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Behind the Scorching Heat in Hong Kong: Urban Challenges in a Changing Climate




It is hot and stuffy when you walk down the streets during summertime in Hong Kong. I believe most residents have already experienced the unbearable heat under the midday sun. Even office workers are unable to hide from the heat, coming back from lunch drenched in sweat. It took a lot of past effort to raise people’s awareness about climate change. But now, we all know what it is like to be a victim of climate change.

Back in the late ‘70s, we used to experience four distinct seasons. We had seasonal closet swaps 2-3 times a year, and winters were so freezing that we had to wear cotton-padded jackets. But nowadays, our closets are full of summer clothes; bulky, warm clothing only comes in handy when travelling.  

Normally, spring in Hong Kong runs from March to May, summer from June to August, fall from September to November, and winter from December to February. Yet, summer and fall have now almost turned into summer. Spring would end in a flash and become summer, and winter has gotten so warm that we only have to wear fall clothes, except for an occasional cold spell or two.

Let’s take a look at Hong Kong’s average temperature, which has risen from 22.9°C in 1961 to 23.9°C in 2022, showing a 1°C increase in 60 years. Don’t underestimate the significance of this 1°C. According to the United Nations Intergovernmental Panel on Climate Change (IPCC), global temperatures have risen by 1.2°C compared to pre-industrial times. The Paris Agreement aims to limit the global average temperature to "well below 2°C above pre-industrial levels". The alarming thing to Hong Kong is: while the global temperature has risen by 1.2°C in the 200 years since industrialisation, the temperature in Hong Kong has risen by 1°C in just the past 60 years.


Long-term time series of annual mean temperature in Hong Kong from 1885-2021 (Image source: Hong Kong Observatory)

If we take a closer look, two-thirds of the 1.2°C rise in global temperature took place after 1975. Apart from greenhouse gas emissions caused by industrialisation, urbanisation is another major reason why "concrete jungles" like Hong Kong are getting hotter, with "urban heat island effect" turning summer into a suffocating furnace.

Hong Kong is a highly-urbanised region in which population growth and increase in buildings have aggravated the urban heat island effect. The large number of buildings and concrete surfaces absorb and store heat, causing the temperature in urban areas to be higher than that in suburbs. Land use changes also pose an impact on temperature. Urban sprawl has reduced vegetation cover, disrupting natural regulation and evapotranspiration processes, thereby exacerbating the urban heat island effect. As a consequence, streets of Hong Kong in summer are filled with hot air from vehicle exhaust and air conditioning. With narrow streets and high-rise buildings trapping the heat, combined with summer heatwaves, it becomes unbearably hot.

 

 

Urban heat island phenomenon (Image source: Green Ribbon)

 

Prolonged hot summers bring discomfort and even health problems to people's daily lives and work. High temperature and humidity in cities are more likely to trigger health risks such as heat stroke and fatigue. In recent years, the number of heat-related deaths and medical visits in Hong Kong and Mainland cities has been on the rise. Rising temperatures can jeopardise food safety and have negative impacts on agriculture, ecosystems and water resources.

In the face of these challenges, the Hong Kong government needs to adopt systematic measures to reduce greenhouse gas emissions, expedite renewable energy development, improve energy efficiency, and promote a low-carbon economy. Secondly, urban planning and new infrastructures must include climate change impact assessment, together with measures to mitigate urban heat island effect, namely increasing green coverage, zero-carbon buildings, parks and green spaces, and shading facilities to reduce heat in urban areas.

Hong Kong is blessed with a vast and diverse natural environment. The conservation and restoration of country parks and wetlands therefore play a vital role in minimising the negative impacts of rising temperatures on ecosystems and water resources, as well as cooling down the city. Enhancing public awareness and adaptability to climate change is also crucial. Over the past 40 years, Friends of the Earth (HK) has spared no effort in raising public awareness of environmental protection and climate change through education and publicity. The government, corporations and the general public must take more responsibility for global warming. It is only through the actions of all that we can create a more livable and sustainable future for Hong Kong.

 


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