PETALING JAYA: The El Nino phenomenon is over. But the climatic event that just passed is not the same as the El Nino of old. The “Little Boy” has evolved.
The weather phenomenon taking place in the 21st century is not the same as what was studied in the last century, said a scientist.
The evolved El Nino could be one of the reasons why weather models that were used to successfully predict the event, including the strong El Nino in 1997/98, were not successful in the 21st century, said Prof Dr Jin-Yi Yu.
The scientist from the Earth System Science Department at University of California, Irvine, said El Nino used to lead to a warming of sea surface temperature off the South American shore in the Pacific Ocean.
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“I proposed that there are two types of El Nino in the Pacific: the Eastern Pacific (EP) El Nino, which appears in the tropical eastern Pacific and the Central Pacific (CP) El Nino, which appears in the tropical central Pacific. “In the 20th century, the EP type of El Nino was dominant.
“During this period, El Nino events were characterised by warming of the sea surface temperature off the South American coast in the Pacific Ocean.
“As we entered the 21st century, the CP type of El Nino became more prevalent.
“The warming of the sea surface temperature now primarily takes place in the tropical Central Pacific, closer to the International Date Line and Australia.
“This warm water often spreads all the way to the coast of North America,” he said in his keynote speech on The Changing El Nino in the 21st Century.
Asked if the two El Ninos take place at the same time, he said: “While it is common for one of these two types of El Nino to dominate, they can occur simultaneously in the same year.”
“The El Nino event that occurred in 2015-16 was an example of these two types of El Nino happening concurrently.
“The 2015-16 El Nino exhibited characteristics of both the EP and CP types.
“The 2015-16 El Nino (which started in the summer of 2015 and ended in the summer of 2016, spanning both years) is considered to be a mixture of the EP and CP types of El Nino.
“It should be noted that the 2015-16 El Nino is one of the strongest El Nino events we have observed in the past 100 years.”
The Pacific Ocean’s climate, said Prof Yu, had seen significant shifts from the 20th to the 21st century.
“Notably, El Nino’s behaviour has changed, impacting its properties, underlying dynamics and overall climate effects,” he said.
These shifts, he added, highlight the urgent need to deepen the understanding of ocean-atmosphere-land interactions in the Maritime Continent to better adapt to climate change.
The Maritime Continent is the name given by meteorologists and oceanographers to the region of South-East Asia, including Malaysia, Indonesia, the Philippines and Papua New Guinea.
Prof Yu said this during the Impact and Adaptation to Climate Change: A Malaysian Context Forum held at Universiti Malaya on Friday.
It was part of a seminar organised by the Institute of Ocean and Earth Sciences on Air-Ocean-Land Interactions In A Changing Climate.
Besides global warming, deforestation in the Maritime Continent, Prof Yu said, has been a key driver of changes in El Nino.
He said this was demonstrated by a computer model that his team ran.
“Our computer model simulated removing all trees from South-East Asia.
“This altered air circulation over the Maritime Continent, allowing the atmosphere to influence Pacific Ocean warm water movement in a way that promotes Central Pacific El Nino events in the 21st century.
“As El Nino evolves, the Maritime Continent has become more powerful in affecting the Pacific climate in the 21st century, making it a crucial hotspot for climate change adaptation and geo-engineering,” he said.
Recent advancements in artificial intelligence and machine learning, said Prof Yu, present an excellent opportunity to advance research in this area, overcoming past challenges related to the complexity and multi-scale nature of interactions among the ocean, atmosphere, land and human activities.
