Korea's surrounding seas are warming at a rate twice as fast as the global average, with a sharp increase in sea surface temperatures over the past 10 years. According to the National Oceanic and Atmospheric Administration (NOAA) on the 3rd, the sea surface temperature around Korea rose 0.87 degrees Celsius from 2012 to 2021, which is 2.02 times the global average of 0.43 degrees. The NOAA has been monitoring global sea surface temperatures since 1981 and released the data through its official website. The sea surface temperature around Korea has been rising steadily, with an average annual increase of 0.083 degrees over the past 10 years. In particular, the sea surface temperature in 2021 was 1.18 degrees higher than the average from 1981 to 2010. The East Sea, which is a marginal sea located in the northwestern Pacific Ocean, showed a significant increase in sea surface temperature. The sea surface temperature in the East Sea rose 1.04 degrees over the past 10 years, which is 2.3 times the global average. The Yellow Sea and the East China Sea also showed a rapid increase in sea surface temperature. The Yellow Sea had an average annual increase of 0.097 degrees, and the East China Sea had an average annual increase of 0.092 degrees. The rapid warming of the seas around Korea is believed to be caused by climate change and the influence of the Pacific Ocean. The NOAA stated that the increase in sea surface temperature is having a significant impact on marine ecosystems and fisheries. The organization emphasized the need for continuous monitoring and research on sea surface temperature to better understand the impacts of climate change. The data released by the NOAA can be used as basic data for research on marine ecosystems and fisheries in Korea. The Korean government and research institutions are expected to use the data to develop strategies for adapting to climate change and managing marine resources. The NOAA's data on sea surface temperatures can be accessed through its official website.

South Korea's surrounding seas are experiencing the most severe warming among global oceans, with sea surface temperatures rising three times faster than the worldwide average over the past decade, according to a recent analysis by South Korea's Meteorological Administration. Sea surface temperatures increased by 0.7 degrees Celsius during this period, compared to a 0.3-degree increase worldwide.

From 2016 to 2025, the Korea Meteorological Administration's marine weather stations recorded a 0.7-degree increase in sea surface temperatures around South Korea, while global average sea surface temperatures rose by 0.3 degrees. The recent ten-year average for the top four warmest years—2024, 2025, 2021, and 2023—occurred after 2021.

The concentration of heat in the ocean, known as "ocean heat content," also shows higher values for South Korea's surrounding waters compared to the global average. Marine heatwaves, which last for at least five days when sea surface temperatures exceed the 90th percentile of the annual mean, have increased by 3.7 times in recent years, from an average of 22.6 days per year to 83.3 days annually.

The intensity of these heatwaves has risen by 0.2 degrees Celsius compared to the annual mean. Off the coast of South Korea, the East Sea has shown particularly significant warming, with a 0.8-degree increase in sea surface temperatures over the past decade, 96.1 days of marine heatwave occurrences, and an intensity of 2.2 degrees.

The ocean heat content has risen by 0.56 gigajoules per square meter, more than double the global average. Despite efforts to reduce carbon emissions, this trend is expected to intensify in the future. According to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) and regional climate change scenarios, sea surface temperatures in South Korea's surrounding waters are projected to rise above recent levels, even with carbon emissions reductions.

In the "low carbon" scenario (SSP1-2.6), sea surface temperatures could increase by 1.8 degrees by the late 21st century, while in the "intermediate" scenario (SSP2-4.5), they could rise by 2.2 degrees. Marine heatwaves are projected to increase by 181 days in the low carbon scenario and 231 days in the intermediate scenario compared to the recent ten-year period, with intensity increases of 0.7 degrees and 0.9 degrees, respectively.

Globally, sea surface temperatures are breaking new records, reaching 21.1 degrees Celsius recently, surpassing the previous high of 21.09 degrees Celsius (2024). This unprecedented rise in global ocean temperatures, typically seen in late spring, highlights the alarming acceleration of ocean warming.