• The report by the Intergovernmental Panel on Climate Change’s working group examines the physical science behind climate change
• It predicts higher temperatures, more rainfall and rising sea levels globally
• To limit global warming to 1.5°C as stipulated in the Paris Agreement, the world needs to achieve net zero emissions by around 2050
• The Government will study the impact of these findings on Singapore

SINGAPORE — The United Nations (UN) predicts higher temperatures, more rainfall and rising sea levels globally in the coming decades, in its latest assessment of climate change.

Southeast Asia will experience more intense daily rainfall and Singapore will also become hotter as a result, said the Ministry of Sustainability and the Environment (MSE) and Meteorological Service Singapore (MSS) in a joint press release on Monday (Aug 9).

On Monday, the Intergovernmental Panel on Climate Change, an intergovernmental body of the UN, released its sixth assessment report by one of its three working groups.

The report addresses the physical science behind climate change and shows how and why the Earth’s climate has changed to date.

The last report by the working group was released in 2013, forming the basis for the 2015 Paris Climate Agreement, a legally binding international treaty on climate change.

It had then said that it was extremely likely that human influence had been the dominant cause of global warming since the mid-20th century.

The latest report, which comes ahead of the Glasgow Climate Change Conference in November, noted that human influence has warmed the atmosphere, ocean and land, leading to widespread and rapid climate changes.

To limit global warming to 1.5°C as stipulated in the Paris Agreement, the world needs to achieve net zero emissions by around 2050 with a total carbon budget of 500 billion tonnes of carbon dioxide left.

The remaining two working groups will release their reports early next year, and a subsequent report combining the findings of all three working groups will be released next September.

In a joint press release on Monday, the Ministry of Sustainability and the Environment (MSE) and Meteorological Service Singapore (MSS) said that the Centre for Climate Research Singapore (CCRS) will contextualise the findings of the report and study its impact on Singapore.

THE FINDINGS

The report warned that temperature change will be more than between 1.5°C and 2°C during this century unless there are deep reductions in greenhouse gas emissions in the coming decades.

The report models five climate change scenarios depending on the level of greenhouse emissions by the end of this century.

The most severe scenario assumes rapid development in non-green technology and economic development driven by fossil fuels.

The least severe scenario assumes sustainable economic growth worldwide with lower resource and energy intensity.

INCREASING TEMPERATURES

The report showed that global surface temperatures will be higher than today by 2050 under all climate change emission scenarios.

In the four lowest emissions scenarios, average surface temperatures are estimated to rise by more than 1.5°C above pre-industrial levels in the early 2030s.

In the highest emissions scenario, the average surface temperature rise will cross the 1.5°C mark earlier — by the end of this decade.

Global average surface temperatures from 2081 to 2100 are expected to increase by at least 1.3°C to 2.4°C under the second least severe emissions scenario.

Temperatures will increase by 3.3°C to 5.7°C during the same period under the most severe emissions scenario.

The latest findings suggest that Singapore will also feel higher temperatures in the coming decades, said the agencies in their press release.

MORE RAINFALL

Rainfall is expected to intensify globally and become more frequent with each additional degree of warming.

By 2100, the annual rainfall over land is projected to be higher than current levels under all five emission scenarios.

Heavy precipitation events will intensify by about 7 per cent for each degree of global warming as a warmer atmosphere is able to hold more moisture.

Southeast Asia will also experience an increase in rainfall during the monsoon seasons and pluvial flooding. This occurs when the ground cannot absorb rainwater effectively or when drainage systems are overwhelmed during an extreme rainfall event.

MSS and MSE noted that Singapore’s average annual rainfall since 1980 has increased at an average rate of around 70mm every decade.

“The intensity and frequency of heavy rainfall events have also increased over the past few decades up until 2012, but these trends were modulated by strong El Niño conditions in 2015 and 2016,” said the agencies.

El Niño is a climate phenomenon involving the warming of the ocean surface in the eastern tropical Pacific Ocean. It generates low-level surface winds which affect the rainfall in various parts of the world, including Singapore.

The agencies said it is “challenging” to pinpoint the cause of past rainfall changes in Singapore with current models as it involves a combination of factors such as global warming and natural climate variability.

Nevertheless, MSS said it will continue to study rainfall patterns, along with the impact of climate change on Singapore’s weather.

SEA LEVEL RISE

The report projected global mean sea levels to rise by between 0.32m and 0.62m by the end of this century under the second least severe emissions scenario.

Under the highest emissions scenario, sea levels are likely to rise by 0.63m to 1.01m by the end of this century.

The report also said that “high impact-low probability” events such as coastal ice cliffs collapsing due to global warming could contribute to more than one additional metre of sea level rise by the end of this century.

While projections in the mean sea level change do not differ significantly from the last report, “high impact-low likelihood” events could have a disproportionate impact on low lying tropical states like Singapore.

MSS said that the CCRS will study the projections in greater detail to strengthen local sea level research and produce more robust projections of sea level change for Singapore.

The centre has started work on the Third National Climate Change Study for Singapore, which provides local climate change projections based on climate models used by the IPCC.

The study is expected to be completed by 2022 and will guide the planning and implementation of measures to safeguard Singapore against the impact of climate change.