British weather set to become more unsettled

British weather set to become more unsettled

British winters are becoming increasingly volatile due to extreme variations in pressure over the North Atlantic according to scientists from the University of Sheffield.

The new research, published on September 9, 2014, in the International Journal of Climatology, shows that weather patterns over the UK have become distinctly more unstable, resulting in contrasting conditions from very mild, wet and stormy to extremely cold and snowy.

Winter weather conditions are commonly defined using the North Atlantic Oscillation (NAO). The NAO is a south-north seesaw of barometric pressure variations over the North Atlantic which indicates the strength of westerly winds impinging on the UK shore and resulting weather patterns.

When westerly winds are strong, known as a positive NAO phase, Britain experiences mild, wet and often stormy weather – like last winter. Weaker or reverse airflow, known as negative NAO phase, typically brings cold, snowy weather, which featured prominently in the winters of 2009/10 and 2010/11.

Climatologists Professor Edward Hanna and Tom Cropper from the University of Sheffield’s Department of Geography and the rest of the team of scientists from University of East Anglia’s Climate Research Unit and the Met Office Hadley Centre, analysed year-to-year monthly and seasonal changes in the NAO since 1899.

Although the experts found that most seasons didn’t show overall long-term NAO trends, winter - especially early winter including the month of December - showed a significant systematic rise in variation over the last century.

The researchers found that over the last 115 years, three out of five all time record high NAO values and two out of five record lows for the month of December occurred over the last decade (2004-2013) , indicating that British winters have become increasingly unsettled.

Researchers found from their statistical analysis that there was a less than 0.04 per cent probability of getting such a clustering of extreme NAO years by chance.

Though this trend could be due to random fluctuations in the climate system, it could equally have been influenced by various driving factors including changing pressure/weather systems over the Arctic, especially Greenland, and changes in energy coming from the Sun.

Professor Edward Hanna, from the University of Sheffield’s Department of Geography, said: “Our study highlights the changing nature of North Atlantic atmospheric circulation patterns that has given the UK more variable winter conditions in recent years.

“We cannot use these results directly to predict this winter’s weather but according to the long-term NAO trend we can say that the probability of getting extreme winter weather – either mild/stormy or cold/snowy - has significantly increased in the last few decades. Further research is needed to show whether or not this increased volatility is linked to global warming. ”

The University of Sheffield and Met Office Hadley Centre are now carrying out further collaborative research to better understand these possible links. If this trend of increasingly variable winter NAO continues, we can expect more volatile UK winter weather in decades to come.

Dr Adam Scaife, Head of Monthly to Decadal Forecasting at the Met Office, said: “This new analysis of historical observations shows intriguing signs of a trend towards more variable winters over the last century.”

Source: University of Sheffield

Reference:

  • "Recent seasonal asymmetric changes in the NAO (a marked summer decline and increased winter variability) and associated changes in the AO and Greenland Blocking Index" - Edward Hanna, Thomas E. Cropper, Philip D. Jones, Adam A. Scaife and Rob Allan - Wiley - DOI: 10.1002/joc.4157

Featured image: February 2009 Great Britain and Ireland snowfall. Credit: CGPGrey.com

Comments

It is I only 5 years ago

Snow is & will be a thing of the past. Children will not see snow anymore.
Trust me. I am a "respected" scientist. Would I lie to you??

Alex 5 years ago

I'ts not NIbiru, it's not radiation, it's not oil spils in the gulf. Look up stupid it's that hot ball of energy that is not as active as it has been in the past. It's called solar cycles. Can you say mini ice age that we had back in the 'very similar' a time in 1645 when a mini ice age hit. Did it cool the earth back then due to humans? Oh yea a lot of volcanic activity helps cool the earth aswell. Do I think humans polute the earth and don't give a crap Yes!


Nuclear Weather 5 years ago

It's called R-A-D-I-A-T-I-O-N contamination.
It's in the Global atmosphere from Japan's 3-core meltdown and melt-through at Fukushima. So, expect it to be here and getting worst for the next 1,000 or so years!

Apollyon 5 years ago

The weather in Britain and elsewhere is becoming more and more unpredictable due to the passage of Nibiru and it's companions. The approach has caused the Earth to wobble excessively which is why the jet stream has these wild gyrations going on. Nibiru will soon be leaving our solar system, and when it does it will latch on to our pole and pull it over, some estimate up to 90deg. The pole shift will take only one hour and in that time the earth will experience earth quakes magnitude 10 or greater and strait line winds of hundreds of miles per hour, maybe even up to 300 mph. There will be no presidential elections in the United States in Nov of 2015 and the US will never have another president. So, what I am telling you is, that these things are going to happen between now and Nov 2015. Just prior to the pole shift the Earth will stop rotating for a day as Nibiru tugs on it. Nibiru will be clearly visible in the Sky and at least a big or more than the moon from the time it first becomes visible to all, you will have approximately four days to try and get to a safer location. Example: inland at least 100 miles and 600ft higher in elevation. The countdown has begun and you have less that 24mo. You can laugh if you want to, I don't care because you won't be around any more along with 2 thirds of the worlds population. By the way, the Gulf Stream has stopped flowing, that happened in 2010. Did you hear about it on Mainstream news?

karenedalton 5 years ago

Blame it on the Gulf oil catastrophe of 2010. Loop current died. Affects weather in Europe.

Ken 5 years ago

It is time that we become re-familiar with the "Precession of the Equinox". Our planet has a wobble that places part of the planet closer to the sun and another part further away. This has been going on for the past 4.5 billion years but this is never mentioned as a cause of climate change even though ancient civilizations were well aware of it. Educate yourselves about it for this will become very apparent. Our planet has experienced major cataclysmic events in the past when the ice caps melted rapidly and caused massive flooding.....this will go on and on.....

John Edward 5 years ago

"and the rest of the team of scientists from University of East Anglia’s Climate Research Unit and the Met Office Hadley Centre"
Hate to be a party pooper, but I hope the climate modeling of the CRU and the Met Office weather prediction ability has markedly improved lately. If memory serves me correctly, they have failed miserably in the past.
I quote: "According to Dr David Viner, a senior research scientist at the climatic research unit (CRU) of the University of East Anglia,within a few years winter snowfall will become "a very rare and exciting event"." (The Independent, 20th March 2000).

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