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Cold winter in a world of warming?

Filed under: — rasmus @ 14 December 2010

Last June, during the International Polar Year conference, James Overland suggested that there are more cold and snowy winters to come. He argued that the exceptionally cold snowy 2009-2010 winter in Europe had a connection with the loss of sea-ice in the Arctic. The cold winters were associated with a persistent ‘blocking event’, bringing in cold air over Europe from the north and the east.

Last year’s cold winter over northern Europe was also associated with an extreme situation associated with the North Atlantic Oscillation (NAO), with the second lowest value for the NAO-index on record (see figure below).

I admit, last winter felt quite cold, but still it wasn’t so cold when put into longer historical perspective. This is because I remember the most recent winters more vividly than those of my childhood – which would be considered to be really frosty by today’s standards. But such recollections can be very subjective, and more objective measurements show that the winters in Europe have in general become warmer in the long run, as explained in the German blog called ‘Wissenlogs’. If there were no trend, then such a low NAO-index as last year’s would normally be associated with even colder conditions over Europe than those observed during the previous winter.

NAO-index for December-March

NAO-index for December-March, which the winter 2009-2010 being associated with the second lowest value on record.

In a more recent press-release, Vladimir Petoukhov and Vladimir Semenov, argue that Global Warming could cool down winter temperatures over Europe, and a reduced sea-ice extent could increase the chance of getting cold winters. Also they propose that cold winters are associated with the atmospheric circulation (see schematic below), and their press-release was based on a paper in Journal of Geophysical Research (JGR), which may seem to have a serendipitous timing with the cold spell over Europe during the last weeks. However, the original manuscript was submitted in november 2009 (before the statement made by James Overland) and accepted in May 2010. One could regard the paper more as a ‘prediction’ rather than an ‘explanation’.

Schematic illustration of proposed effect. Courtesy of PIK.

Although Petoukhov and Semenov’s findings sound plausible, I don’t think they are as straight-forward as they initially seem in terms of their implications for this winter either. For one thing, it is impossible to prove that one single event is due to a change in the long-term, as we pointed out for the case of hurricanes (The 2010 hurricane season this year, by the way, was quite active).

I think it is important to keep in mind that the Petoukhov and Semenov study is based on a global atmosphere model that simulated a non-linear response to the loss of sea-ice in the Barents-Kara seas: initially warm winters, followed by cold, and then warm winters, as the sea-ice extent is gradually reduced.

NCEP/NCAR reanalysis: surface temperature anomaly wrt 1961-1990.

One interesting question is how the Barents-Kara sea-ice affects the winter temperatures over the northern continents. By removing the sea-ice, the atmosphere above feels a stronger heating from the ocean, resulting in anomalous warm conditions over the Barent-Kara seas. The local warming gives rise to altered temperature profiles (temperature gradients) along the vertical and horizontal dimensions.

Changes in the temperature profiles, in turn, affect the circulation, triggering a development of a local blocking structure when the sea-ice extent is reduced from 80% to 40%. But Petoukhov and Semenov also found that it brings a different response when the sea-ice is reduced from 100% to 80% or from 40% to1%, and hence a non-linear response. The most intriguing side to this study was the changing character of the atmospheric response to the sea-ice reduction: from a local cyclonic to anti-cyclonic, and back to cyclonic pattern again. These cyclonic and anti-cyclonic patterns bear some resemblance to the positive and negative NAO phases.

Sea-ice over Hudson Bay

They also show a different response in surface air temperature (SAT) during December, January, and February. From their Figure 2, it is not immediately obvious from that figure that a sea-ice reduction leads to lower SAT during January. This is, however, very much in line with similar analysis that I have carried out with colleagues and struggled to find a consistent response (albeit we looked at the summer season).

But Petoukhov and Semenov provide theoretical support for their observations, and argue that the non-linear response can be explained in terms of ‘convectional-frictional’ and ‘baro-clinic-frictional’ mechanisms. The former includes warming over the areas where sea-ice disappear, and changes in the vertical temperature gradients, stability, and hence friction, while the latter involves a change in the surface friction force associated with temperature changes over distances.

I think that the scientific community will need some time to confirm this link, and there are some
important caveats: For one thing, the spatial model resolution (the size between the boxes in the grid mesh, through which the models represent the world) has an influence on their ability to represent blocking frequency. Hazeleger et al. Has observed that “… different horizontal resolutions … confirm the resolution-dependence found in NWP [Numerical Weather Prediction]”. The atmospheric model used by Petoukhov and Semenov has a fairly coarse spatial resolution (2.8 degrees x2.8 degrees), and it is legitimate to question whether it can reproduce the
frequencies of blocking events realistically, and whether that has a bearing for the conclusions.

But also the fact that the sea-surface temperatures (SSTs) were fixed in these experiments may affect the conclusions. Balmaseda et al. found that the atmospheric response to changes in sea-ice conditions may depend on the background SSTs, at least for the summer months. They also compared results from a coupled ocean-atmosphere model with the results from an atmosphere model for which the SSTs were given. Their unexpected finding was that the atmospheric response in these two cases were very different.

In fact, global atmospheric and climate models are better at describing the large picture than more regional and local characteristics. There is a limit to what they are able to describe in terms of local regional details, and it it reasonable to ask whether the response to changes in regional sea-ice cover is beyond the limitation of the global model. If different models give different answers, then it is likely that the response is not robust.

Another interesting question is whether the sea-ice the is whole story. Not long ago, there were some suggestions of a link between low solar activity and cold winters (this correlation, however, is so weak that you would never notice without statistical analysis. Also see comment here). Do these factors affect the circulation patterns over the North Atlantic? The sunspots tend to vary on a time scale of 10-12 years, but the NAO-index suggests that few of the extreme low values were repeated over two subsequent years. In other words, the NAO doesn’t show the same persistence as the sunspots. It will be interesting to see if this winter will break with previous patterns – if it does, that could be interpreted as a support of Petoukhov and Semenov hypothesis.

It is nevertheless no contradiction between a global warming and cold winters in regions like Europe. Rather, recent analysis suggest that the global mean temperature is marching towards higher values (see figure below), and Petoukhov and Semenov argue that the cold winter should be an expected consequence of a global warming.

Global mean near-surface air temperature from NCEP/NCAR reanalysis. Reanalyses are often not regarded as reliable as more traditional analyses for long-term trends, but can nevertheless give some indication on where the last year lies in terms of the recent past.

618 Responses to “Cold winter in a world of warming?”

  1. 301
    Chris O'Neill says:

    Oakwood @293:

    While we were having milder than average winters,then these were presented as evidence of global warming.

    No they weren’t. Not by anyone who knows what they’re talking about. A single weather event is not evidence for or against global warming.

  2. 302
    suzanne says:

    The first thing that needs to happen is that people stop using the phrase ‘global warming.’ We all need to use ‘climate change’ to accurately talk about what’s happening. Deniers, especially, nit pick about the terminology when it’s a brutally cold winter, and people who are skeptical are not convinced to look into it further if they think all weather should now be warm.

    We need to educate everyone about the facts, and there are plenty of them out there. We also need to do our part to conserve resources. [edit – no ads please]

  3. 303
    Didactylos says:

    And yet the globe warms.

    Nitpickers gonna nitpick, no matter what. Liars gonna lie, too.

    I was particularly irritated by a BBC News story that stated baldly that December will be “coldest since records began” without bothering to state “only in the UK” anywhere in the article.

    Won’t people be confused when the headline in January is “December really hot”!

  4. 304

    #301–But it wasn’t a “single event,” was it? It was a long run of mild winters, and it was both seen to be, and cited, as supportive of the reality of AGW. (For example, I’m in the Atlanta area; and we’ve had weeks of freezing temperatures now. That’s been most atypical over the last fifteen years or so. And, by gosh, we had the first white Christmas since (IIRC the radio comment) 1993.)

    Of course, we also had a very warm summer and especially fall (up until December 1, when somebody apparently flipped the switch labeled “winter.”) And–equally of course–there’s a huge area of the Arctic experiencing very high warm anomalies. So the frigid conditions here don’t spell an end to warming by any means.

    But they are a PR problem.

  5. 305
    Adam R. says:

    Why is it so hard for you to believe that others, equally or far more educated, can have an honest difference of opinion?

    Why is it so hard for you to see the difference between an honest difference of opinion and a shop-worn meme from a denier?

  6. 306
    Dr. Shooshmon, phd. says:

    Given that the earth is currently below it’s historical average atmospheric co2 content, I don’t think that the forcings of co2 can be meaninfully tested. All of these talks of trends are meaningless because these trends are occuring at an unusual time in earth’s history. It is abnormal for the planet to have so little co2. The ice caps are also unusual and so it isn’t very hard for a scientist to predict them melting away eventually. Essentially, all you are doing is identifying ongoing patterns that have already occurred. The fact that these events has already occurred and the planet did not explode invalidates global goring theory.

  7. 307
    Ray Ladbury says:

    gleaner63, Well, except that science isn’t a matter of opinion, is it? It is a matter of evidence. What are we to think of those who 1)refuse to consider the overwhelming evidence; or 2)are aware of it, but either distort or lie about it? Where is the honesty in that?

  8. 308

    Dr. Shooshman – awesome analysis. Really deep. Very insightful. Thanks!

  9. 309
    Maya from the peanut gallery says:

    “I don’t think that the forcings of co2 can be meaninfully tested.”

    Then you haven’t been doing ANY research on the subject. You really need to understand a subject before you try to debate it, ok? Truly, it’s not like thousands of scientists have pulled this out of a magic top hat – there is logic and data to back it up; all you have to do is read it. Until then, what you’re saying makes about as much sense as saying, “Well, we can’t possibly have cities on the planet because for most of the planet’s histories, there haven’t been any cities, and since it’s so unusual and abnormal for there to be creatures with opposable thumbs on the planet, we can’t tell what cities really are.”

  10. 310
    Radge Havers says:

    “Dr. Shooshmon, phd.” @ 306

    Seriously, you think anyone is taken in by that?


  11. 311
    Louise D says:

    Dr. Shooshmon, phd. @ 306 obviously doesn’t have a phd in science or is he being facetious? Some of the people who post here don’t even seem to have a slight understanding of any of the science involved, or how scientific processes work.
    My best present this Christmas was Gavin’s ‘Climate Change, picturing the science’. I heartily recommend it to any one who wants, or needs, to learn more and doesn’t want anything too technical

    [Response: Thanks! I quite agree ;-) – gavin]

  12. 312
    Hank Roberts says:

    > Given that the earth is currently below it’s historical
    > average atmospheric co2 content, I don’t think that the
    > forcings of co2 can be meaninfully tested.

    Earth is above its “historical average CO2 content” the other half of the time. Poor troll.

  13. 313
    FurryCatHerder says:

    gavin’s response @ 293:

    I had less trouble with “Global warming causes warmer winters” years ago when we weren’t having winter anymore. It was 22F here this morning for the low and that’s a recent experience, relative to the past 10 to 15 years. We had several winters where I never wore a long sleeved shirt, and I’m not the most cold-tolerant person on the planet.

    The bigger issue is that “winter” and “summer” seem to be losing their regularity or predictability, not that they are “warmer”. If they were “warmer”, fine. So be it. The bigger danger seems to be that there isn’t the predictability that once existed. Three years ago I was ready to take a chainsaw to my peach trees, and replant with a variety that didn’t require as much cold to make fruit. Now I’m back to the old grind of checking for buds and planning the appropriate application of fertilizer and various other chemicals as the winter wears on. That, to me, is the risk — uncertainty about which way things are going from year to year. Gradual changes are far more adaptable than chaos.

    [Response: Again I have to stress that claims like ‘it’s getting more variable’ etc need to be demonstrated. People’s memories are absolutely hopeless at assessing something like the standard deviation in snowfall or temperature over a few decades. Similarly, while it’s hard to discern changes in the mean over such short intervals, it’s even more difficult to statistically identify changes in the higher moments, let alone decide whether they are attributable to anything in particular. Can I please make a plea for people not to make post-hoc ‘pop’ attributions of anything that happens? Attribution is hard, and not something that can be done on a dime just because it snowed yesterday…. – gavin]

  14. 314
    Brian Dodge says:

    @ Dr. Shooshmon, phd. — 27 December 2010 @ 10:50 AM

    Given that the earth’s civilization is currently well above it’s historical average industrialization, agriculture output, consumption of non-renewable resources, and medical care, I don’t think that the benefits to overall population can be meaninfully tested. All of these talks of trends are meaningless because these trends are occuring at an unusual time in civilization’s history. It is abnormal for the planet to have so much human productivity. The 6.6 billion people now alive are also unusual and so it isn’t very hard for a scientist to predict them melting away eventually. Essentially, all you are doing is identifying ongoing patterns of extinction that have already occurred. The fact that mass die off events(Black Plague, 1918 flu epidemic) have already occurred and the planet did not explode invalidates any argument for the disproportionate value of human life.

    “It was the Law of the Sea, they said. Civilization ends at the waterline. Beyond that, we all enter the food chain, and not always right at the top.”
    Hunter S. Thompson

    And as the ice melts, the waterline rises.

  15. 315
    Dr. Shooshmon, phd. says:


    Who is “you”? On average winters are getting warmer and will continue to do so.

    When you say “on average” what time frame are you talking about? Additionally, I do not like the term “climate change” because to me climate change is the changing of seasons and we’re really talking about sustained higher temperatures.

  16. 316
    kervennic says:

    Few years ago I was reading in the news,following the catastrophic holywood movie based on a local cooling effect, that such a scenario was completely unlikely to happen, since it would take much more time for the gulf stream to slow and by this time the warming effects would have erased the absence of conveyed warmth.

    But now i read the reverse:measure of the gulf stream do show a 30 % decrease since measurement have been started, and everybody seems to get scare because greenland ice sheet melts far faster than predicted which might freeze this warm current… Any “official” comment on that ?

    Winters are now regularly colder in atlantic europe, is that a trend that we can count on in the next 50 years… Is it impossible to model the effect of the gulf stream, which seems to be a quite regular heat current and estimate what will be the subsequent cooling. If such, this will be catastrophic, since the atlantic facade is highly populated and will burn even more fossil fuel in the coming years….

    Or do you thing this cannot be a trend.
    Would be nice to know to get prepared…

  17. 317
    Alpha Tango says:

    Good to see that youre finally talking about how this, and youve even allowed a couple of mild “denier” comments. Lots of plausible theories being proposed, but you should not try to rewrite history and claim that this was expected.

  18. 318
    Ray Ladbury says:

    Dr. Shooshman, personal incredulity does not constitute scientific evidence. Why not try looking at some. There’s lots of it, and it all says we’re warming the planet. Now run along ’til you learn some science.

  19. 319
    Dr. Shooshmon, phd. says:


    Maya you and others have miscontrued my statements. Cities and industrialization are irrelevant to my discussion because I am talking about quantities of co2 in the atmosphere from a historical perspective. You seem to think the human contribution is more important than other life forms, like the dinosaurs.

    [Response: And what was the dinosaurs’ contribution to atmospheric CO2, just out of curiosity?–Jim]

    I’m simply telling you that there isn’t much co2 in the atmosphere, historically speaking. Sure, you could say cities are an anomaly but they are artifical not natural, which is what I am talking about.

  20. 320
    Dr. Shooshmon, phd. says:

    @Brian Lodge

    Brian, I don’t find the human population to be special. There have been billions of other animals also. I think a warmer world could beneficial to the human race, it may not. However, I think that we will not know what the best GAT is until we actually experience it. How is the co2 doubling hypothesis tested? Is it tested against historical patterns or is it computed through models? I think that the temperature rise from a co2 doubling, including feedbacks is highly speculative because it cannot be tested? Gavin, would you agree?

    [Response: Not in the slightest. – gavin]

  21. 321
    john byatt says:

    George Monbiot has chased up a list of references

  22. 322
    Esop says:

    #314 (Alpha)
    Connection between Arctic summer sea ice and European winter temperatures was proposed back in 1914 (Hildebrandsson) and demonstrated in computer models in 2004. Note that in northern Europe, cold November and December has been pretty much the rule in winters since 1988 (18/23), it is January-March period that has been mild. If that happens in the 2011 winter remains to be seen.

  23. 323
    doug says:

    Dr. Shooshmon, phd.

    Apparently you think so highly of yourself, that you don’t mind bothering the leading scientists in the world on this subject, when all you have to do is research it a little bit, like others have said. You don’t realize it, but you really are making yourself look like a fool. If you didn’t notice, on the home page of realclimate there is a guide to get you caught up on the basics. Please do that for us. I recommend that you make yourself anonymous for about two years, follow these discussions, and then post your next comment to someone who is as naive as you are now.

    Then you would be following my pattern. I was just as (un)knowledgable as you when I started reading here two years ago, and now you are bringing out my first comment. Thank you.

  24. 324
    Maya from the peanut gallery says:

    Shooshman, no, I don’t think I misconstrued your statements at all. You seem to have missed my point in a roundabout way: of course cities are irrelevant to your “discussion” because your point makes no sense. If you’ll go back and read it, I prefaced that by saying it would “make about as much sense as saying…”

    What difference does it make if CO2 used to be higher or lower? I mean seriously, it’s irrelevant. The planet used to have a methane atmosphere, too. So what? In absolutely no way at all does that make it any less important that the CO2 is increasing now.

    Yes, I do think the human contribution (although technically, it IS from the dinosaurs) is more important. Of *course* it is. If the increase was natural, it’s highly unlikely that it would be so fast, and it’s the speed of the increase as much as the quantity that’s important.

    Why doesn’t that make sense to you? I mean that as a serious question, not rhetorical. The physics of global warming is well-established, and has been for like a century. There’s no question that humans are causing an increase in CO2 – the “fingerprint” is unmistakable ( The rise is *thousands* of times faster than it would likely be if it were natural. And, it’s now at a level higher than any our species has seen. Ever.

    So, what is your point, exactly? To say the forcings can’t be measured or modeled simply isn’t true. To say that the whole thing is irrelevant because this epoch is “unusual” is ludicrous. You keep saying that CO2 used to be lower, and that really is irrelevant.

    If you’re trying to say you don’t believe us, the science doesn’t care if you believe it.

    If you’re trying to say that we shouldn’t be concerned about climate change because the climate has changed before, know that the climate changes according to the forces acting upon it, of which humans are now far and away the dominant force.

    And by the way, it’s not the sun, there is a consensus, it’s not cooling, the models are not unreliable, the temperature record is not unreliable, it has warmed since 1998, most climate research in the 1970s predicted warming, the next ice age has been cancelled, Antarctica is not gaining ice, Al Gore didn’t get it wrong, it’s not cosmic rays, 1934 was not the hottest year on record, Mars isn’t warming, the hockey stick isn’t broken, it’s not an Urban Heat Island effect, it’s not a natural cycle this time, Arctic sea ice doesn’t melt at this rate because of a natural cycle, and don’t tell me it’s not that bad because it really is that bad.

    Did I miss any?

  25. 325
    doug says:

    Dr. Shooshmon,

    Do you think Gavin and the other scientists (who are among the leading scientists in the world on this subject) should be responding to every naive question you have, when you clearly have not studied the subject? Go to the home page. There’s instuctions on how to get yourself up to speed. I waited two years to comment, and you’ve brought out that comment. I guess that makes me as important as you now.

  26. 326
    Iso says:

    There are a lot of possible climate combinations and sequences to consider, for example, if:

    ENSO = 1 or 0

    NAO = 1 or 0

    NAM = 1 or 0

    NP = 1 0r 0,

    then we get 2 x 2 x 2 x 2 factorial with 16 possible combinations. Add to this frequency and amplitude, not to mention other patterns, and we get many, many different combinations, all of which can contribute to different sequences of combinations, etc…

    Adding Humans as a factor just makes gavin et al job harder…

  27. 327
    Maya from the peanut gallery says:

    Oh I’m sorry, I missed a whole list of them: there is no “warmist” conspiracy, Jupiter and Neptune aren’t warming either, it isn’t warmer than the Medieval warm period, it’s not El Nino, it’s not the Pacific Decadal Oscillation, it’s not the methane, and it’s not the CFCs.

    There’s about 20 others I could list, too, but the one that probably is the most relevant is: The Ordovician glaciation was a brief excursion to coldness during an otherwise warm era, due to a coincidence of conditions. It is completely consistent with climate science. When CO2 levels were higher in the past, solar levels were also lower. The combined effect of sun and CO2 matches well with climate. (Direct quotes from

  28. 328
    bob says:

    Dr Schooshmon : If you will agree with everything schmit,hanson, mann, gore, ladbury and a few other over educated dinks have to say on real climate, You will be suprised how much better educated you are..

  29. 329
    flxible says:

    re Sooshmon – You folks need to understand that this is a parrot repeating the same exact random collection of sounds it’s been squawking on a range of climate related sites for awhile now, mostly contrarian sites, but the same foolishness. He’s even recently assured us his research indicates ice at both poles is massively increasing and will continue so for the coming decade. ;)

  30. 330
    Hank Roberts says:

    > shooshmon
    And friends

  31. 331
    Lawrence Coleman says:

    Still pouring here in queensland aussie. Virtually the entire state has experienced to put that into perspective..queensland is about the same area as 1/2 the USA. Or from the shoreline of california to kansas. Mass evacuations are taking place in many towns throughout the state. The bureau of meteorology has no idea just how high the already flooded rivers will go since this has never occured to nearly such an extent in our history. We are in the middle of uncharted the mercy of the modern global climatic paradigm.

  32. 332
    doug says:

    re 319. Jim, you were wondering what was the dinosaur’s contributions to co2. Haven’t you ever seen the green dinosaur on all the Sinclair gas station signs? Duh.

  33. 333
    FurryCatHerder says:

    Gavin @ 313:

    No, my “memory” isn’t broken and I’ve looked at the temperatures that I keep as well as “proxies” like utility bills. But also, my observations were consistent with “Global Warming” — until the middle of the last decade. For example, the average annual temperature at ABI airport, according to the government, had been about 70F. The average for 2007 was 66.6, and for the last 3 years the average =has= been below the average. January ’10 was tied for “coldest” with ’01, and you have to go back to ’85 to find a colder January. February ’10 averaged 45.9F, and you have to go back to ’78 for find a colder February. Rounding out “winter”, more or less, December ’09 was the second coldest of the past 20 years, and only because I didn’t look further back.

    So, no, not at all my failing memory. And definitely not data WUWT brainwashed me into reading — it’s real live instrument data records from NOAA.

    [Response: Huh? Maybe I’m tired or something, but I don’t see how this is anything to do with what I said. I’ll reiterate though. If you have a noisy process, you need a long time to detect whether there has been a shift in the mean (at a single weather station, that can be decades). You need an even longer time to detect a change in the variance. Thus regardless of how good your memory is, there simply isn’t enough data to reliably say that there has been a change in the variance. There might be a change in the sample variance from one period to another, but detecting a statistically significant change (as opposed to just the kind of thing that might happen for time to time) is hard. Nothing to do with brainwashing, WUWT, or you. – gavin]

  34. 334
    Pete Dunkelberg says:

    Gavin @ 313 “Attribution is hard”

    Perhaps some of us should print that in large letters and tape it to the refrigerator.

  35. 335
    Radge Havers says:

    Might as well deck the wall with shills and folly. It is the season to be jolly (if not the climate). Stoke the fires with coal and petrol. Corral that ancient yuletide troll–laughing, quaffing all together. Heedless of the wind and weather.


  36. 336
    Hank Roberts says:

    kervennic wrote

    “… gulf stream do show a 30 % decrease … greenland ice sheet melts
    far faster than predicted which might freeze this warm current…”

    Would you say where you read that? What’s your source?
    There are copies of copies of all sorts of stories floating around.

    A search on this site is often a good place to find a science discussion.

  37. 337
    SWDoughty says:

    Can I please make a plea for people not to make post-hoc ‘pop’ attributions of anything that happens? Attribution is hard, and not something that can be done on a dime just because it snowed yesterday…. – gavin]

    For my part, I have asked about the different responses in northeastern North America than those in other parts of the continent, based on my own observations, read attributions. Now I find this piece of information which appears to validate the observations.

  38. 338
    Aaron Lewis says:

    Dear Gavin,
    The Arctic sea ice events of 2007, 2008, 2009, and 2010 are specific weather events that can be attributed to AGW as part of larger trends. Then, the changes in NH Atmospheric circulation resulting from additional water vapor in the Arctic as a result of less sea ice can be attributed to AGW. This leads to a long trickle down of weather attribution to AGW. Moreover, additional heat in the atmosphere and the oceans affects each and every storm (and every day between storms). The process may not meet your standards for some purposes, but it may be good enough for some real world decisions, planning, and even engineering.

    As long as you say there is no “attribution” for weather, those real world decisions, treaties, and legislation are going to get put off. (Or, are going to be weaker than they should be!)

    In 2003, I suggested that we would see significant Arctic Sea ice melt within a decade, and you said that such “alarmism was unhelpful.” I was not alarmist, we have had such ice melt events that were “significant” within any normal use of the word. It was you who over estimated the stability of the Arctic Ice System, and you shouted down people that actually had the correct answer. You still over estimate the stability of the Arctic Ice System without noting that amplitude of the oscillations are increasing. This is the way feedback systems behave just before seeking a new equilibrium. Within the next 2 or 3 years we will see additional massive ice loss from the Arctic Sea Ice System.

    You are still shouting down the people with the right answer. The right answer is that AGW is the most important and urgent problem in the world today. Nothing else matters until we have got ourselves on the right track with respect to AGW.

  39. 339
    Brian Dodge says:
    “Slowing of the Atlantic meridional overturning circulation at 25° N”
    Harry L. Bryden, Hannah R. Longworth and Stuart A. Cunningham; Nature 438, 655-657 (1 December 2005)

    “Here we analyse a new 25° N transatlantic section and compare it with four previous sections taken over the past five decades. The comparison suggests that the Atlantic meridional overturning circulation has slowed by about 30 per cent between 1957 and 2004.”

    [Response: We discussed this rather critically at the time, and later data showed that it was very likely that these results were just the unfortunate aliasing of large high frequency variability. This has nothing to do with anything we are discussing above (since North Atlantic SST is very clearly warming). – gavin

  40. 340
  41. 341
    Edward Greisch says:

    Revkin now has an article on the same subject at:

  42. 342
    Andreas says:

    Re #316, kervennic:

    Winters are now regularly colder in atlantic europe

    What is “regularly” and where is “atlantic europe”?

    It’s just the last winter that has been cold in much of Europe, and this one may be cold. Some data (CRUTEM3, land only, climatology last 100 winters; Nov gray, Dec purple, Jan dark blue, Feb ligh blue, Mar cyan; black line is Dec/Jan/Feb mean, filtered by a 17-point binomial filter):

    France (Feb 1956 clipped off below)
    Spain (north)
    Norway (Jan 1989, Feb 1990 clipped off above)
    Germany (east; Feb 1929, Feb 1956 clipped off below, Feb 1990 above)
    Sweden (southeast; Feb 1990 clipped off above)

    BTW, homogeneity of many time series is obviously really bad. GISTEMP lacks homogeneity too, and that seems to be semi-intentional. Hansen et al. 1999:

    We use the version of the GHCN without homogeneity adjustment, as we carry out our own adjustment described below.

    But what is described in section “Homogeneity Adjustment” has nothing to do with homogeneity adjustment; it deals with the adjustment of the trend for possible urban heat island effects instead. UHIs don’t produce any inhomogeneity; inhomogeneity is caused by changes in measurement locations, instruments or procedures.

    However, inhomogeneity isn’t much a problem for more recent data; the main problems lie in the early parts of the records, mostly more than 100 years ago. Some problems may still exist in less developed countries.

  43. 343
    Alex Katarsis says:

    [edit – OT]

  44. 344

    #338 Aaron,

    “The Arctic sea ice events of 2007, 2008, 2009, and 2010 are specific weather events that can be attributed to AGW as part of larger trends. Then, the changes in NH Atmospheric circulation resulting from additional water vapor in the Arctic as a result of less sea ice can be attributed to AGW. ”

    I totally agree, Winter Polar lows are getting more energized over locations of open sea water (which were once iced over), they appear to last longer and penetrate Northwards deeper all within last few decades. But I think that Gavin is dealing with snowstorms which shut down NY city for example. In this case, Dr Masters again explained the Northeaster very well,, Northeasters don’t occur often during La-Ninas. Attribution to AGW in this case is more difficult, but certainly the entire weather scene is surely not predictable according to the theory of climate persistence, using La-Nina template as a way to project reasonably well, falls apart when planetary waves behave differently. An Accuweather meteorologist predicted a “wall of snow” just South of the great lakes for instance, largely because its a La-Nina winter, this “wall of snow” appeared on the NE coast instead . I suggest here that more and more, as AGW kicks in, climate will look rather strange, not just for the Arctic (and its been very very strange here) , but everywhere, being unable to recognize “normal” patterns especially during well known oscillations , this unpredictability is expected as we enter new sea and landscapes caused by greater warming until equilibrium is reached. So I don’t entirely attribute everything to AGW but there are ways to recognize its imprint. I fault those who generalize “you cant attribute” anything to anything because in the end,
    someone else will, and they are not the types who adhere to or respect those who are successful in science, they fill the void of orthodox scientific terminologies with crap.

  45. 345
    Lawrence Coleman says:

    338 Aaron Lewis, don’t forget scientists are treading a very fine line regarding public perception and credibility. Any degree of crying wolf will be seized by the media as ammunition to discredit the scientific community which alerted us to the possiblity of CC in the first place. I think Gavin well understands the situation..he’s got his finger on far more quality data than you have do doubt! I also agree that AGW is by far the most important issue the world has to face..not just now but for at least the next 100 years. Total sustainablity and a virtually zero nett carbon footprint per head of pop. is absolutely essential if the planet and all it’s lifeforms are to survive the next century. People are again forgetting the blue whale in the room..population control! Unless we as a planet regulate our current population and REDUCE it from it’s current unsustainable level any form of CC mitigation is virtually impossible to achieve.
    Here chirps our regualr know your name..who says “Yes but us humans are very intelligent and ingenious at finding solutions to crisis’…What Balderdash! The demographic with the scientific means at it’s disposal also happens to be one of the most selfish, egotistical and materialistic homo sapiens on earth. Me first..what in it for me..etc. How we are going to achieve global CC reversal is by collectively inspired leadership by policy makers and shakers filtering down to and ammending school curriculum to teach kids the importance of working together unselfishly and teach them ways to effectively do their part in the solution and inspire others to do likewise. Another words this will require a whole new mind set for the most wasteful demographic on earth…but the irony is..this is not a ‘new’ is but the ‘oldest’ which we have long forgotten in our brainless and immoral pursuit of ‘stuff’.

  46. 346
    Ibrahim says:

    Can anyone tell me where all the heat goes right now from the condensation to the rain and snow?

  47. 347

    Scots stereotype 306: The fact that these events has already occurred and the planet did not explode invalidates global goring theory.

    BPL: I don’t think you have the faintest idea what AGW theory actually says. Nor do I think you’re a Ph.D.

  48. 348

    Dialect Boy 319: I’m simply telling you that there isn’t much co2 in the atmosphere, historically speaking.

    BPL: I’m simply telling you that you’re wrong. Geohistorically, maybe, but historically, we’ve got higher CO2 now than any time in the last 800,000 years. And who cares what atmospheric conditions were like when the land was uninhabitable? For most of Earth’s history, there was too much land solar UV flux for land life. Should we accept that as normal, too?

    We live now, not in deep geological history.

  49. 349
    Iso says:

    Dear Aaron Lewis,

    What part of ‘many, many combinations’ don’t you understand? You need to be very careful with attribution. Scientists that use dramatisation to further their career and public influence, etc…, need to take a breather. While it is not unreasonable to expect certain effects, such as a contraction of polar winds due to warming, please take the time to understand the system you are affecting, otherwise your results are bubkus. What do the statistics tell you? That it is not due to chance? As a seasoned hardcore AGW denier, I can tell you, that god does not play dice.

  50. 350

    Ibrahim: Can anyone tell me where all the heat goes right now from the condensation to the rain and snow?

    BPL: Start here: