European cities target carbon removal for one-fifth emissions, but few know how

A new analysis of climate-neutrality plans from 103 European cities, including 22 national capitals, has revealed that urban decarbonisation strategies may depend heavily on removing carbon dioxide from the atmosphere rather than eliminating emissions at their source. According to the study, municipalities are planning to use carbon removal to compensate for approximately one-fifth of their expected emissions by 2030. In total, that reliance could represent around 61 million tonnes of carbon dioxide—an amount comparable to Austria’s annual greenhouse-gas emissions.

The research, published in Nature Climate Change and led by the European Commission’s Joint Research Centre, examined how cities define and manage the emissions that remain after planned reductions. These so-called residual emissions are treated as the portion of a city’s climate footprint that cannot be eliminated through available technologies or policy measures. In principle, residual emissions should come only from sectors that are genuinely difficult to decarbonise. The analysis, however, found that many cities still expect substantial emissions to remain in sectors such as energy and transport, where alternatives to fossil fuels and demand-reduction measures already exist.

Across the cities examined, energy accounted for a median of 50 percent of projected residual emissions, while transport represented a median of 31 percent. The finding is significant because both sectors are generally considered more amenable to mitigation than activities such as certain industrial processes, aviation, agriculture or waste management. Renewable electricity, building efficiency, public transport, vehicle electrification and changes in energy demand can all reduce emissions from energy and mobility. If these sectors remain dominant in residual-emissions budgets, the researchers warn, cities may be using carbon removal to compensate for pollution that could instead be prevented.

Quirina Rodriguez Mendez, a scientist at the Potsdam Institute for Climate Impact Research and a co-author of the study, said the cities’ ambition should be recognised, but their definitions of residual emissions are often insufficiently precise. Many plans do not clearly explain which activities will continue emitting, why those emissions cannot be eliminated, or how the required carbon removals will be delivered. This lack of detail creates a risk that removals could become a substitute for rapid structural change. Instead of reserving carbon removal for the hardest-to-abate sources, cities could end up treating it as a general accounting tool for closing gaps in incomplete climate action.

To compare the strength of municipal strategies, the researchers developed the Residual Emissions Strategy Robustness Index, or RESRI. The index assesses whether plans identify residual emissions clearly, quantify them consistently, specify appropriate removal methods and explain how those removals will be monitored over time. The analysis found substantial weaknesses in these areas. Existing estimates of carbon-removal capacity covered only 18 percent of the total residual emissions identified across the cities, suggesting that much of the planned compensation currently lacks a demonstrated physical or technical basis.

This gap is particularly important because carbon removal is not a single technology. Land-based approaches, including planting trees and restoring vegetation, extract carbon dioxide from the atmosphere through biological processes. Yet the carbon stored in forests and soils can later be released by drought, wildfire, pests, disease or land-use change. The permanence of such removals is therefore different from that of geological storage, in which captured carbon dioxide is injected into deep underground formations and isolated for much longer periods. Treating temporary and permanent removals as equivalent can obscure the real climate value of a plan.

The study found that cities overwhelmingly favour land-based removals, even though urban areas face severe limits on available land. Space is under pressure from housing, public health infrastructure, transport systems, energy facilities and food production. Green areas also deliver benefits beyond carbon storage, including cooling, flood protection and biodiversity, but they cannot absorb unlimited quantities of carbon dioxide. The researchers noted that the climate-neutrality plans generally do not include detailed assessments showing where the required land would come from, how much carbon it could store, or how long that storage could realistically be maintained.

More permanent forms of carbon removal appear far less frequently in municipal strategies. Only 32 percent of the plans mentioned at least one permanent-removal option. Bioenergy with carbon capture and storage appeared in 27 percent of plans, biochar in 13 percent and direct air carbon capture and storage in 7 percent. Bioenergy with carbon capture and storage involves growing biomass, using it to produce energy and capturing the resulting carbon dioxide before storing it underground. Direct air capture uses chemical processes to remove carbon dioxide directly from ambient air, although the technology remains energy-intensive and requires substantial infrastructure. Biochar, produced by heating organic material in low-oxygen conditions, can store part of the captured carbon when added to soils.

Carbon credits were included in 40 percent of the plans, but the researchers found that they were frequently poorly defined or presented as a last-resort measure. Credits can represent emission reductions or removals generated elsewhere and purchased by a city to compensate for local emissions. Their credibility depends on whether the claimed climate benefit is additional, measurable, permanent and protected from double counting. The analysis highlights that many cities themselves express distrust toward carbon credits, reflecting concerns that an accounting transaction may be mistaken for a physical reduction in atmospheric carbon dioxide.

The researchers argue that cities should frontload emissions reductions and redesign their strategies so that residual emissions are concentrated in sectors where elimination is genuinely difficult. Demand-side measures could play a major role, potentially reducing emissions by 40 to 80 percent depending on local conditions. Such measures include reducing energy demand through efficient buildings, shifting journeys from private cars to public transport, walking and cycling, improving urban design and encouraging lower-emission consumption patterns. The study concludes that carbon removals may be necessary to reach and maintain climate neutrality, but their use will require transparent monitoring, land assessments, reliable accounting, regulatory clarity and coordinated action by local, national and international authorities. Without those safeguards, ambitious urban net-zero targets could conceal emissions that cities have not yet managed to eliminate.

News Publication Date: 14-Aug-2026

Web References: http://dx.doi.org/10.1038/s41558-026-02691-0

References: Nature Climate Change, DOI: 10.1038/s41558-026-02691-0