The Structural Paradox of Urban Heat Load: How Morphological Evolution Reshapes Global Urban Adaptation and Resilience

Cities, as a core carrier for climate change adaptation and mitigation, are undergoing physical transformation at an unprecedented rate, driving multi-scale environmental changes. However, when we examine the exacerbation of global warming by urbanization, a key, yet insufficiently quantified variable emerges: Urban Cooling Demand (UCD). The growth of UCD is not merely a simple function of population and economic scale; it is more deeply embedded in the complex coupling of urban spatial forms.

Existing research focuses on the impact of climate change on cities, but a structural problem remains regarding the core question of "how cities respond to climate change": how do different growth "patterns" of cities affect their thermal energy demand?

Based on a spatiotemporal data analysis of 88 Indian cities and 52 global cities (2003–2023), we observe that the growth trajectory of UCD is not monolithic. The study reveals three main types of urban volume growth having a decisive impact on thermal load:

First, cities undergoing large-scale, irregular horizontal expansion, despite potentially having lower initial thermal loads, exhibit the fastest UCD growth rates. This suggests that in low-density, large-scale urban sprawl, the non-linear effects of environmental exposure and heat exchange are dominant.

Second, medium-sized cities consistently maintain the highest absolute thermal load demand. This may reflect the accumulation of the urban heat island effect and the critical point of existing infrastructure capacity.

Finally, compact urban forms show a more moderate growth trend. This strongly demonstrates the self-regulating role of urban structure on thermal load—the thermodynamic advantage brought by high density and vertical concentration partially counteracts the thermal load surge from pure scale expansion.

The deeper implication of this phenomenon is that strategic frameworks for urban adaptation and energy efficiency transformation can no longer focus solely on "increasing capacity" or "reducing energy consumption," but must shift towards "optimizing form." Structural changes such as vertical development and internal infill demonstrate significant structural advantages in terms of climate response and energy efficiency, providing urban planners with a key leverage point: changing what the city "looks like," rather than just changing how "big" it is.

From the macro perspective of global civilization evolution, this form-dependent thermal load response reflects a profound structural reorganization of the global urban system. The traditional logic of urban development—unlimited horizontal expansion—is gradually becoming obsolete, replaced by the pursuit of high-density, structured, and climate-sensitive forms. This is not just a problem of urban engineering; it is an issue of urban governance models and spatial politics. Against the backdrop of climate vulnerability faced by cities in the Global South, understanding and leveraging the structural advantages of urban form is an essential path for long-term strategy in building climate resilience and achieving sustainable development.