Rising Arctic temps are changing the jet stream, drawing cold air further south, showing climate change can drive extreme weather in unexpected ways.

Melting sea ice and warmer temperatures in the Arctic are to blame for the brutal cold snaps that have plagued parts of Asia and North America in recent years, according to new research by Korean and European scientists released Monday.

The study, published in the peer-reviewed journal Nature Geoscience, adds to the growing evidence linking rising Arctic temperatures to changing weather patterns across the globe. It also helps further debunk one of climate deniers’ favorite arguments: cold weather proves the world isn’t warming from the buildup of greenhouse gases in the atmosphere.

Deniers reveled in their theory last winter as a record-breaking 110.6 inches of snow fell on Boston and temperatures as low as minus-35 degrees Fahrenheit chilled wide swaths of the Central Plains and Northeast. Republican Oklahoma Senator Jim Inhofe famously brought a snowball onto the Senate floor to “prove” his point and Republican Presidential frontrunner and businessman Donald Trump tweeted in February, “Record low temperatures and massive amounts of snow. Where the hell is GLOBAL WARMING?”

“This research blasts enormous holes in that argument, if the deniers choose to pay attention to these findings,” said Jennifer Francis, a climate scientist at Rutgers University in New Jersey who was not involved in the research.

The concept seems contradictory at first, warmer temperatures in one place causing cold winters in another. But the paper finds that a hotter, less icy Arctic—a region that has warmed twice as fast as the rest of the world over the last two decades—creates a bulge of warm air in the lower atmosphere that forces the jet stream to become wavier, dipping farther south in some places and peaking farther north in others as it moves eastward around the globe. As it dips south into latitudes lower than it used to, it carries with it cold Arctic air.

Climate scientist and lead author of the paper Jong-Seong Kug of Pohang University in Korea and his colleagues found that warming north of western Russia creates colder winters in central Asia and warming north of western Alaska creates colder winters in eastern and central North America.

The scientists triple-checked their findings using temperature and weather data from recent decades, jet stream simulation experiments and global climate models. Kug and his colleagues did not respond to requests for comment.

Francis, who has studied the warming Arctic’s impact on the jet stream, said the study could help forecasters and disaster preparedness officials understand what kind of weather to expect in different parts of the world.

“The results of this study also tell us that the year-to-year differences in the location of greatest ice loss and warming can help predict—and prepare for—severe winters in heavily populated mid-latitude regions,” she said.

However, she also acknowledged that this year’s El Nino and extremely warm ocean temperatures in the Pacific Ocean could interfere with the warming Arctic-cold weather link this winter.

“We’re in uncharted territory,” Francis said. “We don’t have a roadmap for the weather patterns that will occur in these conditions, but it’s safe to predict that ‘unusual’ will be a word that gets plenty of use.”