I'm not so sure about methane (major sources include rice agriculture, landfills, domesticated animals and biomass burning). (realclimate.org)
At a meeting of the American Geophysical Union (December 17, 2008), scientists detailed evidence in support of the controversial idea that the introduction of large - scale rice agriculture in Asia, coupled with extensive deforestation in Europe began to alter world climate by pumping significant amounts of greenhouse gases into the atmosphere over the last 1000 years. (newworldencyclopedia.org)
The study provides definitive evidence «for millet agriculture developing earlier than full - fledged rice agriculture.» (sciencemag.org)