The Global Carbon Project (GCP) released the commentary of the Global CH4 Budget 2024
-Human activities now fuel two-thirds of global methane emissions-

September 10, 2024

Publication (Jackson RB et al., 2024) 日本語要約

Fig.01 : "The Global CH4 Budget 2020"
The global methane budget (Tg CH4 yr-1) for the year 2020 based on top-down methods for natural sources and sinks (green), anthropogenic sources (orange), and mixed natural and anthropogenic sources (hatched orange-green for ‘Biomass and biofuel burning’ and “Combined wetland & inland freshwaters”).

Highlights

  • CH4 emissions from human activities have increased by 20% (61 million metric tons of CH4 per year) in the past two decades.
  • Direct anthropogenic CH4 sources include emissions from fossil fuel exploitation and use, agriculture, waste handling, and biomass and biofuel burning. Those sources represent around 60% of total CH4 sources. Together with other indirect anthropogenic emissions (eg, from rivers, reservoirs) account for at least two-thirds of Earth’s (natural and anthropogenic) CH4 emissions.
  • Methane emissions from fossil fuels are now comparable in size to methane emissions from cows and other ruminants globally, but overall emissions from agriculture and waste sector (e.g., ruminants, rice paddies, landfills) remain approximately twice of those associated with fossil fuels.
  • CH4 accumulation in the atmosphere has accelerated in the past decade, with higher growth rates over the past three years (2020-2022) than any previous observed year since 1986 when reliable measurements began.
  • The concentration of atmospheric CH4 reached 1923 parts per billion (yearly average) in 2023. This is an increase by a factor of 2.6 compared to the pre-industrial level (722 parts per billion) and the highest value in at least 800,000 years.
  • The observed atmospheric CH4 concentrations in the past decade follow the trends of the IPCC most pessimistic illustrative future GHG trajectories, which lead to global mean temperatures above 3°C by the end of this century.
  • For net-zero emission pathways consistent with the Paris Agreement (stabilizing temperatures below 2°C) from pre-industrial levels), anthropogenic CH4 emissions must decline by 45% relative to 2019 levels by 2050
  • The top five country emitters by volume of anthropogenic CH4 in 2022 were China (16%), India (9%), USA (7%), Brazil (6%), Russia (5%). EU27 is 6th with 4% of the global anthropogenic emissions.
  • The EU and Australasia have successfully reduced their anthropogenic CH4 emissions over the past two decades
  • The major emitter of CH4 from coal exploitation is China (53%). The major emitters of CH4 from the oil and gas sector are the Middle East (24%), Russia (18%) and USA (12%).