Why are we still facing extreme cold snaps even as the planet warms to record levels?

Arabia Weather - After a summer full of record-breaking heat, the United States is now facing extreme cold due to a harsh polar surge that brings snowstorms, deadly ice, and strong winds that can be life-threatening.

When cold follows unprecedented heat, it may be fuel for climate change deniers, with some pointing to freezing temperatures as evidence that the true impact of climate change is being exaggerated. However, scientists clearly confirm that cold fluctuations will still occur even if winter temperatures generally increase.

Global heat records exceed cold records - 2023 was the hottest year by a wide margin. Even as the United States struggles to deal with strong flurries of heavy snow now, in the long term, the human-caused climate crisis has led to a worrying trend of declining snow in the Northern Hemisphere.

Some scientists say climate change may even play a role in these ice bursts, as warming in the Arctic increases the possibility that cold Arctic air could sweep south.

What explains the extreme cold?

Our weather is greatly influenced by the jet stream, an undulating river of fast-moving air high in the atmosphere.

When the jet stream swings south, it can push cold Arctic air into North America, Europe and Asia. As it retreats north, it will also push warm air northward. A large high pressure swing over Europe last January led to record warm winter temperatures.

Another factor to consider: the polar vortex, a belt of strong winds that lies high in the stratosphere — above the level of the jet stream — around the North Pole.

The polar vortex is like a rolling torus. In their normal state, they rotate very quickly, trapping significantly cold air in the Arctic region. But they can become turbulent and go off course, stretching and deforming, causing cold air to leak out and impact the jet's path.

How can the polar vortex affect the weather?

The polar vortex is a belt of strong winds surrounding very cold air, which is found high in the stratosphere above the North Pole. The polar vortex is usually stable, keeping the cold air in place. But when disturbed, it becomes less stable and expands, pushing cold air south. This affects the path of the jet stream of air that sits at the bottom of the atmosphere and controls our weather.

It happened in 2021, bringing extreme cold to Texas, killing nearly 250 people and knocking out power in large parts of the state.

This is where the connection between changes in the polar vortex, changes in the jet stream and climate change comes into play. Some scientists believe that polar vortex disturbances and changes in the jet stream are driven by warmth in the North Pole, which is warming up to four times faster than the rest of the planet.

The idea has been gaining traction since a paper published in 2012 by Jennifer Francis, a senior scientist at the Woodwell Climate Research Center in Massachusetts. It was found that as temperatures rise in the Arctic, the difference between cold temperatures in the north and warm temperatures in the south leads to a weakening and greater waviness in the jet stream, which pushes very cold air south.

Her controversial paper marked the beginning of further research in this evolving scientific field.

In 2021, Yehuda Cohen, a climatologist at the Massachusetts Institute of Technology, published research that showed that rapidly rising temperatures in parts of the Arctic, coupled with heavy snowfall in Siberia, are making the jet stream more puffy and throwing the polar vortex off course.

“We're not making an argument that winters are generally getting colder,” Cohen told CNN last year. But the idea that climate change will mean fewer extreme temperature fluctuations is "oversimplifying," he says.

However, this field of science remains largely unsettled, and others have said that the links between rising Arctic temperatures and cold snaps are far from clear.

Although there have been a number of very cold winters in the Northern Hemisphere that have coincided with warm ones in the Arctic, the difficulty is in disentangling cause from effect, according to James Skrein, a professor of climatology at the University of Exeter, whose personal research has concluded that the warming of the Arctic The Northern is not an operator of colder winters.

The extreme temperature drop can be explained by normal, natural changes in climate, according to Skrein. Simply put, even as winter gets hot, there will still be extreme cold conditions.

Climate change can also affect the severity of winter storms, as a warmer atmosphere can hold more moisture, resulting in heavier rain or snow when it falls.

As scientists work to untangle the wealth of complex connections between climate change and extreme cold spells, agreement on one thing is clear: the trend is toward warmer winters.

“If we look at the data, we see that the long shift leads to a decrease in the number of cold extremes and less intensity,” Skrein said.

Source: CNN