The study presents a comprehensive synthesis of the global methane cycle to derive a justified global budget for the 1980s. It compiles geographic and seasonal emission distributions of major sources and sinks of atmospheric methane using methane flux measurements, energy and agricultural statistics, and global digital databases of land surface characteristics and anthropogenic activities. Chemical and physical processes are simulated in a global three-dimensional OH flux study. The atmospheric signatures of each source and sink are simulated using a global three-dimensional tracer transport model. Candidate methane budget scenarios are constructed based on mass balance of methane and its carbon isotopes, and their verisimilitude is tested by their ability to reproduce observed meridional gradients and seasonal variations of methane. Several budget scenarios satisfy all atmospheric observations simultaneously, with a preferred budget comprising annual destruction rates of 450 Tg by OH oxidation and 10 Tg by soil absorption, and annual emissions of 80 Tg from fossil sources, 80 Tg from domestic animals, and 35 Tg from wetlands and tundra poleward of 50°N. Other emissions from landfills, tropical swamps, rice fields, biomass burning, and termites total 295 Tg, but their individual contributions cannot be uniquely determined due to lack of direct flux measurements and atmospheric methane variations in concentrated source regions. The study also discusses the use of isotopic content of atmospheric methane and isotopic signatures of methane from different production and destruction processes to constrain the global methane budget.The study presents a comprehensive synthesis of the global methane cycle to derive a justified global budget for the 1980s. It compiles geographic and seasonal emission distributions of major sources and sinks of atmospheric methane using methane flux measurements, energy and agricultural statistics, and global digital databases of land surface characteristics and anthropogenic activities. Chemical and physical processes are simulated in a global three-dimensional OH flux study. The atmospheric signatures of each source and sink are simulated using a global three-dimensional tracer transport model. Candidate methane budget scenarios are constructed based on mass balance of methane and its carbon isotopes, and their verisimilitude is tested by their ability to reproduce observed meridional gradients and seasonal variations of methane. Several budget scenarios satisfy all atmospheric observations simultaneously, with a preferred budget comprising annual destruction rates of 450 Tg by OH oxidation and 10 Tg by soil absorption, and annual emissions of 80 Tg from fossil sources, 80 Tg from domestic animals, and 35 Tg from wetlands and tundra poleward of 50°N. Other emissions from landfills, tropical swamps, rice fields, biomass burning, and termites total 295 Tg, but their individual contributions cannot be uniquely determined due to lack of direct flux measurements and atmospheric methane variations in concentrated source regions. The study also discusses the use of isotopic content of atmospheric methane and isotopic signatures of methane from different production and destruction processes to constrain the global methane budget.