Hong Kong: The temperature in the inner urban areas of Hong Kong is predicted to rise by two to three Celsius degree in 30 years” time, according to the latest scientific study by researchers at the Department of Land Surveying and Geo-Informatics (LSGI) of the Hong Kong Polytechnic University (PolyU). The study was done by PolyU Professor Janet Nichol and her research student To Pui-hang, together with Chinese University”s Professor Edward Ng Yan-yung, using remote sensing technology and satellite images.
They have mapped the distribution of temperatures for both daytime and night time over Hong Kong at decadal intervals up to 2039, taking into consideration the temperature change due to greenhouse-induced warming as well as the impact of urbanisation. The latter is known as the Urban Heat Island (UHI) effect.
Given no further urbanisation, the annual mean temperature in Hong Kong will rise by 3.0 to 6.0 Celsius degrees by 2100 (according to a study of the Hong Kong Observatory in 2007). However, the mean temperature is predicted to rise by 3.7 to 6.8 Celsius degrees within the same period with a constant urbanization rate as before. The impact of urbanisation effect or UHI magnitude is estimated at 0.08 Celsius degrees per decade.
In predicting future rise in temperature, Professor Nichol has made use of satellite images for baseline air temperature mapping, global climate models for the projection of greenhouse-induced warming, and plot ratio to reflect the degree of urbanization. She also noted that air temperature is more sensitive to the density rather than the height of buildings, though the latter cannot be fully neglected.
The study found that in 2039 most urban areas in Hong Kong would have a two to three Celsius degree increase in daytime air temperature. This indicates an average increase of temperature on a summer day in urban districts, from currently 35 Celsius degrees to just less than 38 Celsius degrees in 2039.
Moreover, over the next three decades night time temperatures in the centre of Kowloon are expected to show at least an increase by two Celsius degrees, reaching over 31.5 degrees at night. This means that most urban districts in the city that are currently “comfortable” at night will become “uncomfortable” by 2039. As a result, those people who cannot afford air conditioners will suffer heat stress both during the day and at night.