As monsoon showers bathe India and China this season, Inchin Closer takes a scientific look at how interlinked our critical rains are to our agrarian economies, leading to food cultivation and political stability. Studies conducted across China, India and the US over decades show that rainfall in India and Southern China have an inverse relationship, during any given year. A weak monsoon phase in India causes heavier rainfall in some parts of China, particularly the Yangtze River. At the same time, northern China gets less rainfall.
According to Asia Times Online, researchers in the United States and China analyzing the Indian and Chinese summer monsoon found shared climatic equations that influence rainfall strength.
“The joint rainfall pattern [under certain climatic conditions, such as tropical temperatures and wind speed over the Indian Ocean] is roughly uniform over India,” says the study by a research team from the Columbia University in New York and the Tsinghua University in Beijing, China. “Over China, on the other hand, the rainfall pattern [under the same climatic conditions] is uniform along east-west direction but varies from the North to the South of China,” it continues.
India and China share an ancient, interlinked monsoon dependency. The Science Journal issue of July 1, 2011 reported stalagmites from caves in China containing an incredible record of changes in rainfall across thousands of years. For instance, any cooling in the northern hemispheric strengthens the Chinese monsoon and weakens the Indian monsoon.
Also drier days in Shanghai could mean wetter days in Mumbai. Joining Chinese and American research, the Indian Institute of Tropical Meteorology in the western Indian city of Pune examined relationship between the break and active phases of the Indian and Chinese monsoon. They found opposite patterns. The active phase of the Indian monsoon corresponded with a break in the Chinese monsoon, and vice versa.
“This study clearly shows that there exists a definite link between break/active phases of the Indian summer monsoon and rainfall over China,” say N V Panchawagh and S S Vaidya, the research duo.
Scientists have also found a co-relation between weak monsoons and the fall of a dynasty in China, whereas in India a weak monsoon demonstrated the need for kings and rulers to hand out more in charity.
In 2008, a Chinese and American team of researchers from the University of Minnesota and Lanzhou University in China analyzed a 4.65 inch (11.8 centimeter) chunk of a stalagmite found in the Wangxiang Cave, near the Qinghai-Tibetan Plateau in Gansu province. The stalagmite was 1,810 years old. The varying chemical composition of oxygen isotopes in its layers revealed the relative strength of monsoon rains for over 1,000 years.
The researchers were stunned to find that a very weak monsoon coincided with the downfall of the dynasties of Tang (618-907), Yuan (1271-1368), and Ming (1368 to 1644).
The study found that China suffered three acute failures of the monsoon, sometime between 860 to 930, 1340 to 1380, and 1580 to 1640. The rainfall shortages caused severe crop shortages and famine. A desperate people revolted as peasant armies that stormed the capital.