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Chilling changes take icy grip on our climate

BITTERLY cold winters could become a feature of Irish life due to climatic changes happening 10km above our heads, experts have warned.

A band of wind which pushes weather systems around the planet could be responsible for the temperatures which made last month the coldest March on record.

Scientists are concerned that the jet stream, a current of high winds some 10km up, is changing.

The stream separates cold air from the Arctic from warmer weather in the tropics, and should recently have pushed the sub-zero easterly winds northwards, allowing us to enjoy a typical mild and wet March.

Instead, it was the coldest March on record, with the mercury plummeting to minus 7.6C in some places.

Average temperatures were up to 3.5C colder than usual, data from Met Eireann shows.

Similar conditions existed in winter 2010, when sub-zero temperatures hit and the country ground to a halt.

The melting of the polar ice caps as global warming takes hold are believed to have changed how the jet stream is functioning.

Over the past 30 years, the sea ice during the summer months has declined by about 40pc.

Professor John Sweeney from NUI Maynooth, says the changes to our weather patterns are not just notable, but "exceptional".

A member of the UN's Intergovernmental Panel on Climate Change (IPCC), which was jointly awarded the Nobel Peace Prize in 2007 with former US vice-president Al Gore, he said the melting of the polar ice caps could be contributing to changes in how the jet stream is behaving.

Last year, when March was the warmest on record, the jet stream was to the east of us, allowing air from the tropics over Ireland, which resulted in temperatures of 22C being recorded in Donegal.

If the jet stream behaved in the same way during July, we would be experiencing a heatwave, Professor Sweeney said.

"There is some research being published at the moment which suggests the probability of these kind of events may be increased by the changes taking place in the Arctic, where we've effectively lost about half of the summer sea ice," he said.

"The link is that as we warm up the Arctic, and the light, icy surface which reflects heat is replaced by the dark sea surface which absorbs more heat, the jet stream is being displaced because it doesn't have to blow so hard to displace the cold."

Displaced

"The jet stream is a way of restricting the heat from the equator to the poles. If the cold is being displaced, the jet stream doesn't have to be so strong and active. It's like a river losing momentum."

He could not rule out bitterly cold weather becoming a feature of the Irish winter.

"We're using the expression global warming when we should be talking about global climate change," he said.

"It doesn't say it's going to happen every year, but you're looking at throwing a dice and seeing what numbers come up."

Met Eireann meteorologist Ray McGrath said experts were not sure why it was changing, and that it could be caused by melting sea ice, or due to natural changes in the climate system.

"The climate and weather system is extremely complex, with a lot of inter-locking components. It's not easy to pull one element out."

Irish Independent