Drought in northern tropics not caused by global warming: Taiwan study

Research team at National Taiwan University reconstructs history of rainfall in Southeast Asia

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(Pixabay photo)

(Pixabay photo)

TAIPEI (Taiwan News) – A research team at National Taiwan University (NTU) has reconstructed 2,700 years of rainfall in Southeast Asia by analyzing stalagmites from caves in southern Thailand, UDN reports.

The research was published in the scientific journal Proceedings of the National Academy of Sciences of the United States of America (PNAS). It suggests that the drought occurring in the lower latitudes of the northern hemisphere in recent years could be a natural phenomenon rather than a result of global warming.

According to professor Shen Chuan-chou (沈川洲), who led the research, the Intertropical Convergence Zone (ITCZ), which accounts for more than 30 percent of the world's rainfall, is moving southward on a millennial scale. As 40 percent of the global population lives within the zone, the trend could bring disastrous effects to both ecosystems and human civilization.

Shen explained that rainfall in southern tropical regions, such as Northern Australia, will increase, while the northern tropical region, such as equatorial Africa, will face more frequent drought, leading to an unbalanced distribution of water resources in the long term.

The recent drought in the northern tropics could be caused by the natural hydrological cycle on a centennial scale, instead of global warming, said Shen. He argued that the modern drought trend is very similar to the drought cycle of the 15th and 16th centuries, while the wet cycle of the 14th and 15th centuries could have led to frequent flooding that destroyed the Khmer civilization of Southeast Asia.

Shen led his team to southern Thailand to collect three stalagmite samples from caves in 2010, spending the next 10 years analyzing the mineral deposits inside the stalagmites. The team managed to reconstruct the history of the past 2,700 years of rainfall to within five months of accuracy.