We present a new assessment
of the global methane (CH4
) budget arising from both natural and human-induced emissions, and how CH4
is destroyed in the atmosphere by chemical reactions and soil uptake. This assessement is a collaboration between research institutes in the Global Carbon Project.
to see the interactive CH4
source emission visualization.
is a potent greenhouse gas that contributes to human-induced climate change. Atmospheric CH4
concentrations have increased 150% since the Industrial Era [IPCC, 2013
] and have been increasing since 2007 after almost a decade of stable concentrations in the late 1990s. Understanding the dynamics of the global CH4
budget and attributing changes to different sources is fundamental for tracking climate change and mitigation options to avert further global warming.
The methane budget:
Includes human-induced emissions from Agriculture & Waste (e.g. livestock and rice paddies) and Fossil fuel production & use (coal, gas/oil extraction). The largest natural emissions come from decomposing organic matter in Wetlands. Biofuel & Biomass burning emissions are natural and human-induced. Other Natural sources (e.g. geological processes, lakes, rivers, termites) are also important, but these sources are not currently very well understood.
Estimating the methane budget:
The CH4 budget is estimated in 14 regions for 5 source categories using "top down (TD)" and "bottom up (BU)" methods. BU uses diverse data inventories, observation-driven methods and process-based models (e.g. energy statistics, agricultural data, biogeochemistry modeling). TD optimally combines measurements of atmospheric CH4 at > 100 stations around the world with a first-guess estimate of CH4 emissions into an atmospheric inversion framework.
As the number of studies is uneven and generally small, uncertainties are reported in brackets as a range between the minimum and maximum estimates. Uncertainties are typically on the order of 30% of the mean for a given type of CH4 emission at a global scale (less for anthropogenic, more for natural). Uncertainties can increase up to 100% (or more) of the mean when looking at CH4 emission type in a region.
As part of its scientific goals, the Global Carbon Project team will further develop more complete and constrained CH4 budgets and provide regular updates.