‘The North Pole is warmer than much of Europe right now.’
That was a Tweet on Sunday (25.02.18) from lead climate scientist at Berkeley Earth, Robert Rohde.
The big chill or ‘Beast from the East’ that has prompted warnings across the United Kingdom and Ireland is responsible for a deluge of colourful descriptions as climate scientists compete with headline writers to come to terms with the ‘wacky’, ‘unprecedented’ and ‘dramatic’ weather patterns in the Arctic.
So what’s behind the drop in temperature and is it part of a bigger trend that might be consistent with climate change models and predictions?
As a rule, it is unwise to read too much into a single or isolated weather event so the question is whether such events appear to be part of a trend consistent with long-term climate change.
Weather patterns are driven by a relatively stable and dynamic exchange of energy in the Earth’s atmosphere. Surplus warm air travels north from the Equator to the poles where there is an energy deficit.
Cold air also moves from the North to the South poles to warmer parts.
What has been described as a ‘Sudden Stratospheric Event’ interrupted the relative stability of this mass of swirling winds in the Arctic – the ‘Polar Vortex’ – that is usually held in balance by temperature differences between the Arctic and the Equator.
As the North Pole has warmed, the Vortex has become less stable.
It is the recent perturbation or splitting of the Polar Vortex that lies behind the current trend with two streams of cold air sent south, one towards the US and the other across Europe.
This stream of frigid air across much of Europe has occurred while anomalous temperatures, amounting to a relative heat wave (up to 1.7 to 4.4 Celsius), have been recorded at the Arctic during a month of complete darkness.
What’s more, these ‘Sudden Stratospheric Events’ are becoming more common.
The New Normal?
Scientists have observed a constant loss of sea ice in both the Arctic and Antarctic since the early 1970s and it is estimated that the Arctic will be free of ice by the middle of the century if not sooner if current trends continued. This is due to global warming.
When climate changes scientists attempt to model these patterns over time they have predicted the kind of anomalies we are currently witnessing. In fact, some researchers (Cohen et al 2015) have given the effect a name: the ‘warm Arctic, cold continents’.
The idea behind the hypothesis is that as global warming reduces Arctic Ocean sea ice and in turn exposes warmer water that releases heat into the atmosphere, atmospheric patterns like the polar vortex will change. That would cause cold Arctic air masses to shoot southward, letting the air up north become relatively hotter.
While the Polar Vortex splitting event is not unprecedented (A similar pattern was observed in 2012/2013), there are concerns about recent observations that lie outside historical ranges.
Climate change is most probably happening before our eyes.