Here’s how climate change is affecting cold weather in SC – The Post and Courier

When you monkey around with Earth’s climate, things are going to get weird.

At least that’s how Judah Cohen summed up the winter storm that blasted the South last week.

The system plunged much of South Carolina into snow, ice and frigid-hot temperatures for the planet’s warmest year since at least the mid-19th century. It may seem counterintuitive, but the Palmetto State’s first snowfall of 2018. it may actually be a result of these warmer climates.

“I think our view of climate change has been oversimplified,” said Cohen, a climatologist at the Massachusetts Institute of Technology. “It was kind of this monotonic trend: The Earth is getting warmer, which will lead to less cold.”

So how could an overall warmer world and a hotter Arctic Circle lead to heavier snowfall in South Carolina?

The answer (or rather the hypothesis) is complex, shrouded in much uncertainty, and the subject of ongoing debate among climatologists and the wider scientific community. But a growing body of evidence suggests that as the Arctic warms and Arctic ice melts, it causes the polar jet stream to stretch and become “more permanent.”

The system is fueled by the temperature difference between the Arctic and lower latitudes. But as the Arctic Circle warms, it creates ideal conditions for the jet stream to stretch north and south.

“It’s a lot like a spinning table top,” explained Steve Vavrus, assistant director of the Center for Climate Research at the University of Wisconsin-Madison. “If it’s spinning really, really fast, it’s pretty straight up and down. The coupling is limited. But once the top starts to slow down, it wobbles and meanders. It’s analogous to what might happen with a jet flow as the winds weaken.

This Wavier Jet Stream could then plunge further into South Carolina, bringing with it cold pockets of air that could increase the likelihood of frigid temperatures and snowfall.

“When the winds weaken and the jet stream becomes more permanent, it basically allows the freezer door to open and allows polar air to dip into the southern latitudes, as we saw last week,” Vavrus said. “With the jet stream’s weaker winds getting more waves, it allows a more southerly penetration of this really cold air into places like the Gulf Coast. That’s basically what the hypothesis is.”

He added that there are many other factors that can affect high-altitude wind systems. El Niño can contribute to a stronger jet stream by keeping polar weather locked to the north. La Niña, which just arrived earlier this month, favors the Wavier Jet Stream, which allows it to dip south.

Last year was the hottest on Earth in the 175-year record, according to NOAA and NASA. The Arctic will remain dark and cold for decades, said Jennifer Francis, a senior scientist at the Woodwell Climate Research Center. So these cold weather incursions are likely to continue for a while. But how often will they happen? That remains to be seen.

“It’s certainly counterintuitive to say longer cold spells that affect southern states may happen more frequently as the globe continues to warm. But that’s just one of the ways our weather patterns are becoming more -strange and less like those before we started dumping heat, trapping gases into the atmosphere,” Francis wrote in an email. “Unusual jet stream patterns and crazy weather will only get worse unless we drastically reduce our burning of fossil fuels and stop destroying forests and wetlands—the Earth’s best natural sinks of carbon from the atmosphere.”