CONCLUSION

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This comprehensive analysis examines the extension of summer seasons on the Korean Peninsula due to recent climate change and associated meteorological anomalies. In 2024, South Korea recorded its hottest year since observations began 113 years ago, with an average temperature of 14.5℃, which was 2.0℃ higher than the long-term average. The annual number of tropical nights reached 24.5 days, representing a 3.7-fold increase compared to the normal period (6.6 days). Sea surface temperatures also reached 18.6℃, marking a 1.3℃ increase compared to the recent 10-year average, demonstrating the severity of climate change.

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Sea Level Changes and Climate System Variations

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Acceleration of Sea Surface Temperature Rise​

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Analysis of sea surface temperatures in the Incheon region reveals a consistent upward trend in April average water temperatures from 2023 to 2025. This phenomenon is primarily attributed to higher-than-normal sea surface temperatures in the Northwest Pacific throughout the year, which increases the temperature of air masses flowing into Korea via maritime routes. The rate of sea surface temperature increase around Korean coastal waters significantly exceeds the global average, with summer temperatures rising approximately four times faster than the global rate.

Sea surface temperatures around Korean waters reached 18.6℃ in 2024, which was 1.3℃ higher than the recent 10-year average (2015-2024) of 17.3℃, marking the highest temperature in the past decade. Particularly notable was September's sea surface temperature of 27.4℃, which was 3.2℃ higher than the recent 10-year average of 24.2℃, showing the largest deviation among all months.

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Intensification of Sea Level Rise

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According to analysis by the Korea Hydrographic and Oceanographic Agency, Korean coastal sea levels have risen by a total of 10.7cm over the past 35 years (1989-2023), with an annual increase of 3.06mm. The acceleration of sea level rise is particularly concerning, with the recent 10-year period (2014-2023) showing approximately 3.9cm of rise compared to 2.8cm in the previous decade (2004-2013), representing a 1.4-fold acceleration in the rate of increase. By region, the East Sea coast showed the highest rate of increase at 3.46mm annually, followed by the West Sea coast (3.20mm) and South Sea coast (2.74mm). This regional variation results from the complex interaction of surface water temperature increases and changing current patterns.

 

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Changes in Atmospheric Circulation Systems

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Strengthening of High-Pressure Systems

The dual pressure from Tibetan high-pressure and North Pacific high-pressure systems has emerged as a major variable in Korea's climate system. When less snow accumulates on the Tibetan Plateau during winter, more solar radiation is absorbed during summer, forming powerful high-pressure systems that move toward the Korean Peninsula and overlap with North Pacific high-pressure systems, generating extreme heat waves. In August 2024, both Tibetan and North Pacific high-pressure systems simultaneously covered Korean airspace, resulting in unprecedented high temperatures.

The strengthening of these high-pressure systems is directly linked to elevated sea surface temperatures. The North Pacific high-pressure system becomes further intensified over the warm seas surrounding Korea, while high sea surface temperatures in the North Indian Ocean cause air to rise actively, developing the Tibetan high-pressure system in the upper troposphere (approximately 12km altitude), which then extends to Korea or induces high-pressure systems to the east.

 

Long-term Impact of El Niño

The El Niño phenomenon that began in 2023 played a crucial role in 2024's record-breaking heat. High sea surface temperatures in the North Indian Ocean caused actively rising air masses to develop Tibetan high-pressure systems in the upper troposphere, which then extended to Korea or induced high-pressure systems to the east of the peninsula. Climate experts predict that global temperatures will increase by an additional 0.2-0.25°C following El Niño, with these effects expected to persist long-term.

 

 

Summer Season Extension and Extreme Weather Phenomena

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Blurring of Seasonal Boundaries

Analysis indicates that when periods with daily average temperatures exceeding 20°C are considered summer, the season now effectively lasts 7-8 months, from April through mid-November, with temperatures warm enough for short sleeves. This represents the realization of the expression that "spring and autumn have disappeared from Korea." In 2024, exceptionally high temperatures persisted through September, with September temperatures reaching 24.7℃, showing a +4.2℃ deviation from the long-term average.

The extension of summer conditions is particularly evident in April temperature records. In 2024, April's average temperature reached 14.9℃, marking the highest since modern meteorological observations began in 1973. This represents a significant departure from normal April temperatures, with several locations recording unprecedented maximum temperatures, including Seoul at 29.4℃ and Yeongwol in Gangwon Province at 32.2℃.

 

Dramatic Changes in Precipitation Patterns

For the first time since 1973, February precipitation (102.6mm) exceeded August precipitation (87.3mm) in 2024. During the summer season, 78.8% of total precipitation was concentrated during the monsoon period, representing the highest proportion since 1973. During this period, nine locations recorded hourly precipitation exceeding 100mm. This phenomenon resulted from the collision of massive water vapor flowing along the edges of the North Pacific high-pressure system with cold air accompanying cut-off low-pressure systems around stationary fronts, intensifying atmospheric instability and developing mesoscale low-pressure systems that produced even stronger rainfall.

The monsoon season in 2024 lasted from June 19 to July 27, with total precipitation of 474.8mm, which was 32.5% higher than the long-term average of 356.7mm. This concentrated rainfall pattern, combined with subsequent drought conditions, created significant agricultural and water resource management challenges.

 

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Socioeconomic Impacts and Future Projections

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Agricultural and Marine Sector Consequences

The prolonged high temperatures from July to September 2024 caused damage to 3,477 hectares of crop cultivation areas, including ginseng, while persistent high-temperature conditions during the breeding season of brown planthoppers resulted in damage to 17,732 hectares of rice fields. Regional distribution of brown planthopper damage showed Jeollanam-do with the highest impact at 9,261 hectares, followed by Jeollabuk-do (3,098 hectares) and Chungcheongnam-do (2,979 hectares).

In marine environments, abnormally high water temperatures led to mass mortality of aquaculture organisms, resulting in damages worth 143 billion won, excluding Incheon, Gyeonggi, and Jeollabuk-do regions. The number of days with abnormally high water temperatures (182.1 days) increased significantly compared to the recent 10-year average, representing a 3.6-fold increase.

 

Public Health Implications

Heat-related illness cases during the summer heat illness emergency room surveillance period (May 20 to September 30) totaled 3,704 cases, representing a 31.4% increase compared to the previous year (2,818 cases). This increase directly correlates with the extension of high-temperature periods and the intensification of heat waves.

 

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Long-term Climate Projections and Adaptation Strategies

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Sea Level Rise Projections

Current projections indicate that if sea levels rise by 1 meter by 2100, approximately 2,340㎢ of coastal areas equivalent to 119 times the area of Yeouido will face flooding risks. According to climate change scenarios from the Intergovernmental Panel on Climate Change (IPCC), even with relatively successful implementation of environmental policies, sea levels could rise by up to 73cm by 2100.

 

Comprehensive Adaptation Requirements

The April 2024 temperature surge serves as a critical warning that new climate systems are already being realized rather than representing merely anomalous weather phenomena. Future projections indicate that summer seasons will become longer and more intense if current trends persist, with corresponding intensification of socioeconomic impacts.

Essential adaptation strategies must include carbon neutrality policy strengthening to reduce ocean thermal expansion, development of high-temperature resistant crop varieties for agricultural resilience, and advancement of coastal flooding prediction systems for disaster preparedness. The acceleration of sea level rise, particularly the 1.4-fold increase in recent decades, necessitates immediate implementation of comprehensive coastal protection measures.

 

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Conclusion

This analysis demonstrates that the Korean Peninsula's summer season already extends from April through November, driven by rapid sea surface temperature increases, rising sea levels, and fundamental changes in atmospheric circulation systems. The 2024 April temperature records, with average temperatures of 14.9℃ representing a departure from historical norms, exemplify the severity of ongoing climate change. The convergence of Northwest Pacific sea surface temperature increases, warm southerly wind intrusion, and stagnant migratory high-pressure systems provides compelling evidence that climate change is dismantling traditional seasonal boundaries.

The 10.7cm sea level rise over 35 years, with acceleration to an annual rate of 3.9mm in recent decades, coupled with sea surface temperature increases of 1.3℃ above recent averages, creates a feedback loop that strengthens high-pressure systems and prolongs heat waves. The dual strengthening of Tibetan and North Pacific high-pressure systems, elevated North Indian Ocean temperatures due to El Niño, and changes in ocean-atmosphere interactions are structurally transforming the Korean Peninsula's climate system.

These complex interactions resulted in record-breaking temperatures and abnormal precipitation patterns in 2024, including the unprecedented situation where February precipitation exceeded August precipitation. Such anomalies highlight the instability of meteorological systems and signal fundamental shifts in regional climate patterns.

The realization that summer conditions now persist for 7-8 months annually, supported by concrete evidence from temperature and precipitation data, requires immediate recognition that the April 2024 temperature surge represents not an isolated anomaly but the manifestation of a new climate regime. Comprehensive adaptation strategies integrating emissions reduction, agricultural resilience, and coastal protection measures are essential to address these accelerating changes in Korea's climate system.