Towards the first cohort of climate-neutral cities: expected impact, current gaps, and next steps to take to establish evidence-based zero-emission urban futures

Cities are increasingly becoming critical climate actors. However, their preparedness and ambition in forging climate-neutral futures is hard to ascertain. In this study, we analyse the Expressions of Interest in the Mission on 100 Climate-Neutral and Smart Cities by 2030, an unprecedented dataset of city inputs to 374 different questions on the transition to (net) zero. We i) delineate emissions baselines, accounting methodologies, and inventories’ completeness (sectors/sources, carriers, gases), ii) analyse emission trends and cities’ capacity to deliver on their climate mitigation commitments, iii) examine the estimated magnitude and origin of residual emissions by 2030 together with the envisioned offsetting strategies, and iv) elucidate gaps, methodological deficiencies, and forms of assistance. Data suggest that if all 362 eligible cities were to reach climate neutrality, approximately 650 MtCO₂eq would be removed. However, this would require at least a quadruple effort in half the time compared to current mitigation achievements. Beyond the challenge of emissions baselining, cities lack adequate data collection and monitoring systems and show little familiarity with non-technological and technological avenues to tackle harder-to-eradicate emissions. Capacity building will be key across multiple (e.g., technical, financial, operational) domains to turn ambitious mayoral commitments into factual contributions to climate mitigation.