Carbon offsetting in city climate action: role, determinants and characteristics

To contribute to Paris Agreement objectives, non-state actors globally are setting voluntary emission reduction goals. Cities represent an important group with emission reduction plans, but vary in how they intend to meet targets. Some cities incorporate carbon offsetting to manage residual emissions. A lack of research exists on the role of offsetting in city plans, and better understanding this approach can inform city climate policy. This study uses a mixed-method design to explore the frequency, characteristics and role of offsetting in city climate action. We quantify how many cities globally include offsetting in their plan, create a random forest model to explore what characteristics of cities and their targets are associated with offsetting, and conduct a text analysis of city documents to explore how cities that intend to use offsets conceptualize the use. We find 363 cities globally with a population over 500,000 have a numeric GHG reduction target; 86 of these include offsetting in their plan. Larger cities, those with a higher per capita GDP, and those with more ambitious climate targets are more likely to offset. Further, of 44 cities included in our text analysis that intend to use offsetting, 29 discuss prioritizing emissions reductions but recognize that offsets will be needed for residual emissions. Less than half the cities discuss environmental integrity of offsets, and many lack detail on how to ensure integrity. Specifying concrete plans regarding offsetting and communicating these decisions is important for effectiveness and integrity of city climate action plans, knowledge sharing between cities, and planning for future offsetting.Most cities with a climate action target have yet to decide or publicly communicate whether they will use offsets to reach their target.Among cities that do intend to use offsetting, many lack details on estimating residual emissions, defining an upper limit on offsets, specifying from where and how to acquire offsets, and how to ensure environmental integrity.If used appropriately, offsets may allow cities to achieve more ambitious targets than otherwise possible.Additional guidance from city climate networks can help cities plan for high-integrity use of offsetting.