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Zhang De'er, chief climatologist at the National Climate Center in China, explains the formation of sand storms to reporters in her office. |
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She turned to her husband, himself a climatologist, for advice.
"At that moment, both of us thought that if no Chinese climate expert dared to stand up and point out the mistake, it would mean China’s paleoclimatic research would come to an end," said her husband, Professor Lu Longhua, himself a well-known Chinese polar climatologist.
So Zhang decided. She and Lu would write to Nature and to the German team, to get a complete set of their observation data and a complete explanation of their argument.
Ten months later, after exchanging ideas with the German team, Zhang and Lu published their own counter-article in Nature.
"I felt content to have used our achievements in paleoclimatology for this discussion," Zhang recalled.
While Zhang agreed with the German team’s conclusion that China during the Tang dynasty (618 – 907) experienced colder winters, she disputed their claim that the climate of the late Tang was drier, and that drought may have contributed to the collapse of the dynasty.
The German team, led by researcher Gerald Haug, said that by analyzing magnetic properties of the sediments and deposits of titanium minerals in a lake in southern China, they inferred that Asian summer monsoon rains were weaker when winter monsoons were stronger.
However, their conclusion does not tally with Zhang’s research of historical climate records.
"(A) wetness index for the past 2,000 (years) based on 36,750 historical climate records shows that China experienced two wet climate phases that bracketed a dry spell during A.D. 700 - 900," Zhang wrote in her counter-argument. "The last 30 years of the Tang Dynasty were relatively wet, not dry."
Though few international media reported on it, the article quickly attracted attention in scientific circles. It made an even bigger impact on China’s academic world. In the past, few Chinese scientists would stand up to question studies completed by their peers in other countries.
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Zhang De'er and Professor Masatoshi Yoshino from Japan's University of Tsukuba, engaged in an academic discussion. |
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"Her strictness in pursuit of scientific truth has been famous in our circle, in addition to her courage to point out the mistake of another scientist," said Dong Wenjie, director of China’s National Climate Center, where Zhang now works.
Zhang’s office is littered with piles of cards containing climate information she has trolled from ancient books and records. But more current books line her shelves, including her own "Collection of China’s 3,000-year Climate Records," which took her ten years to complete, and which is considered a "Bible reference" on China’s history of natural disasters.
Zhang, part of the first group of Chinese scientists engaged in paleoclimatic research in the late 1970s, has spent more than 20 years researching China’s climate records. But her research has often taken her outside the boundaries of her own country.
In 2004, she was chosen for the first working group of the Nobel-winning Intergovernmental Panel on Climate Change, where she co-authored the panel’s fourth assessment report addressing the paleoclimate.
And in 1998, she worked as a visiting scholar at the Belgian Royal Academy of Sciences. While there, she scoured Europe for climate records collected by foreign preachers living in China in the 18th century.
"Foreign preachers were the first people who brought observatory facilities to China, so they should have had many precious early scientific records about China’s historic climate," Zhang said.
With the help of local scientists, she found weather observations dating back 300 years, all made by preachers working in Beijing. In China, Zhang had never come across similar records.
Dong said such efforts further highlight Zhang’s devotion to a science that, for ordinary people, can be "a really tedious job."
In the case of the German paper, Zhang’s attention to detail revealed a historical error: that of a border war in 751, which the team cited as instrumental in the downfall of the Tang dynasty.
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Camel and Riders - late 7th century earthenware sculpture, Tang dynasty (618-907), Metropolitan Museum of Art, New York. |
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"The border war it indicated as the trigger of Tang’s deterioration was actually a very small war, which I could not find in any ancient books but one— and there was only one sentence about it," she said.
The scientist added: "This incident has strengthened my opinion that scientists must be very careful when using substitute materials to explain historic climates. A comparison with historic records is always necessary before we draw conclusions."
This is again the guideline to her current research work: combining historic records and substitute environmental indexes, such as the growth rings of trees, to analyze the rainfall pattern in the past 500 years in China.
"I have made some computer analysis about the floods, droughts, temperature and dust fall, and compared the results with the records preserved in the Forbidden City," she said. "And I have completed another analysis for a time scale of more than 1,000 years."
Though she declined to reveal more about the research result before she submits the paper, Zhang said that her study has shown that global warming will not bring about more sand storms.
Zhang is also going to publish a book about China’s historic locust disasters, with which she is again challenging another study, this time one by leading Chinese zoologist Zhang Zhibin.
But it was her challenge to the German team that clarified her role as a scientist.
"I fully respect Professor G. H. Huag and his great achievement in paleoclimate research. However, I could not agree on the conclusion his team had drawn for Tang Dynasty. I think this academic discussion is necessary," Zhang said.
"At first I only expressed my disagreements in some interviews," Zhang said. "But as more and more domestic media came to ask about my opinions, I felt stronger the responsibility of a scientist to defend the truth."
Wu Chong is a freelance journalist who has written for China Daily and SciDev.net. She is also an editor for Global Environmental Review, a Chinese electronic magazine about environmental news.
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English (英文)
Chinese (中文)