What’s behind South America’s balmy winter?

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Balmy temperatures of 77 degrees Fahrenheit would not be out of place on a nice, spring day in Santiago, Chile’s capital city. The problem is, it’s currently winter in South America.

Chile, its neighbor Argentina and parts of Uruguay are in the grips of an unusual winter heat wave this week, with temperatures across the region soaring into the 80s and 90s F. Conditions in Vicuña, a mountain town in the Chilean Andes, even topped 100 F this week — far above average high temperatures for this time of year.

“Tuesday was the warmest day in northern Chile in about 72 years, so that gives you an idea of how rare and extreme temperatures in recent days have been,” said Raúl Cordero, a climatologist at the University of Santiago.

South America’s mild conditions add to what has already been a brutal summer for much of the Northern Hemisphere. The planet had its hottest June on record and preliminary observations suggest that July could have been the hottest month ever recorded.

High temperatures in Santiago reached 75 F on Wednesday, while several cities in Uruguay hit 86 F.

A day earlier in Buenos Aires, where average August temperatures range from around 50 to 64 F, the city recorded temperatures over 86 F. Argentina’s National Meteorological Service said it was the warmest start to August since record-keeping began 117 years ago.

Cordero said that, like elsewhere in the world, extreme heat events in South America are exacerbated by climate change. He said heat waves have become four times more likely to occur in parts of Chile in recent decades, adding that what’s unfolding this week is a good example of the types of extreme events that will occur more commonly in a warming world.

“We are having these types of warm episodes more frequently, but they are also more intense heat waves,” he said.

This year, however, El Niño conditions are driving anomalies on top of background global warming.

El Niño is a naturally occurring climate pattern characterized by warmer-than usual waters in the central and eastern tropical Pacific Ocean. These events, which happen on irregular cycles that can last up to seven years, have far-ranging effects on global temperatures, rainfall, hurricanes and other extreme weather systems.

As such, El Niño can compound the effects of human-caused climate change, pushing air and sea temperatures even higher.

“This combination of climate change and El Nino is causing record-breaking temperatures all around the world, not only in the Northern Hemisphere, but also here in South America,” Cordero said.

The winter heat wave is expected to linger into the weekend, with some of the most extreme temperatures expected in the Andes region.

Cordero said the lengthy warm spell is particularly concerning in the Andes, where high temperatures are melting snow in the mountains far earlier than normal. This will likely affect the availability of freshwater in the spring, he said, but added that other consequences of the winter heat wave may not be fully felt for months to come.

Drier and warmer conditions could, for instance, make Chile and other parts of South America particularly vulnerable to wildfires in the coming summer.

“When it’s 25 degrees [Celsius, or 77 F], it feels nice because it’s like spring, but people are unable to see the problems associated with these wintertime heat waves,” Cordero said. “Most people right now are not feeling pain. But unfortunately we’ll see these bombs explode in the dry season.”

This article was originally published on NBCNews.com



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