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Is global warming causing extreme weather via jet stream waves?

Posted on 17 July 2014 by John Abraham

As I sit here in a northern part of the United States (Minnesota), a rare summer arctic blast barrels down from Canada on what otherwise is one of the warmest days of the year. Global warming? I could use some global warming today, people are saying.

Not only is this a teachable moment, but it coincides with a major new study on climate connections. First, let’s see the current jet stream. It is wildly undulating, first swinging up into northern Canada before curving back and plunging into the central United States.

Typically, the jet stream represents a separation between cold arctic air and warmer southern air. If you are north of the jet stream, temperatures are cold whereas south of the jet stream it's more likely to be warm.

Image obtained using Climate Reanalyzer (, Climate Change Institute, University of Maine, USA. Image obtained using Climate Reanalyzer (, Climate Change Institute, University of Maine, USA.

With this in mind, and the jet stream shown, you can almost predict the temperature pattern in the next image. The match is incredible and it is clear that my Minnesota cold-blast is more than balanced out by near 90°F temperatures in northern Canada. With all of this, I want to talk about a new study that looks at these fluctuations on a longer term.

Image obtained using Climate Reanalyzer (, Climate Change Institute, University of Maine, USA. Image obtained using Climate Reanalyzer (, Climate Change Institute, University of Maine, USA.

Very recently, a paper Amplified mid-latitude planetary waves favor particular regional weather extremes was published in the journal Nature Climate Change. The authors, James Screen and Ian Simmonds, investigated the role that changes to upper level winds in the atmosphere have on the occurrence of extreme weather. What they found was very interesting.

People who follow this site and the climate literature no doubt are aware that a hotly debated topic has arisen in recent years. I have written about studies that have linked loss of Arctic ice and warming of the Arctic region to more severe undulations in the jet stream. That research is still in its infancy and consequently, very exciting. While the idea that global warming increases jet stream undulations have been challenged by others, it is clear that some recent observations support the hypothesis.

The latest study is related to this topic but still unique. The authors don’t ask the question “are humans changing the jet stream patterns?”. Instead, they ask, “how do undulations in the jet stream affect weather?”. To be fully accurate, the study isn’t just about jet streams, it really deals with mid-latitude planetary waves but for this article, I will use the term “jet stream” as a surrogate for simplicity.

The authors went back into our weather records (1979–2012) and found the 40 months with the most extreme weather (most extreme precipitation and most extreme temperatures). They then evaluated how “wavy” the jet stream was during those extreme months. They found that,

months of extreme weather over mid-latitudes are commonly accompanied by significantly amplified quasi-stationary mid-tropospheric planetary waves. Conversely, months of near average weather over mid-latitudes are often accompanied by significantly attenuated waves.

In common parlance, this means that when the jet stream undulates and travels very slowly, we see more extreme weather. Conversely, when the jet stream travels in a straighter path, the weather is less extreme.

This association itself is not new but it brings the connection of large-scale climatic variations and our local weather to the fore of attention. Perhaps more important, however, are the follow-on observations from the authors. In particular, they report,

Depending on geographical region, certain types of extreme weather (for example hot, cold, wet, dry) are more strongly related to wave amplitude changes than others. The findings suggest that amplification of quasi-stationary waves preferentially increases the probabilities of heat waves in western North America and Central Asia, cold outbreaks in eastern North America, droughts in central North America, Europe, and central Asia, and wet spells in western Asia.

Dr James Screen, a Research Fellow at the University of Exeter and lead author of the study told me,

Click here to read the rest

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Comments 1 to 17:

  1. The play "Extreme Whether" uses Jennifer Francis's research on the Jet Stream and Arctic Ice melt. see:

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  2. 90's in northern Canada---yikes!  What does that do for the permafrost?

    Obviously, we are in for a much warmer Arctic this year.  Methane released from that permafrost will accentuate this years warming of the region for this year and maybe part of next.

    Ice?  What ice?

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  3. For people interested in this discussion, the same study is being discussed over at RealClimate

    Reports from NZ suggest that they are in a 'stuck' system now. Presumably Frances's theory wouldn't account for southern hemisphere phenomena. So is that just natural variation, or are there different dynamics leading to the same patterns in the south?

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    Moderator Response:

    [RH] Hot linked to RC discussion.

  4. Is the site 'The Cryosphere Today' the correct place to go to look at what is actually happening at the earth's poles? They have some graphs that seem very clear and helpful. If it is providing a realistic portrayal of what is going on can I use that site for reference when reading your posts?

    As a latecomer to the climate issues I would very much appreciate your help so I can come to a balanced opinion.

    Thank you so much for your help.




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  5. Edward

    Try Neven's Arctic Sea Ice Blog . It has lots of links to many sources including Cryosphere Today. And some of the regulars there are pretty cluey about the Arctic and sea ice.

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  6. Thankyou Glenn for your kind information. I have looked at the blog you suggest however find it "wanting" the ice to melt. It is important that I have a source of accurate information regarding Ice, sea level rise, global temperatures, precipitation rates etc.

    I seek the truth without bias in any direction so as to be able to compare with a response I am expecting from Paul Wheelhouse the Scottish Minister for Environment and Climate change.

    This is an important exercise as some very critical decisions that can effect the people and economy of a nation are reliant on the information available. On this matter if you can also point me in the right direction for the other climate parameters mentioned above it would be much appreciated.



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  7. I looked at Neven's sea ice blog (linked by Glenn Tamblyn @5 above) and was fascinated by this comment referring to the slow decline in sea ice area.  The comment is made in context that arctic sea ice may not show a record low level in 2014 and may in fact be greater than all of the other post 2010 years.  The comment to which I refer is;

    "And so it might be possible for this melting season to end up in the top 3, despite its bad start and lack of melt ponds.

    But for that to happen, a lot of weather that's conducive to melt, transport and compaction is needed.

    It seems very strange in view of the apparent concern that is shown about the lack of decline in Arctic sea ice volume that the writer should consider it a "bad start" that ice volume might well not be declining.  Surely this is  good unless there are reasons why increases in Arctic sea ice volume are a bad thing.   From this comment one could conjecture that the author considers a lack of decrease in Arctic sea ice volume is not good for the concept of anthropogenic global warming.  Of course that is merely conjecture and I'm sure there must be some other explanation for this extraordinary remark.  However it this comment from John Christianson in the comments section of the blog also tends to make one suspect that surprisingly the slow drop in Arctic ice volume may not seen as a blessing by everyone.  Christiansen writes:

    The colder June temperatures are the main culprit in the slow volume drop.

    "Culprit" seems an unusual choice in the context of a possible halt in the decline of Arctic sea ice volume.  Can anyone explain why a slowdown in the decline of Arctic sea ice volume warrants the concern indicated  by the wording of these comments?

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    Moderator Response:

    [JH] You should pose your question to the commenter on Neven's sea ice blog, not here.  

  8. Edward, you're of course free to go where you want for your info, but you are dismissing neven's blog too prematurely, it seems to me. It's a blog, of course, so there are a variety of voices, and they are real people, so they have a variety of emotional responses to what they are seeing (I see little evidence of your claim that people there 'want' the ice to melt, but they do get excited about dramatic events--a very human response). But mostly they are very concerned about getting an accurate picture of what is going on and they usually keep each other in check if someone is making claims not supported by the data.

    If you want general info on climate change, RealClimate is also quite good. The main posts are generally written by scientists. But again, the blog section is full of comments by people with a variety of view points and levels of knowledge.

    Skeptical Science is another go-to for me.

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  9. My apologies in line one I wrote "Arctic sea ice area"  That should read Arctic sea ice volume.

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  10. Mr Hurst,

    For sea ice info, the 2 best sites I know are NSIDC and Cryophere Today. The comparator function on Cryosphere today is especially handy. I also like their representation of the ice cover with color coding of the coverage density better than the simple "extent" used by NSIDC. For ice volume, PIOMAS is one of the best sources. The Alfre Weggener Institute has also very good information on sea ice.

    Arctic summer sea ice has beaten record lows in 2005, 2007 and 2012. Every time, the record was beaten by a very large margin. Every time, the pseudo-skeptics have nothing but nonsense to say about it. The disappearance of Arctic sea ice is a feature of global warming that had been seriously understimated. It is a "in your face" kind of indicator that can be helpful to convince policymakers to do something about the problem. Hence the tone of some remarks you may read on blogs. Not to mention the fact that pseudo-skeptics claim a recovery is under way every year that the prevoous record low is not broken.

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  11. Fair Comment moderator I'll do as advised.  

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  12. edward, Neven's blog is what it is and absolutely does not collect information. However, there are multiple organisations involved in observing the arctic. Neven helpfully provides this link on the site which shows you data from all of them. Mind you, data on arctic and Antarctica is pretty unequivocal so you shouldn't have any problem working it out. 

    The definitive site for sea level data is here. The various agencies at NOAA are good for much of the weather, ocean data. Realclimate provides this helpful link to data sources for numerous climate data and there is another link here

    [edited to make sense. Thanks to Billthefrog for pointed to a sentence that needed shooting]

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  13. Ashton wrote: "Can anyone explain why a slowdown in the decline of Arctic sea ice volume warrants the concern indicated by the wording of these comments?"

    While the moderator is correct that the best (i.e. only) source for the thinking of another person is that person, I also think the reasoning is fairly straightforward;

    If you accept that the Arctic sea ice is going to disappear, as confirmed by all models and every scientist studying the matter that I am aware of, then the sooner this becomes impossible for all but the most delusional to deny the better the chance that we might start doing something about the causes.

    It seems likely the loss of the Arctic sea ice may be one of the earliest 'world changing' results of AGW. Sea level rise, loss of the Greenland and Arctic ice caps, breakdown of standard weather patterns, loss of croplands on a massive scale, et cetera are all gradual processes that will play out over a longer time period. The Arctic sea ice could go within this decade, and almost certainly will sometime in the next few. That's a very bad thing, but there are a lot of bad things coming. Many of them even worse.

    Many people are hoping that the loss of the Arctic sea ice will end the 'debate' between the facts and the lies. Personally, I'm not so optimistic. Anyone capable of saying in recent years that the Arctic sea ice "is recovering" is fully demented enough to insist that chunks of ice falling off Greenland into the ocean mean that the Arctic sea ice hasn't completely melted and it'll all come back any time now.

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  14. True, CBD, but picking a word or phrase out of context from a blog with millions (I'm guessing) of words and trying to claim you are doing anything worth even raising a question about is pretty darn daft, at best, imho. IIRC, some folks tried to do that kind of thing with some illegally procured emails back a ways with more clearly nefarious intent...

    My mom, when I was doing something dangerously stupid (not uncommon) like cutting toward myself with a sharp knife, would say things like, "That's a good way to put yourself in the hospital." Ash, listening to that, would no doubt conclude that my loving mother was actually hoping that I would give myself a grievous wound that would require hospitalization.

    And of course no one event will 'end the debate' since there is not an actual honest debate anyway. There will be _some_ ice in the Arctic Ocean for a long, long time, since as things warm up there, Greenland will calve more and more of its icesheet into the surrounding waters. So confirmed pseudo-skeptics will be able to point at those ice burgs and say, "See, there's still ice in the Arctic! All those alarmists and catastrophists are wrong and over reacting...[blah, blah, blah]..."

    Back on topic--As far as I can see, Francis's basic model (that Screen's work seems to be a refinement of) applies only to the Northern Hemisphere. If we start seeing a lot of unusually persistent 'stuck' weather patterns in the Southern Hemisphere (as seemed to have just happened in NZ), is there some similar dynamic that could explain it down there? My understanding is that, because of its radically different topography (continent surrounded by ocean rather than ocean surrounded by continents), Antarctica has not warmed anomalously the way the Arctic has. So I'm wondering if a completely different explanation would be needed there.

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  15. @ Edward Hurst


    As others have pointed out, summarily dismissing Neven's blog on the grounds that you don't like the "emotional values" ensconced therein just might be a tad premature.

    It's interesting to see that you are seeking the "unbiased truth" in order to make a comparison with a response you are expecting from the Minister with climate change responsibility at the Scottish parliament. I do not claim to have any personal knowledge of his perspective on the subject, but the fact that the MSP in question - Paul Wheelhouse - is basically an economist doesn't exactly set my mind at rest.

    Please be aware that I'm not for a moment suggesting he is anything like that bloody waste of space that has just been shown the door from the equivalent post in Westminster. In fact, in the Scottish Parliament at Holyrood, Mr Wheelhouse told MSPs he believed that...

    There is no doubt in my mind that climate change poses one of the greatest threats to the world as we know it.”

    However, Mr Wheelhouse does appear to have a somewhat pronounced "green agenda", and whilst there's absolutely nothing wrong with that (at least in my book), when he comes out with comments along the lines of...

    It has been very emotive speaking to sub-Saharan states and the Philippines about the kind of challenges they face today and thinking how much worse it will be in a world in 2050 with a five degree or worse temperature rise. I can’t imagine how bad life will be for some of the citizens of these countries.”  [My underlining]

    Remarks like that not only make me cringe with vicarious embarrassment, but more importantly, they also serve to bolster the meme that climate change is merely some alarmist ploy.

    (NB The source of the above quotes is given here.)

    I obviously don't know the topic on which you are waiting a response from Mr Wheelhouse, but if it was in any way related to the Arctic, I think you'd be advised to seek confirmation from a source such as Neven's.

    (And yes, I do contribute there in a very small way from time to time.)

    slàinte mhath


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  16. Thank you all for your useful comments.


    Edward Hurst

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  17. @Edward - My apologies for my belated response, but given the UK context you may also wish to take a look at another paper by James Screen, which I discuss on my own blog:

    Does the Arctic Sea Ice Influence Weather in the South West?

    @Ashton - I arrive here fresh from the Arctic Sea Ice Blog, where one of my comments precedes your own! I note you have yet to reply to Neven's comment in response to the question you posed over there. Are you now content that the "remark" you highlight above is not in fact "extraordinary" at all?

    @scaddenp - Neven's link doesn't actually cover "all" observations of the Arctic. Particularly if you're interested in Arctic sea ice thickness and/or volume you may wish to also take a look at this collection of my own devising:

    Arctic Sea Ice Graphs

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