Commentary: Climate change in Singapore and what the future brings

WHEN CLIMATE CHANGE WAS KNOWN AS GLOBAL WARMING

Do you recall when climate change was known mainly as global warming? That was because rising temperatures were the earliest signal to be detected.

The world’s average surface temperature has been rising since the first Industrial Revolution, with a rate of increase of 0.1 degree Celsius per decade from 1950 onwards.

For Singapore, the warming was twice as fast because land heats up more easily than the sea and urbanisation replaced self-cooling vegetation with heat-retaining concrete buildings and bitumen roads.

The top 10 hottest years in Singapore since 1950 all occurred within the last 22 years. The elevated temperature baseline brought on by the combined effects of excessive greenhouse gases and urbanisation led to the observed clustering of the hottest years.

READ: Commentary: Rising temperatures will make Southeast Asian economies sweat

This means that Singaporeans are more at risk than ever from heat illnesses, like heat exhaustion.

STRESS ON WATER SUPPLIES IN 2015

Two of the hottest years, 1997 and 2015, are also respectively the driest and second driest years in Singapore on record, from data that dates back to 1869.

These years witnessed strong El Nino events whereby the central equatorial Pacific Ocean is unusually warm and attract convective clouds and rain away from Southeast Asia, leading to intensified solar heating and drought in this region.

Global warming added to the strength of the naturally occurring El Nino, with significant impact on our region.

Three districts in neighbouring Johor underwent water-rationing in August to September 2015, affecting more than 640,000 industrial and household consumers for a month.

In Singapore, the desalination and NEWater plants under Public Utilities Board increased freshwater production to tide us over, so few people noticed the water shortage.

READ: Commentary: Beyond scarcity and security, does Singapore need a new water narrative?

EXPOSURE TO HAZE

But water supply was not the only challenge we faced that year. We were sitting ducks for the transboundary haze that hit us repeatedly from late August to end October.

The 24-hour Pollutant Standards Index (PSI) broke 300 and stayed in the Hazardous range for several hours on Sep 25, 2015. Schools were closed that day to minimise our children’s exposure to the unhealthy air.

The haze was produced by man-made forest fires in Sumatra made worse by the hot, dry weather. Many Singaporeans would recall a severe haze episode similarly aggravated by El Nino back in Oct 1997.

The sombre realisation is that hot, dry years are becoming more often because of climate change.

RISING SEA LEVELS

The past is a guide but let’s look at the future and what could impact us most. The science underlying climate change is easy to grasp.

We learnt as a kid that things expand when heated. The ocean is no exception: Global warming has caused the upper ocean to increase its volume, raising the mean sea level.

This rise is exacerbated by melting ice caps in Greenland and Antarctica as well as glaciers around the world. Tidal gauges in Singapore Strait and Johor Strait show our local sea level has risen at a rate of 2 to 4 cm per decade in the last 25 years.

READ: Commentary: A new hot world and the death of Iceland's 700-year-old glacier

The rate of increase will accelerate as the world burns more fossil fuels to provide energy. The carbon dioxide gas emitted enhances downward infrared radiation at the surface, akin to using infrared lamps to keep food warm, except that we overdo the warming by our incessant consumption of the non-renewable energy.

By 2100, Singapore may experience between half to 1m of mean sea level rise, according to the Second National Climate Change Study published by Meteorological Services Singapore. It’s no wonder the threat of coastal inundation posed by rising sea levels was a key issue PM Lee raised last week.

READ: Commentary: How effectively can Singapore adapt to sea level rise?

UNANSWERED QUESTIONS WHEN CLIMATE CHANGES

Still, there are open questions about climate change that science has not answered or cannot answer. 

Here are two examples that impact Singapore: How the frequency, intensity and duration of tropical storms like Sumatra squalls would change is still unknown. How Aedes mosquitoes which transmit dengue would breed in a changing climate is a matter of research.

The “tipping point” beyond which the world’s climate is irreversibly altered is hard to quantify as a threshold on a measureable index. Future warming also depends on the global collective decision on energy production and consumption, the latter contributed much by urban centres like Singapore. This is an indeterministic problem at the core.

So climate scientists cannot foretell which climate-change scenario the Earth will follow or map out all the details. But should these uncertainties hold us back from action?

The rational response to meet grave risks arising from uncertainty is to “purchase insurance”, like the way we protect our loved ones in buying life policies. For a nation, “insurance” means coordinated mitigation and adaptation policies.

For example, the Ministry of Finance introduced this year the carbon tax to dis-incentivise greenhouse gas emissions. The Ministry of Environment and Water Resources has planned for a second pump house at the Marina Barrage to reduce flash-flood risk during a thunderstorm for low-lying areas of central Singapore.

LISTEN: The Pulse: Climate change and Singapore’s new vulnerabilities

The fact is ironically in 2015, the second driest year on record, on Dec 10 and 11, heavy downpours brought flash floods to Kallang and Boon Lay areas.

This is the kind of unpredictable risks that we seek to defend ourselves against when we face a changing climate in Singapore. There is still time but the stakes are high. We have to act now.

Associate Professor Koh Tieh Yong is a climate scientist at the Singapore University of Social Sciences.