In the US, it is so cold that President Donald Trump to want already the of him-denied global warming. Minus 34 degrees Celsius and less are expected in the Midwest for the next few days. The National weather service (NWS) also warns against “life-threatening, Arctic winds”. Some States have declared the case of a disaster.

The Situation is reminiscent of the January 2014, than in the North of the USA, temperatures up to 50 degrees below zero put the public life in Parts of lame. And in fact, both events have the same cause. The warning about the Arctic cold is taken literally.

In the United States has set in the meantime, the term “Polar Vortex” as a term for the weather phenomenon that in previous decades was, by – and named after its decisive cause: the polar vortex.

If the Jetstream is weakening

actually, it is in the Northern hemisphere, two superimposed polar vortex. The lower is also known as the Jetstream. It is the strongest naturally occurring winds. You blow the whole year round in about a height of ten kilometres from West to East and global temperature differences and High and low pressure areas driven.

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Far above this air flow – in of about 50 kilometers altitude – the polar vortex, the people in the United States in connection with the extremely related to the cold. This is an area of low pressure that forms in Winter over the North pole, and as the Jetstream counter-clockwise moves.

the Jetstream is a powerful, circling the cold polar air to the North pole, such as a graphic of the American Ocean Agency NOAA shows. It separates the cold air at the North pole from the warmer air in the South. The jet stream is weaker – for example, because the temperature differences between the Arctic and the Equator are lower than usual – fray its orbit.

The meandering currents of air can then also bring in the higher-altitude polar vortex. To circles instead of closely around the North pole, spreads out the ice-cold air to the South. One of these cold air streams reached the United States, the Wind ensures that the already cold temperatures feel on the skin, even colder – from felt to minus 45 degrees Celsius.

Video: cold wave makes for mass accidents

REUTERS/Jason Coffelt

to expect to have the place colder, another warmer

In Europe is due to the Arctic cold in the United States, by contrast, no unusually cold weather or even warmer weather. This is due to the fact that cold air hits on the way to Europe on your way over the North sea and the North sea to the warm Gulf stream and the tempering temperature.

on The other hand – and this is in the current case, critical – blows the same mechanism that drives the time, the cold air in the USA, at the same time, warm air from the tropics towards the North. So, while just in the Middle West of the United States, the temperatures are in the double digit minus range, they move elsewhere over the long-term average.

suggests Otherwise as a Trump in a Tweet, is good for the extreme cold, thus not as a proof that there is global warming. On the contrary: scientists discuss whether a weak Jetstream is even due to this and Arctic cold in the USA could be in the coming years, more and more often.