Why despite climate restoration

Hong Kong’s Kowloon Peninsula may be one of the most studied urban climate zones on Earth, but it continues to heat up at a staggering rate.

New research reveals why standard cooling solutions from ventilated corridors to energy-efficient buildings – failing to stop temperature rise in dense cities. The study, published in urban and built environments, suggests that urban warming stems from basic physics that most climate interventions simply cannot solve. Between 1961 and 2017, Kowloon’s annual temperature rose by 0.23°C every decade (almost twice the rate of rural warming), while humidity increased by 0.25 grams per cubic meter every decade. These findings challenge how we view urban climate solutions and suggest that fragmentary fixes don’t work in our increasingly vertical world.

Hot storage issues

Why does the city stay hot even after the sun sets? The answer lies in the huge thermal battery effect that most planners ignore. Buildings in dense cities like Kowloon create what researchers call “a considerable heat storage” during the day, and then slowly release energy throughout the night.

The scale of this problem is shocking. In high-density areas, the total building envelope area may be four to ten times that of the actual land surface. This means that, on every square meter of ground, there are up to ten square meters of heat-absorbing construction surfaces – walls, roofs and exteriors, like giant hot sponges.

To prove this concept, the researchers used “Stone Forest” to create a clever experiment, a natural landscape with high and dense stones that mimicked urban high-rise buildings, and sparse, low-stone areas representing suburban development. Even without any human-generated heat source, the dense stone area shows the same heating pattern as the city Kowloon: cool during the day and warm at night.

Key research results:

• Lush urban areas store and release heat through building materials for continuous night warming
• Mountain wind can capture cities onto cities through the “hot dome” effect
• Urban areas now generate their own wind systems that interact with regional weather patterns
• Construction continues to grow, while wind speeds in urban areas continue to decline
• Current interventions are symptoms, not the basic physics of urban fever

When the wind makes things worse

This is where the urban climate is counterintuitive. Most people think that peaceful, windless days will create the hottest urban conditions. But Kowloon’s research reveals something surprising: Some wind patterns actually make cities hotter, not cooler.

When the northeast mountain wind blows towards the city, they create what scientists call “downstream blockade.” Mountain air merges with the city’s own heat circulation to form a large vortex that captures the warm air in urban areas. This creates a steady vertically round hot air, which actually turns the city into a natural chimney that cannot exhale.

Analysis of data from Hong Kong Observatory confirmed this unexpected finding: Eastern Kowloon actually gets hotter when the northeast wind blows compared to completely static air conditions. This discovery turns traditional urban planning wisdom into mind.

Urban Thermal Circulation System

Modern cities not only sit passively in regional weather systems, but also create their own atmospheric patterns. Hong Kong has become so large and dense that its self-generated thermal cycle now reaches a height comparable to or exceeding the surrounding mountains.

This urban-scale cycle is like a large number of convective cells. Rural air flows horizontally into the city from the ground, heats up, passes through the city center, and then spreads horizontally at higher altitudes, and then merges into the regional airflow pattern. The result is a “hot dome” that can persist regardless of external weather conditions.

Making this particularly problematic is that cities continue to grow horizontally and vertically, enhancing these thermal cycle modes while reducing wind speeds that may provide natural cooling.

Why are the standard solutions insufficient

Traditional urban cooling strategies focus on various elements: more parks, better building efficiency, strategic ventilation corridors. But cities are complex systems, where one of the changing elements often triggers unintended consequences elsewhere.

For example, researchers found that even if all buildings’ exteriors are completely insulated to prevent heat storage, dense cities actually experience worse daytime heating. The heat storage effect of producing nightly heat islands will also save daytime temperatures – avoid it and turn the city into a stove during sunny time.

The study reveals an unsettling reality: many current interventions view urban heat as a series of independent technical problems rather than addressing the fundamental physics of how dense built environments interact with atmospheric systems.

Artificial fever misunderstanding

A crucial finding challenges common assumptions about urban heating. Although air conditioning systems and vehicle emissions do contribute to higher temperatures, Shi Forest experiments show that cities still produce significant heating effects even without any human-generated heat sources.

Increased solar heat in urban canopy layers, coupled with reduced heat through natural ventilation, can produce warming effects, no matter how effective we design mechanical systems. This shows that focusing solely on reducing energy consumption does not solve urban thermal problems.

The implication is stunning: As cities around the world continue to grow vertically to accommodate the expanding population, traditional mitigation methods may become increasingly inadequate.

Global betting

Why do people outside Hong Kong care about Kowloon’s climate challenges? Because this dense peninsula represents the future of human habitation. More than half of the global population now lives in cities, and by 2050, that percentage is expected to reach two-thirds, which will be 2.5 billion new urban residents.

Although it covers less than 3% of the earth’s surface, cities consume 75% of global resources. Urban areas generate 80% of economic growth and most greenhouse gas emissions. Without solving the urban heat problem, there will be no global sustainability.

The efficiency argument for density is still convincing. In high-rise apartments in Kowloon, each family effectively occupies 13 square meters of land, while the 2,000 square meters of equivalent suburban housing is 150 times. However, this efficiency is accompanied by climate punishment that researchers only begin to understand.

A solution beyond fragments

The study requires scientists to consider it a “system system” approach to urban climate. Instead of seeing heat, transportation, energy and building systems as separate challenges, cities require integrated solutions to consider the interactions of multiple urban systems.

This means going beyond traditional urban planning and treating cities as complex climate entities. Future urban forms must balance sustainability, well-being and resilience at the same time, rather than a challenge.

As global temperatures continue to rise and urban populations grow, bets continue to rise. Cities that cannot solve these basic thermal dynamics may find themselves trapped in cycles of energy consumption, heat generation and climate impacts.

The question is not whether we can continue to build dense cities – overall population growth makes vertical development inevitable. The question is whether we can design urban forms that work with basic atmospheric physics rather than oppose them. Kowloon’s continuous heating trend shows that time is short and these answers cannot be found.

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