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In the summer of 2024, the Northern Hemisphere recorded the highest temperatures ever recorded, with extreme weather conditions affecting large parts of the planet. In the United States, exceptional heat waves characterized almost every day, while in Europe, the 2024 Olympic Games were held in full heat emergency, during one of the longest heat waves ever recorded. Between July 21 and 23, the planet experienced the three hottest days ever measured, while August 2024 marked the record as the hottest month in the last 175 years, according to the NOAA (National Oceanic and Atmospheric Administration).
The average global temperature this summer exceeded the 20th century average by 1.52°C. Although this increase may seem modest, climate change causes variations that are not distributed uniformly, with effects that accentuate the frequency and intensity of extreme weather events, such as the heat waves observed in 2024.
One of the phenomena most frequently associated with these persistent waves is the “heat dome“. This particular atmospheric pattern, in combination with the changes to the jet streamplays a crucial role in determining the severity of heat waves, which are now influenced by climate change.
What is a heat dome and its connection to the jet stream?
During the summer of 2024, many meteorologists stressed the relevance of the “heat domes“. These occur when a high pressure system settles over a large area and stays there for a long time. The air, under the influence of this system, tends to descend, further warming and lowering the humidity. This creates a sunny and dry climate, while the high pressure system acts as a “cover“, preventing the dispersion of heat accumulated at ground level. The longer a heat dome persists, the higher the temperatures become, making the environment almost unbearable.
The persistence of these phenomena is closely related to the behavior of the jet stream, a band of intense winds located approximately 10 kilometers of altitudeThis flow moves from west to east, determined by the Earth’s rotation and the temperature differences between the warm and cold air masses of the mid-latitudes.
The jet stream does not follow a straight path, but undulates, creating large fluctuations, known as Rossby waveswhich significantly influence the weather. When the jet stream moves north, it favors the formation of high pressure; when it bends south, instead, it promotes low pressure, with unstable conditions and rain.
The Role of Climate Change on the Jet Stream
Temperature differences between regions of the planet affect the strength of the jet stream. However, the Arctic is warming much faster than other areas, a phenomenon known as Arctic amplification. This reduces the temperature difference between the Arctic and the tropics, slowing the jet stream. As the jet stream slows, its path becomes more wavy, allowing for larger, more persistent waves. These conditions can block high-pressure systems, creating prolonged heat domes that intensify heat waves, such as those experienced in 2024 in several parts of the world.
Winter impacts and future prospects
This anomalous behavior of the jet stream It does not only concern the summer, but also has repercussions on the winters. More pronounced waves can push polar air southwardsleading to extreme cold and winter storms. The consequences of these climate changes are significant and long-lasting. More frequent and intense heat waves, harsh winters and greater weather unpredictability are just some of the effects that will continue to shape the global climate in the coming years, with important implications for human health and well-being.
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