Is global warming causing harsher winters?

Is global warming causing harsher winters?

28th March 2013, Comments 9 comments

Scientists suggest that global warming is the cause of the string of long winters in parts of Europe.

Millions of people in northern Europe are still battling snow and ice, wondering why they are being punished with bitter cold when -- officially -- spring has arrived and Earth is in the grip of global warming.

Yet some scientists, eyeing the fourth year in a row of exceptionally harsh late-winter weather in parts of Europe and North America, suggest warming is precisely the problem.

In a complex tango between ocean and atmosphere, warming is causing icy polar air to be displaced southwards, they contend.

"The linkage is becoming clearer and clearer, I think, although the science has not yet been settled," said Dim Coumou of the Potsdam Institute for Climate Impact Research (PIK) near Berlin.

The theory derives from a long-studied Arctic phenomenon called a positive feedback -- in plain words, a vicious circle.

Rising temperatures are melting the Arctic's floating cap of sea ice, especially in summer.

In 1979, when satellite measurements began, summer ice covered some seven million square kilometres (2.7 million square miles), roughly equivalent to 90 percent the area of Australia.

In September 2012, summer ice hit its lowest extent on record, at just 3.4 million sq. kms (1.31 million sq. miles).

Take away reflective ice, and you have a dark sea that absorbs solar radiation, which in turn reinforces the melting, and so on.

But the theory suggests the added heat, stored over a vast area of surface water, is also gradually released into the atmosphere during the Arctic autumn.

It increases air pressure and moisture in the Arctic, reducing the temperature differential with lower latitudes.

Here's what happens next: The polar vortex, a powerful circular wind that essentially pens Arctic air to the roof of the world, begins to weaken.

Finding itself released, a mass of moist cold air spills southward, bringing snow and chill down into North America and Europe.

And it tends to stay there, because of what happens to the jet stream.

Instead of encircling the northern hemisphere in a sturdy and predictable fashion, this high-altitude wind takes a lazy looping path, zigzagging over the United States, the Atlantic and Europe. The southern parts of the loops get a bout of cold weather that becomes stalled in place.

"Heat that is stored in the (Arctic) ocean can rapidly transfer to the atmosphere, and this affects the dynamics" of northern hemisphere weather patterns, said Coumou in a phone interview.

"We've had a couple of winters (in Europe) where you've had rather shorter-term cold spells, of a duration of maybe 10, 20, 30 days... It's been the same in the continental US and Canada where they've seen similar quite bizarre cold spells but of a relatively shorter period."

Charles Greene, director of the Ocean Resources and Ecosystems Program at Cornell University in New York, said Arctic warming added a joker or two to the climate pack.

"With the changes in sea ice, we set up a situation where we stack the deck, increasing the probability of these invasions of cold Arctic air," he said.

"But what's less predictable is which regions in the mid-latitudes will get hit. We're not sure yet how it will interact with other parts of the climate system in any given year, for instance how it will interact with El Nino and La Nina."

Greene also postulates that Superstorm Sandy last October wreaked its havoc because of a high-pressure zone over Greenland, possibly strengthened by changes triggered by sea-ice loss in the Arctic.

Like a barrier closing off a street, this mass of air forced Sandy to turn sharply west so that it slammed into the US East Coast. Normally, late-season hurricanes follow a northeastern track and peter out at sea.

The warming-and-winter scenario is far from unanimous in climatology. Other experts call for more evidence, especially from longer-term data.

"Looking at what's happening right now, in early spring, it's too early to say whether it is due in part to a temporary climatic swing," said David Salas-y-Melia of Meteo France, the French meteorological agency.

Jeff Knight of Britain's Met Office pointed to a natural climate variation called the North Atlantic Oscillation, whose phases tend to span 30-40 years.

Several decades of relatively harsher winters alternate with relatively milder ones -- but there can also be years within these phases that buck the trend.

"In Europe, the effect of climate variability is quite large," said Knight. "There are possible links to explain why sea ice might influence atmospheric circulation, but the jury is very much still out at the moment."

Richard INGHAM, Claire SNEGAROFF / AFP / Expatica

9 Comments To This Article

  • carrico posted:

    on 13th April 2013, 14:31:15 - Reply

    What's this 'youtube'? You-to-be? To be or not to be? 'Tis the question I've heard. Me, I'm just worried about the grape harvest this fall. Europe has had a tough winter, just like back in '84. I agree, frances, it's scary.
  • frances posted:

    on 10th April 2013, 14:45:26 - Reply

    Global warming is a scam and a fraud to enslave the west with carbon taxes and bring down the economies
    Global weirding? Look up youtube HAARP yes it could well be MAN MADE!
    While you are on youtube look up Agenda 21, New world order, Morris strong, False flags, Climate fraud Lord Monkton.....The UKIP Nigel Farage in the EU is delicious! You will get the complete picture and its
  • Carrico posted:

    on 7th April 2013, 20:44:16 - Reply

    Delicious response, Osita. No I didn't skip that class, I was teaching it. You get an A plus for waking up the rest of the class. 'Arrogance' is such an interesting word: "Claiming for oneself undue importance." From Old French (not Greek or Latin). This is from Webster's Students Dictionary (1962). Who needs Google?
  • osita posted:

    on 6th April 2013, 19:24:23 - Reply

    I think you should google the word oxymoron, Carrico, as you seem to have skipped that class at school ;)

    It is incredibly arrogant of humans to think we can predict the weather. We have been keeping accurate records for a maximum of ... 300 years or so? We know absolutely nothing about weather patterns in the long term, other than the scant evidence that scientists deduce ffor the last few hundred thousand years (from rocks, etc)

    The planet has been here for many millions/billions of years. This could be cyclical for all we know: After all, humans didn't cause the last ice age, or the one before that, or the one before that, or......
    Is the weather now really that bad compared to' the mini ice age' we had in 1645 -1715, for example? We don't know, we weren't there!

    One thing is for sure though: the earth can self-repair, and will do so again once our pathetic species is consigned to its history.
  • carrico posted:

    on 4th April 2013, 10:38:58 - Reply

    Is anybody home out there? We need more comments on this fine article.
  • carrico posted:

    on 4th April 2013, 02:01:21 - Reply

    Overheating causes dehydration.
    What the hell is an oxymoron anyway? A moron full of gas?
    Re global warming: Our winter (calendar year, not water year) in the Pacific Northwest has been exceptionally dry. We're flirting with 70 degrees (F) already. Tulips I'd forgotten about are already blooming.
    What's up with that?)
  • Elvis posted:

    on 29th March 2013, 23:39:21 - Reply

    It's time for the "Oxymoron Headline Game." Post your favourite oxymoron headline. Here are two to get the ball rolling.

    "Overeating Causes Malnutrition"
    "Does Global Warming Cause Hypothermia?"
  • Gary posted:

    on 29th March 2013, 13:21:45 - Reply

    Yeah, sure! I guess if the so-called "theory" doesn't fit the facts, they can just come up with a new theory.
  • carrico posted:

    on 29th March 2013, 09:32:41 - Reply

    "Circle" or 'cycle'? Dang, I need The Gardening Expert to weigh in on this one. Now let me see, whatever was her name..............?
    Over to you, Angela?
    No, that's not right.
    Dang, how do I get to her blog?...........