Warming of the Arctic caused by climate change has increased the number of polar vortex outbreaks, when frigid air from the far north bathes other parts of the Northern Hemisphere in killer cold, according to AP via Eye on the Arctic.

A study published this week in the journal Science is the first to show the connections between changes in the polar region and February’s Valentine’s Week freeze that triggered widespread power outages in Texas, killing more than 170 people and causing at least $20 billion US in damage. Extremely cold temperatures also hit much of Canada that month.

The polar vortex normally keeps icy air trapped in the Arctic. But warmer air weakens the vortex, allowing it to stretch and wander south. The number of times it has weakened per year has more than doubled since the early 1980s, said study lead author Judah Cohen, a winter storm expert for Atmospheric Environmental Research, a commercial firm outside of Boston.

Cohen’s study is the first to use measurements of changes in the atmosphere to help explain a phenomenon that climate models had struggled to account for.