It's hot in Singapore, and getting hotter

Higher urban density is partly to blame, but global warming is the big worry
Amresh Gunasingham Straits Times 14 Mar 10;

The rain returned last week, giving some temporary respite from the scorching heatwave of late.

With the temperature on most days hovering around the 35 deg C mark, and February being the driest month in history, the burning question on my lips is: Why has it been so hot and how much worse can it get?

The why can be explained by two factors - Singapore's rising urban density means the expanding concrete jungle traps more heat than before. There are also the effects of global warming to consider, and it is in this area that the signs look more ominous.

Earlier last week, the first study done by the Government forecasting the impact of climate change on Singapore over the next 100 years showed the present average daily temperature of 26.8 deg C could increase by between 2.7 deg C and 4.4 deg C.

This should not come as a surprise as the days have been getting warmer. Historical data traced back to the 1900s shows Singapore's average daily temperature has been rising, especially in the last 30 years.

Between 1987 and 2007, it rose by 0.6 deg C in total or about 0.3 deg C per decade, which is slightly higher than the global average.

The implications of this are far-reaching as studies show that increases in temperature expose the vulnerable - the sick and the old - to respiratory and cardiovascular disease due to heat stress as well as outbreaks of vector-borne diseases such as dengue. Studies have also shown that the length of time required for Aedes mosquitoes to grow from an egg into an adult insect decreases dramatically as the temperature rises.

At 15 deg C, for example, it takes more than 40 days, but at 30 deg C, it takes only a week.

Speaking in Parliament last Monday, Dr Amy Khor, Senior Parliamentary Secretary (Environment and Water Resources), pointed to the 'double-edged' challenge that soaring temperatures pose to containing dengue.

'The expected warmer ambient temperature... may increase the rate of dengue transmission as mosquitoes reproduce faster and the dengue virus replicates faster and remains infective for a longer period of time,' she said.

The climate change study also noted that sea levels could rise by up to 65cm over the same period.

This, it said, is no cause for alarm because the sea walls and embankments protecting Singapore's coast, and height on which reclaimed land is built, mean that the country can cope.

But experts, such as Associate Professor Wong Poh Poh from the department of geography at the National University of Singapore, say the extent of sea level rise for an island with areas situated as much as 1m below sea level is being underestimated.

Prof Wong was Singapore's sole participant in the Nobel Peace Prize-winning Intergovernmental Panel on Climate Change (IPCC), contributing the coastal chapter of its climate change report released in 2006.

The impact of melting ice sheets from the Arctic and Himalayan regions, for example, is not considered in the projection, because it is not fully understood within the scientific community.

'But the trend of thought points to a multi-metre rise in sea levels,' said Prof Wong.

This would mean that even building reclaimed land at least 1.25m above the highest tide level here - as is the present rule - will not prevent low-lying areas from being inundated.

The adaptation taskforce spearheaded by the Ministry of National Development to tackle global warming says more studies need to be done in time to examine this threat.

The IPCC also predicts an increase in frequency and intensity of extreme rainstorms in South-east Asia.

The last century had brought more heatwaves (warmer days and nights), more rain and more tropical cyclones to the region, causing massive flooding, landslides and droughts that had done untold damage to property, assets and human lives.

With its deep resources and access to the latest know-how, and the fact its geographical position means that it escapes the worst of the elements, Singapore has so far been spared the trail of destruction seen elsewhere.

Yet climatologists say it is difficult to tell how much more rain could come this way. They say charting a trend for rainfall is difficult because there are year-on-year fluctuations characteristic of the region's unpredictable monsoon seasons.

The concern going forward is whether the drains will be big enough or homes built high enough above the ground to prevent flooding.

Singaporeans, especially those in the Bukit Timah and Dunearn areas, got a taste of that last November, when heavy rain caused waist-deep floods that wrecked more than $1 million worth of cars and property. The PUB says it continuously reviews the island's drainage network to improve its capacity to hold stormwater.

More dry spells like the one just past also place a strain on water supply.

With more than half of Singapore's land already used as catchment areas, any significant reduction in rainfall is an immediate concern as it affects the amount of water collected and stored in reservoirs.

It was comforting to note from Minister for the Environment and Water Resources Yaacob Ibrahim in Parliament that water levels in the reservoirs did not dip significantly last month despite the dry spell, largely because the national water agency could turn to two other 'taps' - Newater and desalinated water.

The other hot issue relates to energy, which is sourced from dwindling capacities of fuel that is in ever greater demand worldwide. As it becomes hotter and drier, more energy will be consumed to keep the environment cooler.

In the United States, building contractors estimate that a 1 deg C increase in temperature could translate into between 3 per cent and 5 per cent more energy being consumed per building.

Although there are no similar estimates for Singapore, it is expected to be the same, if not more so, considering how much Singaporeans need their air-conditioning. Air-conditioning usage makes up at least half of an average building's utility bill here.

Several MPs spoke about this in Parliament, citing their experiences with commercial buildings which had 'freezing' temperatures.

The National Environment Agency has commissioned a second study, due out in 2013, that will explore in detail the potential impact of climate change in areas such as public health, energy consumption in buildings as well as biodiversity.

Indeed the science of modelling the interactions of the various components of the climate system - the atmosphere, oceans, land surface and glaciers - far into the future brings a certain level of uncertainty.

What are within human control to an extent are efforts to slow down the effects of climate change by mitigating the amount of carbon put into the atmosphere.

This will require both the developed and developing worlds to agree on a binding agreement aimed at cutting future emissions, following the failure to achieve such a deal at the Copenhagen conference last December.

The chances of achieving this do not look promising, for now at least.

In the larger scheme of things, Singapore can only prepare for the worst while hoping for the best.