New questions raised by climate change
There is a word that appears without fail in March. It’s a cold spring. At the time when plum blossoms and cornelian cherry blossoms begin to burst into flower buds, the temperature drops sharply along with a sudden north wind. Explanations such as the expansion of the Siberian high pressure, the intersection of mobile high pressure and low pressure, and the introduction of northwest winds have already been repeated several times.
In the era of climate crisis, Kkotsaem cold asks new questions. How long will the spring cold that returns from the threshold of spring continue? (Photo Clipart Korea)/News Penguin
However, in the era of climate crisis (change), Kkotsaem cold asks new questions. As the earth heats up, how long will the spring cold that returns from the threshold of spring continue? If the temperature is rising, there is also the question of whether it is a natural trend for the spring cold to disappear as well.
The answer from climate science is clear. Cold springs are not going away in the near future. Even though the average global temperature rises, the winter chill that forms in the Arctic and Siberia still remains. However, as warming progresses, the frequency and duration of cold springs are likely to gradually decrease.
Cold springs that repeat even amidst warming
The average global temperature is clearly rising. According to IPCC and WMO observations, the global average temperature over the past 10 years (2014-2023) is 1.1-1.3°C higher than before industrialization. However, despite this warming trend, the inflow of cold air in late winter, or cold spring cold, did not disappear.
According to long-term data from the Korea Meteorological Administration, Korea’s average annual temperature has risen by 1.8℃ since 1973. In particular, the average winter temperature rise reaches 2.3℃. The number of extreme cold days has decreased from an average of around 10 days per year in the 1970s to 4 to 5 days recently. The overall winter cold is clearly weakening.
Nevertheless, cold springs appeared repeatedly. Cases of late winter cold inflow, in which the average daily temperature in early March plummets by more than 5℃ below normal, have been observed consistently over the past several decades. The national average temperature in early March 2010 was 6°C lower than normal. In March 2018, 1 to 5 cm of spring snow fell in the central region.
This phenomenon is due to the huge cold air reservoir remaining in the north. During the winter, cold air below -30℃ accumulates in the Arctic and Siberia, and extremely cold air masses below -40℃ are formed in inland Siberia. This cold air persists on a scale of thousands of kilometers and moves quickly to the mid-latitudes of East Asia as the upper-level jet stream bends south.
The key to the spring cold is not the average temperature but the movement of cold air. The average winter temperature has increased due to warming, but the northern cold itself has not disappeared. When atmospheric circulation changes in a certain direction, the cold air reaches the Korean Peninsula in late winter or early spring, creating a cold spell.
The photo is from last year, when citizens wore thicker clothing during the inter-seasonal period. This image is intended to help readers understand and has nothing to do with the specific content of the article (This magazine DB/News Penguin)
Path of jet stream and cold air
In the Earth’s atmosphere, there is a strong wind belt flowing from west to east at a height of 10 km in the upper layer. It’s a jet stream. This flow serves as a boundary separating the cold air of the Arctic from the warm air of the mid-latitudes.
If the winter jet stream remains strong, the cold air from the Arctic stays relatively stably in high latitudes. However, when the air current weakens, the flow bends significantly in the north-south direction. At this time, the cold air that stayed in the Arctic or Siberia comes down to the mid-latitudes.
This phenomenon of cold air moving south is called a ‘cold surge’ in meteorology. It is the core mechanism of the East Asian winter cold wave. This phenomenon can also occur in late winter or early spring, and flower spring cold is also created in the same structure.
The change receiving attention in recent climate research is Arctic warming. The Arctic is warming at a much faster rate than the global average. This is called ‘Arctic Amplification’. As the temperature difference between the Arctic and mid-latitudes decreases, there is a possibility that the jet stream flow will weaken and waves will increase.
Some studies suggest that these changes could affect cold wave patterns in mid-latitude regions. However, this hypothesis is still being debated in academia. International climate research estimates that there is still uncertainty about the direct causal relationship between Arctic warming and mid-latitude cold waves.
Changes in cold weather shown by observation data
Looking at long-term observation data, the nature of late winter cold waves is slightly different from the past. The average temperature has steadily risen. It is analyzed that the average winter temperature in most parts of East Asia has increased by 1.5 to 2 degrees Celsius over the past few decades. At the same time, the duration of the chill became shorter. Strong cold spells that used to last for more than a few days now often appear as short events of about a day or two.
However, the cold air inflow itself did not disappear. In some studies, the frequency of cold waves in late winter has decreased, but there have been cases where the intensity has not shown a significant change or has actually become stronger depending on the region. For this reason, climate scientists do not explain the spring cold as a simple decreasing phenomenon. This is interpreted as a phenomenon in which the shape is changing as the average temperature rises.
The earlier spring arrives, the more noticeable the cold becomes.
Another reason why warming makes cold springs more noticeable is the shift of seasons. In recent decades, the start of spring has been moving forward. The blooming time of cherry blossoms on the Korean Peninsula has advanced by more than a week on average. The growth cycle of fruit trees and forest plants is also advancing at a similar pace. This change makes late winter chills appear to occur after the onset of spring, even though they occur around the same time as in the past.
In other words, the drop in temperature, which was still perceived as winter in the past, now occurs after flowers bloom, so people feel it as a stronger spring cold.
In agriculture, spring cold is especially important. Fruit trees suffer great damage even from extremely low temperatures during the flowering period. The fertilization organs of apple or pear flowers can be damaged even if the temperature remains at around minus 2℃ for just a few hours.
According to domestic research data, the flowering time of apples and pears has improved by an average of 7 to 10 days earlier than in the 1980s. On the other hand, the timing of late spring cold weather did not move that quickly. As a result, the risk of the flower blooming period and cold weather actually increasing.
Cold springs that recur throughout the world
Cold spring is not a phenomenon that only occurs on the Korean Peninsula. Spring cold air inflow is repeatedly observed in most mid-latitude regions. In Europe, this is called ‘Spring Cold Spell’. This is a phenomenon in which a sudden drop in temperature occurs as Arctic air moves south in late winter or early spring.
According to an analysis by Copernicus, the European Union’s climate observation program, a cold wave occurred in late spring in central Europe in 2017 and 2021 in April, causing extensive damage to grape and orchard farms. In France and Germany, fruit tree production at that time decreased by 20-30% compared to normal in some areas.
A similar phenomenon occurs in North America. According to data from the National Oceanic and Atmospheric Administration (NOAA), cases of frost have still been observed in the Midwestern United States since April despite average temperatures increasing. In particular, in 2012 and 2020, damage from cold damage was reported in fruit tree and corn growing areas due to the sudden influx of cold air in spring.
The background to this phenomenon is a change in the plant growth cycle. Due to warming, spring flowering in the mid-latitudes of the Northern Hemisphere has been brought forward by an average of 5 to 10 days over the past few decades. However, the timing of late spring frosts did not move that quickly. As a result, the probability that the flowering period and the cold air inflow period overlap has increased.
In climate research, this is explained as ‘Seasonal Mismatch’. As temperatures rise, seasonal changes in ecosystems shift rapidly, but atmospheric circulation and cold air movement patterns change relatively slowly. This speed difference is pointed out as a structural factor that increases the risk of cold damage in spring. As warming progresses, a new climate pattern is emerging in which the frequency of late spring cold waves colliding with the flowering season increases.
Future cold weather predicted by climate models
Long-term forecasting studies using climate models generally suggest similar directions. It is likely that the average global temperature will continue to rise during the 21st century. The average winter temperature is expected to rise further and the overall frequency of cold waves to decrease.
However, it is not likely that the spring cold at the beginning of spring will completely disappear. This is due to the presence of Arctic cold and natural variability in atmospheric circulation. As several factors, such as changes in atmospheric flow and decrease in sea ice, combine, intermittent cold waves may continue to occur. However, in the long term, it is expected that the frequency of occurrence will gradually decrease and the duration will also become shorter.
Some studies suggest the possibility that by the second half of the century, the traditional sense of cold in East Asia, including the Korean Peninsula, will be significantly weaker than it is now. But little research suggests it will disappear completely.
The cold that changes rather than disappears
The conclusions presented by climate science are not simple. Global warming is clearly weakening winter. However, at the same time, the structure of atmospheric circulation is changing and temperature volatility is expanding. As a result, cold air inflows that occur in late winter or early spring are likely to be shorter and more irregular. This means that although it will be warm on average, there may be colder temperatures than expected at certain times.
Rather than a phenomenon that completely disappears, the future of the spring cold is likely to be more of a climate event that becomes increasingly rare but occasionally appears with unexpected intensity. This is why a cold north wind can suddenly blow one spring day even in an age when the earth is warming. This is because the conflicting atmospheric flows between winter and spring have not yet completely disappeared. This spring, cold weather came to the Korean Peninsula without fail.
