Low-Carbon Strategies for Three-Dimensional Urban Form: Global Cooling Demand Is Reshaping the Logic of Urban Planning

Over the past two decades, from the Indian subcontinent to the Mexican highlands, cities have been undergoing a physical-form revolution that is visible to the naked eye but not yet fully understood. Research long reliant on satellite imagery has been accustomed to viewing urbanization as the expansion of built-up area, but the real picture is far more complex: some cities sprawl outward like a pancake being spread, encroaching on farmland; some cities let skyscrapers replace low-rise neighborhoods; and others achieve density growth by infilling leftover spaces. These differences shape the "three-dimensional volume" of cities, yet the scientific community's understanding of how that volume affects key indicators of urban functioning remains as murky as viewing flowers through fog.

A study published in Nature Communications in 2026 provides the first systematic assessment of how three-dimensional urban growth affects "urban cooling demand." The study covers 88 Indian cities and 52 global cities, spanning 2003 to 2023. The researchers found that the evolutionary trajectory of urban cooling demand does not depend on city size or total population, but is determined by the type of spatial growth. Cities dominated by horizontal expansion—especially irregular, low-density sprawl—experience the fastest relative growth in cooling demand, despite their initially low demand; medium-sized cities tend to bear the highest absolute cooling demand; and compact cities exhibit a more moderate trend, showing a structural thermal advantage. This finding elevates urban form from a secondary concern in aesthetic or density debates to a primary strategic variable for climate adaptation and energy transition.

The world is standing at a critical juncture for cooling demand. Global warming is no longer an abstract temperature statistic; it has become the roar of air-conditioning compressors in high-rise buildings, the ambulance calls for heatstroke patients in hospitals, and the peak loads on power grids during heat waves. The Intergovernmental Panel on Climate Change (IPCC) has repeatedly mentioned in its assessment reports the impact of urban structure and form on energy use, but quantitative research has always been scarce. Over the past few decades, scientists and policymakers have focused excessively on area-based indicators such as total urban population, industrial structure, and economic growth, while rarely imagining the city as a three-dimensional entity—a vertical mass that keeps growing taller, thicker, and denser.

Yet the actual process of urbanization is happening precisely on the vertical scale. Over the past two decades or more, global cities have in effect undergone a "floor-area-ratio revolution": cities are transforming from ground-level engines into three-dimensional systems composed of both high altitudes and underground spaces. But different cities have adopted radically different paths toward this system. One path is "expansionary growth"—urban boundaries spread outward like water stains, as low-density housing and industrial parks devour green space in the suburbs. Another is "replacement growth"—old urban districts are replaced by high-density new buildings, and cities grow upward within their original boundaries. Yet another is "infill growth"—vacant lots and temporary spaces are converted into permanent structures. Each of these methods alters the energy exchange processes of urban surfaces in completely different ways: horizontally spread impervious surfaces absorb and store heat more easily, vertical buildings create wind corridors and shadows between structures, and high-density compact neighborhoods—even with large overall volumes—may allow air-conditioning systems to operate more efficiently.The research data highlight an easily overlooked paradox: the cities with the fastest-growing cooling demand are not the tropical megacities we might typically imagine, but rather many medium-sized cities in the Global South that are still in their early stages of expansion. These cities, often without having undergone complete wealth accumulation or established mature urban planning systems, have already grown along the most unsustainable trajectories. Conversely, certain megacities in Asia or Europe, having entered the phase of verticalization and compact development earlier, instead display resilience in the face of climate. This is precisely the classic trap of urban development stages—a mistaken choice of form at the starting line will, decades later, solidify into an energy debt that is difficult to reverse.

The geographic-economic logic underlying traditional urban strategies is failing. For a long time, urban development indicators have been almost equated with physical expansion: more industrial parks, wider roads, larger built-up areas. But this study conveys a clear message to policymakers: the spatial composition of urban growth—not just its rate—determines the energy demand curve. With rising global temperatures now an established fact, a city's cooling demand directly translates into electricity subsidies, grid investments, carbon emission responsibilities, and economic growth potential. Urban density and form are therefore no longer a matter of urban aesthetics debate, but an infrastructure issue concerning competitiveness.

The evolution of cooling demand is also intensifying structural inequalities within the global urban system. Cities in the Global North, already located in high-latitude or temperate climates, face relatively limited increases in cooling demand due to morphological changes; while cities in the low-latitude Global South are experiencing exponential, synchronized growth in both rising temperatures and electricity demand. This demand divergence is likely to reshape the flow of global energy arteries over the next decade: capital and resources will no longer flow only toward urban scale, but toward strategic management capacity of urban form. Cities that can achieve indoor thermal comfort at low cost will gain an advantage in the competition for talent and capital; those that force their citizens to rely on expensive air conditioning will lose attractiveness in global supply chains.

The governance authority over urban form is shifting from a purely local affair to a new form of geopolitical power. Because the built environment, once constructed, has long-lasting lock-in effects, urban energy demand over the coming decades will diverge significantly roughly every ten years. A century ago, cities' choices to lay tram tracks or highways determined the spatial structure for the next seventy years. Today, whether a city chooses to allow peripheral sprawl or encourage internal redevelopment will determine its adaptability in the next climate cycle. The window for policy action is limited: many Global South cities are in a phase of rapid built-up area formation, and every planning decision made today is an irreversible investment commitment.This finding also prompts us to reconsider the core object of a city's strategic decision-making. Urban planners are often accustomed to managing land, zoning, and transportation from a two-dimensional planar perspective, but the world has entered a stage that requires three-dimensional governance. Urbanization no longer demands blueprint-style spatial allocation, but rather a fine-grained control of urban volume—including building height, floor area ratio adjustments, the spatial distribution of green roofs and street shading, and the flow of air through gaps between buildings. This requires city governments to possess unprecedented data analysis capabilities and dynamic calculation systems, rather than continuing to rely on static master plans.

The study, covering 140 cities, further shows that compact urban forms have adaptive advantages across climate zones. Although the "compact city" has been discussed in international urban policy circles for years, it is often regarded as a heritage characteristic of old European cities or high-density Asian city centers and therefore deemed not replicable. The current research provides measurable evidence: under the same climatic conditions, more compact urban forms can better curb explosive growth in cooling demand than sprawling built-up areas. This confirms the necessity of urban long-termism—only by resisting the temptation of low-density expansion in the face of short-term economic pressures can municipal decision-making be sustainable.

Stepping back to a broader perspective, urban form is precisely the key institutional lever during this turning point in climate civilization. Faced with the still-ongoing rapid urbanization of the Global South, the following question becomes increasingly clear: "What is the essential spatial infrastructure of a city?" The study's authors treat cities as fundamental units for climate adaptation and mitigation. In fact, if global cooling demand continues to grow at a faster rate, it will not only drag down the energy transition path set by the Paris Agreement but will also plant new seeds of vulnerability within cities. Heat dissipation and cooling—rather than roads and bridges—will gradually become core vocabulary in twenty-first-century urban strategy.

In the near future, the definition of urban competitiveness will undergo a fundamental change: whoever can provide better thermal comfort and lower carbon costs within a smaller per-capita space will attract human capital with a future-oriented mindset. Some cities are already acting: London and Singapore have incorporated urban massing and energy efficiency into building codes; Mumbai and Jakarta's planning is exploring strategies that combine vertical growth with thermal buffer spaces; Paris is enhancing urban climate resilience by renovating public spaces. The real question is whether those cities whose footprints are still rapidly sprawling outward—many emerging metropolises in Africa, numerous regional centers in the interior of the Indian subcontinent, and urban clusters in Southeast Asia—can realize in time that their morphological choices at this moment are, in fact, an investment or even a wager on the course of civilization.The three-dimensional growth pattern of cities is not an inevitable natural process, but the result of institutional design. Land value regimes, floor area ratio regulations, mortgage lending policies, infrastructure investment preferences, and countless micro-decisions collectively shape the vertical profile of a city. Behind every temperature differential and energy-consumption curve measured in this study lies a corresponding philosophy of governance. History will no longer judge an era's civilizational achievements by its skyline, but by the energy consumed beneath that sky and the comfort of human bodies—the true measure of a ruler's foresight.

Urban adaptation to climate change should not merely await global negotiations on greenhouse-gas emission reductions. A more urgent arena for action exists within each city itself. Governments that can rethink "the shape and volume of cities" amid their growth are the actors who truly secure the initiative for the future.