Abstract:
Methane concentrations in our atmosphere have more than doubled since pre-industrial
times. Although the rate of change of global concentrations has recently slowed, studies
predict that this stabilization will be short-lived. There is a growing need to better
understand the emissions sources for this potent greenhouse gas and to assess possible
reduction strategies. Global methane emissions pathways have been proposed by the
IPCC but the relative contributions from different source types and individual countries is
not well determined. I analyze six main anthropogenic sources including emissions from
enteric fermentation, rice production, landfills, wastewater treatment, coal mining, and
natural gas and oil production. Future changes in the main drivers of population,
economic, and technological parameters can impact methane emissions from these six
sources in Brazil, China, India, Mexico, Russia, and the United States through 2050. I
develop a simple framework to characterize and project methane emissions enabling the
building of a business as usual and multiple alternative scenarios. The methane
concentration implications of these projections are analyzed using a simple climate
model. Finally, a technological potential reduction scenario is proposed by maintaining
baseline assumptions while improving methane capture technologies and options. Under
business as usual assumptions, global anthropogenic methane emissions are projected to
double by 2030 but there is potential to cause a global decrease by 40 % per year of
projected baseline levels which would reduce global temperature changes by 0.5 degrees
Celsius by 2100.
