Why is the US so cold hearted

Weather : What the cold in the USA has to do with the mild winter in Europe

In the US, chilblains are a real threat right now. In contrast, the winter in Europe remains mild for the time being, but not harmless everywhere. In Great Britain, whole areas of land are still under water. During the entire Christmas break, one flood warning followed the next. Meanwhile, heat records are being broken in South America and Australia. The causes of these weather extremes are, however, very different.

Marcus Beyer from the German Meteorological Service explains the cold spell in the USA as follows: “In the west a high pressure area has established itself, in the east there is a low. And in between, the cold Arctic air can penetrate to the Mexican border. ”The temperatures in parts of the USA have dropped to values ​​between minus 15 and 35 degrees Celsius. Warm air masses therefore dominate the picture in northern Canada and Alaska, while Chicago and other cities in the American Midwest currently feel like the North Pole. Europe, on the other hand, experiences a similar weather situation as the western USA. Here, too, it is currently too mild for the time of year.

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It's about the distribution of warm and cold air through the jet stream

According to Beyer, one of the reasons for this is that the sea is warmer than the air. Over the Atlantic, even the cold air from the north is warmed before it flows into Europe. This is not possible in the USA because the large land masses there prevent this effect. There is no sea there to warm the arctic air.

The distribution of warm and cold air follows the so-called jet stream, an air flow that constantly blows along the northern hemisphere. However, the current does not move in a straight line from west to east, but in sometimes smaller and larger wave movements. The waves are particularly big at the moment.

The southern hemisphere is also currently awaiting extreme weather conditions

The Arctic air masses, which currently have large parts of the USA under control, will continue to move eastwards, according to Beyer. Then it would be bitterly cold on the American east coast. In addition, the temperature differences over the Atlantic continued to intensify. In Europe, more severe storms of up to hurricane strength can be expected. The coasts of Great Britain in particular have been suffering from this for weeks. Not only heavy rains, but also stormy winds have further exacerbated the flooding along the coast. Giant waves hit the south coast of Great Britain on Monday. The local weather service issued new flood warnings.

Completely independent of the weather in the northern hemisphere, the southern hemisphere offers extreme weather conditions. In Australia, there was a heat wave throughout the north over Christmas with temperatures of up to 40 degrees Celsius, which is considered to be unusual in its extent. Temperatures have also risen sharply in South America. In both regions, tropical air masses seem to determine the weather. What is certain, however, is that the heat in the south is not the result of an El Nino event. Neither the Australian nor the American weather service see any signs of an El Nino, in which the water masses of the Pacific are warmer. An El Nino could affect the weather worldwide. But there hasn't been an El Nino since mid-2012. In contrast, the opposite phenomenon, La Nina, has been observed several times since then.

None of the current weather extremes can be directly linked to climate change. However, the current weather extremes are in line with the developments that can be or will be expected as global warming advances. Both heat waves are becoming more frequent, as are other extreme weather conditions. Even if the current weather phenomena in the north and south may not be a consequence of climate change, they do show what coastal regions in particular need to prepare for. Sir David King, chief climate advisor to the British Foreign Secretary, says: "We have to prepare for more extreme weather conditions."

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