A new JRC-led article shows how focussing either on the short- or long-term warming effects of methane can affect the effectiveness of climate mitigation policies for agriculture and dietary transitions.
Unlike the other main greenhouse gases (GHGs) 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 paper 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.
Emission metrics impact the choice of climate mitigation policies
Conventionally, the climate impact of a certain sector is evaluated through its annual greenhouse gas emissions, typically using the GWP100 metric, which estimates the change in atmospheric energy balance resulting from a GHG emission (i.e. Global Warming Potential) over a 100 year period. But because 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 our climate targets. The study explores how different valuations of methane affect the ranking of mitigation policies in agriculture and, consequently, the sector’s contribution to global warming.
Mitigation policies focussed on methane’s short-term impact lead to greater emission reductions
The paper highlights that focussing specifically on the short-term effects of methane will lead to larger reductions of emissions compared to polices that do not consider methane’s short-livedness. Such stringent mitigation policies can even result in methane’s contribution to climate change dropping below current levels (since the warming effect of methane disappears). In this respect, decreasing methane emissions have the same overall effect as CO2 uptake or carbon capture and storage technologies. Such policies will however have severe impacts on the agricultural sector in terms of prices and production.
Low meat diets are more effective under weaker agricultural emission reduction policy
The impact of low animal protein diets as a mitigation option strongly depends on the context in which it is occurring. If mitigation policies base themselves on metrics that reflect methane’s long-term behaviour (resulting in a lower relative valuation), methane emission intensity is not as greatly reduced by technical measures. Then, low meat diets appear as a more effective solution to reduce emissions. If policies are less strict, reductions in meat consumption and consequently production in developed economies could therefore become an especially powerful mitigation mechanism.
A combination of stringent mitigation policy measures and dietary changes in countries with high calorie consumption per capita could achieve the most substantial emission reduction levels, helping significantly reverse the contribution of agriculture to global warming.
- Publication date
- 13 December 2021