Short communication: climate impact of Australian livestock production assessed using the GWP* climate metric

Abstract

The livestock industries are responsible for a variety of greenhouse gas (GHG) emissions that vary in atmospheric lifetime and radiative efficiency. Assessing the overall contribution to climate change and the priority of different mitigation actions is not straightforward. Commonly applied climate metrics, such as GWP100, obscure the different timeframes over which climate impacts occur and may not provide suitable information for every decision-making context. The GWP* climate metric has been developed to describe the future warming associated with a change in rate of emission of a short-lived climate forcer, like methane, compared to a pulse emission of CO2, a long-lived climate forcer. This metric can be used to guide climate action aligned with temperature-based climate stabilization goals, as expressed in the Paris Agreement. In this study, GHG emissions were assessed for Australian livestock industries – beef cattle, sheep meat, chicken meat, pig meat, eggs and milk – using both GWP100 and GWP* metrics using data primarily sourced from the Australian Greenhouse Emissions Information System spanning 1990 to 2018. Over this period, all industries increased their production. For livestock industries having substantial methane emissions, important differences were observed between results obtained using the two metrics. In the case of sheep meat production, the industry was assessed as emitting 10.3 Mt CO2e in 2018 using the GWP100 metric. However, using the GWP* metric the GHG emissions footprint was equivalent to 2.85 Mt CO2 removal. The design of the GWP* climate metric makes it particularly suited to the management of emissions in line with climate stabilization goals and there is a need to assess the continuing relevance of GHG mitigation strategies developed using the GWP100 climate metric. Strategies to achieve reductions in methane emissions at the expense of increasing CO2 and N2O emissions are concerning. Assessed using the GWP100 climate metric, these strategies may appear to be making progress in combating climate change. However, they may be achieving a short-term climate benefit while making climate stabilization more difficult.