Why track methane emissions?
Methane is a potent greenhouse gas whose emissions are still increasing. According to the Global Carbon Project, an international climate research organisation, published in July 2020, 60% of methane emissions are of anthropogenic origin.
Origin of methane anthropogenic emissions between 2008 and 2017 by sector (%)
Source: Global Carbon Project 2020
On a global scale, the current increase in methane concentration in the atmosphere is due as much to livestock farming as to fossil fuels. Its geographical distribution is uneven: Europe is the only region in the world to have reduced its methane emissions over the past 20 years. On the other hand, Africa, South Asia, China and the United States are constantly increasing their emissions.
According to the IPCC, this is worrying because methane is a greenhouse gas, or radiative effect*, 120 times greater than CO2. Admittedly, methane is a gas with a short lifetime in the atmosphere: 11.8 years, according to the latest IPCC assessment report (AR6), whereas the lifetime of CO2 is estimated at a century.
However, the IPCC estimates the Global Warming Potential (GWP**) of methane over 100 years at 27.9 and over 20 years at 81.2, compared with a GWP of 1 for CO2. The 100-year time horizon used until now by convention to establish greenhouse gas emission balances has not favoured taking into account the mitigation potential of methane emissions.
A change of convention, legitimised by science, is thus to be expected in support of international decarbonisation objectives, which must now be set in the short and medium term. Increasing the weight of methane emissions will make it a priority to reduce them. As the climatologist Hervé Le Treut states: “Reducing CO2 emissions without dealing with methane is no longer possible; we must act on both in parallel.