Abstract
Methane’s short atmospheric life has important implications for the design of global climate change mitigation policies in agriculture. Three different agricultural economic models are used to explore how short- and long-term warming effects of methane can affect the cost-effectiveness of mitigation policies and dietary transitions. Results show that the choice of a particular metric for methane’s warming potential is key to determine optimal mitigation options, with metrics based on shorter-term impacts leading to greater overall emission reduction. Also, the promotion of low-meat diets is more effective at reducing greenhouse gas emissions compared to carbon pricing when mitigation policies are based on metrics that reflect methane’s long-term behaviour. A combination of stringent mitigation measures and dietary changes could achieve substantial emission reduction levels, helping reverse the contribution of agriculture to global warming.
Generated Summary
This research article investigates the effects of methane (CH4) on the cost-effectiveness of climate change mitigation policies in agriculture, and the potential benefits of low-meat diets. The study employs three agricultural economic models to explore how the short- and long-term warming effects of CH4 influence the efficacy of mitigation policies and dietary shifts. The models used include CAPRI, GLOBIOM, and MAGNET, which provide detailed representations of the agricultural sector, cross-sectoral linkages, and greenhouse gas (GHG) emissions by agricultural production activity. The study’s methodology involves analyzing how mitigation policies, particularly those focusing on short- or long-term effects, impact emission reductions and their consequences for the agricultural sector. The research also explores the effects of carbon pricing and dietary transitions on reducing greenhouse gas emissions. The study uses various scenarios, including carbon price implementations and shifts towards low-animal-protein diets, to assess their effectiveness. The choice of a particular metric for methane’s warming potential is crucial in determining the optimal mitigation options, with metrics based on shorter-term impacts leading to greater overall emission reduction.
Key Findings & Statistics
- In a business-as-usual scenario (BASE) with no GHG mitigation policy, global agricultural CH4 emissions are projected to increase by over 50% between 2010 and 2070, potentially reaching 170-240 Mt yr−1 in 2070, depending on the model.
- Under the baseline scenario, increasing CH4 emissions alone induce a warming of about 0.1°C, and about 0.175°C together with N₂O.
- Implementing a carbon price of US$150 t−1 (CP150) to the agricultural sector based on GWP100 yields an average reduction of 12%, 28% and 40% in CH4 emissions in 2030, 2050 and 2070, respectively, compared to the baseline.
- The implementation of a carbon price of US$500 t−1 (CP500) to the agricultural sector based on GWP100 yields an average reduction of 23%, 40% and 53% in CH4 emissions in 2030, 2050 and 2070, respectively, compared to the baseline.
- CP150 yields CH4 emission reductions of about 41% and CP500-ST 60% in 2070, with greater emission reduction achieved when using the short-term effects of CH4.
- When dietary shifts are combined with carbon pricing, induced warming from CH4 compared to 2010 turns negative for both carbon prices.
- Adding dietary shifts to carbon pricing that focuses on either the short-term or the long-term effect of CH4 emissions does not change the main results compared to a situation without dietary shifts.
- Dietary shifts alone have a lower impact than carbon pricing on emission reduction at least for the given assumptions (Fig. 3c).
- Dietary shifts lead to a 13% reduction in 2070 compared to the baseline in the absence of carbon pricing.
- Adding a carbon price has minor additional impact.
- Production drops between 15% and 18% depending on the carbon pricing regime and the carbon price level when dietary shifts are considered.
- In the absence of dietary shifts, production only decreases between 2% and 8% depending on the carbon price regime and level.
- Under the baseline, increasing CH4 emissions alone induce a warming of about 0.1°C, and about 0.175°C together with N₂O.
- Carbon pricing (US$150 t-1) to the agricultural sector based on GWP100 yields an average reduction of 12%, 28%, and 40% in CH4 emissions in 2030, 2050, and 2070 respectively.
- Adding dietary shifts to carbon pricing that focuses on either the short-term or the long-term effect of CH4 emissions does not change the main results.
- Dietary shifts lead to a 13% reduction in 2070 compared to the baseline.
- If no dietary shifts are considered, production only decreases between 2% and 8% depending on the carbon price regime and level.
- Carbon pricing regime has a limited effect on overall agricultural production, but a stronger effect on producer prices.
- Carbon pricing regimes that focus on either the short-term or the long-term warming impact of CH4 emissions result in a 1 percentage point deviation of production compared to carbon pricing using the conventional GWP100.
- In 2070 compared to the baseline, global livestock per-capita calorie consumption is reduced in the dietary shift scenarios by about 4-18% in 2030, 13-31% in 2050 and 23-36% in 2070, depending on the model.
Other Important Findings
- The choice of emission accounting metrics has an impact on climate mitigation policy options.
- The study highlights that emission accounting metrics influence climate mitigation policy options.
- Decreasing CH4 emissions from agriculture can have a negative warming effect, as revealed when using the GWP* metric.
- The global warming impact remains unchanged until 2050 and starts decreasing while getting close to 2070, mainly due to a regional convergence of world animal protein consumption and technology adoption induced by carbon pricing.
- Carbon pricing regimes that focus either on the short-term or the long-term warming impact of CH4 emissions result in a 1 percentage point deviation of production compared to carbon pricing using the conventional GWP100.
Limitations Noted in the Document
- The models used are based on a comparative-static modeling framework, which may not fully capture dynamic decision-making.
- The study disregards the costs associated with monitoring emissions and implementing dietary shifts, potentially overestimating the efficiency of mitigation options.
- The study’s analysis is based on a global perspective and does not fully consider regional variations and specific consumption effects.
Conclusion
The study underscores the significant impact of CH4 emissions on agriculture and the choice of metrics for assessing their impact. Using different CH4 valuations, the study highlights that the choice of emission accounting metrics significantly impacts climate mitigation policy options. The choice of metric is key to determining optimal mitigation options. Metrics based on shorter-term impacts lead to greater overall emission reductions. The study’s results also suggest that the promotion of low-meat diets is more effective in reducing greenhouse gas emissions when mitigation policies are based on metrics that reflect methane’s long-term behavior. The study shows that carbon pricing can lead to a substantial reduction in CH4 emissions, partially reversing warming. The study shows that a combination of stringent mitigation measures and dietary changes could achieve substantial emission reduction levels, helping reverse the contribution of agriculture to global warming. The impact of low-animal-protein diets as a mitigation option is strongly influenced by the context in which this trend is occurring. Furthermore, the results suggest that emission mitigation policies could have an ambiguous effect on livestock production, depending on the valuation of CH4. If society gives more value to the long-term effect of CH4, then a carbon pricing regime based on the long-term warming impact of CH4 relieves pressure to reduce cattle herds. The carbon pricing regime plays a much smaller role if a dietary shift causes the reduction in ruminant production, and in that case, only one-tenth of the drop in ruminant production is reversed.