Experts cite climate change and rapid industrialisation to explain fluctuating rainfall
Amresh Gunasingham, Straits Times 16 Jul 09;
NEW data shows Singapore's rainfall has been dwindling over the last 30 years and more extreme weather changes are predicted to hit the region in the coming years.
A report from the Energy Studies Institute (ESI) at the National University of Singapore (NUS) has found that from 1907 to 1967, average annual rainfall levels were up to 80mm above the long-term average of 2,346mm. But since 1967, rainfall has mostly remained at less than 40mm below the long-term average.
The study was based on data over the last 100 years obtained from the National Environment Agency's (NEA) Meteorological Services Division.
Confirming the findings, a spokesman for the NEA said: 'There was a gradual decreasing trend in rainfall, mainly due to a natural variability in Singapore's climate.'
The years 2006 and 2007 saw rainfall peak above the long-term average, but this was an exception to the trend, the report noted.
Some experts pointed to factors such as Singapore's rapid industrialisation during the 1970s to explain the pattern of falling rainfall.
'The effects of global climate change have been more pronounced only during the last two decades, so the rainfall change occurred a little too early,' noted Professor Lim Hock, founding director of Temasek Laboratories, which conducts research into areas of science and technology identified as critical to Singapore.
'The significant change in the landscape and ground cover condition of Singapore can affect the local distribution of clouds and rain, and hence, the observed reduction in rainfall.'
Singapore, with limited land for catchments to collect and store rainwater and with no groundwater, is also vulnerable to water scarcity issues.
Climate change - where the frequency of extreme weather patterns such as droughts and floods is expected to increase - was another factor, said experts.
The findings support forecasts made by the UN Intergovernmental Panel on Climate Change (IPCC) that annual rainfall levels in South-east Asia will fall in the first half of this century, said Associate Professor Ho Juay Choy, principal research fellow from ESI, who led the research effort.
Global warming predictions point to South-east Asia suffering from 'water stress', which refers to periods of extreme drought, brought about by a lack of fresh water supply.
'Climate change will likely affect health, agricultural, economic activities as well as water supply,' said Prof Ho.
Reduced rainfall was part of a wider trend in the region, particularly in Indonesia, Vietnam and Malaysia, Prof Ho added.
The only exception to the trend was the Philippines.
The United Nations predicts that by 2025, 1.8 billion people worldwide will be living in conditions of absolute water scarcity.
Professor Liong Shie-Yui, principal research fellow at NUS' Tropical Marine Science Institute, said it was important to consider that rainfall levels also vary substantially year-on-year.
For example, it is not uncommon for rainfall to peak at 3,200mm one year and drop to 2,200mm the next.
Despite the variability of shifting weather patterns, Singapore's integrated approach to water management means it is well equipped to cope, said Prof Liong.
For example, desalination and Newater - sources which have the advantage of being independent of fluctuations in rainfall - have been added to its water supply.
'These measures have enhanced our resilience against climate-change uncertainties such as fluctuating rainfall,' he added.
amreshg@sph.com.sg
# Thunderstorm days: An average of 14 thunderstorm days per month was recorded over the past 50 years. Although considered high, this is consistent with the local weather patterns.
# Wet days: There were 169 wet days on average in Singapore over the last 50 years. A wet day is defined as one in which there is more than 0.2mm of rainfall recorded.
# Temperature: Temperature variations over the past 50 years confirm a trend of temperatures rising more in the last 20 years.
SOURCE: ENERGY STUDIES INSTITUTE
