Prather, M and Gauss, M and Berntsen, T and Isaksen, I and Sundet, J and Bey, I and Brasseur, G and Dentener, F and Derwent, R and Stevenson, D and Grenfell, L and Hauglustaine, D and Horowitz, L and Jacob, D and Mickley, L and Lawrence, M and von Kuhlmann, R and Muller, J F and Pitari, G and Rogers, H and Johnson, M and Pyle, J and Law, K and van Weele, M and Wild, O (2003) Fresh air in the 21st century? Geophysical Research Letters, 30 (2). -. ISSN 0094-8276
Ozone is an air quality problem today for much of the world's population. Regions can exceed the ozone air quality standards (AQS) through a combination of local emissions, meteorology favoring pollution episodes, and the clean-air baseline levels of ozone upon which pollution builds. The IPCC 2001 assessment studied a range of global emission scenarios and found that all but one projects increases in global tropospheric ozone during the 21st century. By 2030, near-surface increases over much of the northern hemisphere are estimated to be about 5 ppb (+2 to +7 ppb over the range of scenarios). By 2100 the two more extreme scenarios project baseline ozone increases of >20 ppb, while the other four scenarios give changes of -4 to +10 ppb. Even modest increases in the background abundance of tropospheric ozone might defeat current AQS strategies. The larger increases, however, would gravely threaten both urban and rural air quality over most of the northern hemisphere.
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