An international team of researchers has provided detailed data on increasing concentrations of methane in the atmosphere, a potent greenhouse gas (GHG).
The second most abundant human-related GHG with a global warming potential, even larger than that of carbon dioxide (CO2), methane (CH4) has entered the spotlight again. After a period of stabilisation in the early 2000s, atmospheric emissions and concentrations of CH4 are rising, according to a study published in the journal ‘Earth System Science Data’. “The surface dry air mole fraction of atmospheric methane (CH4) reached 1857 ppb [parts per billion] in 2018,” as noted in the journal article.
“This increase is attributable in large part to increased anthropogenic emissions arising primarily from agriculture (e.g. livestock production, rice cultivation, biomass burning), fossil fuel production and use, waste disposal, and alterations to natural methane fluxes due to increased atmospheric CO2 concentrations and climate change,” the research adds.
The study, which received support from the EU-funded projects METLAKE, VERIFY and Nunataryuk, also shows that emissions caused by direct human activity, or anthropogenic sources, account for about 60 % of total methane emissions. A news release lists various sources of methane: “30% from enteric fermentation and manure management; 22% from oil and gas production and use; 18% from handling solid and liquid wastes; 11% from coal extraction; 8% from rice cultivation; 8% from biomass and biofuel burning. The rest is attributed to transport (e.g. road transport) and industry.”
The same news release states that the rise “in methane concentrations follows trends of future scenarios that do not comply with the objectives of [the] Paris Agreement.” It also emphasises that “Europe seems to be the only region where emissions have decreased … depending on the approach used for the estimation. This decrease is mainly related to the agriculture and waste sector.”Methane is a significant contributor to global warming because it traps heat in the atmosphere. In the news release, researchers Simona Castaldi and Sergio Noce from VERIFY project partner Euro-Mediterranean Center on Climate Change comment: “We know well that carbon dioxide is the major driver of climate change, but methane has undoubtedly an important role in this process.” According to the journal article, the “relative importance of CH4 compared to CO2” is due to “its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated.”
Methane’s atmospheric lifetime, about 12 years, is much shorter than that of CO2, which lingers for more than a century. However, methane has larger global warming potential – 28 times higher than CO2 over a 100-year time period, regardless of climate feedback, the same study comments. Therefore, not only CO2 emissions but also CH4 emissions need to be reduced in order to meet the objectives of the Paris Agreement.
The METLAKE (Predicting future methane fluxes from Northern lakes) project aims to quantify and predict methane emissions from lakes that are among the largest natural sources of CH4. Similarly, the VERIFY (Observation-based system for monitoring and verification of greenhouse gases) project is developing a system to quantify estimates of GHG emissions more accurately by examining carbon stocks and the fluxes of CO2, CH4 and nitrous oxide across the EU. Nunataryuk (Permafrost thaw and the changing arctic coast: science for socio-economic adaptation) looks at the impact of thawing coastal and subsea permafrost on the global climate.
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