In preindustrial times, natural geological sources of methane from fossil fuels were vastly lower than previously thought, according to a paper published in Nature . This result implies that modern human-generated emissions of methane are therefore much larger than previously suggested.
Methane is a potent greenhouse gas, and its emissions have an important role in overall global warming. Fossil fuel extraction and use are among the largest sources of methane emissions. However, the exact contribution of different sources to overall methane totals - whether from human activity or natural geological sources - are unclear.
Benjamin Hmiel and colleagues used ice core measurements from Greenland from between 1750 and 2013 and previous data from Antarctica to show that natural geological methane emissions to the atmosphere were around 1.6 teragrams (1.6 trillion grams) per year up to a maximum of 5.4 teragrams per year. This is an order of magnitude smaller than the estimates that are currently used in emissions calculations. These findings indicate that fossil fuel emissions owing to human activity are underestimated by about 38 - 58 teragrams per year - that is, are underestimated between about 25% and 40%.
The authors say that these findings emphasize the human impact on the atmosphere and climate and will help inform strategies for targeted emission reductions to mitigate the effects of climate change.
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