JAXA Japan Aerospace Exploration Agency

Global Warming Enhances Ozone Transport from
the Stratosphere to the Troposphere
-Further Accelerates Global Warming -

Japan Aerospace Exploration Agency (JAXA)
Japan Marine Science and Technology Center(JAMSTEC)

Outline

Hajime Akimoto (Director of Atmospheric Composition Research Program), Masaaki Takahashi (Group Leader, joint appointment of professor at Center for Climate System Research, University of Tokyo), and Kengo Sudo (Research Fellow) at Frontier Research System for Global Change (FRSGC: joint project of JAMSTEC and JAXA), has found that ozone transport from the stratosphere (Note 1) to the troposphere will be enhanced by global warming as studied by chemical/climate model experiment (Figure 1 and 2). It is suggested that the enhanced intrusion of ozone to the troposphere will further accelerates global warming.

This research outcome was published in Geophysical Research Letter (Vol. 30, No. 24), by American Geophysical Union, and distributed in Japan at the end of February.

Background

Impact of climate change induced by global warming, on chemical species formed in the atmosphere such as ozone, and its feedback of the chemistry change to the climate is called chemistry-climate interaction, which is becoming one of the major concerns in various sectors. Particularly, tropsopheric ozone (Note 2) is recognized as the third most important greenhouse gas in the IPCC Third Assessment Report, and its relevance to global warming/climate change attracts much attention.

In order to study climate change accompanied by the increase of greenhouse gasses, FRSGC has developed a chemical climate model, "CHASER" (Note 3), jointly with Center for Climate System Research, University of Tokyo (CCSR), and National Institute for Environmental Studies (NIES), which can calculate chemical processes in the troposphere and its impact on climate on a global scale. So far, future change of distribution of air pollutants such as ozone, and their climate effect have been predicted.

Results

Using the A2 Scenario of IPCC (Reference 1), increase of tropopsheric ozone has been calculated, and it was elucidated that there will be a big difference in vertical distribution of ozone between the cases with and without considering global warming. Result of experiment considering warming shows great enhancement of ozone in the upper troposphere at mid and low latitude. The reason was found to be due to the enhancement of atmospheric circulation both in the stratosphere and troposphere, resulting the increase of stratospheric intrusion of ozone to the troposphere (Ref. 2).

It is known that ozone in the upper troposphere has a strong greenhouse effect and its increase has marked effect on the increase of earth surface temperature (Reference 3). Therefore, the present result implies that global warming enhances ozone in the upper troposphere, the ozone enhancement possibly further accelerates warming.

Contacts
Frontier Research System for Global Change
Contact: Ms. Ota
Tel: +81 (0)45-778-5687 (direct)
URL: http://www.jamstec.go.jp/frsgc/eng/index.html
JAXA, Public Affairs Department
Tel: +81-3-3438-6107/6108/6109
URL: http://www.jaxa.jp/index_e.html
JAMSTEC, Public Relations Office, General Affairs Department
Tel: +81 (0)46-867-9066
URL: http://www.jamstec.go.jp/jamstec-e/index-e.html

Note 1:Stratospheric ozone:
In the stratosphere oxygen atom (O) formed in the photolysis of oxygen (O2) by ultraviolet (UV) light in the sun radiation produces ozone (O3). Ozone is in turn photolyzed to regenerate O an O2 by absorbing UV light, which is harmful to living thing on the earth.

Note 2: Tropospheric (surface) ozone:
In the troposphere ozone is produced from oxygen atoms formed in the photolysis of nitrogen dioxide (NO2) emitted from automobiles and factories. Ozone is a major component of photochemical smog and toxic air pollutants to living things. According to IPCC Third Assessment Report, ozone is recognized as the third most important greenhouse gases following to carbon dioxide and methane.

Note 3: CHASER (Chemical AGCM for Study of Atmospheric Environment and Radiative Forcing) :
Chemical-climate model in which photochemistry is incorporated CCSR/NIES/ FRSGC atmospheric general circulation model (AGCM). It can calculate emission, atmospheric transport, chemical reaction wet removal etc. of precursor pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxide (SO2), and simulate formation and global distribution of ozone, sulfate aerosol, etc.

Note 4: Hadley Circulation:
Atmospheric circulation which rises near equator and descend near 30 degree north and south.