Between 1999 and 2001, China experienced consecutive years of high
temperatures and its average temperature rose. At the first China
Climate Conference held last March, experts predicted that China's
climate would go on warming up over the next 50-100 years. What
influences will this warming-up have on the Chinese environment?
And what measures should be taken to reduce its destructiveness? A
reporter for the
Science Times recently interviewed Ding
Yihui, special advisor on climate changes of Chinese Meteorological
Administration and former co-chair of
Intergovernmental Panel on Climate
Change (IPCC), who is now engaged in study in this field. On
reviewing all statistics at hand, he thinks that the warming
climate has a great influence on Chinese environment, some of which
are destructive, especially in sensitive and fragile areas.
Therefore, China must take measures to prevent and solve the
problem.
On Land: Trouble Comes from Water
According to Professor Ding, the rising temperature will worsen
drought conditions in the northwest, north and northeast areas of
China. Take the northwest as an example, the warm climate will
increase the rainfall by 20-30 mm (0.8-1.2 inches) in this area,
but the evaporation volume will increase by 10-15 percent. If the
present evaporation volume is 1,500-3,000 mm (59-118 inches), the
increased evaporation volume is far greater than the increased
rainfall. It is estimated that between 2030-2050, the northwest
China will be short of 20 billion cubic meters (26 billion cubic
yards) of water, 10 times of the water now stored in Miyun
Reservoir in Beijing. Also, the drought weather will lead to
thickening of sand layers, especially in the transition area from
farmland to herding land. The chance for sandstorms is high.
Professor Ding refuted the notion that a warm climate will prevent
a cold wave from going southward, thus limiting sandstorms. A
sandstorm occurs under two basic conditions: The sand source and
corresponding climate such as a big wind, Ding said. The warmer
climate will reduce the occurrence of big winds, but cannot prevent
gales under special conditions, while the sand source will surely
become "optimized." Therefore, the future for sandstorms is not
that bright. For instance, the State Climate Center has confirmed
that March 20-24 sandstorm this year was the most severe sandstorm
in the past 10 years, which affected not only Republic of Korea
(ROK) and Japan, but also the United States far away. Statistics
from relevant departments of the ROK also show that the country saw
more than 160 sandstorms in the past 50 years, but 100 of these
occurred after 1990. Based on these facts, survey results showing
that "sandstorms were reduced between 1954 to 2000" are unreliable.
On the contrary, the government should adjust the observation
stations now in existence and conduct systematic and thorough
investigations by time and province to get more convincing
data.
What's more, the warmer climate will accelerate the melting of
glaciers in western regions. By 2050, half of the present
glacierets will disappear. As a result, the fresh water in storage
will decrease. As a resource formed during a long time of history,
the disappearing of glacierets is irreversible.
According to Ding, disasters such as mud-rock flow and landslides
will also occur frequently in southwest China if the urbanization,
land development, vegetation destruction and increasing rainfall
brought about by warm climate are not brought under control. Worse
still, the karst topography will increase, the dangerousness of
which is no less than that of desertification in arid regions.
In
areas short of artificial irrigation, Ding said, three major grains
-- wheat, rice and corn -- will see their output reduced by 5-10
percent. But food security can be guaranteed before 2050. In the
field of forestry, tree species will decrease and bio-diversity
will be destroyed. It is estimated that by 2050, coniferous forest
in frigid zone of northeast China will basically disappear, and
grassland in temperate zone will be reduced on a large scale.
Except for some tropical rainforests where areas will be increased,
most forest area will be reduced, but the rate will be no more than
10 percent.
On Ocean: Far-reaching Influence
Professor Ding said that compared with land system, the ocean is
influenced in a broader sense by warming climate. The period of
being affected will last up to 1,000 years.
The influences are mainly as follows: First, the rising of sea
level due to heat expansion and glacier thawing. In the past 100
years, the sea level in coastal areas has risen by 20-30 cm
(7.8-11.8 inches), while in the following century, the rise will
reach 88 cm (34.6 inches). Many areas will be swallowed up by sea
water. Second, possible ice age in the warm period of north China
because of the weakening or ending of Thermohaline Circulation
(Heat-Salt Circulation). The heat-salt circulation refers to the
relatively warm south surface sea water bringing heat to the
relatively cold sea surface in the north, then sinking down to
deeper water and returning. The heat exchanges between sea water is
of great help to adjusting temperature gaps in the atmosphere,
thereby guaranteeing a temperate climate. However, the warming
climate will shorten the temperature gap between north and south
sea water. At the same time, the increased rainfall in high and
middle latitude will lead to desalinization and density weakening
of sea water, neither of which is beneficial to the heat-salt
circulation. In history, the weakening of heat-salt circulation in
the Atlantic Ocean once resulted in an ice age in northern Europe.
Further study is needed to determine whether the affected heat-salt
circulation in the Pacific Ocean will lead to low temperature in
north China. Third, the accelerated destruction of biological
systems in the ocean, especially the death of some marine animals,
might break down some chain in the balanced biological system. For
example, the death of corals in South China Sea should receive high
concern from relevant departments. As for fishery, the catch will
be reduced.
Measures to Be Taken
How to deal with the environment problems resulting from rising
temperatures? Professor Ding advocates accelerating research in
related fields and trying to lower damage to the minimum. He said
work must be done in the following four aspects.
First, to improve the weather forecasting ability in China,
especially the accuracy in regard to both time and place. The focus
should be on the next 100 years. Now it has been available in the
world to predict the weather in a place in a certain month of a
certain year. China must improve the capability of computers while
taking as many factors as possible into consideration, and set up
an advanced weather forecasting model. It is reported that the
Ministry of Science and Technology has invested 15 million yuan
(US$1.8 million) in the research project in relevant fields.
Second, to set up an independent basic-level evaluation system
suitable to Chinese conditions on the basis of forecasting. Using
this system, China will be able to discern fragile zones in climate
exchange, give quantitative estimation of data related to fragile
zones in the next 50-100 years and connect it with risk disasters.
For example, with estimated data, scientists can decide when a
disaster will occur, how intense it will be and how much loss it
will inflict.
Third, to do a good job in "adaptation" and "reduction." Adaptation
means we must take measures to adapt ourselves to natural changes.
For instance, to cope with the problem of a rising sea level, we
must build dams to prevent this problem and plant trees to absorb
more carbon dioxide. Under this premise, we can reduce influences
of disaster through an alarm system and try to avoid destruction
brought on by human activity. Also to cope with the rising sea
level, we should reduce underground water pumping, thereby slowing
down the subsiding of land. Ding emphasized that the state needs to
draw out an overall strategy of adaptation and reduction.
Fourth, to keep up with international pace in the study of
"dangerous level." Now a hot issue in the world is: What level of
carbon dioxide density will bring irreversible influence to
climate? Britain believes the maximum carbon dioxide density should
be 750ppm, while China thinks it be 368ppm. If the 750ppm accepted
as an international carbon dioxide emission standard, Chinese
economic development will be obstructed. However, we cannot set an
emission standard suitable for Chinese conditions at present.
What's more, the insufficiency of the study will also lead to some
construction risks. The US-based Nature magazine
recently published an article predicting the flood rate at 29
large-scale reservoirs of the world and areas around them
(including Three Gorges of China). It proposed that as the carbon
dioxide density increases, the flood rate rises. If the emission is
four times of the present level, half of the 29 reservoirs will see
flood risks eight times more than at present. If we can estimate
the "dangerous level" in advance, we will avoid hidden troubles as
most as we can in designing reservoirs.
Professor Ding Yihui will report the influences of rising
temperature on Chinese environment soon. The state will take
measures accordingly to overcome unfavorable effects.
(科學時報 [Science Times] by
Yao Weijie, translated by Li Jinhui for China.org.cn, May 30,
2002)