A breakdown of normal polar winds in winter raises the chance of extreme cold – and a resulting spike in energy demand – in Europe, new research shows.
Normally, strong and stable westerly winds circle high above the Arctic in the winter, in what is known as the "stratospheric polar vortex".
About once every two years, the vortex temporarily breaks down, in what is called a "sudden stratospheric warming" (SSW) – heating the vortex but causing cold air near Earth's surface to spill south to locations including Europe and North America.
The new study, led by the University of Exeter, found that SSWs raise the chance of extreme electricity demand (defined as at least 20% above average) in northern and central Europe by 1.5-3 times.
Cold weather after SSWs – such as during the 2018 "Beast from the East" – typically arrives a few weeks after the stratospheric polar winds shift, meaning that SSWs can give governments and energy providers a warning to prepare for extreme demand.
"In February 2018, the polar vortex split in two," said Dr Regan Mudhar, now at the University of Lausanne.
"These events don't always affect surface temperatures, but this one was followed by severe cold weather in the UK and much of northern Europe.
"We analysed the relationship between SSWs and extreme electricity demand, driven by demand for heating, and found a clear link.
"Extreme cold weather creates multiple risks – including high energy demand – and our findings can be used to help prepare for future events."
The study found that the change in energy demand differed between nations.
For example, Scandinavian countries – which are largely well adapted to extreme cold – saw a smaller increase in energy usage when temperatures fell.
Meanwhile, France – which has a highly electrified energy system – experienced a much steeper increase in demand.
Dr Hannah Bloomfield, from Newcastle University, added: "The UK is relatively well adapted to cold weather at present due to our reliance on gas central heating.
"However, as we transition to net-zero, a lot of the traditional gas heating must be electrified (i.e. replaced with heat pumps) and then periods of cold weather with low wind will become increasingly challenging to keep the lights on at a low cost to consumers."
Dr Mudhar said: "We are, and will continue to, experience warming driven by greenhouse gas emissions, but SSWs will very likely still happen, bringing cold weather with them.
"This means that, though it is crucial that we continue to cut emissions to mitigate climate change, it's important to consider how prepared we are for extreme events such as these, as we transition toward renewable energy sources."
The study was funded by the Natural Environment Research Council GW4+ Doctoral Training Partnership.
The paper, published in the journal Meteorological Applications, is entitled: "The influence of sudden stratospheric warmings on extreme European electricity demand."
