An analysis of 103 European cities’ 2030 climate neutrality plans, including 22 capital cities, shows that municipalities plan to rely on carbon removal to compensate for about a fifth of their emissions. This will require removing roughly 61 million tonnes of emissions from the atmosphere, close to Austria’s annual emissions.
The study, published in Nature Climate Change and led by the Joint Research Centre of the European Commission, with contributions from scientists at the Potsdam Institute for Climate Impact Research (PIK), found that most residual emissions identified by cities come from the energy and transport sectors, with median shares of 50 per cent and 31 per cent respectively.
The report said this raises concerns about the effectiveness of cities’ strategies, urban constraints and strict timelines, particularly as energy and transport are generally considered sectors that can be more easily decarbonised.
“These cities are pursuing extremely ambitious decarbonisation targets, which is to be applauded and should serve as an inspiration to others. But they are using vague criteria to determine where residual emissions will come from, and might not have given enough consideration to options that would eliminate these emissions in the first place,” said Quirina Rodriguez Mendez, scientist at PIK and co-author of the study.
The study developed the Residual Emission Strategy Robustness Index to assess the robustness of cities’ strategies for dealing with residual emissions. The index identified weaknesses in monitoring and quantifying how much carbon dioxide removal is available to cities and when it can be deployed.
Current estimates of carbon removal capacity cover only 18 per cent of total residual emissions identified in the plans.
“It’s really important that these removals actually happen and are transparently accounted for so that bad practice doesn’t reduce them to mere hot air,” Rodriguez Mendez said.
The study recommends that cities strengthen existing plans by bringing forward emissions reductions and limiting residual emissions to sectors that are genuinely difficult to decarbonise. It also recommends demand-side measures, which could reduce emissions by 40 to 80 per cent, depending on the context.
The 103 cities analysed overwhelmingly rely on land-based carbon removals, including tree planting. The study raises concerns about the permanence of such removals and the availability of land in cities, where housing, health and energy needs compete for limited space.
Current climate neutrality plans do not include detailed assessments of land availability, according to the study.
Permanent carbon removal is less common in city plans, with only 32 per cent mentioning such options. These include bioenergy with carbon capture and storage in 27 per cent of plans, biochar in 13 per cent and direct air carbon capture and storage in 7 per cent.
Carbon credits feature in 40 per cent of the plans, but are often poorly specified and used as a last resort. The study also notes widespread distrust of carbon credits among cities themselves.
The authors suggest that maintaining climate neutrality may require cities to gradually complement temporary carbon dioxide removal with more permanent removal options. This would require regulatory clarity, infrastructure development and predictable support, particularly for permanent carbon removal technologies.
The study said such efforts would also depend on national and international governance bodies working together.