Three-scope carbon emission inventories of global cities

Abstract

A major challenge for cities taking action on climate change is assessing and managing the contribution of urban consumption which triggers greenhouse gas (GHG) emissions outside city boundaries. Using a novel method of creating city-level input–output tables, we present the first consistent, large-scale, and global assessment of three-scope GHG inventories for 79 members of the C40 Cities Climate Leadership Group. These inventories cover the emissions from sources located within city boundaries (Scope 1), emissions occurring as a consequence of the use of grid-supplied electricity, heat, steam, and/or cooling (Scope 2), and all other GHG emissions that occur outside the city boundary as a result of activities taking place within the city (Scope 3). We find that, by only accounting for territorial emissions, without Scope 3, the 79 C40 cities under-report 4% of global annual GHG emissions from six key infrastructure-related transboundary sources (73%) and from service-related sectors (27%). In contrast, when only accounting for consumption-based emissions, the C40 cities would miss the mitigation target on 41% of their territorial emissions. We argue that cities should complement their GHG inventories, adding full Scope 3 to Scopes 1 and 2, and develop low-carbon consumption strategies in addition to current infrastructure-focused action on climate change.