Abstract

Abstract for: Cows and climate: questioning the greenhouse gas accounting of livestock methane impacts

Introduction Methane from livestock is a substantial source of global warming. Because CH4 is so potent as a GHG, new targets for reducing CH4 have been adopted . Because CH4 is dynamically so different from CO2, there are problems over how to report its climate impacts. A new metric, GWP star, has been proposed as a better way to report CH4 emissions. Policymakers need fair and reliable metrics for measuring progress on climate change.
Approach A SD model based on a reduced complexity climate model is used to evaluate current and proposed metrics of CH4's CO2 equivalent contribution to climate change. The model takes the form of a user friendly tool that specialists and nonspecialists alike can use to evaluate these metrics as well as the climate response to proposed CH4 reduction goals.
Results GWP star penalizes developing countries with growing economies, while GWP100 downplays developed countries’ progress on reducing emissions. A cumulative version of GWP* seems more “fit for purpose” as a GHG accounting framework. It is a more fair and reliable metric than GWP star or GWP100. GWP100 and cumulative GWP star are better at tracking modeled climate response to emissions. Our user-friendly model could improve dialogue in the debate over livestock methane and climate change.
Discussion Stakeholders need a transparent and comprehensible tool for translating CH4 emissions to climate response. Our tool could fill that need. Despite its simplicity, the model does a reasonable job of replicating historical trends in atmospheric GHG concentration and warming. By exploring the inner workings of the model, users can build trust in the results and develop a deeper understanding of the uncertainties and tradeoffs of climate accounting long recognized by climate scientists.

Introduction	Methane from livestock is a substantial source of global warming. Because CH4 is so potent as a GHG, new targets for reducing CH4 have been adopted . Because CH4 is dynamically so different from CO2, there are problems over how to report its climate impacts. A new metric, GWP star, has been proposed as a better way to report CH4 emissions. Policymakers need fair and reliable metrics for measuring progress on climate change.
Approach	A SD model based on a reduced complexity climate model is used to evaluate current and proposed metrics of CH4's CO2 equivalent contribution to climate change. The model takes the form of a user friendly tool that specialists and nonspecialists alike can use to evaluate these metrics as well as the climate response to proposed CH4 reduction goals.
Results	GWP star penalizes developing countries with growing economies, while GWP100 downplays developed countries’ progress on reducing emissions. A cumulative version of GWP* seems more “fit for purpose” as a GHG accounting framework. It is a more fair and reliable metric than GWP star or GWP100. GWP100 and cumulative GWP star are better at tracking modeled climate response to emissions. Our user-friendly model could improve dialogue in the debate over livestock methane and climate change.
Discussion	Stakeholders need a transparent and comprehensible tool for translating CH4 emissions to climate response. Our tool could fill that need. Despite its simplicity, the model does a reasonable job of replicating historical trends in atmospheric GHG concentration and warming. By exploring the inner workings of the model, users can build trust in the results and develop a deeper understanding of the uncertainties and tradeoffs of climate accounting long recognized by climate scientists.