In this blog post, we’ll examine how global warming is affecting South Korea’s climate and seasonal changes.
South Korea’s Climate Transformed by Global Warming
“The point of no return for global warming is fast approaching. Someday, Earth could turn into a scorching Venus, where sulfuric acid rain falls.”
During his lifetime, Stephen Hawking repeatedly warned of the severity of global warming. As he warned, humanity is now facing a climate crisis caused by global warming. In this post, we will examine how global warming is affecting South Korea’s climate.
As recently as February of this year, temperatures were below freezing, but they suddenly rose above freezing in March. In mid-March, temperatures that had been above 15°C suddenly dropped below freezing on the 21st, even bringing snow. The weather fluctuations were so extreme that people began saying, “March has all four seasons.” The expression “Winter yesterday, summer today” is no longer an exaggeration.
Summer weather is also showing a different pattern than in the past. Even during the monsoon season, rather than rain continuing for several days at a time, there are repeated episodes of heavy rain falling intensely for short periods before stopping. Furthermore, instances of heat waves occurring even during the monsoon season are becoming more frequent. Climate changes that were rare just a few years ago are now gradually becoming the norm. So, what changes are currently taking place in South Korea’s climate?
The first observable change is that the pattern of the monsoon is shifting. In the past, the monsoon was influenced by the monsoon front and tended to last for a relatively long period. The monsoon front is a stationary front formed by the temperature difference between the Okhotsk Sea air mass and the North Pacific air mass. When the cold, humid Okhotsk Sea air mass and the warm, humid North Pacific air mass are in balance, the front does not move significantly and causes sustained precipitation, primarily in the region north of the front. Generally, the monsoon lasts for about a month; as the strength of the two air masses shifts, the monsoon front repeatedly moves north and south before finally ending as the North Pacific air mass becomes dominant.
However, recent monsoon seasons have exhibited characteristics different from those of the past. The most notable feature is the frequent occurrence of what is known as “shower-type monsoon rain.” Shower-type monsoon rain refers to a pattern where rain falls suddenly and heavily, stops within a short period, and then resumes repeatedly. While the monsoon is typically characterized by high temperatures and humidity, there has been an increase in cases where heat waves occur even during the monsoon season. Furthermore, the average relative humidity in the Seoul area in early July has also shown a tendency to be higher than in the past.
How do shower-type monsoons occur? One of the causes is atmospheric instability. Generally, the atmosphere remains relatively stable when cold air is located at the bottom and warm air at the top. However, when warm air is at the bottom and cold air at the top, the atmosphere becomes highly unstable. The more unstable the atmosphere, the more active the updrafts become; as the rising air cools and reaches the dew point, condensation occurs, leading to the easy formation of rain clouds. In recent summers, it has become common for hot, humid air flowing in from the south to meet cold air from the north at high altitudes, further exacerbating this instability.
Second: Earlier Onset of Tropical Nights and Heat Waves
The second change is that the start of tropical nights is occurring earlier and earlier, while their end is occurring later and later. In the past, tropical nights were mainly concentrated in midsummer, but recently, their duration has been gradually increasing. Heat waves are also starting earlier and lasting longer.
A tropical night is defined as a night during which the minimum temperature between 6:00 p.m. and 9:00 a.m. the following day is 25°C or higher, while a heatwave, according to the Korea Meteorological Administration, refers to a condition where the daily maximum apparent temperature is expected to reach 33°C or higher for two or more consecutive days, or where damage equivalent to this is anticipated. In the past, it was common for heatwaves and tropical nights to begin after the monsoon season ended and the North Pacific High expanded strongly. However, recently, there has been an increase in cases where heat waves and tropical nights occur even before the monsoon season ends, and there is a trend toward these phenomena starting earlier and ending later.
Why are heat waves and tropical nights arriving earlier and lingering longer? The “heat dome” phenomenon is cited as one of the causes. The “heat dome” phenomenon refers to a situation where a strong high-pressure system at an altitude of approximately 5–7 km above the ground lingers over a specific region for an extended period, trapping hot air in a dome-like formation. In the past, even when influenced by the North Pacific High, westerly winds played a role in dispersing the heat. The westerlies are closely related to the jet stream that flows in the upper troposphere; they tend to strengthen as the temperature difference between high and low latitudes increases. However, as the Arctic region warms rapidly due to global warming, the temperature difference between latitudes is decreasing, leading to frequent instances where the jet stream weakens or becomes highly meandering. These changes are analyzed as one of the factors creating an environment where heat domes persist for longer periods, thereby increasing the frequency and duration of heat waves and tropical nights.
How are the seasons changing?
The third change is that the lengths of the four seasons are gradually shifting. As the duration of heat waves and tropical nights lengthens, summer is becoming progressively longer. In contrast, spring and fall are becoming relatively shorter, and winter is also showing a pattern where cold snaps and heavy snowfall are concentrated.
In the past, the seasonal divisions were relatively distinct: spring from March to May, summer from June to August, fall from September to November, and winter from December to February. However, recent climate observation data confirms that spring and fall are becoming shorter while summer is getting longer. Although the exact start and end dates of each season vary from year to year, numerous studies consistently show an overall trend toward longer summers and shorter springs and falls.
Global warming is cited as the primary cause of these seasonal changes. Global warming refers to the phenomenon in which the concentration of greenhouse gases—particularly carbon dioxide—in the atmosphere increases due to factors such as the growing use of fossil fuels, thereby intensifying the greenhouse effect and causing the Earth’s average temperature to rise continuously. This rise in temperature is bringing about changes in climate and seasons worldwide, including in South Korea, and is also affecting various meteorological phenomena such as precipitation patterns, heat waves, and cold snaps.
Looking at recent climate trends, tropical nights tend to begin earlier and end later. Heat waves are showing a similar pattern. The monsoon season is also shifting away from the pattern of continuous rain over several days, as seen in the past, toward more frequent episodes of intense, concentrated rainfall that lasts only a short time before stopping. Furthermore, the seasons are gradually shifting, with spring and fall becoming shorter and summer becoming longer.
How should we respond to climate change?
South Korea’s climate is becoming increasingly difficult to predict. While it is true that not all individual weather phenomena can be explained solely by global warming, the recent increase in heat waves and tropical nights, the rising frequency of intense torrential downpours, and changes in the monsoon pattern are known to be closely related to climate change.
The heat dome phenomenon, changes in the jet stream, and increased atmospheric instability are also being studied as major factors contributing to these changes. If global average temperatures continue to rise, the duration of heat waves and tropical nights is likely to lengthen further, and precipitation variability is also likely to increase.
The monsoon season is also showing a trend toward more frequent localized torrential downpours than in the past. As a result, the number of instances where heavy rain falls in a short period is increasing, raising the risk of flooding and waterlogging. Additionally, the number of days with high summer discomfort indices and high perceived temperatures is gradually rising.
Furthermore, the increase in greenhouse gas emissions resulting from human activities is identified as the root cause of these changes. As the use of fossil fuels increases, carbon stored in the Earth’s crust is released into the atmosphere in the form of carbon dioxide and other gases; consequently, the greenhouse effect is intensifying, causing global average temperatures to rise. This climate change is not a problem unique to South Korea but a challenge that the entire world must address together.
The international community has been making various efforts to address climate change. Building on the Kyoto Protocol, countries are now establishing and implementing greenhouse gas reduction targets centered on the Paris Agreement. South Korea is also participating in global efforts to combat climate change by promoting carbon neutrality policies, expanding renewable energy, and implementing greenhouse gas reduction measures.
To mitigate climate change, not only government and corporate policies but also individual actions are crucial. Lifestyle habits such as reducing unnecessary electricity use, walking or taking public transportation for short distances, and minimizing energy consumption can help lower greenhouse gas emissions. As these small actions accumulate, they can bring about meaningful change in the fight against climate change.
