Our Press Released Reseaches

This newsletter provides an overview of the research activities covered in this year's press releases.

Ozone Pollution Across the Continents
- Air Pollutants from East Asia Accelerate Global Warming -

The Atmospheric Composition Research Program, under the leadership of Program Director Dr. Hajime Akimoto, released results of research about the generation and spread of ozone, which is one of the causes of global warming.

Dr. Hajime Akimoto (Program Director, Atmospheric Composition Research Program)

S peaking of trans-boundary air pollution, one may often hear the story that pollution such as acid rain is transported from China to Japan. One of recent topics, however, is air pollution across the continents, e.g. pollutants from Asia are transported to America, from America to Europe, and from Europe to Asia. We have recognized the importance of this issue and started the study from the early stage of the Atmospheric Composition Research Program of FRSGC.

Recent research by Oliver Wild and Hajime Akimoto (PD) has revealed that ozone formed in the troposphere from the air pollutants (nitrogen oxides, carbon monoxide, and hydrocarbons) emitted in each continent, East Asia, North America and Europe is transported in a long-range and affect to another continent.

Fig1 : Increased in East Asia Emissions


This graph shows the average increase in the concentrations (ppt) of ozone in altitudinal and latitudinal directions when ozone precursor emissions from East Asia are increased by 10%. The impact extends to North America and Europe, and is particularly strong over North America.

Speaking of ozone about 90% of ozone in the earth's atmosphere resides in the stratosphere and only about 10% exists in the troposphere. This relatively small amount of tropospheric ozone, however, acts as greenhouse gas in the upper layer to cause global warming, and behaves as toxic air pollutants near the earth surface to be harmful for the health of human and ecosystem.

In particular, this research has revealed that ozone formed from air pollutants emitted in East Asia is efficiently transported vertically to the upper troposphere and easily transported to North America and Europe by westerly wind to accelerates global warming effectively (Fig 1).

On the contrary, ozone formed from the pollutants emitted in Europe is transported to the east in the lower layer and enhances ozone pollution in East Asia. Ozone formed from pollutants emitted in North America behaves just in-between the case of East Asia and Europe; it gives a large effect on Europe in the middle layer of the troposphere since the distance over the Atlantic is much shorter than the Pacific Ocean and Eurasian continent.

Fig2 : Impact on East Asia (Sapporo, Japan) of Rise in Ozone Levels in Europe

Further, the amount of ozone transported e.g. from Europe to East Asia is the highest in spring followed by in autumn as shown in Fig. 2. It is well-known that ozone in near the earth surface in remote area in the northern hemisphere has spring peak. Such a phenomena was found to be mostly due to trans-continental long-range transport of ozone.

The results of this study have been published in the November 16th issue of Journal of Geophysical Research.


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