The Carbon Removal Budget: theory and practice

Carbon dioxide removal (CDR) is a necessary complement to emissions reductions to achieve a state of global net zero emissions and stabilise future warming. Despite its utility, CDR remains poorly understood. Due to a range of constraints, CDR is a fundamentally finite resource, which we currently do not have enough of to achieve and go beyond global net zero. This has wide-ranging but underexplored implications for the technical and economic feasibility of our collective net zero transition. At the same time, both the opportunity and obligation to undertake CDR are not equally distributed amongst actors and geographies. As a result, there are ongoing questions as to how we can increase the supply of quality CDR whilst at the same time ensure equitable distribution of that same CDR, both within and between countries and non-state actors. To explore these phenomena, we introduce and define the concept of a Carbon Removal Budget (CRB), illustrate how it can apply to different contexts and scales, and distinguish it from the related but distinct concept of the carbon budget. We further estimate the global CRB, review its constraints and quality considerations and outline potential utilisation pathways and principles. We then examine the potential application of the CRB as a tool on which both public and private decision-makers can use to assess the feasibility of their nationally determined contributions and/or net-zero transition plans. In this manner, we illustrate how CRB forecasts can be used today to help build the net zero future of tomorrow.