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

Over the past decade, several estimates have been developed to establish source strengths of various atmospheric trace gases. Interest is, in part, driven by international agreements wherein governments are required to establish emission inventories and to develop means to stabilize or reduce national emissions. Although techniques and models for quantifying gas fluxes have improved considerably for some gases and sources, the uncertainties in the national, regional, and global budgets for a number of atmospheric compounds remain. In this paper, we review estimates of the emission of methane from 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 emission value for China are reviewed. A comparison among them yields a suggested 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.