Extreme heatwaves, atypical monsoon surges, and other noteworthy findings are among the 5 key takeaways highlighted in Singapore’s 2023 climate report

March 24, 2024

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Singapore is witnessing more extreme weather events. The record hot temperatures and unexpected monsoon surges have raised concerns about the city-state’s resilience to climate change impacts. These events serve as reminders of the importance of adaptation measures and sustainable practices to mitigate the effects of climate change.

Last year marked Singapore’s fourth warmest year on record, equalling the temperatures recorded in 1997 and 2015. The month of May stood out as the hottest in 2023, with both May and October registering their highest temperatures ever recorded for those months in Singapore’s climate history.

Following a relatively cool beginning to the year, the intense heat of May brought about the highest temperature of the year: 37 degrees Celsius on May 13 in Ang Mo Kio. This tied with April 17, 1983, as Singapore’s highest recorded temperature in history.

These observations were part of the Meteorological Service Singapore’s Annual Climate Assessment Report for 2023, which examined the climate trends throughout the year.

The report highlighted that Singapore’s warming trend aligns with global climate patterns. Alongside the scorching temperatures in May, two notable weather events stood out in 2023: a delayed monsoon surge from late February to early March and hazy conditions in October.

As temperatures rise, heat stress has become a major concern in Singapore.

The report now includes a special focus section on this issue, prompted by the National Environment Agency’s issuance of Singapore’s inaugural heat stress advisory in July.

Here are five key points from the report:

FOURTH WARMEST YEAR ON RECORD

The temperature trends observed in 2023 underscore a consistent warming pattern in Singapore over recent years. According to the report, last year’s annual mean temperature of 28.2 degrees Celsius tied for the fourth warmest year on record since 1929, alongside 2015 and 1997.

Over the past decade, from 2014 to 2023, Singapore experienced its highest mean temperature at 28.06 degrees Celsius, surpassing the previous record by 0.05 degrees Celsius. This marks the third consecutive decade to set a new high-temperature record.

The year started with cooler-than-average temperatures from January to March, attributed to La Nina conditions and increased northeasterly winds, with March being the coolest in the last decade.

However, starting in April, Singapore saw warmer-than-average weather, with May recording the highest mean temperature of 29.5 degrees Celsius, 0.9 degrees Celsius above the long-term average.

October stood out as exceptionally warm, with a mean temperature of 29.0 degrees Celsius, surpassing the previous warmest October in 2002 by 0.3 degrees Celsius.

2024 EXPECTED TO BE WARMER THAN 2023

Moving forward, projections indicate that by mid-century, the temperature experienced in Singapore during 2023 will be deemed cooler than average, as days are projected to become hotter. These forecasts were outlined in the Centre for Climate Research Singapore’s third national climate change study, referred to as V3, which was unveiled in January.

All three scenarios presented in the study, including low, medium, and high emissions scenarios, indicate varying temperature increases by mid-century and end-century. The mid-century period spans from 2040 to 2059, while the end-century period refers to 2080 to 2099.

By the end of the century, Singapore could experience extremely hot days, with temperatures surpassing 35 degrees Celsius for as many as 351 days in a year.

Projections also indicate that annual average daily mean temperatures will rise to a range between 28.5 degrees Celsius and 32.9 degrees Celsius, while annual average daily maximum temperatures are expected to increase to a range between 31.9 degrees Celsius and 36.7 degrees Celsius.

HIGH HEAT STRESS DAYS

In 2023, Singapore experienced 37 days of high heat stress, characterized by hourly average Wet-Bulb Globe Temperature (WBGT) readings of 33 degrees Celsius or higher. WBGT is a globally recognized measure that takes into account factors like air temperature, humidity, wind speed, and solar radiation to provide an accurate assessment of heat stress conditions. The highest occurrences of high heat stress days were in April, May, June, and October, with May seeing the most (10 days) followed by October (eight days).

Future projections outlined in the V3 study indicate a substantial increase in high heat stress days for Singapore. By 2059, estimates suggest an average of 75, 87, and 113 days under low, moderate, and high emissions scenarios, respectively. This represents a two to fourfold increase compared to 2023.

Looking further ahead to 2099, the frequency of such intensely hot days could surge to between 207 and 326 days on average under the high emissions scenario. Research indicates that rising temperatures, extreme heat, and high heat stress can lead to various adverse effects.

EXCEPTIONALLY WET FEBRUARY AND MARCH

In 2023, Singapore experienced its seventh wettest year since 1980, with a total rainfall of 2,866.1mm, surpassing the long-term average by 13.1 per cent.

The island witnessed exceptionally heavy rainfall in February, recording an average of 342mm compared to the long-term average of 132.1mm, making it the fourth wettest February on record. March also saw significant rainfall, ranking as the fifth wettest March since 1980. While La Nina typically brings wetter conditions, the Met Service noted that the unusually high rainfall at the start of the year was only partially influenced by this phenomenon.

These observations suggest that besides La Nina, other factors likely contributed to the unusually heavy rainfall experienced during this period.

OTHER NOTABLE WEATHER EVENTS

One of the contributing factors to the unusually heavy rainfall in Singapore during early 2023 was a rare late monsoon surge in late February and early March, which was identified as a significant weather event in the report.

This surge led to widespread heavy rainfall across the island, particularly in the eastern and southern regions, with all climate stations recording over 100mm of rain. Notably, Kallang and Sengkang witnessed the highest daily total rainfall ever recorded in February and March, respectively.

In addition to the heavy rainfall, the monsoon surge also brought cooler temperatures to Singapore, with some days experiencing maximum temperatures below 28 degrees Celsius. The lowest temperature recorded during this period was a record-low of 21.1 degrees Celsius at Newton.

Another noteworthy weather event highlighted in the report was the hazy conditions and deteriorating air quality in October. The highest 24-hour Pollutant Standards Index (PSI) recorded during this time was 123, classified as “unhealthy” (PSI 101-200).

These conditions were attributed to increased hotspot and smoke haze activities, initially observed in Kalimantan and later spreading to Sumatra, Indonesia.