Last month in Shanghai, the ¡°Plum Rain¡± season, usually starting in mid-June and lasting until early July, saw an unusual lack of rain, excepting only a small number of storms. Afterwards, scorchingly hot weather occurred.

There have been more than 10 successive days with temperatures above 35 degrees centigrade since the end of June. On July 3, the highest temperature reached 39 degrees centigrade, the highest on the same day for more than 71 years. (On July 3, 1934, the highest was 38.2 degrees centigrade).

¡°It has never happened before that in early July there have been four successive days above 38 degrees centigrade,¡± said Dai Xinfu, chief weather forecaster of the centre in Shanghai. ¡°Such hot days usually come after mid-July.¡±

A key reason for this year¡¯s lack of rain and high temperatures coming ahead of time in Shanghai was that the western Pacific subtropical anticyclone, which determines the amount of rain, stayed in the south of the country too long ¡ª those areas received ¡°double portions of rains¡± causing floods in May. It skipped Shanghai, hopping suddenly to the north of China, Professor Yu Zhihao of Nanjing University explained.

From June 1 Shanghai entered its flood season, which lasts until September 30. It was forecast that the total amount of rainfall during the ¡°Plum Rain¡± season would be 23 for 29 centimetres, however, it turned out to be only one-tenth that amount, according to Zhang Zhenyu, an official with the Municipal Flood Control Headquarters.

Heat island

On the other hand the so called ¡°urban heat island effect¡± has made people in the downtown feel the temperatures even more strongly.

The downtown areas are displayed on a large screen in the surveillance room of the Shanghai Weather Forecast Centre and often appear in the darkest colour ¡ª the darker the colour, the higher the temperature.

A large population, high-density highrise buildings and huge consumption of energy are the major reasons for the intensification of the heat island effect. ¡°Exhaust from cars and factories, clouds of dust above construction sites and the usage of air-conditioners all raise temperatures,¡± Yu said. ¡°The original laws of climate have been changed. Changes of weather have become dramatic, rather than smooth and slow as they used to be.¡±

Animals and plants are the first to be ¡°cheated¡± by changed climate. Early this year, flowers bloomed ahead of time in spring and migrant birds flew back to the north earlier than usual.

Along with the abnormality of climate, catastrophic weather phenomena appear more frequently and create greater damage. Such phenomena include floods, drought, strong winds (such as typhoons and tornadoes) and extremely high or low temperatures.

¡°Among these, storms and typhoons pose the greatest threats to the city,¡± said Zhang from the Flood Control Headquarters. This year¡¯s lack of rainfall has eased the pressure on flood control, however. Two typhoons are expected to strike the city this summer, with the first coming at the end of July or early August, and forecast to be strong.

But some of the negative influences of abnormal climate remain unseen, only revealing themselves in the long term.

¡°The city could be a beautiful coastal city if the environment was well-treated by the municipal government,¡± Yu said. ¡°But what we have seen so far is a little disappointing in this aspect. Shanghai has become hotter than Nanjing, Wuhan and Chongqing, which are the three hottest ¡®ovens¡¯ in China.¡±

The shortage of electricity, especially in summer due to increased usage of air-conditioners, has also been a factor retarding the economic development of the city, according to Yu.