A Global Systematic Map and Database of Climate Change Research on Cities – Insufficient Research Covers Fast-Growing Cities

The Intergovernmental Panel on Climate Change (IPCC) will prepare a special report (SR) during the 7th assessment report (AR7) cycle to summarise climate change evidence in cities. Here, we provide a systematic overview of topics in 55,000 urban studies using machine learning. We show that urban research is growing faster than other climate change research. In case studies, small and fast-growing cities, especially in Asia, Africa, and Oceania, are under-researched compared to large and mature cities, pointing to lacking resolution on urban planning for mitigation and adaptation. Additionally, we find that poorly reviewed topics, particularly mitigation, are less represented in recent assessment reports. Influential omitted evidence covers specific technological solutions, such as radiative cooling, smart energy systems, and urban public transport. We outline how to close evidence gaps for a more robust underpinning of the IPCC SR on cities, offering our comprehensive global research map as an accessible tool.