What's up with the weather?


Yesterday evening, I stood at a bus stop in Minneapolis wearing no socks, no gloves, and no hat. The breeze was warm. The birds were singing. Clearly, something is deeply wrong here. In fact, 2012 has brought the warmest start to a January on record in the Twin Cities. We're also in the middle of a major drought, which, this time of year, means no snow on the ground.

All of that has consequences—just this morning Minnesota Public Radio was talking about the economic impact the drought has had on snowmobile-based tourism in this state. What everybody wants to know: Is this caused by climate change? Is this what it will be like next year, too?

That's really hard to say. Remember: The really solid stuff scientists can tell you about climate change comes from analysis of trends over decades—for instance, when you look at global temperature anomalies over 50 years and find that the last time the global mean monthly average was lower than the 20th century average was back in February 1985. That's because, while anthropogenic climate change exists, it's not the only thing influencing the local weather or the global climate. The climate system involves a lot of different phenomena, which act alone and together. We can see a pattern of warming that can be linked to rising carbon dioxide levels in the atmosphere. But there's other stuff going on, too, which affects year-to-year fluctuations within the decades-long pattern.

In this case, says Jeff Marsters on the Weather Underground blog, the abnormally high temperatures are related to oddities in the jet stream—air currents in Earth's atmosphere. And those oddities may, or may not, be the result of anthropogenic climate change.

The cause of this warm first half of winter is the most extreme configuration of the jet stream ever recorded, as measured by the North Atlantic Oscillation (NAO). The Arctic Oscillation (AO), and its close cousin, the North Atlantic Oscillation, are climate patterns in the Northern Hemisphere defined by fluctuations in the difference of sea-level pressure in the North Atlantic between the Icelandic Low and the Azores High. The AO and NAO have significant impacts on winter weather in North America and Europe--the AO and NAO affect the path, intensity, and shape of the jet stream, influencing where storms track and how strong these storms become. During December 2011, the NAO index was +2.52, which was the most extreme difference in pressure between Iceland and the Azores ever observed in December (records of the NAO go back to 1865.) The AO during December 2011 had its second most extreme December value on record, behind the equally unusual December of 2006. These positive AO/NAO conditions caused the Icelandic Low to draw a strong south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward over the U.S. and Europe.

The December Arctic Oscillation index has fluctuated wildly over the past six years, with the two most extreme positive and two most extreme negative values on record. Unfortunately, we don't understand why the AO varies so much from winter to winter, nor why the AO has taken on such extreme configurations during four of the past six winters. Climate models are generally too crude to make skillful predictions on how human-caused climate change may be affecting the AO, or what might happen to the AO in the future. There is research linking an increase in solar activity and sunspots with the positive phase of the AO. Solar activity has increased sharply this winter compared to the past two winters, so perhaps we have seen a strong solar influence on the winter AO the past three winters. Arctic sea ice loss has been linked to the negative (cold) phase of the AO, like we observed the previous two winters. Those winters both had near-record low amounts of sunspot activity, so sea ice loss and low sunspot activity may have combined to bring a negative AO.

Image: Crazy (awesome) Minnesota Christmas weather, a Creative Commons Attribution (2.0) image from shilad's photostream. Please note the lack of snow, the fact that there is open water on Lake Harriet, the presence of ducks, and the lack of hat and gloves on that woman. This is not normal for Minnesota in December. 



  1. So are you saying that the jury’s still out over whether we can blame the lack of snow on Republicans?

  2. “Is this caused by climate change?” is not only hard to answer, it’s the wrong question. Weather is a chaotic system, so you can’t talk about cause and effect in the same way that you can in simple linear systems. Attribution science (the part of climate science that studies the impact of climate change on extreme weather events) tends to focus on how much climate change increases or decreases the frequency (or recurrence) of different kinds of extreme. So a better question would be “Is this the kind of thing we can expect more of due to climate change?”.

    For an up-to-date white paper on attribution science, see the paper by Peter Stott et al presented at the WCRP conference a few months ago:

    1. I don’t have time to read the paper. Can we expect more extreme weather due to climate change? I suspect the answer is yes.

      1. If “extreme” just means different from what we would expect based on the climate we grew up with, then it’s a tautology. A different climate by definition will bring different weather patterns. Which in turn means most places on earth will experience some kinds of record-breaking weather, because it will be different from the weather when the records were made.

        If extreme means destructive, then the answer is probably also yes, for the simple reason that warmer air holds more moisture, and has more energy. With respect to any specific *kind* of extreme weather, it’s much harder to say. However, the extra energy probably means stronger winds, and the extra moisture probably means more extreme rain and snowfalls. However, water also evaporates faster from plants and soils in a warmer climate, so droughts are more likely. How these different trends affect each other is hard to forecast. And nobody yet can explain the weird patterns of the Arctic oscillation that Jeff Masters notes – it’ll probably take a few years of research to figure that out.

    2. “Weather is a chaotic system, so you can’t talk about cause and effect” — Actually, chaotic systems are highly deterministic so yes we can talk about cause and effect. What is more difficult is predicting future behavior but the causes are well known and understood.

      1. @neon:disqus : you missed the most important part of what I said: “…in the same way that you can in simple linear systems”. So an event can have very different outcomes, depending on which region of the system’s behaviour it’s in. And as it’s really hard to measure *exactly* which state it’s in, it’s really hard to say anything deterministic about the weather; best we can do is talk about probabilities.
        It’s irrelevant that chaotic systems are deterministic if you can’t measure the current state precisely.

        1. “it’s really hard to say anything deterministic about the weather” —- Not at all. It’s very easy to say what the causal factors are that determine particular weather events.

          It seems to me you are confusing causality with predictability. People make this same mistake with the social sciences when they believe that sociology (and other disciplines) are somehow “soft” sciences. In fact the actual science for the social sciences is *better* than that for some physical sciences.

          What causes global warming has been known and understood for 30 years and the basic science behind it has not changed one iota since then.

          1. Neon: It is you who are confused. I’m talking about weather, you’re talking about climate. Too many people confuse the two. I have no argument with you about climate change and its causes. The problem is that we really don’t know much about how climate change will impact local weather systems. To my mind this makes climate change all the more worrying: we know we’re messing up the climate, and we really can’t predict where and when it will bite us. It’s like flying blind over dangerous terrain.

  3. I am not suggesting that current weather is the result of climate change. But this is the sort of odd ball weather that is predicted by climate change.

    So, not to say this is currently caused by climate change, but it is certainly what is in store for us going forward.

      1. The flip side is a dying ecosystem that when it goes will take *everything* with it. Ecosystems are very resilient and can take and take and take a lot of abuse. Until they don’t….. and then everything goes down.

  4. 7 hours north of you in Winnipeg (the frozen wasteland of Canada) we have almost no snow. Has been +7 Celsius for the last three days with our normal yearly temperature normally below -20. I’ve been outside running in a t-shirt. December and January have broken almost all held records for each consecutive day.  Seriously, something is messed up.

    1. Haven’t had any frost/freezes this fall and winter at even higher latitude in Europe. 
      Today in the garden I saw the blossoms of roses, crocuses (croci), rhododendrons, daisies, poppies, and many more. 
      The last two winters I shoveled snow almost daily. 
      Weather is being extreme. 
      But we ain’t seen nothing yet.

      1. We’re in Northern China and it’s the same story. We had a couple of pretty minor snows in late November/early December, then nothing. It does get fairly cold, but not nearly as bad as the last few winters.

  5. This oscillation (or whatever you want to call it) has completely destroyed the chances at having any winter fun this year.. winter walks, ice skating, skiing, you name it, it’s probably not going to happen.

    It’s inevitable that there’s going to be SOME winter weather, but we’re already close to the midpoint of January, which means it’s already time to start thinking about spring. So even if temperatures were to suddenly drop, it’s not going to last for long.

    Summary: worst. winter. ever.

  6. Yep, the high today for Chicago is 54.  January is usually a bitter, freezing nightmare.  This is nice, but disorienting.

  7. During the ice age, humanity was driven to near extinction. New York, Canada and the most of the Northern hemisphere did not even exist. I suspect mankind will handle global warming far better than it does global cooling.

    1. That depends on how hot things get.  At least in winter you have an endless supply of fresh water…(assuming it’s snowing.)

  8. I know it’s anecdotal and isn’t proof of anything, but where I live in northern California we get, on average, a bit over eleven inches of rain in December and about ten and a half inches in January. They’re our two wettest months. However, we only got a day or two of very light rain all December and not a drop this January so far, with none predicted any time soon. We’ve had no snow. It’s January 10th and it warm enough that I have my windows open. 

      1. Wet or dry, it’s almost always predicted to be a record fire season in the west. Wet conditions create lots of underbrush which feed fires, and dry conditions make what’s there more likely to catch fire. What would reduce fires in the west would be a wet and cool summer, which does happen from time to time, but even that means that the fuels begin to build up for future fire seasons. That’s why fire is, as it has been for a long long time, a regular feature of the western landscape…the only thing that really has made it worse is that now modern humans and their highly valued material culture is now spread across it while not designed to resist the inevitable fires, and on which our society spends enormous amounts of resources and efforts to protect, or failing that, replace with stuff that typically is just as vulnerable, if not more vulnerable, as the stuff that just got burned-up. Crazy, isn’t it? 

  9. This is very weird for Minnesota in January. My son is a high school cross country skier whose team is stuck practicing on the same man-made snow track in Theodore Wirth Park every day. There is really no other location to ski on unless they travel 15o miles to the north – Giant’s Ridge in Biwabik, MN – which the team has done several times this year already.

    On the plus side, our heating bill is looking great.

    1. Ha!  The only sport I lettered in! 
      My senior year we didn’t have snow to speak of but it was reasonably cold.  We did one of the Winona races on the lake because there wasn’t snow at St. Mary’s (the usual track).  We had to move the regionals to Cable, WI onto a portion of the Birkebeiner Trail.  Giant’s Ridge was the “team trip”.  That would’ve totally sucked to go that far for a regular conference race.  Your son has my utmost sympathy. 

  10. Say my city cuts its police force by 50%. A month later I get mugged. A reporter asks me: “Do you think this mugging was the result of the cuts?” 

    Scientifically speaking, can I say that? Where’s my control? And even if I have a controlled experiment and statistical significance, I’ll still get an incorrect result one time out of twenty. And then there’s Gödel, and Hume, and all the problems of brought up by skeptical philosophy. If your epistemology is rigorous enough, there isn’t anything left you can state as fact.

    What we’re left with is common sense and plain speaking. 

  11. Lack of snow in November and December ended up meaning Michigan (SE, anyway) broke the record for wettest year ever recorded (132 years of recorded data). 

    On the bright side, it’s not too cold to go play hockey at the outdoor (refrigerated) rink.

  12. I think we should look on the bright side.  All the fuel oil we don’t burn this winter will be great for the environment.

  13. I’ve seen cherry trees starting to bloom and bulbs were out at the NY Botanical garden.  This is going to get seriously weird in February, either full bloom or massive die-offs prior to spring.

    1. I remember a few years ago we had a really really freaky February up here in Ontario, when it was crazy warm and the bulbs all started coming up.  I thought it would be a disaster because it would get cold again and kill them.  And when it did return to winter weather the green shoots wilted some and looked miserable, but burst into bloom as usual when Spring finally did arrive sometime in May. 

      Moral: I don’t know what the F*&k is up with this weather, but bulbs are tougher than you might think.

  14. weather reporters are mostly right when they talk about what the weather was YESTERDAY… but then they are not always right! No one knows but I just have one question; when was the weather ever stable? there are HUGE variations in weather and always will be… it’s just the nature of earth!

    1. “The nature of Earth” is neither ineffable nor immutable. Obviously climate could change (and has changed) without human activity. It is just that it would change in different ways and at different times than now.

      When it comes to pollution – any pollution – we are shitting where we eat and justifying it all by whining “Are you sure it would be better if we went to the toilet? It is just such a long walk away!”

  15. Same happened to me! Today I was at the bus stop wearing  shorts and a tee-shirt. And it was only 32ºC.
    Greetings from Chile ;-).

  16. December 25, 2011 was the warmest day on record at the South Pole: 9 degrees F above zero.

    That should scare anyone.

  17. I can tell you where all the snow is.  Cordova, Alaska has gotten 18 feet so far this winter.  Anchorage is now over average for the whole winter.  If you want show we can send you lots.

  18. I have no temperature horror stories (this week), but the dewpoint was under 0°F for a week and was -12° for a day.  Much cracking and bleeding was done.

  19. I thinks it’s important to note that we just witnessed an abnormally low and long solar minimum. Solar activity is only now picking up. Before long there will be a lot more energy in our atmosphere. But there’s enough reason to be worried already. The warming arctic is releasing gigantic amounts of methane into the atmosphere. Much, more and sooner than expected. As a greenhouse gas methane is 20x worse than CO2. Sorry for the bad news. But it will get worse. …And the people making the decisions still don’t get it.


  20. the warm, humid winter in the UK has been depressing too, the same jet stream, not one cold, frosty day all winter and we had no autumn, summer was wet and cooler than “autumn”. I adore snow and love cold weather and the UK is mild but we usually have cold snaps but this year double figures, tee shirt weather on Xmas day. Not fun.

    1. Where I am it has been lovely weather.  Temperate with no need for airconditioning.  Which is not at all like summer I am used to.  It is not even hitting 30 C most days.

  21. Well we are in the middle of summer here in Victoria, Australia and looking out the window the clouds are thick in the sky and the breeze is quite cool. In fact my feet are cold. Usually we would be sweltering in the high 30’s.

  22. I live in Minneapolis, and I have not forgotten last year’s winter. Snowpocalypse and Snowmageddon in the same winter. I’m enjoying this. The epic extreme swings are rather disconcerting though.

  23. Maggie, I love it when you use local photos! It always make me feel part of a secret MLPS club.

    That particular spot (I call it the Duck Lookout) on Lake Harriet is a bird watching favorite of mine and, compared to last year, looks totally different.

    For one, the two figures standing in the background would be getting their feet wet. There is usually a break between shore and the little right hand island. It’s amazing how low the water was this fall. I could actually make out the resident muskrats little house in the long island strip that is 20 ft straight out from the railing.

    The other is the fact that there is open water! Lake Harriet is usually totally frozen! I wonder how that is affecting the fish. I know it’s a problem for the birds.

    The warm weather has brought back some migatory birds early and upped normal winter bird counts. The traditional (in the birding world) Christmas Bird Count had amazing numbers this year in Minnesota. If we have a cold snap, many of these birds are going to have a hard time finding food or may possibly die of the cold. Birds that stay all winter are equipped with the biological tools to deal with the cold. Our migratory bird friends are not. I hope they don’t end up freezing their fluffy butts off.

  24. Part of the problem with the question “is this unusual weather caused by global warming?” is a lack of appreciation of probability. Climate weather, so you can’t say that this is an unusually warm day, or month, or winter “because of” climate change.  What you can say is that such things will become a lot more frequent in the future because of climate change. Get used to it.

    An example that sometimes helps. Suppose you buy a lottery ticket every week. You know the drill — usually you win nothing, sometimes you win a little, once you won $100, and you know from the news that once in a while, someone gets millions. Suppose that your state decided to change the lottery rules, effective January 1, to make it more likely to win. So you buy your ticket today and, sure enough, you win, say $200.  Did you just win “because of” the rule changes? Not really — you could have won $200 on any of your previous tickets too. And you could just as well have won nothing under today’s rules. So you can’t say you won because of the new rules, but you can say that winning is likely to be more common under the new rules.

    Climate is the set of rules that governs the weather lottery. Replace “winning” by “losing” in the above and you have what it takes to answer the question, “no socks in the winter in Minnesota … is this due to climate change?”

  25. Not to snow on your parade here but it seems the old adage of ‘be careful what you wish for’ applies very much so for most of the midwest. That shit looks treacherous.

    But OTOH, this whole climate change business seems to be getting more and more noticeable with out doing any sort of ‘science’. It’s just common knowledge that midwestern winters are supposed to be cold, bitter and nasty; not warm, passable and  -as evidenced by the comments here- likable. (Aside from the snow, I love snow I just don’t like traveling in snow.)

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