Special Topic: Global Environment and Atmospheric Pollution
Methane Emission Inventory
-Construction of Gridded Database of Methane Emissions for Input of Model-
It is expected that construction of accurate model predicting the change of atmospheric compositions will play an important role in understanding of climate change and global environmental issues. In this topic, we would like to introduce our approach to the construction of a high-accuracy and high-resolution emission database to input into such model calculations, with focusing on estimations of methane emissions in the Asian region.
Kazuyo Yamaji
Atmospheric Composition Research Program
Frontier Research System for Global Change (FRSGC)

Constructing a High-accuracy and High-resolution Emission Database in Asia

   Human activity has greatly altered the atmospheric composition and trace gas concentration, and gave impacts on global environment accordingly. Atmospheric modeling plays an important role in understanding the chemical and physical mechanisms of transformation and transportation of atmospheric trace species, and the prediction of future climate changes and global environmental issues. To run such kind of atmospheric model, it is necessary to have emission inventories of the trace species with high-accuracy and highresolution as input data. For this purpose, our group has been developing emission inventories of trace species for South, Southeast, and East Asia. We introduce some results of methane emissions.

Asia as an Important Methane Source Region

  Methane is a major greenhouse gas next to CO
2. It also plays an important role in atmospheric photochemistry. Atmospheric methane concentration has more than doubled since pre-industrial era, which may have significantly affected global environment. Agricultural activities, especially enteric fermentation and rice cultivation, are the biggest anthropogenic methane sources. Up to 90 % of the global rice fields are in Asia, where there is also a large livestock population. Thus, this area seems to be a major area for methane emission. However, due to the difference in estimation method and data source, and the difficulty in obtaining reliable information of each Asian country, the estimates of methane emission from this region have large uncertainties. To develop atmospheric composition model that considers the rapid socioeconomic change in Asia, we are trying our best to give accurate and high-resolution methane emission database for the present day and the future as well.

Fig. 1 Methane emissions from agriculture activities (paddy fields and livestock) in major countries in Asia in 2000.

A High-resolution Methane Emission Database Derived from Region-specific Emission Factors and Detailed Country Statistics

  Our group estimated annual methane emission by using region-specific emission factors that were derived from large amount of field measurements, climate, and agricultural activitiy information, e.g., water management, organic fertilizer use, and quantity and quality of livestock feed and by using detailed statistics at country or province level (especially for India, China, and Japan). Figure 1 shows that methane emission from agriculture sector (rice field and livestock) in Asian countries in 2000 amounted to 55 TgCH4, which accounts for 10 % of the global total methane source, is less than many of the previous estimates. This was mainly because we have a much smaller estimate of methane emission from rice fields, and this smaller estimate was a result of involving much more field measurement results and distinguishing various water management practices and the use of organic fertilizer in rice fields. Considering that 90 % of rice fields in the world exists in Asia, we postulate that the role of rice field in global methane budget has been overestimated in the past. We hope our estimation will contribute to the IPCC Fourth Assessment report.
   Figure 2 shows gridded methane emission from agriculture in Asian countries in 2000, with a resolution of 0.5 degree. It indicates very big regional difference, with hot spots in Bangladesh, west Java, and Mekong River delta.
   Now we are working on predicting future emissions and database by considering the rapid land use change, population growth, and economic development in Asia.

Fig. 2 Gridded emission database (0.5º x 0.5º) of methane from agriculture activities (paddy fields and livestock) in Asia in 2000.

   C o l u m n

Report on the ABC (Atmospheric Brown Cloud-Asia) Open Public Symposium

   Last year, on September 23rd, The ABC Open Public Symposium entitled "Air Pollution in Asia and Our Life" was co-hosted by the Ministry of the Environment; the Ministry of Education, Culture, Sports, Science and Technology; and the Japan Marine Science and the Technology Center/Frontier Research System for Global Change at U Thant International Hall/United Nations University. About 150 people took advantage of this opportunity to hear and take part in discussions on environmental issues.
   After a few words from each co-host, including an introduction, the three guest speakers gave their presentations. Dr. S. C. Lonergan from the United Nations Environment Programme (UNEP) spoke on "Air pollution, economic activity and society in a post-Johannesburg world"; Dr. V. Ramanathan from the University of California talked on "Atmospheric brown clouds: S. Asian, tropical & global impacts", and Dr. P. Crutzen, winner of the 1995 Nobel Prize for Chemistry, and the former Director of the Atmospheric Chemistry Division at the Max Planck Institute for Chemistry, spoke on "The role of the tropics in atmospheric chemistry and climate". Each presentation was followed by a Q&A session.
  After a break, we resumed with a panel discussion, with Ms. Aiko Doden, an NHK news broadcaster, as moderator. Starting with Dr.Teruyuki Nakajima (from Tokyo University)'s talk concerning "The influence of human activity on the climate", we held a discussion on the tradeoffs between development and economic growth, air pollution and the environment, and poverty.
   The closing remarks were made by Dr. K. Suzuki from the United Nations University/Institute of Advanced Studies (UNU/IAS). He commented that the problems ABC has been working on, which link developing and developed countries, have become more and more significant in the context of global warming. Dr. Suzuki stressed the importance of education for sustainable development, improvement of research skills in developing countries, and the need for technology transfer.
   We would like to thank you all of you who have joined us.


Frontier Newsletter/No.25
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