【気候科学】化石燃料の生産・利用によるメタン放出の推定値が上方修正される

Methane emissions from fossil fuel industry and natural geological leakage are up to 110 per cent greater than current estimates, according to a detailed analysis of methane sources published in Nature this week. These results imply a greater potential than previously thought for fossil fuel industry efficiency improvements to mitigate the effects of human activity on the climate. Moreover, the research indicates that fossil fuel methane emissions do not seem to be increasing over time.

Methane is the second-most important greenhouse gas (after carbon dioxide) that has warming effects in Earth’s atmosphere. Our understanding of exactly where and how much of this gas is being produced from many different natural and anthropogenic sources is currently limited. Stefan Schwietzke and colleagues re-evaluate the global methane budget, using a detailed data set of long-term global methane emissions and methane carbon isotope records. They find that total fossil fuel methane emissions (from industry and leakage from natural geological sources) are 60 to 110 per cent greater than previously estimated. Notably, after accounting for geological seepage, methane emissions from the production and use of natural gas, oil and coal are 20 to 60 per cent higher than current emission inventories suggest.

The authors also report that the fraction of leaked methane from natural gas production may have declined from around 8 per cent to around 2 per cent over the past three decades. This finding indicates that improvements in the natural gas industry may have already helped to reduce methane emissions, but more needs to be done to offset the increase in natural gas production.