It is undeniable that cities have far-reaching impacts on every aspect of life. Currently, half of the world's population, around 4.5 billion people, living in cities around the world. Cities account for more than two-thirds of the world's economic production and three-quarters of global greenhouse gas emissions. As cities grow, the population will increase further, with the global urban population expected to reach 7 billion by 2050. Our scientific knowledge and evidence support the idea that cities are the primary culprits of climate change. Meanwhile, they are also critical in bringing in sustainable development by adopting innovative ways to mitigate, adapt, and respond to the impacts it has brought. The Intergovernmental Panel on Climate Change (IPCC) published the sixth Assessment Report (AR6), which includes three Working Group reports covering the latest scientific understanding of climate change and research on global climate change impacts, mitigation, adaptation and vulnerability. The Summary for Urban Policymakers report (SUP), released during the 27th United Nations Conference of the Parties (COP27) last November under United Nations Framework Convention on Climate Change, is a synthesis report that reveals insights from the three IPCC reports on cities facing climate change. This paper will highlight the key points and explain the roles of science and technology in mitigating and adapting to climate change in Hong Kong.

The impacts of climate change on cities

Fig 1: The trend of global surface air temperature between 1958-2018, showing various cities recorded a notable temperature increase. Source: Summary for Urban Policymakers, SUP.

SUP report begins by stating that a climate crisis is underway. Human-induced climate change that causes extreme weather, is affecting every corner of the planet and various ecological systems. Its impact on cities is particularly severe. As shown in Fig 1, many cities have recorded significant temperature rises over the past six decades: 1.5°C in Seoul, 2.33°C in Tehran (Iran), and 2.6°C in Kolkata (India). Meanwhile, the average temperature in Hong Kong went up by 0.41°C. We cannot underestimate this 0.41°C. According to the Hong Kong Observatory, a rising sea temperature that causes higher sea levels and more rainfall, and frequent extreme weather are the results of this slight increase. Some climate scientists predict that the sea level will rise by 0.5 meters in 2050, which would multiply the risk of flooding; higher temperatures also warm up the oceans, triggering red tides and causing a large number of marine creatures to die due to a lack of oxygen. Moreover, global warming prompts the breeding of mosquitoes, exposing more people to the risk of diseases.

IPCC points out that cities and urbanisation can worsen climate change, which in turn brings adverse impacts on the cities and their surrounding areas. The urban heat island effect is such an example.

Urban Heat Island Effect

The urban heat island effect occurs when the temperature of an area is higher than that of the surrounding areas, especially at night. The warming effect is particularly significant in cities because they absorb and retain more heat and have a weaker natural cooling capacity than the surrounding countryside areas.

The urban heat island effect is caused by several factors, with urban geometry being the main factor, namely the number, height and density of urban buildings. Tall buildings with close proximity absorb and store heat while weakening the airflow. Fig 2 shows that urban geometry can bring the temperature of an urban area up by as much as 1.7°C. Human activities are very concentrated in cities and the heat released from the urban industrial and domestic heating/cooling systems, electricity use, and other sources directly warm up the atmosphere. The concrete in urban buildings and the asphalt on roadways also contribute to climate warming, as these heat-absorbing materials retain heat during the day and re-emitting it at night. Taken together, these three factors can drive up the city temperature to 4°C. Water bodies such as oceans and lakes, and vegetation such as parks and forests can slightly mitigate the warming effect. Unfortunately, cities usually have fewer of these natural cooling resources.

In addition to the urban heat island effect, Hong Kong, as a coastal city, is also exposed to the risks of rising sea levels and flooding. The risks of rising sea levels, frequent tropical cyclones and heavy rainfall associated with coastal storms, will expose the city to strong winds and flooding, which will most likely damage infrastructure such as housing, transportation networks, power supply systems, and even lead to casualties. If these disasters occur individually, the damage may not be catastrophic, but when multiple disasters occur simultaneously, the consequences would go beyond estimation and the damage caused may far exceed the impact of individual disasters. Storm surges and river flooding can cause severe flooding for many cities and low-lying areas; heat, drought and strong winds can cause hill fires. Unfortunately, it is expected that the likelihood of such natural disasters occurring in the face of climate change. Last year, for example, there was extreme weather in many parts of the world, including flooding in Pakistan that affected over 30 million people and took more than 1,000 lives. Climatologists pointed out that the floods may have been a result of the heat wave in Pakistan between April and May last year. The warmer atmosphere means more moisture, resulting in heavier rainfall in Pakistan during the monsoon season from July to September. The high temperatures also triggered the collapse of a glacial lake, making the floods unstoppable. Many parts of China experienced persistent heat waves last year that led to severe drought and insufficient hydropower, and with high temperatures driving up the electricity demand, several areas saw power shortages.

Fig 2: The density and height of buildings, the heat released from human activities and heat-retaining properties, as well as fewer water bodies and vegetation are the factors that amplify the urban heat island effect in the cities. Source: Summary for Urban Policymakers, SUP.

Cities must accelerate carbon reduction

COP27, held in Sharm el-Sheikh, Egypt last November, reaffirmed the goal of limiting global temperature rise to 1.5°C. As a developed city, Hong Kong also shares the responsibility to address the impacts of climate change. Despite the setting of a target to achieve carbon neutrality by 2050, the Hong Kong Government and industries such as electricity, infrastructure and transportation should incorporate the Science Based Target approved by the IPCC and the International Energy Agency (IEA) into its climate action plan. The emission reduction target should include a clear mid-term plan, a finalised timeline, and an explanation of how they can help achieve the final reduction target.[1] Some corporates have adopted Science Based Targets in their carbon reduction reports, such as the Sectoral Decarbonisation Approach (SDA) developed by the Science Based Targets Initiative (SBTI). These standards can help develop a more specific carbon reduction approach to meet the Paris Agreement. These approaches also provide figures to assess the carbon reduction progress of Hong Kong's major sources of emissions. Specifically, the Hong Kong Government should aim higher in its carbon reduction target for 2030 and reduce greenhouse gas emissions by 45%, based on the emission level of 2005, or even reduce such emissions by 60% if the Science Based Targets are adopted. The Hong Kong Climate Action Blueprint 2050 proposes to increase the proportion of renewable energy supply in Hong Kong by 7.5 to 10% by 2035. However, as early as 2017, a study conducted by the Hong Kong Polytechnic University revealed that Hong Kong enjoys sunshine more than half of its day and the city is therefore highly suitable for solar power generation. According to the data collected from high-resolution airborne laser scanning and geographical information systems, over 70% of the buildings in Hong Kong are suitable for installing solar photovoltaic panels, with a total area amounting to 39 km[2]. The potential annual solar energy output can reach 4.67 Gwh, accounting for 10.7% of Hong Kong's energy demand, which is even higher than the maximum target set by the government. Among all the renewable energy sources, solar and offshore wind power should be prioritised over the problematic approach of converting waste into energy. The government should re-examine policies that are possibly hindering the development of renewable energy facilities to significantly increase the use of renewable energy.

Scientific research and technology in climate justice

The daily carbon emissions from Earth lead to accumulating GHG in the atmosphere. It is only when zero carbon emission is reached, the accumulated GHG can begin to drop. The IPCC AR6 report states that it will take 5 to 10 years to see the impact of GHG accumulation for both low and high carbon emissions, and more than 20 to 30 years to see the change on global surface temperature. In other words, a global temperature rise of 1.5°C after 20 years will happen regardless of how much effort is made in carbon reduction as the GHG continues to accumulate in the atmosphere. Even though COP27 managed to maintain the 1.5°C target, only a small number of countries have committed to a more aggressive carbon reduction programme. One of the keys to reaching the 1.5°C target is for countries to take stock of their resources and capabilities and submit Nationally Determined Contributions (NDCs) following the Paris Agreement. However, the current NDCs estimate a global temperature rise of 2.5°C, a far cry from the target. In terms of fuel consumption, the Climate Conference held this year only encouraged phasing down on coal-fired electricity generation, instead of phasing out fossil fuels such as petroleum and natural gas. This casts doubt on the determination of countries to reduce carbon emissions is in doubt. Based on the current progress of carbon reduction in Hong Kong, it still needs to face the warming effect of climate change.

The IPCC has once highlighted that the impact of climate change is particularly and unequally detrimental on vulnerable groups, who are affected by climate change to a greater extent than the general population. Climate change, structural poverty, social and economic inequality, have exacerbated the plight of vulnerable groups. Earlier on, CarbonCare InnoLab released a report "A just transition for Hong Kong, Building Partnerships to Achieve a Climate-just city" (the Just transition report), which is Hong Kong's first attempt to achieve climate justice. It is hoped to resolve the differences in the implementation of actions and strive to make climate justice a reality for the whole society through a dialogue with various sectors and industries in Hong Kong. Non-governmental organisations participating in the community dialogues have shared a common vision for the future of Hong Kong, with the expectation that our climate actions are to build a just and inclusive environment. This is reflected in seven key areas: physical and mental health, cost of living, access to information, work environment and arrangements, transportation, community support and services, and green living. From the past dialogues in the community, it was found that research and technology are crucial in achieving an inclusive and just climate action.

Climate justice and a just energy transition

A just transition identifies adverse impacts of climate change on poor and vulnerable groups in social, economic, health, and other perspectives. Vulnerable groups are the victims of climate change and they are usually the least responsible for its cause, such as low-income communities, ethnic minorities, indigenous groups, people with disabilities, children and the elderly, grassroots workers and women, as well as people in developing countries with low per capita emissions. Yet, they are also more susceptible to the impacts of climate disasters. Therefore, it is hoped that by incorporating human rights into long-term climate mitigation and adaptation strategies, we can address the climate crisis and climate-induced social inequities, creating a better future for the present and future generations. When any particular climate action is carried out, we must also prioritise the well-being of the above-mentioned vulnerable groups while promoting a green economic transition. Climate justice is achieved by letting the people affected by climate disasters fully participate in process of justice, considering the susceptible and vulnerable groups in terms of the uneven distribution of their adaptive abilities to climate change, the historical responsibility for climate change and those who are affected by the mitigation measures. A just transition will promote a low-carbon and climate-resilient economic transition while ensuring that the rights of workers, women, and vulnerable groups are protected. Climate action must be planned and implemented in a way that benefits all, without marginalising anyone.

Hong Kong experienced a prolonged heat wave last July, including 21 hot days during which the daytime temperatures reached 33°C or above, and 25 hot nights where the lowest temperature was 28°C or above, with 21 consecutive hot nights breaking the Observatory's record. Outdoor workers are vulnerable to increasingly frequent high temperatures due to the nature of their work. In a community dialogue on outdoor workers, participants suggested that the city could take reference from other Asian countries, such as Japan and Korea which adopt a non-mandatory measure and a more systematic and scientific Wet-Bulb Globe Temperature (WBGT) to assess the risk of heatstroke for workers working under high temperatures, and proposed a suitable work environment, workflow, health management measures accordingly to guide workers to cope with extreme weather. The measurement system has been widely used in many prefectures in Japan and Korea to guide construction sites and schools and has been well received by local residents. The Guidelines on Prevention of Heatstroke at Work by the Labour Department is currently under public consultation. The guidelines are based on the Hong Kong Heat Index and require employers to take precautionary measures in accordance with the measures to protect employees from heatstroke at work.

Hong Kong Heat Index

Hong Kong Heat Index, HKHI, jointly developed by the Hong Kong Observatory and the Faculty of medicine at The Chinese University of Hong Kong, is an index that monitors heat stress. It is calculated from a comprehensive measurement of temperature, humidity, airflow and radiation, providing a more accurate heat stress level and the risk of heatstroke in reality than solely looking at the temperature itself. The HKHI is based on the WBGT Index, which consists of measured Natural Wet Bulb Temperature (Tnwb), Globe Temperature (Tg) and Dry Bulb Temperature (Tdb). It also considers the coefficients applicable to high humidity conditions in Hong Kong during summer, hospital admission data and heat stress measurements from 2007 to 2011, to reflect the local heat stress in Hong Kong.

The Guidelines on Prevention of Heatstroke at Work point out that employers should arrange hourly breaks for employees based on their workload when the index at King's Park reaches around 30 or above. Trade unions and non-governmental organisations put forward several proposals during the consultation period, in a hope that the guidelines can better meet the actual working conditions of outdoor workers. Japan, for example, which also adopts WBGT Index, has encouraged employers to install WBGT devices in workplaces, among which portable WBGT devices can even measure the WBGT of difference locations in a workplace, which can monitor the risk of workers being exposed to heatstroke.

Fig 3: Japan encourages employers to install WBGT devices in workplaces

Through conducting scientific research, we can better understand the realities and needs of people with mental illness when dealing with climate change. Recent academic scientific papers show that climate change is highly likely to induce mental health problems. The IPCC AR6 Report of Working Group 2 (WG2) also mentions the impact of climate change on mental health, citing a study by Professor Emily Chan and her team at the Jockey Club School of Public Health and Primary Care, Faculty of Medicine in The Chinese University of Hong Kong, on the relationship between temperature and psychiatric illness in a subtropical region with an average temperature of over 21°C.[3] The team found that the higher the temperature in Hong Kong, the higher number of hospitalisations in psychiatric patients. They also discovered that both frontline healthcare workers and community workers have little awareness of the relationship between climate change and mental health. Due to a lack of relevant information and studies, frontline doctors do not consider extreme weather in their diagnoses and treatment, failing to identify the relationship between the two and making it difficult to provide prior support. Professor Chan's research indicates that scientific research is conducive to understanding the plight of vulnerable communities and that it must also be integrated with climate action to achieve climate justice.

"Smart Environment" is a key area of the Hong Kong Government's "Smart City Blueprint for Hong Kong", which incorporates the carbon and energy reduction targets in the Hong Kong Climate Action Plan 2050. The use of technology can help the city to mitigate and adapt to climate change. Nonetheless, several aspects should be emphasised to achieve climate justice. The idea of Smart Environment is concerned with data systems, automation systems and Internet of Things technologies, but relevant climate technologies currently in use, such as urban climatic maps and airflow assessments, are only understood and managed by professionals. Furthermore, persons with physical or mental disabilities may not be able to use the technology to access information in a timely manner, such as the warning about climate disasters. The city should promote public education on the requirements and knowledge of such technology, to enable the public, especially the vulnerable groups, to use smart technology to obtain information regarding climate and carbon footprint. The system applied in the Smart Environment should also publish content that is easily understood by the general public and improve user experience. It is vital to deliver information effectively to the vulnerable groups through technology and acknowledge data security and privacy while achieving climate justice.

"Smart City" and climate change

The concept of Smart City is based on the belief that technology can improve people's quality of living by creating wealth and employment opportunities and addressing the worsening climate crisis, an expectation more widely held by the public. A Smart City can improve energy efficiency. In Hong Kong, for example, the "Smart City Blueprint" includes green building design, provision of smart water meter system, electric vehicle charging facilities and real-time parking vacancy information, etc. In terms of promoting energy transition, a Smart City not only provides applicable technology solutions and updates, but also promotes effective regulation and reform of the energy industry, managing the entire energy supply chain. For instance, Vietnam, which is phasing out coal, is actively promoting renewable energy by developing a smart grid to predict and manage the supply and demand of renewable energy. It aims to meet the demand for electricity without overloading the grid.[4]

Other than the energy sector, climate change is also shaping smart city planning in other ways. Data and simulation are the core strategies in coping with climate change. As many of the cities are facing life-threatening situations, a Smart City can help simulate countermeasures to flooding and extreme heat, reducing the threat to infrastructure and necessary services. For example, satellite data can help predict early warnings and monitors rainfall in real-time. Also, data from rivers and drainage systems can be collected using the Geographic Information System. Digital modeling and analysis can shape smart city planning, especially for the prevention of flood risk and making climate issues more predictable.


Numerous pieces of scientific evidence show an imminent threat from the climate crisis, and densely populated cities with concentrated economic activities play a critical role in the fight against climate change. Cities produce most of the world's greenhouse gas emissions so they must make more efforts to reduce the emissions accordingly. On the other hand, cities have more resources to cope with climate issues. As a developed city, Hong Kong should not be left out of the fight against climate change. And more importantly, its carbon reduction measures and policies should not lag behind others.

As the impacts of climate change hit the vulnerable groups unequally harder, CarbonCare InnoLab advocates for an inclusive and just climate action. According to the experience of outdoor workers, people with mental illnesses and the development of Smart City, we need to capitalise on science and technology to handle the impacts of climate change. Finally, it is necessary to consider the well-being of the vulnerable groups who are more susceptible to the influence of climate change.


  1. Science Based Targets provide a clear path for corporations and financial institutions to reduce greenhouse gas (GHG) emissions, which helps prevent the adverse impacts brought by climate change. The carbon reduction target, being considered 'science-based', must be consistent with the Paris Agreement's goal of limiting global warming to 1.5°C above pre-industrial levels. For more information, please visit
  2. Polytechnic University of Hong Kong. "Potentials of generating clean solar energy in Hong Kong," viewpoint/v1/index.html
  3. Chan EYY, Lam HCY, So SHW, Goggins WB, Ho JY, Liu S, Chung PPW. Association between Ambient Temperatures and Mental Disorder Hospitalizations in a Subtropical City: A Time-Series Study of Hong Kong Special Administrative Region. Int J Environ Res Public Health. 2018 Apr 14;15(4):754. doi: 10.3390/ijerph15040754. PMID: 29662001; PMCID: PMC5923796.
  4. Acharya, D., "Smart, sustainable, urban: how smart city schemes can prepare Asia for climate change," Arup, 2022.

Mr Kwok Hiu Chung, Senior Programme Officer, CarbonCare InnoLab
January 2023