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Project Leader	Hitoshi MUKAI National Institute for Environmental Studies (NIES) 16-2 Onogawa, Tsukuba, Ibaraki 305-0053 JAPAN Tel: +81-298-50-2536 Fax: +81-298-50-2569 Email: lnmukaih@nies.go.jp
Funding	US $27,000
Participating countries	Australia, Canada, China, France, Japan, Korea, New Zealand, USA

Introduction/Background
Atmospheric CO2 is produced not only by human activities but also nature itself. Understanding of CO2 fluxes from nature, such as land biota and oceans is essential to discuss/promote CO2 reduction for the prevention of global warming. At the same time, CO2 flux from nature is affected by global climatic events, such as El Nino Southern Oscillation (ENSO). The Asia Pacific region includes important areas such as the equatorial area of the Pacific and Southeast Asia, where ENSO causes dramatic annual CO2 fluxes. For this reason some laboratories in this region have been carrying out CO2 measurements over the Pacific Ocean.
CO2 isotope ratio measurement is usually used to identify sources of CO2. Several scientists in this region are carrying out such isotope ratio measurements of CO2 by using monitoring stations, airplanes and ships. The National Institute for Environmental Studies (NIES) in Japan is also measuring latitudinal distribution of carbon and oxygen isotope ratios of CO2 over the Pacific using two ships. However, inter-calibration among these measurement programmes has not been carried out sufficiently. A small difference in the scale between laboratories may cause a serious problem in calculation of CO2 geographical flux. Current differences exceed the required levels, and therefore adjustment of their scales to one common scale is necessary to make the analysis more reliable.

At the Fifth APN Inter-Governmental Meeting in Pakistan, Mr. Onogawa from the National Institute of Environmental Studies (NIES) in Japan proposed a workshop to plan a strategy for the inter-calibration of CO2 measurements. This workshop was supported by NIES and organised by APN.

Outline of activities conducted
The workshop was held 9-10 November at the International Congress Center in Tsukuba, Japan. There were 22 presentations over two days. The workshop provided an opportunity to exchange information between regional communities and discuss the methodology for isotope measurement of atmospheric CO2 in the Asia-Pacific region. It also involved comparison of isotope measurement methodologies from each laboratory and a discussion on the possibility of inter-calibration of CO2 isotope measurement in the Asia-Pacific region. At the same time, the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia outlined a plan for a worldwide inter-calibration for CO2 concentration and isotopes (GLOBALHUBS). They are now seeking a means to organise many institutes throughout the world.

Outcomes/Products
Through the workshop, the high potential on isotope analysis of carbon dioxide in the Asia-Pacific region was confirmed. Each laboratory had a different strategy for maintaining their measurements and precision. Automatic extraction and GC technique were applied to treat many samples and to minimise sample size. In this case, usage of air standard was strongly recommended to keep the continuity of the data. Because each analytical instrument used different calculation methods, it should be unified. As for the primary standard, calibration of oxygen isotope ratio was found to be difficult still. Some trials of co-operative analysis of reference material produced in NIES were initiated in order to check the scale of isotope analysis. The homepage on co-operative analysis can be found at: http://www.members.aol.com/mhmukai/NACIShome.htm

Future directions/Follow-up work
NIES is trying to distribute reference material in the community to compare the scale in each laboratory and seek the analytical solution. Advanced comparison work using air standard will also be necessary as a next step. As for GLOBALHUBS, international inter-comparison plan, a concrete and realistic regional HUB plan including an international funding strategy, should be discussed by an executive committee in the near future. It is desirable that APN workshops will be held periodically to follow-up such an international activity.