Cities towards zero emissions: a reality check on the assessment of co-benefits and trade-offs

• Most climate neutral-to-be cities overlook climate policy co-benefits / trade-offs. • The focus is on environmental, social, health, and economic aspects in this order. • Systematic assessments link to lower emissions and higher climate engagement. • Bigger and wealthier cities conduct more comprehensive policy evaluations. • Service provision and financial support are common tools to alleviate social issues. Urban climate change mitigation is an opportunity for cities to achieve a multipurpose agenda if they leverage co-benefits and trade-offs of greenhouse gas reduction. This study examines the approach of 353 cities committed to climate neutrality by 2030 within a common European framework - the Climate-Neutral and Smart Cities Mission - representing diverse geographical, economic, and demographic contexts. The analysis builds on a comprehensive questionnaire and uses a combination of statistical analyses (rankings, answer combinations, classifications) and content analysis. Less than half of the cities (171) assess co-impacts of actions to reduce emissions. Their assessment commonly covers environmental aspects (notably those related to resilience and green space), followed by social aspects, while health-related and economic dimensions receive less attention, on average. Larger cities and those with higher GDP per capita are more likely to conduct comprehensive assessments, indicating disparities in resources and institutional capacity. Almost 90 % of the cities assessing specific social impacts report implementing related measures, concentrating on energy efficiency, transport accessibility, and support for vulnerable populations. However, strategies remain generic and untargeted to specific vulnerabilities. Overall, the analysis reveals a need for integrated policy development, capacity-building, strategic partnerships, effective citizen engagement, robust monitoring setups, and dedicated communication strategies to fully harness the holistic and multifaceted potential of climate action.