The past week has seen some brutal weather hitting the US and Canada. With cold Arctic air plunging south down to the US midwest, six states have seen temperatures lower than the south pole and at least eight people have died due to the extreme cold.
The UK, too, is braced for snow this week, but nothing close to the scale seen in the US.
The very cold weather prompted President Trump to tweet: “What the hell is going on with Global Waming? [sic].” This followed an earlier tweet that it “wouldn’t be bad to have a little of that good old fashioned Global Warming right now!”
Trump’s comments received widespread derision from scientists and the media, with many articles pointing out that Trump is confusing short-term weather events with long-term climate, and that extreme cold weather still occurs in a warming world.
The cold, snowy weather has also been accompanied by a flurry of stories about the “polar vortex” and how it can bring extreme weather to the northern hemisphere mid-latitude regions of North America, Europe and Asia. But that is not the only way that the Arctic can affect conditions further south.
Over the past decade or so, a growing body of research has proposed ways in which rapid Arctic warming can lead to harsh winters, summer heatwaves and even floods and droughts across the mid-latitudes.
Some scientists say that climate change and Arctic sea ice loss are the root cause of these events, but others are more circumspect.
In this detailed Q&A, Carbon Brief speaks to scientists about the potential connections between Arctic warming and extreme weather across the mid-latitudes, what those theories look like, and how the evidence measures up.
What is the theory?