Larger, faster-growing livestock and changes in manure handling practices produced an 11% increase in global methane emissions between 2006 and 2011, presenting a new challenge to agricultural practices and making it marginally more difficult for countries to reach their Paris agreement targets, according to a study in the journal Carbon Balance and Management.
The study took a new look at projections of farm methane output produced by the Intergovernmental Panel on Climate Change (IPCC) in 2006. Methane is a relatively short-lived greenhouse gas, but it’s many times more potent than carbon dioxide while it remains in the atmosphere.
“Our revised estimates of global livestock methane emissions are larger than ones made using IPCC 2006 default information, but with significant variation among global regions,” study co-author Dr. Ghassem Asrar, director of the Joint Global Change Research Institute at the U.S. Pacific Northwest National Laboratory, told Carbon Brief. “Global atmospheric concentrations of [methane] have been increasing steadily since 2007. Our revisions suggest that global methane emissions by livestock explain about one-half to three-fourths of this increase.”
The IPCC estimates were based on data from the 1980s and 1990s, but animals and farm practices have changed since, Carbon Brief explains. “Many countries, including the U.S. and Canada, have changed the way they manage animal manure in recent decades. Manure is increasingly being stored in centralized lagoons, which has a larger methane footprint than more traditional types of manure management.”
An analysis for Carbon Brief by two University of Leeds researchers showed the remaining atmospheric carbon budget declining to accommodate the increase in methane emissions. “The revisions roughly approximate to using up to three months allowed emissions of CO2. The new study reinforces that solutions to address methane emissions are more needed than ever, and they can also bring considerable co-benefits for society,” said Prof. Piers Forster and research scientist Chris Smith. “Yet, we should not lose sight of the need to focus on CO2 to meet Paris targets.”