The Global Methane Balance 2024 released on September 10, 2024, as part of the Global Carbon Project* (GCP), shows that human activities emitted a record 400 million metric tons of methane in 2020, and now contribute to two-thirds of global methane emissions.
With contributions from LSCE colleagues Marielle Saunois, Adrien Martinez and Philippe Ciais
A team of climatologists from several laboratories, including LSCE (Laboratoire des Sciences du Climat et de l’Environnement; CEA/CNRS/UVSQ), highlights the key points of the balance sheet.
Methane concentrations have risen faster over the past five years than at any time since data recording began. Understanding where and why this is happening is a central objective of the Global Methane Budget, a study conducted within the GCP. Two-thirds of the world’s methane emissions are now of anthropogenic origin, a result that can no longer be sustained if we are to maintain a habitable climate.
Average global surface temperatures broke all records in 2023, at 1.45 ± 0.12°C above pre-industrial levels (WMO 2024). The world has reached the threshold of a 1.5°C increase in average global surface temperature, and is already beginning to feel the full consequences.
Methane (CH4) is the second most important greenhouse gas after carbon dioxide (CO2). It has contributed to a warming of 0.5°C in the 2010s compared with the late 1800s, equivalent to half the warming associated with CO2 emissions (IPCC 2021). Methane is rising faster in relative terms than any other major greenhouse gas, and is now 2.6 times higher than in pre-industrial times.
Global methane sources and sinks
Despite increasing political attention to methane as a potent greenhouse gas, methane emissions continue to rise. The most important sources of emissions are wetlands and aquatic environments (lakes, ponds, rivers, reservoirs, etc.), agriculture and waste, as well as the extraction, transport and use of fossil fuels. Direct anthropogenic emissions, based on estimates using atmospheric measurements, currently account for around 65% of global emissions. Almost all the main sectors of anthropogenic emissions increased substantially between 2000 and 2020. Methane emissions from the extraction, transport and use of fossil fuels are now comparable to direct methane emissions from cows and other ruminants worldwide, but emissions from agriculture and waste, including landfills, remain around twice those associated with fossil fuels.
Measuring emissions to maintain a livable climate
Methane is receiving increasing political attention due to its potential to reduce warming over the coming decades. Better quantification and attribution of methane sources are needed to support these mitigation efforts at local, regional and global levels. Closer real-time estimates of methane sources, for example, will be facilitated by new satellites such as MethaneSAT and CarbonMapper, to identify and quantify methane super-emitters.
As part of the forthcoming Global Methane Budget efforts, national methane budgets are likely to be produced for key countries. Uncertainties regarding methane emissions remain very high for natural sources, such as wetlands, freshwater systems and natural geological sources.
Assessments of CH4 emissions in inland freshwaters need to be carried out using process-based models based on common system delimitations and simulation protocols.
Source: CEA press release