The impacts of methane on climate, ecosystems and health

The authors note that methane concentrations in the atmosphere have been increasing rapidly in recent years, caused in roughly equal parts by fossil fuels and agricultural/waste sources.

Points discussed by the paper include:

• The timeframe used to measure the climate warming impacts of methane, including both 20-year and 100-year versions of conventional Global Warming Potential, as well as newer metrics including GWP* and Combined-Global Temperature Potential. For more on GWP*, see the TABLE explainers Agricultural methane and its role as a greenhouse gas and Methane and the sustainability of ruminant livestock.
• Climate warming caused by the chemicals produced as methane oxidises in the atmosphere - tropospheric ozone, stratospheric water, and carbon dioxide.
• Damage caused by tropospheric ozone to human health, plant growth (resulting in crop losses), and the ability of ecosystems to absorb carbon.
• Feedback loops that could lead to further methane emissions, for example from wetlands and permafrost.
• The effects of climate change on the oxidation rate of methane, both in the atmosphere and by soils. It is not yet fully settled which direction these effects will work in, but the authors conclude it is likely that climate change will amplify atmospheric concentrations of methane.

Abstract

In this article we review the physical and chemical properties of methane (CH₄) relevant to impacts on climate, ecosystems, and air pollution, and examine the extent to which this is reflected in climate and air pollution governance. Although CH₄ is governed under the UNFCCC climate regime, its treatment there is limited to the ways in which it acts as a “CO₂ equivalent” climate forcer on a 100-year time frame. The UNFCCC framework neglects the impacts that CH₄ has on near-term climate, as well its impacts on human health and ecosystems, which are primarily mediated by methane’s role as a precursor to tropospheric ozone. Frameworks for air quality governance generally address tropospheric ozone as a pollutant, but do not regulate CH₄ itself. Methane’s climate and air quality impacts, together with its alarming rise in atmospheric concentrations in recent years, make it clear that mitigation of CH₄ emissions needs to be accelerated globally. We examine challenges and opportunities for further progress on CH₄ mitigation within the international governance landscapes for climate change and air pollution.

Reference

Mar, K.A., Unger, C., Walderdorff, L. and Butler, T., 2022. Beyond CO2 equivalence: The impacts of methane on climate, ecosystems, and health. Environmental science & policy, 134, pp.127-136.

Read the full paper here. See also the TABLE explainers Agricultural methane and its role as a greenhouse gas and Methane and the sustainability of ruminant livestock.