Temperature neutrality and Irish methane policy

ABSTRACT

Methane emissions reduction can make an effective contribution to national climate policy objectives in countries with high ratios of methane to carbon dioxide emissions. This paper explores the physical science basis for Irish climate policy targets in a ‘split-gas’ approach i.e. separate targets for CO${}_2$ and methane. Explicit calculations of Ireland's historic and future warming contribution show that the planned phaseout in fossil-CO${}_2$ emissions by 2050, together with relatively modest but sustained falls in methane emissions from agriculture, can lead to early stabilization of Ireland's contribution to global warming. It is proposed that this ‘temperature neutrality’ concept provides a pragmatic framework for aligning national climate policy with Article 2.1(a) of the Paris Agreement in countries with high shares of agricultural methane emissions. National methane reductions required to achieve temperature neutrality by a target year are shown to depend on realized future atmospheric methane concentrations, with lower concentrations requiring stronger national reductions and vice versa.

Policy Insights

• Temperature neutrality (TN) is a physically well-defined concept that can be used to balance emissions of methane and long-lived greenhouse gases and to align national with global climate policy goals.

• Policymakers in countries with significant shares of agricultural methane emissions should evaluate the relative merits of Global Warming Potential (GWP${}_{100}$) net-zero and temperature neutrality approaches when setting policy targets.

• Simple Climate Model assessments of national warming contributions help inform emissions targets in countries with significant agricultural methane emissions.

KEYWORDS:

• Methane policy
• temperature neutrality
• short-lived climate forcers
• national climate policies
• ruminant agriculture
• simple climate models

Acknowledgments

The author would like to thank an anonymous referee and Professor Lisa Ryan for valuable comments and feedback. This work was funded by the Department of Energy, Climate, and Communications, Government of Ireland under the EMPowER project. In addition, the author wishes to thank the Energy Institute and the School of Economics, University College Dublin for supporting this work.

Data availability

The 1850–2019 Irish territorial emissions dataset used in this paper can be downloaded from https://doi.org/10.5281/zenodo.7004406. An R package containing the Hector analysis can be installed from https://github.com/Phalacrocorax-gaimardi/climr.

Disclosure statement

No potential conflict of interest was reported by the author(s).