Research findings indicate that due to global warming, heatwaves and droughts are frequently occurring simultaneously across Eurasia, from Eastern Europe to East Asia.
An international research team led by Jeong Ji-hoon of Sejong University noted on the 3rd that "human-induced global warming is creating a new atmospheric circulation pattern that exacerbates heatwaves and droughts across the Eurasian continent." The research results were published in the international journal Science Advances on the same day.
Since the 1980s, summer heatwaves and droughts have frequently occurred on the Eurasian continent, and their intensity has also significantly increased. The researchers aimed to find the reasons why, in the last 20 years, these two phenomena have often appeared in the same regions, while previously they occurred separately in different areas.
Previously, the cause was found in a broad change in atmospheric flows, known as "global teleconnection." This refers to the phenomenon in which weather or climate changes in one area of the earth affect the climate of another area thousands of kilometers away.
This study revealed that a type of global teleconnection pattern known as the "Eurasian cross-heatwave-drought wave train (TEHD)" plays a key role in the heatwaves and droughts in Eurasia. TEHD is a class of atmospheric waves that connects high pressure starting from Europe and Russia through Central Asia to East Asia.
This atmospheric pattern is closely linked to rising sea surface temperatures in the North Atlantic and increased precipitation in the African Sahel region. When warming raises North Atlantic sea temperatures, strong air flows occur in the upper atmosphere. If there is significant rainfall in the African Sahel region, it supplies heat to the upper atmosphere, further stimulating the atmospheric wave. When a liquid absorbs heat, it evaporates into gas, while conversely, when gas (water vapor) transitions back into liquid (rain), it releases heat.
When rising sea temperatures and increased precipitation overlap, atmospheric flows are stimulated, strengthening the high pressure in Eurasia, which leads to heatwaves and evaporates moisture from the ground, causing serious droughts to occur simultaneously with the heatwaves. High pressure traps hot air, preventing heat from escaping, which intensifies both the heat and drought.
The research team conducted a comprehensive analysis of tree ring data collected from 33 locations across Eurasia over 300 years to examine changes in the TEHD pattern. Tree rings reflect how much a tree has grown each year, serving as a "natural record" of the climate conditions during that time.
The analysis revealed that the intensity of the TEHD pattern in recent decades has been the strongest in the past 300 years. Particularly, it has been strongest since 2010. The major heatwave in Russia in 2010 and the drought in East Asia in 2022 occurred during years when the TEHD pattern was extremely intense.
Predictions made with the latest climate models indicate that if carbon emissions continue at the current rate, the TEHD will likely intensify throughout the 21st century. This means that both the frequency and intensity of heatwaves and droughts are expected to rise. In contrast, the patterns of global circulation teleconnection show no significant changes or have even weakened.
The Eurasian region is one of the world's major grain-producing areas. Extreme heatwaves and droughts in this area could impact the global food supply chain. Additionally, water shortages due to drought could severely affect not only humans but also natural ecosystems.
The research team stated, "Climate change could cause various issues such as wildfires, reduced agricultural production, threats to food security, water shortages, and ecological destruction," adding that "the risks are increasing and much more proactive responses are needed to mitigate them."
References
Science Advances (2025), DOI: https://doi.org/10.1126/sciadv.adr7320