Like a Furnace

The summer has passed but its cruelty will perhaps always be remembered. It has been labeled as the hottest summer in China’s history since nationwide records began in 1951， with nearly half of the country’s population sweltering in a prolonged heat wave.

The nationwide average temperature stood at 22.3 degrees Celsius from the beginning of August， 1.3 degrees Celsius higher than the average level in previous years， said Chen Zhenlin， a spokesman for the China Meteorological Administration （CMA）， on August 29.

“On August 6， the heat reached a peak， affecting more than 700 million people in 19 provinces and regions，” said Wang Youmin， a researcher with the National Meteorological Center under the CMA.

In Shanghai， mercury in thermometers swelled to 40.6 degrees Celsius on July 27 and August 6， breaking a 140-year-old record and prompting local meteorological authorities to issue a code red temperature warning on those days. China uses a four-tier， color-coded weather warning system， with red being the most severe， followed by orange， yellow and blue.

Data from the National Meteorological Center also show， as of August 13， eight of the worstaffected provinces， including Zhejiang， Jiangsu and Jiangxi， had recorded an average maximum temperature of 35.6 degrees Celsius since July， with temperatures at 477 weather sites recording new records.

According to local government reports， at least 40 people died from heat-related health problems in south China this summer. In Shanghai， more than 10 people died from heat stroke.

“The hot days were mainly caused by the North Pacific Subtropical High being particularly strong，” said Sun Leng， a senior engineer with the CMA’s Climate Data Center. The North Pacific Subtropical High is a semi-permanent anticyclone， which means that it is an almost continuously highpressure region that causes large-scale circulation of wind round it.

Sun added that the North Pacific Subtropical High is a particularly important factor in determining the summer climate in China.

But meteorological experts also admitted that human activities have also contributed to the increase in temperature.

According to Zhou Fuduo， a professor at the College of Civil Engineering and Architecture of Zhejiang University， some of the summer discomfort experienced stemmed from the urban heat island （UHI） effect. The UHI effect is where a metropolitan area is significantly warmer than its surrounding rural areas due to human activities.

“We can see that those who died from heat stroke lived in cities，” Zhou said.

planning errors

The term UHI comes from the fact that in an air-temperature-distribution graph， the hightemperature part has a shape of an “island.”

Starting in the early 19th century， studies of these “heat islands” focus on the man-made effect of a temperature gap between a city’s downtown and suburban areas and the resulting impacts on the urban ecological environment.

“There is a clear relationship between high temperatures and urban planning，” said Yu Kongjian， Dean of Peking University’s College of Architecture and Landscape Architecture.

In his opinion， air duct blockage， wetland degradation and loss， reduction of green spaces， enlargement of urban areas and the popular usage of glass curtain walls in constructing modern office complexes will all further worsen the UHI effect. He warned that even a small miscalculation or mistake in urban planning may lead to the destruction of the entire ecological system.

“In general， our city planners put a lot into the design of traditional infrastructure but don’t spend enough time on infrastructure，” Yu said， adding that this summer’s heat waves were belated warnings against today’s unsustainable city planning practices.

“Proper city planning requires the use of science， and scientific models and calculations tell us that you must leave enough space to be reserved as ‘permanent non-construction areas’ between different districts that can provide buffer zones for the city，” Zhou said.

He complained that these buffer zones， including farms， wetlands and green areas， which should have been kept in larger cities， are often misused for building business districts or residential areas.“The larger a city expands， the stronger its UHI effect is，” he said.

Since the 1970s， Zhou has begun studying the UHI problem affecting Hangzhou， the capital city of Zhejiang. When he began his research， the temperature gap between the city’s urban and suburban areas was just 2 to 3 degrees Celsius. But today， the gap has reached 7 to 8 degrees Celsius.

Except for meteorological factors， the changes in the city’s population， energy consumption， transportation methods and building areas have contributed to the growing UHI effect， Zhou explained.

Urban planning divides urban areas into three categories： areas appropriate for construction， restricted construction areas and areas forbidden to construction. “Those restricted and forbidden areas should be reserved for ecological construction projects， but today’s city planners often neglect using scientific planning and sell the areas to business people for commercial purposes，” Zhou said.

Hangzhou is surrounded by mountains on three sides. In summer， it relies on the wind from the Qiantang River in the southeast to help the urban areas cool down. However， the city’s planners have started changing the development strategy for the city and decided to develop the area surrounding the river into a business zone.

A number of skyscrapers have already been erected along the both sides of the Qiantang River.“The consequences of this badly thought out plan was presented to planners this past summer，”Zhou said， warning that more extremely hot sum-mers will be experienced in the coming years due to Hangzhou’s unbalanced planning.

According to local meteorological authorities， Hangzhou was hit by 40.6 degrees Celsius on August 6， the highest temperature there since 1951.

Another factor adding to the severity of the UHI effect is the occupation of waterways.

“One of the main activities in the previous 30 years of China’s construction has been to fill rivers，” said Liu Bo， Director of the Publicity and Education Center at the Sanitation Bureau of Changde City， central China’s Hunan Province.

Today， the traditional water systems and wetlands have been replaced by watertight road surfaces in many cities. “In some cities， the urban hardness ratio has reached over 80 percent， while the natural infiltration rate for rain has decreased below 20 percent，” Liu said.

Liu has long been calling for reducing the hardness of surfaces in cities. He said， “A modern city should be a spongy city， combining its urban sewage system with the city’s natural water system， including rivers， lakes and underground water sources tightly together.”

Xuan Chunyi， an engineer with the Beijing Climate Center， has studied urban water systems for many years. “Whether a city has is decentralized or centralized water systems， the increase in a city’s total water surfaces reduces the severity of the UHI effect，” he said.

“The UHI effect in Chengdu， capital of Sichuan Province， had increased year on year before 2003. With green areas and wetlands expanding in the city in recent years， the intensity of the effect has declined，” said Dan Shangming， a retired senior engineer with the Sichuan Provincial Meteorological Bureau.

Green remedies

“To alleviate the UHI effect， it is imperative to increase the areas allocated to bodies of water and green foliage，” said Li Yanming， a senior engineer at the Beijing Research Institute of Garden.

Research shows that when a city’s foliage coverage surpasses 40 percent， the urban heat effect will be lowered notably. According to satellite remote sensing data， the building of a central green area has helped erase the original four heat islands in the Lujiazui area in Shanghai.

“There are too few green areas in Chinese cities，” Zhou said. According to him， an indispensable factor for an “advanced” city in foreign countries is that its per-capita green coverage should reach 30 square meters， but in China， a nationally designated“garden city” only requires about 10 square meters for each person.

In recent years， city planners have started putting importance on the placement and preservation of green areas， but Zhou said that a new mistaken idea has also emerged alongside this—the “green patch plus flower” planning undertaken in most Chinese cities.

“We put too much emphasis on landscape. In reality， green work is a multi-level project， requiring proportionally putting trees， shrubs， flowers and ground cover plants together，” Zhou noted.

Yu believes that for every city， the ecological meaning should be more important than the landscape consideration of its green work. “It’s only a great quantity of trees that can make real relief to the UHI effect，” Yu said.

He emphasized that one of the major projects undertaken in city green work has to provide areas of shade provided by trees between buildings， and this requires particularly tall trees in large numbers.

However， in order to make room for infrastructure construction， many local governments have chosen to move or even cut down existing trees.

In 2011， the authorities of Nanjing， capital of Jiangsu， decided to move some of the city’s French plane trees， which were planted between 1912 and 1949， to make way for the construction of a subway line. This decision incited protests from local residents. Eventually the plan was called off due to public pressure.

Without destroying trees or even planting more， the outlook for China’s green system construction is still not optimistic. “In green area planning， there are upper and lower limits. Our planners always choose the lower limits，” Zhou said.

Take the green work along the Qiantang River in Zhejiang for example. The 1，000-meter-wide river requires a 100- to 150-meter-wide green corridor on each side， but only a 30-meter-wide belt is built along each side of the river today. “The tiny green belts will go a very little way in relieving the UHI effect in the area，” Zhou said.

Li Shuhua， a professor at the School of Architecture of Beijing-based Tsinghua University， has led research into the effects of Beijing’s river lands. The research concluded that “only those green belts surpassing a width of 45 meters can reliably absorb the surrounding heat and reduce the strength of the surrounding UHI effect.”