Exchange of methane from rice fields: National, regional, and global budgets

Over the past decade, several estimates have been developed to establish so urce strengths of various atmospheric trace gases. Interest is, in part, dr iven by international agreements wherein governments are required to establ ish emission inventories and to develop means to stabilize or reduce nation al emissions. Although techniques and models for quantifying gas fluxes hav e improved considerably for some gases and sources, the uncertainties in th e national, regional, and global budgets for a number of atmospheric compou nds remain. In this paper, we review estimates of the emission of methane f rom rice fields both on a global scale and on a country scale, using China as an example. Several reported methods of obtaining an annual methane emis sion value for China are reviewed. A comparison among them yields a suggest ed emission value of 13.0 +/- 3.3 Tg yr(-1) and a range from 9.7 to 16.2 Tg yr(-1). Several strategies are suggested for future requirements to obtain greater accuracy in regional and country emission values.