Intercontinental Transport of Ozone Pollution Air Pollutant Emissions in East Asia Accelerate Global Warming

November 8, 2001

The Atmospheric Composition Research Program (ACRP) is a division of the Frontier Research System for Global Change (FRSGC), which is a joint project of NASDA and JAMSTEC. Using a three-dimensional global chemical transport model (CTM), the Program Director Dr. Hajime Akimoto and ACRP researcher Dr. Oliver Wild have shown that ozone formed from air pollutants emitted in each of the continents of the northern hemisphere-East Asia, North America, and Europe-is subject to long-range intercontinental transport.

This research revealed that the ozone formed from air pollutant emissions in East Asia, in particular, is transported to the upper troposphere, and carried on the westerlies to North America and Europe, thereby promoting global warming. Focusing attention on the Earth's surface, however, East Asia was found to be affected by ozone pollution from Europe. The results of this research will be published in the November 16 edition of the American Geophysical Union's Journal of Geophysical Research.

The Intergovernmental Panel on Climate Change (IPCC) 2001 Report states that tropospheric ozone is as important a radiative forcing agent as methane in global mean terms, and that attainment of air quality targets could be threatened in the majority of the northern hemisphere (note 1).

Further, tropospheric ozone is the second most important greenhouse gas in the Northern Hemisphere after CO2 (notes 2 and 3). The radiative forcing due to ozone varies widely depending on the region, and responds comparatively quickly to changes in emission levels compared with the long-lived greenhouse gases such as CO2.

Until this research, however, the importance of for long-range intercontinental transport of ozone across the whole of the Northern Hemisphere had not been quantified.


When NOx, CO, and hydrocarbon emissions were increased together by 10% over each of the industrial regions of East Asia, North America, and Europe using a three-dimensional global transport model (note 4), the changes in the distribution and amount of ozone found in the troposphere were revealed.(fig.1)

The data showed that raising air pollution levels in East Asia causes increased ozone to be effectively lifted high into the trosphere, where it may be and easily transported to North America and Europe on the westerlies, thereby contributing significantly to the greenhouse effect (figs. 2 and note 3).

When the air pollution levels in Europe are raised, however, the increased ozone is transported at comparatively low altitudes, thereby intensifying ozone concentrations closer to the Earth's surface over East Asia (fig 3.).


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