Love it or hate it, winter weather has swept across Germany in the past week, with some parts of the country seeing up to 80 centimetres of snow. For climate change deniers, this chilly spell seems like ample evidence that the planet is not heating up - but scientists actually think that climate change will mean that these dramatic cold snaps could become a more regular occurrence in future. Here's why. 

What is the polar vortex?

The polar vortex is a huge ring of winds that surround both the North and South Poles in their respective winter seasons. These winds sit high above the surface of the Earth (between 10 and 50 kilometres), in the part of the atmosphere known as the stratosphere. 

The polar vortex itself does not cause wintry spells of weather, but if the vortex becomes disturbed in any way, it can start a chain of events that can lead to cold snaps and heavy snow, as cold air moves away from the pole to adjacent continents. This type of disturbance in the polar vortex is precisely what has caused the recent harsh weather in Germany. 

Instability of the polar vortex may become more frequent

According to research undertaken by the Potsdam Institute for Climate Impact Research (PIK), the number of days where the polar vortex has been unstable has increased significantly over recent decades. This is most likely because the Arctic is heating at a much faster rate than the rest of the world - according to the PIK, temperatures in the Arctic have risen more than twice as fast as the global average over the past 40 years. 

Dörthe Handorf, from the Alfred Wegener Institute at the Helmholtz Centre for Polar and Marine Research, says that this rapid rise in temperatures, which is especially strong in winter, weakens the jet stream, and thereby contributes to the instability of the polar vortex. Researchers therefore assume that extreme-cold weather events will become more frequent in the coming years as Earth continues to warm. 

The effects of global warming can therefore not only be seen through warmer weather and higher temperatures, but also through an increase in the number of extreme weather events.