Abstract
Agriculture is the largest single source of global anthropogenic methane (CH4) emissions, with ruminants the dominant contributor. Livestock CH4 emissions are projected to grow another 30% by 2050 under current policies, yet few countries have set targets or are implementing policies to reduce emissions in absolute terms. The reason for this limited ambition may be linked not only to the underpinning role of livestock for nutrition and livelihoods in many countries but also diverging perspectives on the importance of mitigating these emissions, given the short atmospheric lifetime of CH4. Here, we show that in mitigation pathways that limit warming to 1.5°C, which include cost-effective reductions from all emission sources, the contribution of future livestock CH4 emissions to global warming in 2050 is about one-third of that from future net carbon dioxide emissions. Future livestock CH4 emissions, therefore, significantly constrain the remaining carbon budget and the ability to meet stringent temperature limits. We review options to address livestock CH4 emissions through more efficient production, technological advances and demand-side changes, and their interactions with land-based carbon sequestration. We conclude that bringing livestock into mainstream mitigation policies, while recognizing their unique social, cultural and economic roles, would make an important contribution towards reaching the temperature goal of the Paris Agreement and is vital for a limit of 1.5°C.This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.
Highlights
Agriculture, including associated emissions from deforestation, accounts for about 21% of total annual anthropogenic greenhouse gas emissions when emissions are weighted using the Global Warming Potential with a time horizon of 100 years (GWP100; [1])
We use the concept of marginal warming to describe the increase in temperature that would occur with, compared to without, a given set of emissions, which directly relates to the warming that could be avoided through future mitigation actions
Our analysis demonstrates that the marginal warming from future livestock CH4 emissions amounts to more than one-third of the marginal warming from CO2 emissions in mitigation pathways consistent with limiting warming to 1.5°C
Summary
Agriculture, including associated emissions from deforestation, accounts for about 21% of total annual anthropogenic greenhouse gas emissions when emissions are weighted using the Global Warming Potential with a time horizon of 100 years (GWP100; [1]). The UK and all states of Australia have adopted targets for net-zero emission of all greenhouse gases including methane for 2050; modelled pathways to achieve such goals include carbon dioxide removals along with substantial reductions in livestock CH4 emissions, but the scale of both carbon dioxide removals and of livestock CH4 reductions are politically contested [33,34,35,36] Given this context, the purpose of this study is twofold: one is to clarify the extent to which global reductions in CH4 emissions from livestock are necessary to support the temperature goal of the Paris Agreement (§2), touching on whether such reductions might be seen as fair and consistent with the way CO2 emissions are treated.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
