Urban Thermodynamics Reconstruction: How Spatial Morphology Drives Global Urban Cooling Demand and Climate Resilience

In the context of climate change, cities are no longer just carriers of human activity but also core battlegrounds for climate adaptation and mitigation strategies. The thermodynamic evolution of cities—the generation and change of Urban Cooling Demand (UCD)—is a key indicator for understanding how cities survive and develop under multi-scale environmental pressures. However, the current quantitative understanding of UCD remains at the macroscopic urban scale, lacking insights into how different spatial development paradigms (such as horizontal expansion, vertical densification, infilling) interact to affect the structure of the thermodynamic system. This knowledge gap hinders us from formulating truly climate-responsive and energy-efficient urban strategies.

This study focuses on how the evolution of urban form reshapes thermodynamic demand. The evolution of the physical form of cities is mainly manifested in three dimensions: first, horizontal or lateral expansion, i.e., the development of the urban edge towards engineered landscapes; second, structural development, which is the vertical growth of buildings; and third, infilling, the transition from open space to infrastructure. These processes collectively constitute the city's "volumetric growth," and different types of volumetric growth patterns contribute heterogeneously to UCD.

The research reveals a core paradox: although urbanization itself is the main driver of thermodynamic change, the specific form of that change is determined by the specific morphology. Cities that undergo large-scale, irregular horizontal expansion exhibit relatively faster UCD growth rates, even if their initial demand is lower. In contrast, medium-sized cities maintain the highest absolute cooling demand. This suggests that cities are not a homogeneous system; their thermodynamic response is highly dependent on their spatial structure and growth logic.

A more strategic finding is that compact urban forms exhibit a mild UCD trend, implying that the spatial structure itself inherently contains structural advantages for climate resilience. This is not a simple effect of scale but an intrinsic regulatory mechanism of form on heat distribution and external climate impact.

This driving role of spatial form on cooling demand has profound policy implications in the context of climate change. If urban planning and infrastructure investment continue to be guided by a single, linear scale of expansion, we may be overlooking the multiplicative effect of urban form on climate adaptation. A truly climate-responsive urban strategy must move beyond the simple pursuit of "bigger" or "smaller" and focus on "how to grow"—that is, how to actively guide the city's thermodynamic trajectory by optimizing vertical density and managing the permeability of urban boundaries, thereby achieving deeper improvements in energy efficiency and thermal comfort.

Therefore, future urban research and strategic deployment must incorporate the dynamics of urban form into the foundation of climate adaptation and sustainable development models, transforming cities from passive objects of climate impact into active agents shaping their own thermodynamic destiny.