Globale Auswirkung des Straßenverkehrs auf die chemische Zusammensetzung der Atmosphäre
Road traffic represents one of the main sources of emissions to the atmosphere. This work determines the impact of road traffic emissions on the chemical composition of the atmosphere by a numerical modelling study with ECHAM4/CBM-IV. For the first time, global impact of non-methane-hydrocarbon-emissions (NMHCs) from road traffic is presented. Annual, global emissions from road traffic following a consumption-based approach amount to (8.8 +/- 1.8) Tg [N] nitrogen oxides, (206 +/- 86) Tg [CO] carbonmonoxide, and (34.4 +/- 18.9) Tg NMHCs. Road traffic emissions cause an increase of ozone, which is an important trace gas for the oxidizing capacity and the radiative budget of the atmosphere. In industrialized regions of the northern hemisphere the increase exceeds more than 20%. In remote regions an increase of more than 10% is calculated. Tropical latitudes show a relative contribution of more than 6% due to road traffic up to 10km. NOx-emissions account for about 70% of this ozone increase. Further, road traffic increases and decreases the concentration of hydroxyl radicals (OH) depending on geographical region and season. This again affects the oxidizing capacity and the lifetime of methane. In summer, road traffic causes in northern extratropics a 3% increase of OH, and in winter a decrease of 10%. These changes in chemical composition cause an indirect radiative forcing to the atmosphere. Ozone increases due to road traffic emissions (NOx, CO, NMHCs) result in an annual and global mean radiative forcing of 0.058 W/m^2. The indirect forcing due to road traffic-induced changes in the lifetime of methane amounts to 0.006 W/m^2. This forcing is temporal and spatial inhomogeneous, and can even possess a positive sign (e.g. in spring). Results show that NMHC-emissions considerably contribute to the global impact of road traffic emissions.
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