SINGAPORE: The recent spells of hot weather that Singaporeans have been experiencing may not be just temporary heatwaves.

The island is heating up twice as fast as the rest of the world – at 0.25 degrees Celsius per decade – according to the Meteorological Service Singapore (MSS). It is almost 1 deg C hotter today than in the 1950s.

What is even grimmer news – Singapore’s maximum daily temperatures could reach 35 to 37 deg C by year 2100, if carbon emissions continue to rise at the same rate, warned Dr Muhammad Eeqmal Hassim, senior research scientist with the MSS Centre for Climate Research Singapore.

Other countries already experience hotter temperatures than this – but the reason this spells trouble for Singapore, is that humidity is high here all year round,

This could lead to potentially deadly situations, as the programme Why It Matters found out. (Watch the episode here)

“When temperature and humidity get high enough, our bodies struggle to cope,” he explained. “We get higher heat stress levels. It can actually be quite lethal for us.”

WIM killer heat humidity effect

Higher temperatures cause more water to evaporate, exacerbating humidity levels.


Professor Matthias Roth of the department of geography at the National University of Singapore (NUS) attributed the rising temperatures to global warming and the Urban Heat Island (UHI) effect – caused by the heat generated from human activities and trapped by urban surfaces such as buildings and roads.

For example, Dr Roth and programme host Mr Joshua Lim measured the temperature in rural Lim Chu Kang, an area of farms and forests, at a balmy 24.8 deg C one night.

The temperature in built-up Orchard Road that same night was measured at 29.1 deg C – four degrees warmer.

WIM killer heat temperature sensor

Dr Roth adjusting the temperature sensor.

One giant contributor to the UHI effect: The reliance on air-conditioners. Housing blocks and office buildings effectively end up ejecting hot plumes that heat up the surroundings.

Describing the effect of a stack of air-conditioner units, Professor Gerhard Schmitt – head of a research team called “Cooling Singapore” at the Singapore-ETH Centre – said: “The bottom one is ejecting heat to the outside, but this heat is then sucked in by the next one, and the next one and the next. The higher you go, the higher the temperature that comes out.”

That means the household on top could end up paying higher electricity bills for running the air-con, he noted.

WIM killer heat air con


What are the risks if Singapore keeps getting hotter?

The problem is the high humidity, which means perspiration doesn’t evaporate as quickly. The body has to work harder to stay cool, which can lead to heat exhaustion and heat stroke.

As a gauge, the current relative humidity in Singapore varies from more than 90 per cent in the morning to around 60 per cent in the mid-afternoon when there is no rain, according to the MSS website. Relative humidity frequently reaches 100 per cent during prolonged periods of rain.

Heat stroke occurs when core temperature exceeds 40 deg C and the body is unable to sufficiently dissipate the heat. It could lead to organ damage and death.

WIM killer heat humid chamber

35 deg C feels different at 40 per cent and at 90 per cent humidity levels.

Marathoner Dr Derek Li, who came close to a heat stroke during a leisurely cycling trip in Desaru, described how his body started to seize up and he felt dizzy.

“I realised that I wasn’t sweating as much as usual, my mouth was dry and my eyes were dry. Those are usually the classical signs heading towards a heatstroke,” said the experienced athlete and medical doctor. “It caught me by surprise.”

He took a week to recover.

For a country as hot and humid as Singapore, the National University Hospital said it has fewer than 10 cases of heat stroke a year.

WATCH: Why these ‘cooling’ sports products don’t work in Singapore’s weather (3:18)

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