Children play in a fountain at central Seoul's Gwanghwamun Square in June 2024 during a heat wave. Korea Times file

The Korea Meteorological Administration (KMA) issued a stark warning on Sunday, forecasting that heat waves will become more frequent and intense due to climate change, with the possibility of intense heat lasting from May to September.

Its newly released "Heat Wave White Paper," detailing the evolving patterns of heat waves and tropical nights in Korea, reveals alarming shifts in temperature trends. According to the report, the first day of a heat wave now arrives earlier in the year, while the last day occurs later, signaling a lengthening and intensification of these extreme heat events. The report also forecasts that the duration of heat waves will continue to increase, especially if greenhouse gas emissions remain unmitigated.

"Recent records show a shortening of the recurrence cycle of heat waves and tropical nights, which is closely linked to the rise in global temperatures driven by climate change," the white paper stated.

The report's findings are based on extensive research, including historical data and future climate models. It highlights how the average date for the first heat wave of the year has moved up from coming between July 3 and 13 in the 1990s to June 27 to July 6 in the 2010s. In addition, tropical nights — nights when temperatures do not drop below 25 degrees Celsius — have become more common, with last summer's total of 22 tropical nights setting an all-time high.

In a particularly worrying trend, the duration of heat waves has increased substantially in recent decades. In 1994, Korean regions saw a record-high average of 27.5 days of extreme heat, a figure considered a once-in-a-generation event. However, by 2018, that average had risen to 29.5 days. Last summer, heat waves lasted 4.3 days on average in July and 16.9 days in August.

The "SSP1-2.6 scenario," part of the Shared Socioeconomic Pathways (SSPs) framework used by the Intergovernmental Panel on Climate Change (IPCC), projects a global temperature increase of 1.8 degrees by 2100.

The white paper projects that by the end of this century, the number of heat wave days could rise dramatically, depending on global efforts to reduce greenhouse gas emissions. Under the SSP1-2.6 scenario, which assumes substantial efforts to reduce emissions, heat waves could persist for 8.7 days on average by 2100. In the more extreme SSP5-8.5 scenario, where emissions remain high, that number could climb to 17.4 days.

The report also predicts that average maximum daily temperatures during the hottest period of the year will rise significantly, from the current 25.5 degrees to 28.6 degrees by 2100 under the SSP1-2.6 scenario, and up to 32.4 degrees under the SSP5-8.5 scenario. These rising temperatures are expected to exacerbate the already severe impacts of extreme heat, especially in regions that are already suffering the most.

"Without significant reductions in greenhouse gas emissions, we are likely to see unprecedented levels of heat across the Korean Peninsula and East Asia by the end of the century," said an official from the Heat Wave Research Center at the Ulsan National Institute of Science and Technology (UNIST). "These extreme weather events will become more frequent and intense in areas already experiencing severe heat."