A Chinese meteorologist has taken issue with a study led by German scientists and published in British science journal Nature, which argues that long droughts were an essential factor in the fall of the Tang dynasty.

The Tang dynasty, which spanned nearly three centuries from AD 618 to 907, is considered the most prosperous and open epoch in China's history, synonymous with a flowering of art and literature and thriving trade with the outside world.

The newly published Nature report, based on research led by German scientist Gerald Haug, claims that there have been three periods of strong winter monsoons in the past 15,000 years.

The most recent of these three periods coincides with the Tang dynasty. It was a time of unusually cold weather, prolonged drought and poor summer rains, the scientists wrote. The droughts led to crop failures that sparked peasant uprisings which eventually led to the collapse of the dynasty.

Zhang De'er, a researcher with the China Meteorological Administration, said that the researchers' claim of strong winter monsoons in the period around 700 to 900 tallied with what Chinese scholars had deduced from the study of historical documents.

"The climate did turn cold in the later period of the dynasty. Chinese scientists have been aware of that for a long time," Zhang said.

"The Haug team has done a first-class job in studying sedimentary cores taken from a lake in south China's Guangdong Province, and it's good to see that their research confirms Chinese scholars' theories," Zhang said.

"But cold weather is not necessarily linked to dry summers. Our climate analyses over nearly 500 years from 1470 to 1979 found that chilly winters are often accompanied by rainy summers," Zhang said.

"The Haug team says the summer monsoons during the Tang dynasty were weak but the evidence for it is debatable," he said.

"Historical records suggest that - despite the freezing frosts, snow and ice in winter because of the strong monsoons - there was abundant summer rainfall in the later Tang period," he said.

According to Zhang, the Tang dynasty went through two periods of relatively rich rainfall, one from 711 to 771 and the other from 810 till the end of the dynasty.

He said there was not enough evidence to support the German scientists' hypothesis of a long-term drought.

"The decline of a dynasty is a very complicated matter. Politics, the economy and ethnic conflicts are all factors, not just the climate and the environment," he said.

An insurgency called the Anshi Rebellion lasting from 756 to 763 is commonly regarded as the turning point in the Tang Dynasty's fortunes.

The wars stripped the court of troops, wealth and its credit among the people and - even if the dynasty held on for another 144 years - it never recovered its previous glory, according to Chinese historians.

Editor: Wing