| Summary: | The development of the ozone concentrations near the ground in northern Europe during the past 20 years is characterized by a decrease in the highest concentrations and an increased in the lowest and medium high concentrations. Rising background ozone concentrations over the entire northern hemisphere is most likely the explanation for the increase in the lower concentration range. The yearly, maximum 8-hour mean ozone concentration is significantly decreasing in southern Sweden, while it remains unchanged in northern Sweden. Model predictions, as well as trend analysis based on observations implies that the target value within the Swedish Environmental Objectives, intended to prevent negative impacts on human health, will still be exceeded by the year 2050. There is no statistically significant change over time for AOT40 April-September over Sweden during the past 20 years. The target value within the Swedish Environmental Objectives, intended to protect vegetation, based on AOT40, is exceeded in southern Sweden but not in the north. If the future emissions of ozone precursors decrease by 2050 according the scenarios in the CLEO Eurobase, as well as the RCP 4.5, then the target value to protect the vegetation will not be exceeded in Sweden as well as over most parts of northern Europe. In these scenarios, however, it is assumed that the hemispheric background ozone concentrations do not change substantially, which is uncertain. If the estimates of vegetation ozone exposure were instead based on ozone flux, then the critical level for ozone impacts on vegetation used within the LRTAP convention would still be exceeded in southern Sweden by the year 2050. This report is only available in Swedish.
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