Assessing the contribution of enteric methane emissions from Uruguayan livestock to global warming using an alternative metric

For years, livestock production has been accused of having a supposed impact on global warming. This message permeated broad sectors of public opinion. Recently, questions have arisen about the metrics used to determine the potential contribution of different greenhouse gases. The differences between the atmospheric decays of short- and long-lived climate forcers (SLCFs and LLCFs) and the inadequacy of single-pulse metrics, such as the global warming potential (GWP), to describe sustained emission sources over time, prompted the development of new estimators to compare the warming potential of gases other than CO2. Alternatives such as GWP* show a considerable reduction in the contribution of SLCFs compared to GWP100. This article assesses the differential warming contribution of enteric methane emissions from Uruguayan cattle from 1900 to 2023 using GWP and GWP* and their potential usefulness in negotiating future emission reduction commitments. Data on livestock population and feed were used to calculate annual feed intake and methane emissions. The total cumulative emissions, as calculated using the GWP* method, represented 56% of the CO2-equivalent value estimated using the traditional metric (1,139 versus 2,027 Mt CO2e). Furthermore, the downward trend in annual CO2 warming-equivalent emissions over the past three decades (-60.6%) has been accompanied by a significant reduction in emissions intensity (-13.0%). Considering GWP* as an additional metric can contribute to Uruguay's positioning for future commitments and provide evidence of its compliance.