European cities are promising climate neutrality by 2030, but many of those plans appear to rest on a major assumption: that someone somewhere will remove tens of millions of tons of carbon pollution later.
A new analysis shows that bet may be far shakier than the headlines around city climate pledges suggest.
Here's what to know
To fulfill the plans reviewed, 103 European cities — among them 22 capitals — are counting on about 67.2 million tons of carbon dioxide to be taken out of the atmosphere by 2030, enough to balance roughly one-fifth of their planet-warming pollution. As Down to Earth reported, that is roughly equal to Austria's annual emissions.
A study published in Nature Climate Change and led by the European Commission's Joint Research Centre, with contributions from scientists at the Potsdam Institute for Climate Impact Research, found that current estimates of carbon removal capacity cover only 18% of the residual pollution listed in those city plans.
Down to Earth said large shares of those residual emissions come from energy and transport, which accounted for 50% and 31%. Because those sectors are often seen as easier to clean up than some hard-to-decarbonize industrial processes, the finding raises concern that cities may be deferring cuts they could make sooner.
Quirina Rodriguez Mendez, PIK scientist and co-author of the study, praised the ambition but warned of weak planning.
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"These cities are pursuing extremely ambitious decarbonization targets, which is to be applauded and should serve as an inspiration to others," Rodriguez Mendez said. "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."
More background
To evaluate how credible those strategies are, the researchers created what they called the residual emission strategy robustness index. According to Down to Earth, it flagged weaknesses in how cities monitor and quantify available carbon dioxide removal, along with uncertainty around when any of it could actually be deployed.
That creates a risk that climate promises become more about accounting than outcomes. If carbon pollution cuts are delayed in energy and transportation, people may continue to live with avoidable pollution, traffic-related health burdens, and dependence on planet-warming fuels for longer than necessary.
What's being done?
As Down to Earth reported, the study called for tougher plans that bring pollution reductions forward and confine residual emissions to sectors that are genuinely hard to decarbonize.
The researchers also highlighted demand-side measures that could cut air pollution by 40% to 80%, depending on the context, according to Down to Earth. In practice, that can mean shaping cities so people need less energy and take fewer high-polluting trips — through transit access, walkability, and building efficiency, for example.
"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.
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