6300 ppb h and is estimated to decrease by 570 ppb h as a result of the agreed European emissions reductions by 2010. A similar but opposite change results from the enhanced biogenic emissions of volatile organic compounds due to increased temperatures by 2050. According to the SIZES scenarios, the tropospheric background concentrations will increase considerably until about 2050. After this, exposures begin to decline in those scenarios which emphasise new technologies and environmental aspects (8100 ppb h by 2050 in the B1 scenario), but increase monotonically in the A scenarios driven by economic growth.