When Patagonia was hit by a wave of unusual, extreme weather, it measured temperatures as low as -15°Celsius (5° Fahrenheit). It is winter in the Southern Hemisphere, but those temperatures were beyond normal.

Ducks froze to death in ponds. Sheep were stuck in piles of snow. And military personnel transported food to affected areas for people and livestock.

"This is an unusual phenomenon," said Raúl Cordero, a climatologist at the University of Santiago de Chile. But he added it was not the first of the season and "may not be the last."

What's the origin of the extreme cold in Patagonia?

The low temperatures in Patagonia and the Southern Cone of Latin America (Argentina, Chile, Uruguay, Paraguay and southern Brazil) are due to the arrival of cold air from Antarctica.

High pressure at the southern tip of the continent pulled polar air northwards. That happens when the polar vortex — a belt of strong winds that keeps cold air over the South Pole — is weak.

"The unusual weakness of the Antarctic polar vortex increases the likelihood of polar air masses escaping to inhabited areas in the southern hemisphere. In other words, the likelihood of cold waves increases," said Cordero.

The cold wave [Ed.: the opposite of a "heat wave"] of July 2024 was the second time in three months that that had happened in the region.

What are the implications for global temperatures?

Cordero said the cold snaps in Patagonia are unlikely to affect the global climate. Rather, he said, it would be the other way around: It will be changes in the global climate that contributed to a weak Antarctic polar vortex, resulting in the cold waves in the Latin America's Southern Cone.

"While these low temperatures were recorded in populated areas of the Southern Cone, the highest temperatures ever observed were recorded in the upper Antarctic atmosphere," said Cordero.

Australia and New Zealand were also likely to be affected by extreme cold snaps, he said. And, indeed, a weather station in Queensland, Australia, recorded the coldest night in 120 years on July 18, 2024.

But the researcher said the cold wave could have a small positive impact at a more local level.

Patagonia's icefields cover more than 10,000 square kilometers (3861 square miles) on the border between Chile and Argentina. They "lose on average between 10 billion and 15 billion tons of ice every year. Although recent cold spells will not change this trend, they may at least make this year's balance less negative," said Cordero.

Is climate change behind the extreme cold?

Some research focused on the Northern Hemisphere indicates that such cold waves may be due to climate change.

A 2012 study by the Woodwell Climate Research Center in Massachusetts, US, suggested that accelerated Arctic warming had affected air streams that controlled the climate. That would increase the likelihood of extreme events in mid-latitudes, causing or contributing to droughts, floods, cold and heat waves.

Another study published by researchers at the Massachusetts Institute of Technology (MIT) in 2021 suggested that Arctic warming had contributed to the frequency of severe winters in the US.

The researchers found that changes in the Arctic could change the stratospheric polar vortex, causing very cold air to move southward, leading to extreme cold waves.

Cold waves and climate change: Not enough scientific proof

This evidence is a matter of debate, however, and part of the scientific community disagrees.

"I don't think Arctic warming has a big role in the cold extremes over midlatitudes. Our work has shown these are likely explained by natural variability and have occurred despite, rather than because of, global warming," said James Screen, Professor of Climatology at the University of Exeter, and contributor to the United Nations' Intergovernmental Panel on Climate Change (IPCC).

Experts agree that such winters will become less and less common on the planet if CO2 in the atmosphere continues to rise.

"In most parts of the world, the warming effects of climate change will exceed any potential cooling effect from shifting weather patterns due to Arctic warming," said Screen.

Cordero agrees that "[these] cold waves will not change the warming trend in Patagonia, which is as evident as in the rest of the world."

Extreme cold does not counter global heating

Despite a scientific consensus on global heating, such cold episodes have been used by climate deniers to defend their positions.

"[They] are confusing short-term variations in weather with long-term variations in climate," said Screen. "A single cold extreme is a weather phenomenon."

But when we look at how cold extremes have changed over multiple decades, he said, they have become less frequent and less severe globally.

"Global warming is an upward trend in the average global temperature. A few cold snaps, however extreme, are not going to change this trend," said Cordero. 

Edited by: Zulfikar Abbany

Sources:

Evidence linking Arctic amplification to extreme weather in mid-latitudes; published by Jennifer A. Francis, Stephen J. Vavrus in the journal Geophysical Research Letters (March 2012) https://doi.org/10.1029/2012GL051000

Linking Arctic variability and change with extreme winter weather in the United States; published by Judah Cohen et al. in the journal Science (September 2021) https://www.science.org/doi/10.1126/science.abi9167