[转帖] China gives history lesson on warming

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China gives history lesson on warming

While world weighs how to fight climate change, Chinese recall past glories wh
en mercury rose
Stephen Chen Dec 08, 2009

If 3,600 years of history is anything to go by, Chinese civilisation has flour
ished when temperatures have been at their warmest and declined when the clima
te cooled.It is a relationship that could hold lessons for today, says Profess
or Xie Zhenghui, deputy director of the Chinese Academy of Sciences' Internati
onal Centre for Climate and Environmental Sciences."

Ask the scientists and some will warn the growing season for farmers will beco
me shorter, the weather more extreme and sea levels higher. Moreover, they say
China, as the biggest emitter of the greenhouse gases that cause warming, ris
ks being blamed by other countries for disasters around the world. Others see
potential benefits. More carbon dioxide in the atmosphere would accelerate the
growth of crops, higher temperatures would open up for cultivation land in no
rthern areas such as Inner Mongolia that are too cold to grow crops today, war
mer air over the oceans would bring more rain to China's drought-plagued inter
ior and the frequency of extreme weather would eventually decrease once temper
atures stabilised, they say.

"Chinese historical records show that the temperature would stabilise after a
sharp climb. Mother Earth has a lot of mechanisms to adjust herself to a new e
quilibrium," Xie said. "In my opinion, the sooner the temperature increases th
e better. The longer it takes, the more extreme weather we will have to face.
Extreme weather is the hallmark of transitional periods. Once we enter the war
m and stable periods like those in the Han and Tang dynasties, we will be fine
."

History was a word on the lips of many in the Danish capital as the biggest an
d most important UN climate change conference yet opened, with organisers warn
ing diplomats from 192 nations that this could be the last, best chance for a
deal to protect the world from calamitous global warming.The conference, the c
limax of two years of contentious negotiations, convened in upbeat mode, but m
ajor issues holding up a binding agreement have still to be resolved.

Conference president Connie Hedegaard, a former climate minister of host Denma
rk, said: "This is our chance. If we miss it, it could take years before we go
t a new and better one - if we ever do."

As the division of opinion among Chinese experts suggests, predicting the futu
re may be beyond contemporary climate science. But the past may indeed hold le
ssons. For thousands of years, Chinese scholars have kept meticulous meteorolo
gical records; such information was crucial for the government to plan and gui
de agricultural production. Everything was archived, from the date each year t
hat ice began forming at the mouth of the Yellow River to the flowering and se
eding patterns of certain plants. The data allows scientists today to chart a
reliable pattern of climate change in China over three and a half millennia.

From the prosperity of the Shang dynasty 3,600 years ago to the ruin of the Br
onze Age, the cultural peak of the Tang dynasty in the seventh to 10th centuri
es and the subsequent ravages wrought by horsemen from the north, Chinese civi
lisation has reached its highest points when temperatures have been warmest an
d its lowest points when they have cooled.

Wang Zijin, an environmental historian at Beijing Normal University, said the
relationship between temperature and success was no coincidence. When the weat
her cooled, agricultural output fell, wealth contracted, discontent rose and C
hina became more vulnerable to invasion from the north."In the long term, warm
ing may not be a curse but a blessing [to China]," he said. "If the temperatur
e continues to rise, we may not see the return of elephants but it will be ver
y possible that rice and bamboo can again grow along the Yellow River. Xinjian
g, Gansu and Inner Mongolia will become much more habitable than today."

This relationship between temperature and dynastic potency was first drawn by
meteorologist Zhu Kezhen in a 1972 paper. Zhu plotted on a graph temperatures
in the Yellow River region from 1500BC to 1950. Based on archaeological artefa
cts and historical documents, the graph charted the rises and falls in average
temperature.It showed that there were three extended periods of warm temperat
ures.

The first coincided with the Shang dynasty (1600BC-1046BC), when the annual av
erage temperature reached as high as 11.3 degrees Celsius. This period saw the
emergence of the first comprehensive set of Chinese characters, massive const
ruction of palaces and cities, large-scale farming and the production of syste
matic astronomical records and sophisticated bronze wares.

The second extended period of warm temperatures lasted more than 700 years, fr
om the Eastern Zhou dynasty (770BC-256BC) to the Western Han dynasty (206BC-9A
D), when average temperatures peaked at 10.7 degrees Celsius. In the Eastern Z
hou, China's territory expanded from the Yellow River to Guangdong, Yunnan and
Sichuan. There was an enormous bamboo forest along the Yellow River, while th
e Yangtze River cut through lush rainforest. At this time slavery was abandone
d, iron tools became popular in farming and Confucius and other scholars estab
lished the philosophies that still shape Chinese society. By the time temperat
ures started to dip, China had built the Great Wall and a national road networ
k and conquered Xinjiang, Vietnam, Taiwan and Korea.

A third warm period, when average temperatures peaked at 10.3 degrees, coincid
ed with the Tang dynasty, widely seen as the peak of Chinese civilisation. Som
e historians estimate China accounted for 60 per cent of global gross domestic
product during this era. From textiles, ceramics, mining and shipbuilding to
paper making, China led the world. And there were more poets in the Tang than
at any time in history. In between these great dynasties, average temperatures
plunged and chaos reigned. The Chinese empire retreated, and was even driven
into the sea by the invading Mongols who established the Yuan dynasty (1271-13
68). The longest period of relative cold lasted from the end of the Tang to th
e fall of the Qing dynasty in 1911.

Now temperatures are on the rise again, matched by scorching economic growth.
According to the Yellow River Conservancy Commission, the average annual tempe
rature was 10.3 Celsius from 2001 to 2007 - the same as in the Tang dynasty.Zh
u's research was based on records which make for interesting comparisons with
the present day. Rice could be harvested twice a year to the north of the Yell
ow River in the Eastern Zhou dynasty, whereas the region is generally dry now.
Plum trees were common along the Yellow River in the Tang dynasty, but since
then have only grown further south. Xu Ming, chief author of a study by global
environmental group WWF on the impact of climate change in the Yangtze River
region, said China should focus less on prevention and more on mitigation - wa
ter redistribution facilities, tree planting and developing new crops. "China
should do something within its limited capacity to reduce greenhouse gas emiss
ions, but no matter what we do, global warming is inevitable," said Xu, a prof
essor at the Institute of Geographic Sciences and Natural Resources Research u
nder the Chinese Academy of Sciences. A rise in sea levels would pose a threat
to coastal cities, which could end up below sea level and needing protection
by dykes, he said. "Adaptation requires a tremendous amount of money, resource
s and advanced technology. China is far from ready."