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A multi-model assessment of pollution transport to the Arctic

Description: We examine the response of Arctic gas and aerosol concentrations to perturbations in pollutant emissions from Europe, East and South Asia, and North America using results from a coordinated model intercomparison. These sensitivities to regional emissions (mixing ratio change per unit emission) vary widely across models and species. Intermodel differences are systematic, however, so that the relative importance of different regions is robust. North America contributes the most to Arctic ozone pollution. For aerosols and CO, European emissions dominate at the Arctic surface but East Asian emissions become progressively more important with altitude, and are dominant in the upper troposphere. Sensitivities show strong seasonality: surface sensitivities typically maximize during boreal winter for European and during spring for East Asian and North American emissions. Mid-tropospheric sensitivities, however, nearly always maximize during spring or summer for all regions. Deposition of black carbon (BC) onto Greenland is most sensitive to North American emissions. North America and Europe each contribute {approx}40% of total BC deposition to Greenland, with {approx}20% from East Asia. Elsewhere in the Arctic, both sensitivity and total BC deposition are dominated by European emissions. Model diversity for aerosols is especially large, resulting primarily from differences in aerosol physical and chemical processing (including removal). Comparison of modeled aerosol concentrations with observations indicates problems in the models, and perhaps, interpretation of the measurements. For gas phase pollutants such as CO and O{sub 3}, which are relatively well-simulated, the processes contributing most to uncertainties depend on the source region and altitude examined. Uncertainties in the Arctic surface CO response to emissions perturbations are dominated by emissions for East Asian sources, while uncertainties in transport, emissions, and oxidation are comparable for European and North American sources. At higher levels, model-to-model variations in transport and oxidation are most important. Differences in photochemistry appear to play the ...
Date: March 13, 2008
Creator: Shindell, D T; Chin, M; Dentener, F; Doherty, R M; Faluvegi, G; Fiore, A M et al.
Partner: UNT Libraries Government Documents Department

The Global Atmospheric Environment for the Next Generation

Description: Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using twenty-five state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, whilst the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models, and show a reasonable agreement with surface ozone, wet deposition and NO{sub 2} satellite observations. Large parts of the world are currently exposed to high ozone concentrations, and high depositions of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 {+-} 1.2 ppbv (CLE), and 4.3 {+-} 2.2 ppbv (A2). Only the progressive MFR scenario will reduce ozone by -2.3 {+-} 1.1 ppbv. The CLE and A2 scenarios project further increases in nitrogen critical loads, with particularly large impacts in Asia where nitrogen emissions and deposition are forecast to increase by a factor of 1.4 (CLE) to 2 (A2). Climate change may modify surface ozone by -0.8 {+-} 0.6 ppbv, with larger decreases over sea than over land. This study shows the importance of enforcing current worldwide air quality legislation, and the major benefits of going further. Non-attainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.
Date: December 7, 2005
Creator: Dentener, F; Stevenson, D; Ellingsen, K; van Joije, T; Schultz, M; Amann, M et al.
Partner: UNT Libraries Government Documents Department