For landfills , estimated methane emissions rose from 1.6 million metric tons in 1860 to 40.3 million metric tons in 1994. Total estimated anthropogenic methane emissions rose from 79.3 million metric tons in 1860 to 371.0 million metric tons in 1994. Within the agricultural sector, livestock replaced rice as the leading component. The authors state these estimates to be a first approximation to actual emissions. As noted in the introduction to this section in Trends Online , the estimates for the 1980s of total anthropogenic methane emissions, and of emissions related to fossil fuels, are consistent with estimates from the Intergovernmental Panel on Climate Change.
Uncertainty results from the use of proxy variables.
Additional uncertainty results from estimates of emissions factors for years without published estimates. References British Geological Survey. United Kingdom Mineral Statistics . Central Statistical Office. Monthly Digest of Statistics .