What’s with the extreme weather?

February 13, 2014
  • Thames Barrier operated 29 times since December
  • River Thames at high levels for longer than any time since 1883
  • US: Blizzards in the south, drought in the west and warm weather record in the north
  • What causes the extreme weather in the northern hemisphere? Jonathan Meagher from Allianz Re explains

The number is “29.” That’s only one of the many records set this winter, a season that is moving towards becoming the stormiest and wettest in the UK in 250 years.

“At the moment the Thames Barrier has been operated 29 times since the beginning of December 2013,” said Toby Willison in an interview with CNN Europe. The importance of this number became clearer when the regional director or the UK environment agency added that since its completion in 1982, the flood barrier has only been used 154 times.

Storms have been battering Britain for weeks. Especially hard hit are the southwest regions of England and Wales. Coastlines are suffering from landslides and floods; high rainfall from the storms is starting to have a cumulative effect. Inland rivers are bursting their banks, while some areas have been flooded for almost a month. Railways are underwater and around 1000 homes have been evacuated along the flood-hit Thames valley, reports The Guardian. In fact, the river Thames has been at exceptionally high levels for longer than any time since 1883. Even London is threatened: its protector, the Thames Barrier, is now powerless before the new flood waters because the direction of the threat has shifted; this time it is flowing downstream.

On the other side of the Atlantic winter has put on a powerful display as well. Instead of rain, the country has been buried under ice and snow. For weeks, winter has held North America in the freezing grip of a polar vortex. Yet even as “catastrophic” and unprecedented blizzard and artic conditions besiege the south and the governors of Georgia and Louisiana have declared states of emergency, California is suffering a record drought as a result of the cold air pool.

Meanwhile, the arctic region of Alaska has enjoyed warmer weather with areas from Nome to Seward recording temperatures up 68 degrees fahrenheit (20 degrees C) above average. Records have been smashed, roads buried under landslides and plants turned green in a spell of warm weather rarely seen before

What makes this winter in northern hemisphere so exceptional? “The two patterns of extreme weather in the UK and the east coast of the US are linked by shifts in the polar jet stream,” explains atmospheric scientist Jonathan Meagher who works as a senior analyst for Allianz Re.

“The deflection of the jet over North America has caused record low temperatures as far south as Texas and Florida. This in turn has supplied the energy for the series of strong storms over the North Atlantic that have impacted the UK over the winter.”

It is not only the United Kingdom that has been hit; at times much of the continental European coastline was affected. Further east, over the Mediterranean Sea, low pressure systems developed and pressed moist air against the Alps resulting in major floods in Italy, record snow levels in the mountains and freezing rain that paralyzed Slovenia.

The losses are only slowly becoming visible. In North America “the impact of cold weather and snowfall was most evident in travel delays, power outages, and general disruption to economic output. Initial estimate has put the cost at $5 billon,” says Meagher.

As for the UK, so far there have been no large insured losses reported yet. “However, if this weather pattern continues, river levels are likely to also increase and with that the likelihood of a major flood event,” said Meagher on a day (Feb. 12th) that the Met office later upgraded the UK weather warning again.

While winter weather is devastating large parts of the northern hemisphere, on the other side of the world Australia is again facing record heat waves. In what has become almost an annual event, massive bush fires are threatening the fringes of another major city, Melbourne this time. In fact, 2013 was the hottest year since records began in 1910.

‘‘These record high temperatures for Australia in 2013 cannot be explained by natural variability alone," David Karoly, a scientist at the University of Melbourne, told The Sydney Morning Herald. "This event could not have happened without increasing greenhouse gases, without climate change."

Michael Grimm, Greg Langley

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