SINGAPORE – The Meteorological Service Singapore (MSS) declared the onset of El Nino on Aug 11, later than when the World Meteorological Organisation announced El Nino conditions on July 4.
The difference is partly due to how El Nino affects different regions, said MSS.
Those monitoring weather in the central equatorial Pacific would have more sensitive thresholds. Those farther away tend to be affected by well-established El Nino events only where there is coupling between the tropical Pacific Ocean and atmosphere that was not clearly evident at the start of July.
As at Friday, Australia and New Zealand have yet to declare the onset of El Nino.
A climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean, El Nino is the warm phase of a larger phenomenon called the El Nino-Southern Oscillation (Enso), with La Nina at the cool end, and a neutral in-between phase.
Despite a prolonged La Nina cooling sea surface temperatures from September 2020 to March 2023, both 2021 and 2022 were warmer than any year prior to 2015.
In 2023, July was so far the hottest month the world had ever seen. And as global temperatures rise, experts fear that the warmer El Nino would bring about drier weather conditions in this region and increase extreme weather events around the world.
1. How much hotter and drier can Singapore get?
Based on past El Nino events affecting Singapore, MSS said the warmest temperatures are typically in March to April of the year after the onset of El Nino, forecasting monthly mean temperatures to be warmer than normal in the coming months.
Atmospheric scientist Erik Velasco expects El Nino to peak in mid-September, with dry conditions possibly extending to January or February 2024.
The Indian Ocean Dipole (IOD), another climatological phenomenon associated with fluctuations in sea temperatures in a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia, is another critical indicator to forecast dry conditions in addition to Enso, said Dr Dhrubajyoti Samanta, senior research fellow at Nanyang Technological University’s Earth Observatory of Singapore.
According to Dr Velasco, forecasting models suggest a positive IOD may develop in the coming months. Historically, he said, positive indices of above one for both IOD and El Nino have demonstrated a strong correlation in episodes of severe transboundary haze, as witnessed in the spikes seen in 1997, 2006 and 2015.
Rapid global warming causing warmer conditions everywhere will result in a warmer April and May 2024 locally – even without the effects of El Nino, forecasts Dr Dhrubajyoti.
2. El Nino generally brings about drier weather, but Singapore has seen rain. Why is this so?
This is due to the south-west monsoon conditions that typically occur from June to September, said Associate Professor Lim Tit Meng, chief executive of Science Centre Board.
During the season, tropical cyclones near Singapore in the western Pacific Ocean and the South China Sea can bring heavy rainfall to parts of the Asean region, and indirectly influence the weather in Singapore.
“Rain in recent weeks has kept the ground moist,” said Dr Velasco, cautioning that El Nino has just started, with a dry spell later in 2023 possibly leading to a smoke-haze episode triggered by wildfires in neighbouring islands.
3. What is the impact of climate change on El Nino in the region surrounding Singapore?
“This year’s El Nino phenomenon has behaved abnormally in the region, contrary to what is happening in the rest of the world,” said Dr Velasco, noting that El Nino usually brings hot and dry weather to the maritime South-east Asia region, which includes Brunei, Indonesia, East Malaysia, Singapore, the Philippines and Timor Leste.
Instead, the region has seen rain in recent weeks while the temperature increase has not been as high as in other parts of the world.
Globally, the effects from climate change have been much more severe than expected, Dr Velasco observed.
Climate change bears a huge responsibility for what is happening around the world in terms of heatwaves, droughts, hurricanes and floods, but “we cannot totally blame climate change for not seeing typical weather under El Nino conditions yet”, he said.
There are still many knowledge gaps on the local impacts of climate change, he added.
“Climate change is still a very new science, and meteorological models have not been fully capable of capturing all the phenomena triggered by it. Thus, we cannot accurately predict its impacts at regional and local scale.”
Although July was declared the hottest month ever across the planet, Dr Velasco said that “luckily, South-east Asia experienced a much lower temperature increase compared with other parts of the world”.
“But conditions could change in a few weeks,” he cautioned.
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