The bushfires that swept through Australia last year were connected to a phenomenon known as the Indian Ocean dipole (IOD), which is expected to become more frequent due to climate change, a geologist studying coral fossils said yesterday.
National Taiwan University Department of Geosciences professor Shen Chuan-chou (沈川洲) since 2001 has been working with Australian and US researchers to study climate systems in the Indian Ocean.
Led by Australian National University Research School of Earth Sciences professor Nerilie Abram, the team published a paper on IOD in the journal Nature on March 9.
Photo courtesy of Nerilie Abram via CNA
The bushfires resulted from a positive IOD event, when the region east of the Indian Ocean becomes drier and there is a reduced chance of rainfall in Australia, Shen told an online news conference held at the Ministry of Science and Technology in Taipei.
To understand the change in climate over the past centuries, the team drilled the cores of live and fossil coral off Sumatra, Indonesia, as coral can be viewed as a thermometer of ocean temperature, Shen said.
Shen’s laboratory used radiometric uranium-thorium dating techniques to identify the ages of the coral samples.
The most important finding was that the climate systems in the Indian and Pacific oceans are “interconnected,” which previously had been a disputed hypothesis, he said.
While similar dating techniques used by other laboratories might have a margin of error of one to two years, Shen said that his laboratory had reduced the margin of error to as little as three months.
The team found that positive IOD events often occur in conjunction with El Nino in the central Pacific Ocean, he said.
Models show that strong IOD events have been increasing and they might become more extreme due to global warming, he added.
Nonetheless, an IOD event in 1675 was estimated to be 42 percent stronger than one documented in 1997, showing that such events are also possible without human-caused global warming, Shen said.
Referring to previous studies of El Nino, Shen said that climate oscillations in the Indian Ocean also affect the climate of Taiwan.
If the temperature in the central Pacific is rising, more typhoons form in the summer and more strike Taiwan in the fall, while rainfall in spring decreases, causing droughts in southern Taiwan, he said.
The government should formulate more policies to mitigate the effects of climate change, Shen said.
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