The study presents a three-dimensional model synthesis of the global methane cycle, aiming to derive a justified global budget of methane for the 1980s. Atmospheric methane observations and isotopic content were used to constrain hypotheses about sources and sinks. The study compiled geographic and seasonal emission distributions of major methane sources and sinks using methane flux measurements, energy and agricultural statistics, and global digital data bases. Chemical destruction of methane in the atmosphere was calculated using three-dimensional OH fields. The signatures of sources and sinks were simulated using a global three-dimensional tracer transport model. Candidate methane budget scenarios were constructed based on mass balance and carbon isotopes. The scenarios were tested against observed meridional gradients and seasonal variations of methane. Several budget scenarios satisfied all atmospheric observations, 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. Emissions from landfills, tropical swamps, rice fields, biomass burning, and termites total 295 Tg, but individual contributions cannot be uniquely determined due to lack of direct measurements. The study used a three-dimensional atmospheric tracer transport model to simulate atmospheric methane response to sources and sinks. Observations from the NOAA/CMDL network and other sources were used to analyze methane concentrations and isotopic content. The study found that methane emissions from wetlands, rice paddies, and animals contribute significantly to the global methane budget. The results showed that methane concentrations vary seasonally and geographically, with highest concentrations in the northern hemisphere. The study also found that methane emissions from wetlands, rice paddies, and animals are influenced by temperature, land use, and agricultural practices. The study concluded that the global methane budget is complex and requires further research to better understand and project secular trends.The study presents a three-dimensional model synthesis of the global methane cycle, aiming to derive a justified global budget of methane for the 1980s. Atmospheric methane observations and isotopic content were used to constrain hypotheses about sources and sinks. The study compiled geographic and seasonal emission distributions of major methane sources and sinks using methane flux measurements, energy and agricultural statistics, and global digital data bases. Chemical destruction of methane in the atmosphere was calculated using three-dimensional OH fields. The signatures of sources and sinks were simulated using a global three-dimensional tracer transport model. Candidate methane budget scenarios were constructed based on mass balance and carbon isotopes. The scenarios were tested against observed meridional gradients and seasonal variations of methane. Several budget scenarios satisfied all atmospheric observations, 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. Emissions from landfills, tropical swamps, rice fields, biomass burning, and termites total 295 Tg, but individual contributions cannot be uniquely determined due to lack of direct measurements. The study used a three-dimensional atmospheric tracer transport model to simulate atmospheric methane response to sources and sinks. Observations from the NOAA/CMDL network and other sources were used to analyze methane concentrations and isotopic content. The study found that methane emissions from wetlands, rice paddies, and animals contribute significantly to the global methane budget. The results showed that methane concentrations vary seasonally and geographically, with highest concentrations in the northern hemisphere. The study also found that methane emissions from wetlands, rice paddies, and animals are influenced by temperature, land use, and agricultural practices. The study concluded that the global methane budget is complex and requires further research to better understand and project secular trends.