Why are there periods of intense cold even when the world is experiencing record-breaking warm weather?

Scientists say that severe cold spells will still occur even when winters are generally warm.

Residents clear snow after a snowstorm on January 9 in Iowa, USA. Photo: Cody Scanlan/The Register/USA Today Network — Residents clear snow after a snowstorm on January 9 in Iowa, USA. Photo: *Cody Scanlan/The Register/USA Today Network*

After a record-breaking hot summer, many parts of the U.S. are once again grappling with blizzards, freezing temperatures, and life-threatening cold winds, CNN reported on January 15. However, this is no reason to deny the effects of climate change and global warming.

2023 was the hottest year on record, with the global average temperature reaching 14.98 degrees Celsius, nearly 1.4 degrees Celsius higher than pre-industrial levels. In the long term, the human-induced climate crisis is leading to an alarming trend: the disappearance of snow in the Northern Hemisphere. Some scientists even suggest that climate change may be contributing to cold spells in the US, as warming in the Arctic increases the risk of frigid polar air spreading southward.

Weather is heavily influenced by jet streams – fast-moving air currents high in the atmosphere. As the jet stream moves south, it can push cold Arctic air down into North America, Europe, and Asia. As the jet stream recedes north, warmer air also moves further north. Last January, Europe experienced a record-breaking warm winter.

Another factor to consider is the polar vortex—a belt of strong winds at high altitudes in the stratosphere—higher than the jet stream—around the Arctic. The polar vortex is like a spinning top. In its normal state, it spins very quickly, "trapping" cold air in the Arctic region. But it can be disrupted and deflected, becoming distorted, causing cold air to escape and affecting the path of the jet stream. This happened in 2021, causing Texas to experience a severe cold snap that killed nearly 250 people and left much of the state without power.

The connection to climate change also lies here. Some scientists believe that the disruption of the polar vortex and changes in jet streams are being driven by warming in the Arctic. This region is warming about four times faster than the rest of the planet.

However, some other scientists argue that the link between Arctic warming and cold spells remains unclear. There have been many instances where very cold winters in the Northern Hemisphere coincided with warm winters in the Arctic, but the difficulty lies in separating cause from effect, according to James Screen, a professor of climate science at the University of Exeter.

Screen suggests that these severe cold spells may simply be due to normal climate fluctuations. In other words, even when winters are warmer, severe cold spells will still occur.

Climate change could also affect the severity of winter storms, as a warmer atmosphere will retain more moisture, leading to more intense rain or snowfall.

Scientists are still working to unravel the complex link between climate change and extreme cold spells, but they all agree that the current trend is warmer winters. "If you look at the data, we see that in the long term, global warming is causing cold spells to occur less frequently and become less severe," Screen stated.

Thu Thao (According to CNN )

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