National Temperature Neutrality, Agricultural Methane And Climate Policy: Reinforcing Inequality In The Global Food System

Abstract

This study critically examines the use of ‘no additional warming’ approaches, such as temperature neutrality (TN), to determine national climate policy on agricultural methane (CH4). The reduced-complexity climate model MAGICC was used to quantify future national warming contributions for Ireland (a country with high per-capita CH4 emissions driven by large-scale dairy and beef production) under a business-as-usual pathway and three alternative scenarios: (1) TN, (2) a split-gas emission target, or (3) net-zero greenhouse gas emissions by 2050. TN implicitly ‘grandfathers’ CH4 emissions, ‘rewarding’ modest emission reductions even when per capita warming remains high, thereby shifting the mitigation burden and constraining the developmental space for low-income, food-insecure countries. Weaker CH4 emission reduction ambition, i.e. use of TN at the national level, is often justified on the basis of protecting global food security, because it can avoid ’emission leakage’ from countries that export livestock products with below-average GHG intensities. However, this study demonstrates such justifications have little merit given that global trade in animal-sourced foods largely benefits wealthy markets, and often relies on imported feed, contributing to indirect land use change. The study concludes that the TN approach is not a robust basis for fair and effective national climate policy, and risks a potentially costly underestimation of both long-term CH4 mitigation and carbon dioxide removal in the context of national planning for an equitable, sustainable, food secure future.

Generated Summary

This study critically examines the use of ‘no additional warming’ approaches, such as temperature neutrality (TN), to determine national climate policy on agricultural methane (CH4). The reduced-complexity climate model MAGICC was used to quantify future national warming contributions for Ireland under a business-as-usual pathway and three alternative scenarios: (1) TN, (2) a split-gas emission target, or (3) net-zero greenhouse gas emissions by 2050. The research investigates the implications of adopting a TN approach as a basis for national climate objectives and assesses how national TN compares with other transition pathways. The core methodology involves climate modeling to understand the impact of different emission scenarios, specifically focusing on the effects of agricultural methane and its contribution to global warming. The study’s scope is centered on Ireland’s climate policy and its implications for the global food system, particularly in the context of agricultural methane emissions, climate justice, and food security.

Key Findings & Statistics

• Methane (CH4) is responsible for 0.5 °C of the total warming increase attributed to GHG emissions from 2010 to 2019 relative to pre-industrial levels (1850-1900) [1].
• Carbon dioxide (CO2) has contributed 0.8 °C in the same period [1, 2].
• Since 2006, CH4 emissions have increased rapidly and between 2020 and 2023 growth has accelerated [2-4].
• The sector accounted for around 40% (144 Tg CH4 per year) of global anthropogenic CH4 emissions for the period 2010–2019 [2].
• If current dietary patterns and agricultural practices continue, global food consumption could contribute 0.7 °C-0.9 °C of warming by 2100, with CH4 being responsible for up to 60% of projected warming from business-as-usual (BAU) food consumption [12].
• 158 countries have committed to reducing anthropogenic CH4 by 30% across all sectors by 2030, compared to 2020 levels, as part of the global methane pledge [13].
• The BAU-IE scenario represents current mitigation through existing measures.
• The TN (TN-IE) scenario is based on the CCAC carbon budget report [20], which sets a national energy systems budget of less than 350 Mt CO2e, an afforestation rate of 8 kha per year, and an overall reduction of 39% in CH4 and 48% in N2O emissions, relative to 2020.
• Two SG scenarios (SG1-IE and SG2-IE) assume afforestation rates of 16 kha per year and overall CH4 reductions of 50% and 32% and N2O reductions of 71% and 57%, respectively.
• The final scenario, NZ-IE, represents an all-gas NZ transition with an afforestation rate of 25 kha per year and a 68% reduction in CH4 emissions and 83% reduction in N2O emissions.
• High-income countries contribute only ~10% of global agricultural CH4 emissions.
• High- and upper-middle-income nations account for the bulk of emissions.
• Over 47% of the global population resided in low- and lower-middle-income countries, while ~35% resided in upper-middle-income countries and ~17% in high-income countries.
• Although the global prevalence of under-nutrition was estimated at 9%-10%, more than 80% of undernourished people were in low- and lower-middle-income countries, with less than 5% residing in high-income countries.
• High- and upper-middle-income countries primarily trade ASFP among themselves, while lower-middle- and low-income countries receive only 4.9% and 0.8% of the total trade value, respectively.
• High- and upper-middle-income countries together account for ~75% of iLUC.

Other Important Findings

• The study finds that the TN approach implicitly ‘grandfathers’ CH4 emissions, ‘rewarding’ modest emission reductions even when per capita warming remains high, thereby shifting the mitigation burden.
• Weaker CH4 emission reduction ambition, i.e. use of TN at the national level, is often justified on the basis of protecting global food security, because it can avoid ’emission leakage’ from countries that export livestock products with below-average GHG intensities. However, this study demonstrates such justifications have little merit.
• The study concludes that the TN approach is not a robust basis for fair and effective national climate policy, and risks a potentially costly underestimation of both long-term CH4 mitigation and carbon dioxide removal.
• NZ-IE and SG1-IE show a decline in warming contribution over time.
• TN-IE and SG2-IE achieve temporary stabilisation by mid-century, but warming resumes in the second half of the century as the conditions for TN are not maintained.
• In SG2-IE and TN-IE, CH4-induced warming rebounds more quickly due to insufficient continuous reductions.
• In all scenarios, while the temperature contribution of CH4 declines through 2040, it rebounds in later decades, especially in SG2-IE and TN-IE, where TN is lost as early as 2056.
• In NZ-IE, however, the initial CH4 reduction is deep enough that, while a rebound does occur, it levels off, allowing TN to be maintained.
• The majority of high emitters are high- and middle-income countries.
• The economic classification shows that low-income countries contribute only ~10% of global agricultural CH4 emissions, despite making up a substantial portion of the global population.
• High- and upper-middle-income nations account for the bulk of emissions, reinforcing the role of industrialised agriculture in driving the production of CH4 emissions.
• The map highlights some key feedback loops that govern the dynamics of global ASFP production, with distinct drivers shaping high-income and low-income market outcomes.

Limitations Noted in the Document

• The study uses the reduced-complexity climate model MAGICC, which, while calibrated against higher complexity models, still has inherent limitations.
• The study focuses specifically on agricultural CH4 and does not include all CH4 sources.
• The study acknowledges that higher or lower emissions baselines shift national TN earlier or later.
• The study’s analysis of iLUC is based on FAOSTAT data and UN Comtrade data which may have their own limitations.
• The CCAC [20] TN scenario analysed in this study did, briefly, achieve TN, but failed to account for small cumulative warming from residual CH4 emissions [41] and declining background CH4 emissions.
• The paper’s framing embeds assumptions that reinforce global inequity.

Conclusion

The study underscores the critical examination of ‘no additional warming’ approaches, such as temperature neutrality (TN), for national climate policy, particularly concerning agricultural methane (CH4). The analysis, using the reduced-complexity climate model MAGICC, reveals that TN, while seemingly aligned with global climate goals, can inadvertently reinforce existing inequalities within the global food system. The core finding is that the TN approach, as proposed by Ireland’s CCAC, allows for higher CH4 emissions compared to more ambitious scenarios, potentially undermining global mitigation efforts. This approach, the study argues, is not a robust basis for fair and effective national climate policy, potentially underestimating both long-term CH4 mitigation and carbon dioxide removal. The study’s findings demonstrate that the TN approach, while aiming to achieve climate neutrality, may inadvertently lead to an unsustainable path for Ireland’s agricultural sector. The prioritization of TN risks a costly underestimation of long-term CH4 mitigation and CO2 removal. The study’s conclusion highlights that the adoption of a split-gas (SG) approach, with separate targets for short-lived and long-lived GHGs, may provide greater transparency and align better with a 1.5°C pathway, although this depends on the level of ambition applied to CH4 and other gases. The study’s critical examination reveals the urgent need for a more equitable and sustainable food system transition, urging for national climate policies that account for broader implications and prioritize food security, sustainable development, and poverty eradication. Ultimately, the study emphasizes that a truly sustainable global food system must ensure food and nutritional security for current and future generations, moving beyond the limitations of the TN approach.

DOI

10.1088/1748-9326/adf12d