Methane, a potent greenhouse gas, released in the atmosphere

CH₄ a more potent greenhouse gas than CO₂

There is now a widespread scientific consensus on the profound influence of human activity on the global climatic system, particularly through increased emissions of greenhouse gases like CO₂ and CH₄ since the pre-industrial era.

Although CH₄ is roughly 200 times less abundant in the atmosphere than CO₂, it is a more potent greenhouse gas than CO₂. The comparative impact of CH₄ on climate change is more than 86 times greater than CO₂ over a 20-year period (IPCC, 2013).

However, due to its relatively short lifetime of ~9 years, it is now recognized that one of the most efficient methods to mitigate warming due to greenhouse gases on decadal time frames is to cut CH₄ emissions (Shindell et al., 2012).

Natural and anthropogenic CH₄ sources

Atmospheric CH₄ concentrations have more than doubled since the pre-industrial period, reaching a new high of 1889 ± 2 ppb in 2020, as shown by the latest analysis of observations from the WMO Global Atmosphere Watch (GAW) Programme (WMO News Bulletin, 2021). This odourless, transparent gas is released into the atmosphere by a wide variety of both natural and anthropogenic processes, see Figure 1.

• 40% of the emitted CH₄ is of natural origin (wetlands, freshwaters, wildfires, termites, geological sources..).
• 60% comes from anthropogenic sources, such as waste management, fossil fuel exploitation, ruminants and rice agriculture.

Removal of CH₄ is primarily due to oxidation by OH, resulting in an atmospheric lifetime of CH₄ of ~9 years.

Although its main sources and sinks have been identified, there remain many uncertainties regarding the balance between those sources and sinks as we can see from Figure 1 (Kirschke et al., 2013). In addition, CH₄ is a challenging atmospheric component to study as its non-monotonous changes in the last decades and its interannual variability remain not fully understood (Nisbet et al., 2014).

Figure 1 : Anthropogenic and natural sources of CH₄. Figures taken from the Global carbon project. Figure from the Global Carbon Project; based on Kirschke et al., 2013.

 Figure 2 : Monthly mean maps of the BIRA-IASB IASI tropospheric CH₄ column between 4 and 17 km for the year 2014.

Methane data

IASI CH₄ data products (profiles, download files)

References

• IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Cia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.
  
  
• Kirschke et al. (2013), Three decades of global methane sources and sinks, Nature Geoscience, doi:10.1038/ngeo1955.
  
  
• Nisbet, E. G., Dlugokencky, E. J. and Bousquet, P.: Methane on the rise-again., Science, 343(6170), 493–5, doi:10.1126/science.1247828, 2014.
  
  
• WMO News Bulletin (2021)