|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.
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 CO2.
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
o l u m n
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
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,
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