Yuzuru Matsuoka

Agricultural activities account for almost 50 and 60% of the total anthropogenic CH₄ and N₂O emissions, respectively in 2005 (IPCC. 2007. Climate change 2007. Mitigation of climate change, Working Group III contribution to the fourth assessment report of the intergovermental panel on climate change summary for policymakers and technical summary). Thus, we developed an integrated model to estimate global CH₄ and N₂O emissions and reduction potentials related to agricultural production from 2000 to 2030. In this model, the amounts of implemented countermeasures for greenhouse gas mitigation are calculated as an optimal problem to minimize the total reduction costs under several marginal abatement costs. As a result, we determined the most cost-effective countermeasures, regions and emission sources with high reduction potentials in 2030. Global CH₄ and N₂O emission in agricultural activities was 4.0 GtCO₂ eq/year in 2000 and will increase to approximately 40% (up to 5.6 GtCO₂ eq/year) by 2030. Moreover, in 2030, the total maximum reduction potential will be about 1.4 GtCO₂ eq/year which accounts for 35% of the total of CH₄ and N₂O emissions in agriculture in 2000. Particularly, livestock manure management and rice paddy are expected to be emission sources that have high reduction potentials. We identified a “daily spread of manure” as one low-cost countermeasure with high reduction potential based on the analysis of reduction potentials by countermeasures.

Introduction It is predicted that global climate change will have significant impacts on the society and economy of the Asia–Pacific region, and that the adoption of measures to tackle global climate change will impose a large economic burden on the region. Also, if the Asia–Pacific region fails to adopt such countermeasures, it has been estimated that its emissions of greenhouse gases (GHG) will increase to over 50% of total global emissions by 2100. To respond to such a serious and long-term threat, it is critical to establish communication and evaluation tools for policymakers and scientists in the region. The Integrated Assessment Model provides a convenient framework for combining knowledge from a wide range of disciplines, and is one of the most effective tools to increase the interaction among groups. The Asia–Pacific Integrated Model (AIM) is one of the most frequently used models in the Asia–Pacific region (Kainuma et al., 2003; Shukla et al., 2004). The distinctive features of AIM are: (1) it involves Asian country teams from Japan, China, India, Korea, Thailand, and so on; (2) it has detailed description of technologies; and (3) it uses information from a detailed geographic information system to evaluate and present the distribution of impacts at local and global levels. Besides preparing country models for evaluation at the state and national level, we have also developed global models to analyze international economic relationships and climate impacts in order to evaluate policy options from a global viewpoint.