British summer’s endless rain flows from the Arctic’s melting ice
Britain’s dismal weather could be a direct consequence of the melting of the Arctic sea-ice, according to research.
This year has been the latest in a series of wet summers and may prove to be the worst yet. New rainfall records for April and June have already been set, and if recent conditions continue the record for rain over the course of a whole summer could also be broken.
As the sixth consecutive damp summer drags on, scientists say it could have its origins far away to the north.
Researchers at the University of Sheffield and two universities in the United States found that as the layer of ice over the Arctic Ocean retreats because of global warming, plumes of cold air are forced south. This has a knock-on effect across the planet, setting off extreme weather conditions in the middle latitudes of the northern hemisphere from America to Britain and Russia.
Just as the UK began its recent run of summer washouts, the Arctic ice started to melt at a dramatic pace, reaching record levels of shrinkage. And that trend has continued, with a steady decline that shows little sign of halting.
Arctic sea ice is the refrigerator of the top half of the globe, helping getting rid of excess heat from the tropics into space.
With less ice, the Arctic is dangerously over-heating, and that is upsetting the balance in temperature between the Arctic and the Tropics.
That in turn has led to a weakening of the jet stream, the powerful winds between five and seven miles up in the atmosphere, driven by the clash between cold polar air and hot tropical air. As the jet stream has attenuated, it has been meandering around the northern hemisphere in big loops like a sluggish river. Those loops have left the UK and other northern European countries at the mercy of cold and wet outbreaks of weather.
Other countries are afflicted by extreme heat on the opposite side of the jet stream, such as the US which is experiencing temperatures not seen since the Dust Bowl era of the 1930s.
Professor Jennifer Francis, a climatologist at Rutgers University in New Jersey, said the loss of sea ice this spring was more dramatic than in any previous year.
“The extremes of weather this summer are likely related to melting of the Arctic sea ice,” she said. “This March saw record rate of loss and a greater area of ice loss than has ever been.
“And it’s not only the sea ice loss affecting the weather. The snow cover was so light over North America and Siberia last winter that it’s melted much earlier and so the land warmed up much earlier than normal, and that’s a pattern we’ve been seeing the past few years.”
The extreme meandering of the jet stream has been behind many other dramatic weather events of recent years, including the phenomenal heat, drought and wildfires in Russia over the summer of 2010 that sent the jet stream on a huge detour southwards to Pakistan, causing historic and catastrophic flooding there that left more than 2,000 people dead and 10 million displaced.
“It’s not only the weakening and weaving in the jet stream. There are more are more loops in the jet stream lying in a north-south direction, rather than the more usual east-west, and when we get this pattern, as now, the waves tend to move more slowly, so the weather tends stick around a lot longer,” Prof Francis said.
The findings coincide with new research published yesterday by the Met Office and a number of other institutions around the world proposing that man-made climate change is driving up the likelihood of freak weather conditions.
Extremes of warm and cold have become far more likely over the past 60 years, according to the study of last year’s weather. The scientists also found that the temperatures across western Europe in 2011 were almost 1.5C warmer than would have been expected from the weather patterns alone.
Dr Peter Stott, head of climate monitoring and attribution at the Met Office, said mankind had a “marked impact” on the planet’s weather.
“While we didn’t find evidence that climate change has affected the odds of all the extreme weather events we looked at, we did see that some events were significantly more likely,” he said. “Otherwise we’re seeing that human influence is having a marked impact on some types of extreme weather.”
In a separate report published today, the Committee on Climate Change questions whether the UK will be able to cope with the heavy flooding climate change will bring to the country over the next two decades.
Funding for flood defences is being hacked back in real terms at precisely the moment when it is most needed, according to the new study.
As many as 610,000 homes across Britain could be at “significant risk” of flood damage if there is no commitment to match or better previous levels of investment. The Environment Agency currently estimates that it needs £20 million more on top of inflation just to keep up with the pace of climate change.
The independent body also found that a widespread trend for paving over gardens has made a big contribution to the increased danger of flooding. The proportion of gardens that are covered in “hard surfacing” nearly doubled from just over a quarter in 2001 to almost half in 2011.
Lord Krebs, the chair of the Adaptation Sub-Committee, said extreme weather conditions would become far more common over the coming years as climate change took its toll.
“We must take adaptation more seriously if we are to manage the growing risks of floods and droughts,” he said. “Without action by households and businesses to prepare for these inevitable weather extremes the country faces rising costs, unnecessary damage and future disruption.”
http://www.thetimes.co.uk/tto/weather/article3471739.ece
Al eerder heb ik over dit onderwerp gepost. Mijn inziens staat ons nog heel wat te wachten.
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