An international study has revealed fresh insights into global methane emissions using innovative multi-isotopic atmospheric measurements.
Researchers using advanced isotopic analysis, including radiocarbon and stable isotopes of carbon and hydrogen, were able to accurately distinguish between the different sources of methane (CH4) emissions.
Essentially, by looking at the “fingerprints” of methane molecules, the researchers could measure the small differences in the types of carbon and hydrogen atoms in the methane. With this, they could tell which methane came from fossil fuels and which came from other sources.
“There are many different sources of methane in the atmosphere,” says Professor Heather Graven, a climate physicist and co-author of a paper published in the Journal of Geophysical Research: Atmospheres.
“Isotopic measurements are very useful for separating different sources because different sources have different isotopic compositions.
“For example, radiocarbon is produced in the atmosphere and is incorporated into plants, so CH4 from agriculture or wetlands has 14C in it. But 14C decays over time and fossil fuels are so old they don’t have any 14C”.
This research is the first to integrate multiple isotopic datasets to precisely quantify global methane emissions from fossil fuels, biogenic, geologic, and biomass-burning sources across the historical timeframe from 1750 to 2015.
“Such precise data are crucial for effective climate policy and mitigation strategies,” says Dr Andrew Smith, a co-author and Principal Accelerator Scientist.
The study found that the amount of methane coming from fossil fuels was about 130 teragrams (that’s 130 trillion grams) per year for the period from 2003 to 2012. Notably, these numbers closely match the Global Carbon Project estimates – a network of scientists and institutions investigating greenhouse gases – contradicting earlier claims of significantly underestimated fossil methane emissions.
“In addition to the previous isotope studies, some studies of point sources suggested that fossil fuel CH4 emissions are underestimated,” says Graven. “Since our study looks at global emissions, the fossil fuel emissions may be underestimated for some point sources and overestimated for other sources. Overall, the specific details of fossil fuel emissions – where and how they are occurring – are still not known very well, even though we can say that the global total from scientific inventories is consistent with atmospheric isotope data.
“The specific details of fossil fuel CH4 emissions and other CH4 emissions need to be better understood to ensure climate change mitigation policies are effective”.
Why is measuring methane so important?
