Why has this winter been so cold in Europe?

This post was chosen as an Editor's Selection for ResearchBlogging.orgI’ve written a couple of posts recently looking at the cold UK weather in context and how snow forms.

What I haven’t done, though, is looked at why it’s been so cold over Europe this winter (as well as last year’s winter).

It just so happens that a paper came out in the Journal of Geophysical Research recently (Petoukhov and Semenov, 2010) that might hold the answer.

They looked at whether changing the sea ice concentration in a particular area of the Arctic (the  Barents-Kara sea) in a long run of a climate model changed the conditions over Europe.

Their reason for doing this was that the very cold winter of 2005/06 was accompanied by very low sea ice in this region – they don’t mention 2009/10 and 2010/11 at all, though, as they would have been writing the paper before these cold European winters occurred.

To isolate the effect of the sea ice in this one region they use a mean state (a “climatology”) for most of the planet in the model but change the amount of ice on the  Barents-Kara sea. The results are quite surprising.

The winter wind patterns over Europe change dramatically when they changed the ice concentration from 80-100% to 40-80%. You can see this in the figure below, which is from the paper but I’ve highlighted the key areas on the wind plot and removed some of the panels.

Mean surface air temperature and 850 hPa wind anomalies for February from the model runs using 2 ice scenarios.

(When they set the sea ice close to 0%, Europe goes into a different state that is similar in temperature to the 80-100% case.)

So why does Europe get cold in a model world where the Barents-Kara sea has 40-80% sea ice concentration? In this model run, the result of this level of sea ice is to set up a big anti-cyclonic (high-pressure) anomaly over the pole. In the northern hemisphere air rotates clockwise around a high so this explains the switch in wind direction that drives the change over Europe. However, the hypothesis they present as to why the sea ice change leads to a high pressure anomaly over the pole is not straightforward and probably deserves a bit more study.

So, in essence, this all seems to be saying that it’s climate change that has led to our very cold winter! I can imagine some people finding that hard to swallow but here’s a quote from the paper that sums it up better than I just have:

Our results imply that several recent severe winters do not conflict the global warming picture but rather supplement it, being in qualitative agreement with the simulated large-scale atmospheric circulation realignment.

Anyway, all interesting stuff and I look forward to seeing some more analysis, especially a better climatology of winter temperatures in Europe and Arctic sea ice to see if that fits in with this hypothesis and a better physical model for the different changes linked with different sea ice concentrations.

UPDATE (10th Jan 2011): I just read someone claiming to have “debunked” this paper by showing that sea ice concentration and European temperature don’t correlate. However, this completely misses the non-linearity of the relationship. I think it’s fine to question the findings of the paper but I suspect that to “debunk”, or verify, the findings using the actual sea ice and temperature measurements you’d have to pick apart the contributions of other factors (e.g. polar jet changes, ENSO teleconnections) and then find some way of characterising the non-linear nature of the relationship with B-K sea ice.

ResearchBlogging.orgV. Petoukhov, & V. A. Semenov (2010). A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents Journal of Geophysical Research, 115 : 10.1029/2009JD013568

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14 Responses to “Why has this winter been so cold in Europe?”

  1. omnologos Says:

    do you know of any weather phenomenon or series thereof that would conflict with “the global warming picture”?

    • andyrussell Says:

      I suppose the famous one is the lack of warming in upper troposphere as measured by weather balloons i.e. it should’ve been warming. That problem was cleared up a couple of years ago in Nature Geosciences. Here’s a link if you’re interested:

      http://www.nature.com/ngeo/journal/v1/n6/abs/ngeo208.html

      Other than that, I suppose I could guess some stuff that wouldn’t be consistent with a warming atmosphere forced by GHG emissions. I suppose if hurricane numbers orand intensity go down but you’d still have to make assumptions about other things staying the same, which is kind of what the paper in the main post shows perhaps isn’t a great assumption.

  2. Tweets that mention Why has this winter been so cold in Europe? « Our Clouded Hills -- Topsy.com Says:

    [...] This post was mentioned on Twitter by Ian G. Stimpson
    and marius a. eriksen. marius a. eriksen said: RT @Geoblogfeed: Why
    has this winter been so cold in Europe? http://bit.ly/f12uSj
    [...]

  3. Ed Darrell Says:

    Actual cooling of the climate would conflict. Plant zones
    turning colder would be one conflict, but most plant zones in the
    Northern Hemisphere have been warming for 80 years. Birds changing
    their migration so they go less far north, and farther south, would
    suggest a conflict with global warming. Sea levels dropping
    dramatically would conflict. Milder weather over the globe, with
    fewer cyclones, fewer serious cyclones, would suggest no warming.
    Warming suggests wilder weather — warmer warms, cooler cools, more
    severe droughts, more severe rains. That’s what we see in most
    places. You know, all that stuff that is predicted with warming —
    go the other wary.

    • Maurizio Morabito Says:

      Ed – that’s not so simple. Apart from impossibly vague statements (what is the measurable meaning of “wilder”? has the weather never been wild before? or since when is weather=climate?) there always appears to be space for rather convenient “adjustments” to the theory (such as a series of cold winters suddenly getting linked to global warming) or game-changers (such as disregarding radiosonde temperature measurements after figuring out some other way to discover warming in upper troposphere).

      Just-so stories have been plaguing several sciences in the past, and climate science doesn’t look immune to them.

      Note also that “cooling of the climate” would mean having to wait 30 years or so, and any observation such as birds going far less north would be dismissed as “weather not climate”. Even the IPCC AR4 mentions more than 3,000 “significant changes” in Europe that are _not_ consistent with warming, only to march forward on regardless.

      The answer to that would usually be “look at the 25,135 significant changes in Europe that are consistent with warming”. But then aren’t we been told now that global warming might as well mean European cooling? Talk about role-reversal: one could use the IPCC figures to invalidate “the global warming picture” exactly because there’s so many significant changes consistent with warming. ???

      It all sounds very confusing and the aim of defining properly falsifiable aspects of “the global warming picture”, let alone of “the anthropogenic global warming picture” remains as difficult to achieve as ever.

      • andyrussell Says:

        I’m not sure that the convenient “adjustment” idea works – the JGR paper was first submitted on 16 November 2009 i.e. before the cold winters of 2009/10 and 2010/11. I think it still needs a lot of testing but it’s interesting work nonetheless. Even if it hadn’t been published, the European cold snap didn’t make much of a dent in the 2010 positive temperature anomaly.

        As for the upper-level radiosondes, I think it was a really clever way of checking how wrong the balloon temperature measurements were. It may have shown that they weren’t very wrong and then it would’ve been a full blown Nature paper (not just Nature Geosciences) as it would’ve been a real problem for the theory. But it didn’t.

      • omnologos Says:

        Andy – once again, it’s not that simple. Check this comment at Skeptical Science,
        where there is a link to a blog post by Chris Colose showing that
        “if there truly was no tropical hotspot in observations, it would
        actually imply, if anything, a higher climate sensitivity”. So
        we’re back to square one. And the cold started in 2008 8-)

      • andyrussell Says:

        Not sure what you mean by saying the cooling began in 2008. Globally, regionally, seasonally? Winter 2008 in Europe wasn’t particularly noteworthy.

        The P+S paper is only looking at a specific region of Europe for winter. Anyway, even if you could’ve predicted the following 2 winters in Europe from the 2008 one, I’m not sure what that implies.

        And, as I said before, there’s no need to explain away the last 2 European winters in terms of global warming as they’re not particularly significant globally. Its just an interesting paper!

      • omnologos Says:

        I just wish you were less dismissive of the problem (=the
        overabundance of after-the-fact rationalizations in climate
        science). Now for example Bastardi is having a field day quoting
        The New York Times of 15 Jan 2000,
        where Michael Oppenheimer (the relatively well-known Princeton
        “climate scientist”) “points to global warming as perhaps
        the most significant long-term factor
        ” concerning mild
        winters in the Big Apple.

      • andyrussell Says:

        I’m dismissive of it in this case as the paper was written before the last two cold winters – I already said that.

        More generally, there’s an important difference meteorology and
        climatology that I think you need to consider in your criticism.
        Climate models aren’t designed to make predictions about regional events like a few cold weeks in Western Europe (although it seems that the MetOffice seasonal forecast was quite good, not that they publish them anymore).

        Meteorological journals, on the other hand, are full of process studies like P+S as you need to understand events like this to improve weather forecast models. You can’t really do these studies before the event has happened because, well, it’s obvious isn’t it? Some of these analyses, like this one, are then useful for climate analysis.

        To be honest, I’m not that bothered about the motivation of the research. If the science adds up then that seems like the important point.

    • omnologos Says:

      And so my second wish is that weather research would
      finally be decoupled from climate research, just as in medicine,
      palliative studies are not always linked to cures :-) As for the
      met office, looks like they went for a Derren Brown, by forecasting
      opposite outcomes to different people only to claim they’d been
      right…well, either of them, yes, of course…

  4. ResearchBlogging.org News » Blog Archive » Editor’s Selections: Giraffes, Alzheimer drugs, the physics of gravity and the cold, cold winter Says:

    [...] Why has this winter been so cold in Europe? Yup, it’s definitely been a little chilly and white here in Germany, so this article unsurprisingly caught my attention. Climate researcher Andy Russell talks about a recent paper that looks at the effect of sea ice concentration in part of the Arctic on the winter temperatures here in Europe. Don’t believe the denialists, and tell your friends – European cold winters and climate change are compatible. [...]

  5. RB Editor’s Selections: Giraffes, Alzheimer drugs, the physics of gravity and the cold, cold winter Says:

    [...] Why has this winter been so cold in Europe? Yup, it’s definitely been a little chilly and white here in Germany, so this article unsurprisingly caught my attention. Climate researcher Andy Russell talks about a recent paper that looks at the effect of sea ice concentration in part of the Arctic on the winter temperatures here in Europe. Don’t believe the denialists, and tell your friends – European cold winters and climate change are compatible. [...]

  6. Dave Says:

    Thing is its cold all over the place, not just Europe. I live in the SW United States and its been a pretty cold winter, several nights below 0 F and many day time temps below freezing. And of course its been bitter cold all over the US this winter. I also saw some articles on the cold winter in Korea dated late January 2011. So I’m not sure a local phenomenon explains the cold in Europe.

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