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Global Methane Emissions Have Risen Nearly 10 Percent Over Last 20 Years

Over the last two decades, global emissions of methane – a powerful greenhouse gas with a global warming potential 28 times larger than carbon dioxide – have risen by nearly 10 percent, jeopardizing the 1.5-2°C warming targets set by the Paris Agreement.

In 2017, atmospheric levels of methane (CH4) were about 2.6 times greater than—or 150% above—pre-industrial levels, according to new research from Future Earth’s Global Carbon Project. Because methane is responsible for 23% of the global warming produced by all greenhouse gases so far, there is an urgent need to understand and quantify a global methane budget in order to assess realistic pathways to mitigate climate change.

Methane Emissions timeline

To meet this need, the GCP has mobilized a large group of multidisciplinary scientists to synthesize and stimulate new research to improve the global methane budget. In order to assess the proper fluxes of CH4 emissions and sinks and quantify the global methane budget, researchers used a variety of tools and data, comparing the results using top-down studies and bottom-up estimates.

Findings for the 2020 Global Methane Budget indicate that global CH4 emissions have increased by 50 million tons between 2000-2006 and 2017. Human activities contribute to about 60% of total global methane emissions, especially within the fossil fuel, agricultural, and waste sectors, which together make up nearly two-thirds of anthropogenic CH4 emissions.

Methane, an odorless gas, is also involved in ground-level formation of ozone, which is an air pollutant and bad for human health. Methane’s atmospheric lifetime (about 12 years) is much shorter than carbon dioxide’s, which can remain in the atmosphere for more than a century, meaning efforts to reduce methane emissions could have more immediate impacts on climate change. Over a 20-year period, the global-warming potential of one tonne of atmospheric methane is similar to that of around 85 tonnes of CO2, according to the Intergovernmental Panel on Climate Change.

The production of fossil fuels – including natural gas, oil, and coal – contributed 108 million tonnes of methane emissions in 2017, a rise of 17%, while agricultural methane emissions, driven by rising red meat consumption around the world, rose by almost 12%, to 227 million tonnes in 2017, while. Of agriculture and waste sector’s subcategories (livestock production, rice cultivation, landfills, and wastewater handling), livestock is by far the largest emissions source.

Methane emission and sink sources

Research also found that emissions have increased most markedly in Africa, the Middle East, China and South Asia, with Europe being the only region where methane emissions seem to have dropped in recent years thanks to declining cattle numbers and policy efforts to reduce emissions such as from landfills and manure.

The current anthropogenic methane emissions trajectory is estimated to lie between the two warmest IPCC-AR5 scenarios, i.e., RCP8.5 and RCP6.0, corresponding to temperature increases above 3°C by the end of this century. This trajectory implies that large reductions of methane emissions are needed to meet the 1.5-2°C target of the Paris Agreement.

Researchers in this effort note that their findings still contain uncertainties and that improved emission inventories and estimates are needed. Yet, the publications on the global methane budget are crucial to methane mitigation, which offers rapid climate benefits and economic, health, and agricultural co-benefits.

The Global Methane Budget is part of the Global Carbon Project efforts to develop a complete picture of the carbon cycle by establishing complete, consistent scientific knowledge to support policy debate and actions to mitigate greenhouse gas emissions to the atmosphere, and will continue to be regularly updated with the most recent and reliable scientific findings.