Weather

We may have to get used to wet summers like we've seen recently across the UK, according Dr Edward Hanna from Sheffield University in an interview which you can see on Inside Out and Look North tonight.

According to Dr Hanna and an international team of scientists, melting summer Arctic ice may be weakening the jet stream, leading it to meander and become slow moving.

This effectively means that weather patterns become locked in for long periods of time.

The jet stream is a ribbon of strong winds high up in the atmosphere, a result of the temperature contrast between northern latitudes towards the Arctic, and latitudes further south.

Because the Arctic is warming faster than any other region on earth, this temperature contrast is getting weaker, leading to a less powerful jet stream in summer.

Crucial to the UK and Northwest Europe is Greenland, a huge mountanous land-mass which can act as a barrier to the jet stream.

If the jet stream is weaker than normal, two things can happen.

It can either split, with one arm going northeastwards, with the other travelling southeastwards towards the UK.

Or the whole jet stream can be deflected southeastwards towards the UK.

The result in both cases would be wet, cool, unsettled conditions as we have seen since 2007.

Not every summer is likely to be poor.

The slow-moving jet stream may become positioned to the north of us, leading to warm settled conditions.

But because of our position relative to Greenland, these summers are likely to be the exception to the rule.

Dr Hanna says if this theory is correct and summer Arctic ice melt continues, there is also likely to be a higher risk of extreme rainfall events such as we have experienced in 2007 and again this year.

The research, which was carried out jointly by experts from NOAA (National Oceanic and Atmospheric Administration), Rutgers University, University of Washington, and the University of Sheffield, was published in the journal Geophysical Research Letters.

You can see more on this on BBC Look North from Leeds, on BBC1 at 6.30pm, (Sky channel 956, Freesat 966) or on BBC1's Inside Out at 7.30pm (Sky 956 & 957, Freesat 966 & 967).

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  • Comment number 149. Posted by Spanglerboy

    on 24 Dec 2012 23:34

    I have had the same problem accessing page 2 but got in by right clicking and opening in a new tab. I seem to recall the BBC blogs had a similar problem some time ago. Any road up, now I am in I will wish you all a very merry festive season and a happy new year and disappear for a bit.

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  • Comment number 148. Posted by QuaesoVeritas

    on 23 Dec 2012 18:57

    #147. - ukpahonta wrote:
    "I know it's geeky and only aimed at code programmers but you can get the tee shirt and mug that says "It's not a bug, it's a feature!""

    It was what the I.T. people at work used to tell me when I found a problem they couldn't fix!

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  • Comment number 147. Posted by ukpahonta

    on 23 Dec 2012 09:34

    #146 QV

    I know it's geeky and only aimed at code programmers but you can get the tee shirt and mug that says "It's not a bug, it's a feature!"

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  • Comment number 146. Posted by QuaesoVeritas

    on 23 Dec 2012 08:01

    #145. - ukpahonta wrote:
    "Nope, my mistake, problems still exist maybe the BBC can get a technician out in the New Year, bit like a plumber, although there are enough managers to discuss it!"

    While refreshing page 2 taking you to page 1 is irritating, I doubt if it will be seen as a problem by anyone at the BBC.
    I suspect it is a "feature", not a "bug", i.e. intentional.

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  • Comment number 145. Posted by ukpahonta

    on 23 Dec 2012 00:16

    Nope, my mistake, problems still exist maybe the BBC can get a technician out in the New Year, bit like a plumber, although there are enough managers to discuss it!

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  • Comment number 144. Posted by ukpahonta

    on 23 Dec 2012 00:11

    I have a feeling that the refreshing problems have been corrected and a refresh of page 2 takes you to page 2. Just testing.

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  • Comment number 143. Posted by greensand

    on 22 Dec 2012 21:57

    Don’t like a dead fred, so a little bit of “actuals”:-

    Latest trends as at Nov 2012

    HadCRUT4 :-

    30 year – significantly positive at 0.16C per decade (last seen 1999)
    16 year – slightly positive at 0.05 per decade (last seen 1980)
    10 tear - slightly negative at -0.04 per decade (last seen 1979}

    HadCrut3 :-

    30 year – significantly positive at 0.15C per decade (last eeen 1999)
    16 year – slightly positive at 0.02 per decade (last seen 1977)
    10 tear - slightly negative at -0.07 per decade (last seen 1977}

    Before anybody tries to hand wave away 10 years as only noise, go ask the MO why every year they produce, Decadal (10 year) Forecasts and One year (12 month) forecasts. This point is especially relevant to those who feel it necessary to promote a single month’s data provided it is in their opinion “one of the warmest” whilst at the same time try to dismiss a decade's data as “noise”.

    PS these are actual present day least squares trend lines, not moving averages centered on 15 years ago. So no accusations of “cherry picking” please keep that particular critique for where it is apt – moving averages, which are at present only illustrating what happened 15 years ago.

    As always "The trend is your friend" and remember the lighter the colour of the tie the more food it will attract! (Brian Marber circa 2000)

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  • Comment number 142. Posted by greensand

    on 21 Dec 2012 23:07

    141. ukpahonta wrote:

    "Pay attention:"

    I did, and now my head hurts!

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  • Comment number 141. Posted by ukpahonta

    on 21 Dec 2012 22:33

    #140 greensand

    Pay attention:

    lsvalgaard says:
    December 21, 2012 at 8:30 am

    dr. lumpus spookytooth, phd. says:
    December 21, 2012 at 8:04 am
    you really can’t attribute global warming to man’s emissions

    since I don’t, your point is moot.

    lsvalgaard says:
    December 21, 2012 at 9:24 am

    ConfusedPhoton says:
    “CO2 the last 300 years has risen considerably as have temperatures…”
    Misleading as usual.

    Not at all, CO2 is now considerable higher than it was 300 years ago as is temperature. You should not take that as showing that CO2 is the reason for the temperature rise.

    ;-)

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  • Comment number 140. Posted by greensand

    on 21 Dec 2012 22:11

    @139. john_cogger:

    Went back, had a look, quite a good turn out, all the major players were on stage c/w full supporting cast.

    Not sure that I actually spotted any one saying that the Green House effect is false... But I did get the distinct impression that it would not be long before a shout of "it's behind you!" rang out. A comment far more likely than one of "we just don't know"

    Don't get me wrong good things can come out of a knockabout of the type fostered by WUWT and it's ilk but this one has a long way to go and the real life experiment of cycle 24 and 25 might actually be shorter. Not that anybody knows anything about cycle 25 yet.

    In an attempt feed my need of logic I will go back to what I think is actual observational data.

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