From Hazards to Integrated Risks: Decoding Disparities in Global Urban Heat Research

Abstract: Global warming and rapid urbanization are intensifying the complexity of urban thermal environments, exacerbating heat exposure disparities across diverse scales and demographics. Within the IPCC framework, urban heat risk emerges from the dynamic interaction of hazard, exposure, and vulnerability. While significant progress has been made in quantifying these components—leveraging remote sensing for hazards, human mobility for exposure, and socioeconomic indices for vulnerability—a large-scale synthesis evaluating the global evolution and integration of these research paradigms remains absent.

To bridge this gap, this study conducted a comprehensive search on the Web of Science using a Boolean strategy encompassing three core dimensions: urban thermal hazards, population exposure, and social vulnerability. This process yielded a corpus of over 7,000 peer-reviewed papers published between 2000 and 2025. Leveraging a Large Language Model (LLM), we autonomously extracted geographical metadata and thematic focus from the abstracts. Furthermore, this study analyzed the research dynamics and epistemological shifts in urban heat risk research based on searching results. Our findings reveal: (1) An unprecedented explosion in academic interest, with annual publications surging 150-fold, reflecting the urgency of heat adaptation. (2) A clear paradigm shift from a historical preoccupation with physical hazards toward holistic, multidimensional risk frameworks, particularly over the last five years. (3) A persistent thematic imbalance; hazard assessments still dominate (accounting for over 85% of literature), while human exposure and social vulnerability remain significantly underrepresented. (4) A pronounced "digital divide" in knowledge production, with research heavily concentrated in China and the United States. This leaves critical data voids in highly vulnerable regions of the Global South, including parts of Africa and Southeast Asia. This study underscores the necessity of bridging thematic and geographic divides to foster equitable global urban heat resilience.

Keywords: Urban heat risk, Hazard-exposure-vulnerability, Spatial inequality, Research evolution