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The Geologic Research of National Taiwan University Has been Published on Nature Climate Change: Unveiling the Myth of the Summer Rain in Taiwan, the Record of the Sea Surface Temperature in the South Pacific Ocean

he geologic research teams from National Taiwan University and Louisiana State University, led by Professor Chuan-Chou Shen of the NTU Department of Geosciences and Professor Kristine DeLong, have been doing their teamwork for seven years. With their exclusive dating technique and using the odds of coral calcium, they have successfully reconstructed the record of the sea surface temperature in the South Pacific Ocean and the variability patterns of the climate change. Their research has shown the precise results for the very first time in the human history over the past 350 years. Moreover, they proved it true that the summer rain in Taiwan is related to the high sea surface temperature of the South Pacific Ocean. This top research has just been published in the international scientific journal, Nature Climate Change, with the attention around the world. To present this great achievement, National Taiwan University thus held the press conference with the presentation, hosted by NTU President Si-Chen Lee, in the first administration building at the main NTU campus on June 26th. This was reported by the mass media with the comprehensive cover story and the attention from the public.

By giving the speech for the press conference, NTU President Si-Chen Lee stated that, according to their assumption from this discovery in the research, it will be a period of high temperature for the next ten years in the South Pacific Ocean if the climate patterns remain the same. With the severe effects of the global warming, the summer rain in Taiwan will probably be increasing gradually and getting worse by year. Hence, the Taiwan government should have the emergency strategy and the proper precaution to prevent from any possible severe situation.

According to Professor Shen’s presentation, he pointed put the fact that the South Pacific Ocean plays a very crucial role in affecting the global climate change, since it is the biggest ocean in its width in the world.

Last year in 2011, Professor Huang-Hsung Hsu of the Academia Sinica and NTU Department of Atmospheric Sciences worked on a project with, Yun-Lan Chen, the researcher of the Central Weather Bureau. By using the temperature records over the past hundreds of years, eventually they found the pattern that the summer rain in the Northeast Asia, Taiwan included, is closely related to the variability of the sea surface temperature in the South Pacific Ocean. It appears that there is the pattern of synchronous change according to their research. This discovery has already been published in Geophysical Research Letters.

In addition to that, the 2011 Scientific Report on Taiwan’s Climate Change, published by the National Science Council, also pointed it out that the long-term record of the weather condition in Taiwan shows that the patterns of the rain season changes a lot over the fifty years in Taiwan. It has been obvious that the period of rain season has been shortened; however, there have been more and more heavy rain. Such a extreme weather condition in Taiwan prompted the scientists and researchers to think about whether it is only part of the natural cycle or it is the consequences under the influence of the global warming. Moreover, will the frequency of the heavy rain be lowered any more? Or will it be going on with more rain and making the weather condition even worse? We are facing the issue that we have to do something and develop an emergent strategy about this climate change in Taiwan.

In order to figure out the changing climate patterns, Professor Shen’s research team collected five trace elements in coral skeletons from Amédée Island in the South Pacific Ocean, and they have been analyzing the odds of the coral calcium in order to reconstruct the sea surface temperature there by using the trace elements in coral skeletons for seven years. The odds of coral calcium can be viewed as the thermometer to measure the sea temperature. To be specific, each rising sea temperature can cause the decreasing odds of coral calcium in the coral skeleton to 0.8%. That is to say, the odds of coral calcium are crucial for the observation of the sea temperature since they measure the changes themselves. By using their exclusive and precise U-Th dating technique, Professor Shen’s research team has successfully reconstructed sea surface temperature in the South Pacific Ocean during the years between 1649 to 1999. With the application of their world-top technique, the detailed records of the past 350 years proved the fact that there is the related connection between the summer rain in Taiwan and the sea surface temperature in the South Pacific Ocean.

Moreover, the NTU research team has already found that the sea temperature in the South Pacific Ocean has been rising ever since the late 1890s. The average of the sea temperature has increased 1 Celsius degree over the past one hundred years. The reason why the rising sea temperature in the South Pacific Ocean can affect the summer rain in Taiwan a lot lies in the Hadley circulation in the West Pacific Ocean, which transports the natural force from the low-latitude areas to the high-latitude. Hadley circulation goes up in the tropical Northwest Pacific Ocean and drops down in the Southwest Pacific. However, the rising sea surface temperature in the Southwest Pacific Ocean hinders the dropdown of the cold air there, and therefore, it diminished the Hadley circulation in the south and made it unable to deliver water and force to the north. As a result, this phenomenon led to the severe summer rain in these Asian countries: Japan, Korea, Taiwan, and the Philippines.

The concern is that it will be the cycle period of the rising sea temperature in South Pacific Ocean for the next ten years, and this is going to make the summer rain worse and much heavier in Taiwan. Thus, Professor Shen suggested that the sea temperature in South Pacific Ocean will definitely be rising in the next ten years according to their records by using the trace elements in coral skeletons. If the climate patterns stay the same, according to the research team’s discovery, the frequency of the heavy summer rain in Taiwan will probably be worse and more often.

In spite of the climate pattern in South Pacific Ocean, there has been the exception with the eruption of volcano before. For examples, Tambora volcano in 1815 and Krakatoa volcano in 1883 both made the sea temperature drop down with the ashes in the atmosphere. Also, the records show that the sea surface temperature has not been affected by the sunspots activities.

This research project was sponsored by the financial aid from the National Science Council and National Taiwan University. For detailed research results, please read the online publication of Nature Climate Change for the full text, Sea surface temperature variability in the southwest tropical Pacific since AD 1649”, 2012, Vol. 2, doi: 10.1038/nclimate1583 on June 24th, 2012: http://www.nature.com/nclimate/index.html

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