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More intense and frequent rainfall expected

SINGAPORE - Singapore and South-east Asia can expect more intense and frequent rainfall events in future, and extreme temperatures that the Republic currently experiences occasionally could become the norm.

More intense and frequent rainfall expected

Pedestrians seeking shelter from the morning rain..Photo: Ernest Chua. 26 June 2013.

SINGAPORE - Singapore and South-east Asia can expect more intense and frequent rainfall events in future, and extreme temperatures that the Republic currently experiences occasionally could become the norm.

Speaking to the media this afternoon (Sept 28), a day after the United Nations Intergovernmental Panel on Climate Change (IPCC) released its fifth Assessment Report (AR5) Summary for Policymakers in Stockholm, the Centre for Climate Research Singapore (CCRS) gave an overview of what the report’s findings mean for Singapore.

The South-east Asian region could see an increase in average temperature of 3 to 4°C by the period of 2081 to 2100 under the most severe climate change scenario, and a rise of 0.5 to 1°C under the least severe scenario, said CCRS director Dr Chris Gordon.

A 3 °C rise in average temperature over Singapore would mean:

- Daily maximum temperatures of 34 °C that now occur 10 per cent of the time, will become the average daily maximum

- A 25 per cent increase in rainfall rate for daily rainfall events every 20 years, from 294mm to 367mm

Already, Singapore’s rate of warming in the past 62 years was 0.26 °C per decade – more than double the global trend of 0.12 °C per decade. This could be due to regional variations in man-made global warming, long-term climate variability in the region and urbanisation.

Rainfall intensity in an hour has also increased from 80mm to 107mm between 1980 and last year, although it is currently not scientifically possible to attribute this to global warming.

Another IPCC finding of particular relevance to Singapore is the enhanced estimates of sea level rise, said Dr Gordon. The AR5 projects a rise of 0.26m to 0.82m by the period of 2081 to 2100, depending on the level of greenhouse gas emissions. But specific projections for Singapore must take into account regional variations and local land movements, he said.

Research is being done by the Earth Observatory of Singapore to estimate the amount and rate of downward motion of land around the island that may result from a large earthquake in West Sumatra, which the observatory expects to take place in the coming decades.

Land subsidence will increase the rate of sea level rise – following the 2004 Aceh-Andaman earthquake, parts of Thailand have been moving downward by up to 1cm yearly, according to Assistant Professor Emma Hill of the Earth Observatory.

The latest AR5 models will be used in Singapore’s Second National Climate Change Study, which began last November. Its first phase, consisting of climate projections, is expected to complete by end-2014. Together with the United Kingdom Meteorological Office, the CCRS will provide localised and updated projections of temperature, rain, wind and sea level changes.

The projections will then be used by infrastructure agencies for climate impact assessments, expected to end by 2015 or 2016, said Ms Wong Chin Ling, director-general of the Meteorological Service Singapore.

Dr Gordon said that IPCC findings, while not a surprise to climate scientists, provide stronger projections about intensity of rainfall for wet regions in the tropics and should give greater confidence to policymakers about what the effects of climate change actually are. The projections should aid planning in areas such as drainage going forward, he said.

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