Unchecked emissions spell hotter, wetter days for Singapore

Singapore’s Second National Climate Change Study forecasts rising sea levels, higher temperatures, and more extreme rainfall in the region if no action is taken to mitigate greenhouse gas emissions and curb climate change.

If the global community does nothing to reduce greenhouse gas emissions by the end of the century, Singapore should brace itself for more extreme wet weather, hotter days, and sea levels that are as much as a metre higher than today.

These are the findings of the city-state’s Second National Climate Change study, released Wednesday, which analysed how the climate projections made by the Intergovernmental Panel on Climate Change (IPCC) in their fifth assessment report (AR5) would affect Singapore. AR5 was finalised in 2014.

At a media briefing held at the Meteorological Service Singapore’s (MSS) Centre for Climate Research Singapore (CCRS), researchers shared projections about how climate change would affect Singapore in two different scenarios. 

The first, ‘business as usual’ (BAU), assumes that the use of fossil fuels continues worldwide with no mitigation, resulting in greenhouse gas (GHG) emissions rising throughout the 21st century.

The second ‘low-emissions’ scenario assumes that emissions will peak in about 2050 and decline after that.

These projections were the result of research conducted during Phase 1 of the climate change study, which concluded earlier this year. Policymakers will now use the findings to examine the impact of climate change on areas such as water resources and drainage, biodiversity and greenery, and infrastructure.

“This in turn will guide government agencies in their planning and will serve to shape Singapore’s climate change resilience plans” said MSS in a statement, adding that key findings from the analysis  can be expected by the end of the year.

The study, commissioned by the National Environment Agency (NEA) in 2013 and conducted by CCRS and the UK Met Office Hadley Centre, was based on data from nine models that were used in the IPCC report.

Concluded earlier this year, it presented projections for average weather patterns from 2070 to 2099, relative to a baseline period of 1980 to 2009.

In the BAU scenario, average surface temperatures could increase by 4.6 degrees from the baseline and average 32°C during 2070 to 2099. Furthermore, while the average maximum daily temperature was 31.8°C in the past three decades, it could hit almost 37°C in the future.

In comparison, the average daily temperature increase in the low-emissions scenario will be about 2.7°C, while daily maximum temperatures will be about 34.6°C.

Chris Gordon, director of CCRS, noted that “higher temperatures lead to increases in heat stress”, which refers to the discomfort people experience in hot and humid weather. “This is important for people working outdoors,” he said. 

In 2070 to 2099, the number of the number of ‘warm days’ between February and May - defined as days when the temperature exceeds 34.1 degrees - could increase from 25 days a year now to every day, in the BAU scenario.

In the low-emissions scenario, up to 108 days (out of about 120 days) between February and May are likely to qualify as warm days.

Very wet days

While the study did not predict any significant changes in annual rainfall, it showed that wet months could become wetter and dry months, drier. 

In many parts of the world, rainfall will be the factor that determines the health of a country’s population and the future of their economies.

Julia Slingo, chief scientist, UK Meteorological Office

By the end of the century, Singapore could have 67.5 per cent more rain during the wet season - typically occuring between November and January - compared to about 262 millimetres per month during the baseline period. This figure could be capped at 42.9 per cent if emissions peak mid-century. 

Conversely, the dry periods that typically occur during February and from June to September are set to get even drier in both scenarios, the study found.

These decreases in rainfall during dry seasons would be experienced throughout the region, and could be a “significant issue for Indonesia”, where it could increase risks of forest fires and haze production, said Gordon.

The researchers also noted that Singapore should brace itself for more episodes of extreme wet weather, characterised by rainfall so intense that it usually occurs only once every 20 years.

While these “very wet days”, which are associated with greater flood risks, contributed to 22.8 per cent of annual rainfall from 1980 to 2009, this figure could be 44 per cent in the worst-case scenario by the end of the century.

In the more moderate projection, very wet days would account for 35.3  per cent of annual rainfall.

Julia Slingo, chief scientist of the UK Meteorological Office, noted that climate scientists should pay close attention to rainfall patterns and ensure data was up to date, because “in many parts of the world, rainfall will be the factor that determines the health of a country’s population and the future of their economies.”

Sea level is an equally crucial factor in Singapore, a low-lying island state. The study projected that sea levels could rise by as much as 0.76 metres, in the worst-case scenario, although some models used in the analysis put the figure at a metre. In the alternate scenario, sea levels could rise by between 0.25 and 0.6 meters.

Staying resilient in a changing climate

Singapore has already been working on initiatives that strengthen its resilience to a changing climate, and the government has also set aside at least S$50 million for studies on the issue.

These measures include building sea walls and stone embankments along most of the country’s coastline, ensuring that all new coastal lands are reclaimed to at least 2.25 metres above the highest recorded tide level, and ensuring that Singapore’s drainage system can cope with heavier rainfall without flooding.

As policymakers begin to analyse the projections, the researchers emphasised the fact that the projected figures also factored in a certain degree of natural variation in global climate patterns which occur regardless of man-made global warming.

This introduced an element of uncertainty into whether climate change was directly responsible for the trends identified in the report, said Gordon.

“Adaptation policy must therefore be able to adapt to the science,” he said. 

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