Unlike the other main greenhouse gases (GHG) and particularly carbon dioxide (CO2), methane (CH4) has a short atmospheric life (around 10 years). Its warming effect is significant in the short term but diminishes in the long term. Depending on the time scale considered, methane’s contribution to agricultural emissions and climate change may vary substantially. This has important implications in the design of global climate change mitigation policies for agriculture.
Based on projections from three agricultural economic models, the study just published in the journal Nature Food shows how different valuations of methane, reflecting either a short- or long-term focus, may affect the cost-effectiveness of mitigation policies and the benefits of low-meat diets.
Conventionally, the climate impact of a certain sector is evaluated through its annual greenhouse gas emissions, typically using the Global Warming Potential over a 100 year period metric ̶ GWP100 ̶ which estimates the change in atmospheric energy balance resulting from a particular type of GHG emission. However, as GHG emissions are reported as CO2-equivalents (which is a very stable GHG), GWP100 can fail to capture how the relative impacts of different gases change over time.
The short-lived character of methane emissions has been arguably overlooked in most assessments of emission reductions required from the agricultural sector to achieve climate targets. The authors explored how different valuations of methane affect the ranking of mitigation policies in agriculture and, consequently, the sector’s contribution to global warming.