Singapore had about 122 more dangerous heat days in 2024

The impacts of climate change on Singapore’s weather are already being felt, with scientists estimating that the Republic experienced 122 extra days of dangerous heat in 2024.

Without climate change, the country would experience only four such days, found a new climate report published on Dec 27.

The report defined dangerous heat days as days when mean temperatures were hotter than the warmest 10 per cent of temperatures observed over the 1991 to 2020 period.

The latest report was done by scientific research organisation World Weather Attribution (WWA) and Climate Central, a non-profit group of scientists and communicators.

Extreme weather events, such as heatwaves, can happen naturally, but are made worse by climate change.

Climate change today is driven by ever-increasing amounts of planet-warming gases being released into the atmosphere from human activities, such as burning fossil fuels.

The field of study in which the fingerprints of climate change are detected in extreme weather events is known as attribution studies.

For the study, the researchers relied on temperature data from 220 countries and territories from the ERA5 dataset, which is produced by the EU’s Copernicus Climate Change Service (C3S), the bloc’s earth observation programme.

The researchers compared the temperatures in each location in 2024 with the temperature trends observed in the preceding decades, between 1991 and 2020.

The Singapore data was extrapolated from the data for the broader South-east Asian region. The mean daily average temperature across South-east Asia in 2024 was 27.4 deg C. This is 0.8 deg C hotter than the average year from 1991 to 2020.

“Singapore has a very distinct climate, which highlights the impact of global warming more than most countries do,” Climate Central research associate Joseph Giguere told The Straits Times.

Temperatures in Singapore do not vary hugely throughout the year, unlike in countries that experience larger ranges of temperatures on any calendar day year to year. As Singapore has a relatively stable climate, shifts in temperature over the years can be strongly attributed to climate change, said Mr Giguere.

“Because of this, the distribution of temperatures that we see today has shifted dramatically from the temperatures that Singapore would experience in a world without climate change,” he added.

While urbanisation can also affect a person’s experience of heat as concrete traps heat, the study did not look at the impact of urbanisation on warming.

Singapore uses the wet bulb globe temperature (WGBT) – which accounts for not just air temperature, but also humidity, wind speed and solar radiation – to measure heat stress.

Under a heat stress advisory launched by Singapore’s National Environment Agency (NEA) in 2023, periods of high heat stress are indicated by WGBT levels of 33 deg C or higher, and people are advised to minimise outdoor activities under such conditions.

The heat stress advisory aims to minimise the risk of heat-related illnesses such as heat cramps, heat exhaustion or, in severe cases, heat stroke, which can be fatal, NEA said. Extreme heat can also affect people in other ways, as well as lead to hospitalisation.

Mr Giguere added that small coastal countries close to the equator have similar temperature trends to Singapore.

When global temperatures are considered, the study found that climate change added 41 extra days of dangerous heat in 2024, compared with the 1991 to 2020 baseline, for the average person.

But 18 of 20 countries that experienced the most added days of dangerous heat – referring to more than 130 additional dangerous heat days – were small island developing states like the Solomon Islands.

Across data taken in 220 countries and territories, the highest number of dangerous heat days added by climate change is 173 in tiny Micronesian island Nauru, which sits near the equator, and the lowest is South Korea’s 12 days.

The latest report comes after the declaration by climate scientists from C3S that 2024 is the hottest year on record.

It is also the first year in which average global temperatures rose more than 1.5 deg C above the pre-industrial period, according to the EU’s C3S.

Scientists have warned that if warming exceeds 1.5 deg C above pre-industrial levels, climate change impacts could be catastrophic. The previous hottest year on record was 2023.

In 2023, Singapore experienced 93 additional dangerous heat days and would only have experienced six dangerous heat days in a world without global warming, Mr Giguere told ST.

Associate Professor Jason Lee, director of the Heat Resilience and Performance Centre at NUS Medicine, noted that the latest study had used statistical methods to determine how many extra hot days Singapore experienced in 2024.

While such methods could provide a big-picture perspective of how temperatures in Singapore are affected by climate change, other types of locally collected data could help to determine how this could affect human health. This could include, for example, mapping temperature trends with actual incidents, such as hospitalisation rates.

While there is always room for better measurements of impacts of heat, effective solutions need to be urgently implemented and resources to be allocated to the most vulnerable populations, he added.

“We cannot be getting used to setting such new records,” he said.

He added that heat stress not only can lead to more illnesses and deaths, it also reduces productivity and affects people’s livelihoods.

“Heat directly affects the tenets of human health and well-being – diet, exercise, and sleep. Failing to cope with extreme heat means health and healthcare systems will suffer,” he said.

Prof Lee also led Project HeatSafe where the project brings together several studies and fieldwork by NUS researchers and partners to investigate how rising temperatures affect the health and productivity of people here and in the region.

One study found that the hot weather affects couples’ fertility and birth outcomes and rising temperatures could further reduce Singapore’s resident total fertility rate.

In equatorial regions such as South-east Asia where heat and humidity are constant, Prof Lee said there is a need to study how an effective heat warning system can work here.

“While spikes in ambient temperatures are unlikely, it does not mean the extreme heat is not an issue for us,” he said.

The report reviewed extreme weather events such as floods, heatwaves and droughts, and found that climate change intensified 26 of the 29 weather events studied by WWA. In total, 219 events met WWA’s criteria used to identify the most impactful weather events.

For example, scientists found that climate change made the high sea temperatures that fuelled Hurricane Helen – which left more than 230 people dead across six US states – 200 to 500 times more likely and increased its rainfall by 10 per cent.

Scientists involved in the latest report also said that climate change is exposing millions more people to dangerous temperatures for longer periods of the year and if not tackled, the number of dangerous heat days will continue to increase each year and threaten public health.

To tackle this, the report proposed a faster shift away from burning fossil fuels, improvements in early warning systems, real-time reporting of deaths caused by heat and international finance to help developing countries become more resilient.

Dr Friederike Otto, lead of WWA and senior lecturer in climate science at Imperial College London, said: “We do have the knowledge and technology to move away from fossil fuels, towards renewable energies, lower demand and halt deforestation.

“In 2025, every country needs to step up efforts to replace fossil fuels with renewable energy and prepare for extreme weather.”