The sea surface temperatures in the eastern Pacific has been warmer than normal, indicating the onset of an El Niño condition. (European Space Agency)

Explainer: El Niño and Southeast Asia

Weather happens because nature seeks stability. Excess heat, moisture or pressure in one place will move to fill gaps elsewhere. Imagine pouring water into a pool: the water level will rise instantly at one end before it flows to the lower ends of the pool.

What holds true for a pool also holds true for the oceans. At the Pacific Ocean, heat, winds and moisture interact in a major climate phenomenon called the El Niño Southern Oscillation (ENSO). ENSO alternates among three phases, of which El Niño is the warm phase. 

(Image: This year, sea surface temperature in the eastern Pacific Ocean has been warming up more than average. | Image by European Space Agency)

Normally, strong easterly winds blow across the Pacific, like a fan blowing across a pail of water. The winds raise the western Pacific waters slightly above the eastern Pacific. However, every 2–7 years for reasons yet unknown, these easterly winds weaken. Then, the waters reverse and head back east. This switch carries the warmer sea waters and clouds from the western Pacific to the central and eastern Pacific. That’s the El Niño phenomenon.

Sea surface temperatures were much warmer in the eastern Pacific Ocean in 2015, a year of strong El Niño event. (NASA Earth Observatory)
Sea surface temperatures were much warmer in the eastern Pacific Ocean in 2015, a year of strong El Niño event. (NASA Earth Observatory)

As a result, countries in Southeast Asia, including Malaysia, experience prolonged clear skies, which could lead to heatwaves and droughts. 

On the opposite side of the Pacific, heavy rains and floods hammer the Americas.

Asian societies have long endured the wrath of El Niño. Historical and botanical studies found that El Niño was linked to nearly all major droughts of the 17th century in Southeast Asia. Famines and plagues ensued; some killed as much as two-thirds of the local populations in the ancient kingdoms of Kedah, Java, and Siam. 

More recently, the strong El Niño episodes of 1997/1998 and 2015/2016 provided fuel for fires that burned millions of hectares of forests across Indonesia. Millions of people in Malaysia, Indonesia, and Singapore breathed in smoke for months.

Scientists monitor the central and eastern Pacific for signs of El Niño. When the 3-month average sea surface temperature there rises 0.5 Celsius above normal (based on a 30-year historical record), El Niño has begun. Signs tend to emerge in May–July, and the impact builds up to peak in December and early the next year.

Normally, Malaysia receives the most rain in October to December. “You would be expecting rain, but when El Niño happens, the rain does not come,” says climatologist Liew Ju Neng of Universiti Kebangsaan Malaysia. “So that’s when people feel the largest impact.”

[Editor: SL Wong]

  1. NASA Earth Observatory. "El Niño."
  2. Met Office, UK Weather. "El Niño: What is it?" 

Also read: What’s in store, El Niño? to explore how historical data informs what future climate Malaysia can expect.

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