Jason Mc Guire, Fionn Rogan, Hannah Daly, James Glynn, Olexandr Balyk and Brian O’Gallachoir Full paper

Key Messages • A Global Carbon Budget is the total estimated cumulative CO2 that the world can emit while staying within a certain global temperature target, e.g. 1.5C, 2C • To align national climate ambition with both Article 2 (1.5C & 2C temperature target) and Article 4 (carbon neutrality by 2050) of the Paris Agreement, countries can develop a national carbon budget consistent with a Global Carbon Budget, based on an “effort sharing methodology” • On its own, a net-zero emission target (e.g. in 2050) may not align with a Global Carbon Budget • For governance purposes, national carbon budgets can be sub-divided into time periods (e.g. 5 years) and allocated to sectors (e.g. transport, buildings, public sector, etc.). This allocation process needs to be analytically robust, transparent, and involve wide stakeholder consultation • In this document, we propose an approach to building a national carbon budget for Ireland based on this framework, compare with international experience and discuss open issues.