12 December 2016

The Global Methane Budget 2000 - 2012

Atmospheric methane concentrations are approaching the most greenhouse-gas-intensive scenarios

Science

Unlike CO2, atmospheric methane concentrations are now rising faster than at any time in the past two decades and, since 2014, are approaching the most greenhouse-gas-intensive scenarios. The reasons for this increase are still debated. Our new analysis suggests that a likely explanation of the recent rapid rise in global methane concentrations is in large part driven by increased biogenic emissions mostly from agriculture, rather than increases from fossil fuels or wetlands.

Impact

Methane is a potent greenhouse gas 28 times more powerful than carbon dioxide on a 100 year time horizon, and its concentration in the atmosphere has increased by 150% since 1750. Methane global emissions are estimated at 559 TgCH4 y-1 [540-570] for 2003-2012 as inferred by an ensemble of ‘top-down’ approaches. A possible slower destruction of methane in the atmosphere (sinks) could also be a contributor of the observed atmospheric increase. 

Summary

Atmospheric methane concentrations are now rising faster than at any time in the past two decades and, since 2014, are approaching the most greenhouse-gas-intensive scenarios. Anthropogenic emissions represent about 60% of total methane emissions. Emissions from agriculture activities and waste management (enteric fermentation, manure management, rice cultivation, landfills and waste-water handling) represent about 60% of the anthropogenic emissions. Livestock (enteric fermentation and manure management) and rice cultivation contribute one third and 10%, respectively, of anthropogenic emissions.  Fossil fuel (coal, oil, and gas) production and use have increased over the past decade and contributed about one third of anthropogenic methane emissions.

Contact
William J. Riley
Lawrence Berkeley National Laboratory (LBNL)