Evaluation and prediction of the effects of climate variation and global warming on rice production in Monsoon Asia.

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The objectives were to evaluate the current climate variation effects on regional rice production in Monsoon Asia, and to predict the impact of anticipated global warming on rice yield in the region. The results from 4-year research may be summarized as follows :(1)Temperature increase in rice growth season was recognized in Western Japan where the minimum and maximum temperatures have rised by 1.5℃ and 1.0℃ from those in 1960's, which is giving negative effects on rice yield.(2)It was found that the yearly variation in rice yield in Monsoon Asia has changed to increasing trend around 1990 from the previous dereasing trend reflecting mainly the increasing yield fluctuation in India. The yield in India tended to be above the average in La Nina years and below that in El Nino years. Rice yields in India and China are variating in opposite directions each other. This implies that, once those two big rice production countries should have concurrent yield reduction due to adverse climates, it will give enormous impact on rice supply in Monsoon Asia.(3)A dynamic model was developed for simulation of doubling CO_2 climate effect on rice yield based on analysis of ecophysiological genotype-by-environmental interaction processes of rice growth. This model well explained growth and yield of different rice genotypes grown in widely different climatic regions in Monsoon Asia. The model predicts a global warming of more than 3℃ and doubling CO_2 concentration will reduce rice yields of most Monsoon Asia except north temperate areas, with more pronounced effects in Japonica type rice.