The northern polar jet stream (it has a counterpart in the Southern Hemisphere) is driven partly by the temperature contrast between masses of icy air over the North Pole and warmer air near the equator. Climate change, true to the predictions of the past half century, has led to faster warming in the Arctic than in the temperate zones. So the temperature difference between the two regions has been lessening.
Research suggests that this reduction in the temperature difference is robbing the jet stream of some of its strength, making it wobblier and contributing to more temperature extremes.
What’s the jet stream’s role in extreme weather?
The jet stream is strongest in winter, when it has the greatest effect on weather in more densely populated parts of North America and Eurasia.
When it rolls along in relatively steady waves, normal weather ensues, with spells of cold, snow and intermittent warm-ups.
But when it coils far to the south, bitter cold Arctic air spills southward along with it.
The Polar Vortex Explained
Wriggling like a garden hose, each southward kink in the wind tends to be balanced out by a northward bend somewhere else. That can lead to the western states, even Alaska, being unusually warm and dry while the middle of the country and the eastern states freeze.
How is the jet stream changing?
Research shows that over the past several decades, the jet stream has weakened. There’s also evidence that as it wobbles, it can get stuck out of kilter, which can lead to more persistent weather extremes, including heat waves, cold snaps, droughts and flooding.
Scientists say there is strong evidence that human-caused global warming has altered the strength and path of the powerful winds.
Dan Gearino’s habit-forming weekly take on how to understand the energy transformation reshaping our world.
on Twitter: "Let’s put millions of us back to work in climate and care jobs while advancing racial and social justice.
