Are we still capable of getting a <1c CET month?

[Anti-Mild]

Before this disasterous Winter started I posed the question of whether it was still possible for the synoptics of this country to bring about a sub 1c month. At the time the results suggested that 81% of people believed it was still possible for the UK to experience a very cold month.

I have re-posted the same poll to see if the Winter has changed peoples opinions on this subject, and consequently, as the 2 are surely linked, on GW.

Thanks for your indulgence !

AM

Edit: Oops, I tried to get a poll on this but it aint worked! Bear with me while I find a mod to change it!

Edited February 27, 2007 by ChrisL

[John Cox]

Hi Anti-Mild,

I have every confidence that we can.

We here on nw get too caught up on stats, the past, the even larger teapot and of course global warming.

The weather will do what it wants, when it wants and when we least expect it.

[Gray-Wolf]

I think that as 'warming' increases their will be a 'temporary period' each year when the cold, generated by 24hr nights, will be 'displaced ' by warmer airs from further south. I could envision ,if we were unlucky/lucky, coping for some potent 'plunges' of cold air at the back end of Feb/beggining of March and if a few 'tagged together' we could end up with low CET's.

[Anti-Mild]

Thanks to Chris for inserting the poll........oo-err, that sounds a bit rude!!

[VillagePlank]

On the basis that I consider this winter's UK warmth to be primarily a throw-back to a very warm, and late, summer, I think the answer has to be a resolute 'Yes!'

[summer blizzard]

I said yes, had my internet not have gone down in late November, my anologue based teleconnections forecast would have gone for all three months to be above average, with December being the warmest month against the norm (wrong) and gradually decreasing CET values against the norm.

Therefore, while i would not have gone for such a warm winter, i would have gone for an above average winter.

Edited February 27, 2007 by summer blizzard

[Duncan McAlister]

Yes - the coldest month on record was -3.1, the coldest month last century was -2.1 and February 1986 had a CET of -1.1 which is not really that long ago. Adding GW (0.8c) to all these figures still gives a <1c month. Last winter showed we can still get the synoptics, it's just that the coldest temps never coincided with a calendar month.

Edited February 27, 2007 by Duncan McAlister

[Snowly does it]

Theoretically I think we can, but given the scarcity of months that cold generally and with wamring thrown in such an event would require a combination of factors hard to envision.

Theoretcially yes but I really don't expect one.

[Stratos Ferric]

No, not even a remote possibility...

The upper plot suggests that the baseline for a winter month is now between 2-4C.

The lower plot shows that the current sequence without a cold month is not unprecedented, however, a couple of points made previously in connection with the two previous sequences of "uncold" winters:

1 - both had plenty of months in the range 1-4C, the present sequence has fewer and only a single one below 2.0.

2 - both were seasonal anomalies. The current sequence is part of year round warming.

[acbrixton]

SF: It is rarely that I take ussue with such posts.

1. The graphs (and and in particular the first graph (are well choosen and immuminating) as are those recently posted making the point about year wide-local CET warming.

2. It is certainly striking that over 5 year stretches the incidence of such months has fallen fron 1 or 2 in the periods 1960 to 1980/85 3 in 1985/90 but in the since 1986/7 there have been only 3 months below between 2 and 3c which were below.

3. I can aslo appreciate the arguments put froward by TWS and you suggesting that to get noteably cold now there are plausible factors such as higher Sea Surface Temperature Anompalies) SSTAs (causing modification of continental and especially northerly air masses; increasing the thermal gradent esp around the (Greenland Iceland Nefoundland) GIN area leading to more vigourous cyclonogenesis in winter) and northerly movements of the planetary pressure belts with both of thos factors affecting the power and trajectory of the Polar Front Jet (PFJ).

leading to weaker/less northern and eastern blocking.

4. Whilst I can therefore understand that the chances of a sub-zeroc CET month ever occurring again (in either the sgort/medium of foreseeable future) highly remote I just cannot see that it is simply impossible.

Have I missed somethng?

Kind rregards

ACB

[Coopsy]

I agree you cannot simply dismiss the remote possibility if in fact the possibilty can in theory still exist

[Duncan McAlister]

Stratos I could be reading this wrong but is Feb 1986, at -1.1c, not almost 2 degrees below the 'minimum threshold' for that time? Also, what makes these thresholds set in stone?

[Thundery wintry showers]

I think it is possible, on the grounds that if the synoptics of January 1963 (CET -2.4) were to be repeated, even allowing for SST anomalies and the warmer global baseline, we'd still most likely be looking at a sub-zero CET, let alone sub-1C.

However, it's also a very remote possibility as I think the climate has shifted such that very cold synoptics happen less frequently, and when they do, they tend to be shorter-lived.

Factoring in changes in synoptics caused by general climate change, realisitcally it would appear that the most we can expect is the kind of anomaly we saw on 1-23 March 2006 (CET of about 2.8 over that period, about 3C below the long-term average). That would still be consistent with the notion that under very favourable circumstances, even factoring that in, we could just sneak a <1C CET in January. Long odds against though.

[Anti-Mild]

Well even though the level of response to this poll second time round is lower, there has still been enough, and it seems that a mild winter has shaken a lot of peoples faith as the amount of people who suggested that a <1c winter month was possible has dropped from 81% to 71% - interesting!

What would the figure have changed to if we had had a cooler than average winter? Indeed, what will the figure be if I ask the same question in November? I expect it will depend on what happens between now and then. Will the unprecedented above average spell continue or will we have a couple of cool months?

[Greyowl]

I think we still could get a month of low cet. Even with AGW and everything else. Our weather as we have seen is unpredictable and capable of throwing up suprises.

[The Penguin]

Of course.

The problem with getting too hung up with trends is that their only indication of future events is through historic ones. The global and CET temperature records tell us that change is more likely to be swift and sudden than gentle and well heralded.

Winter is still winter, and I agree with the previous comment that in the context of <1C temperature rise anomalies, a sub zero month is not only possible but probable.

[Stratos Ferric]

SF: It is rarely that I take ussue with such posts.

...4. Whilst I can therefore understand that the chances of a sub-zeroc CET month ever occurring again (in either the sgort/medium of foreseeable future) highly remote I just cannot see that it is simply impossible.

Have I missed somethng?

Kind rregards

ACB

You're correct; it is not impossible, but let's say that it is looking like it's nearly impossible on the basis of the assumption that 1-it as stopped happening, it has stopped even remotely happening; and 2- that it has stopped happening is not mere misfortune; it is possible, as TWS and I (and some others) do, to mage a coherent argument for macro level circulation to have changed to such an extent that prolinged winter blocking simply has become a thing of the past. In practical terms what we have now is a return period of, say, instead of 1:20, something closer to 1:200. Measured in terms of perception (that return period being longer than twice any lifetime) it simply has gone past the point at which it is a perceivable phenomenon.

[Stratos Ferric]

Stratos I could be reading this wrong but is Feb 1986, at -1.1c, not almost 2 degrees below the 'minimum threshold' for that time? Also, what makes these thresholds set in stone?

Correct. However, 1986 in relative terms was 4.5C below the ten year mean at the time, and 2C below the baseline. Applying the same relative margin to next winter would mean that Feb would come in at around 0.9C (based on 4.5C below current 10 year mean) or around 1.5-2C (based on 2C below the baseline I've drawn).

Whether or not you see the threshold as set in stone depends largely on your knowledge and acceptance of probability theories in particular and statistics in general. It is very hard to make the case (though it doesn't stop a few on here trying to do so), when looking at the facts in a cold (it's about the only sense in which the numbers nowadays do get anywhere near cold as well) and dispassionate way, for cold months or cold winters simply on the basis that they haven't happened. Not only that, but the trend is a warming one (i.e. away from it ever happening). As I have pointed out previously, there have been previous patterns of warm winters (or more precisely and correctly series without consistently cold winters), but these have NOT been accompanied by the year round warming that we are now seeing. For this one factor alone I would argue that the change in our climate is fundamental, and not merely a consequence of periodic shift in seasonal pattern (though this latter may be happening to some extent alongside current background warming).

[acbrixton]

You're correct; it is not impossible, but let's say that it is looking like it's nearly impossible on the basis of the assumption that 1-it as stopped happening, it has stopped even remotely happening; and 2- that it has stopped happening is not mere misfortune; it is possible, as TWS and I (and some others) do, to mage a coherent argument for macro level circulation to have changed to such an extent that prolinged winter blocking simply has become a thing of the past. In practical terms what we have now is a return period of, say, instead of 1:20, something closer to 1:200. Measured in terms of perception (that return period being longer than twice any lifetime) it simply has gone past the point at which it is a perceivable phenomenon.

SF thanks: I think that puts it rather well...

regards

ACB

[mcweather]

Sub zero CET months like Jan 63 feb 47 and feb 86 were always anomalies against even the generally colder regime that existed back in those times..

Crucially the point those months made was that if the synoptics are in your favour then a dirty great anomaly is what you will get. Even with GW the russian interior can still get horrifically cold and if the wind is in the right direction at the right time of year then a sub zero month is still a possibilty albeit a rare possibilty but a possiblity nevertheless.

[Snowly does it]

I think SF puts it rather well. A sub-zero month has the return value now of 'ain;t gonna happen'

I think a sub 1c month is perhaps in my estimation an 'I'll see one before 2050' level of return.

As likely as the Defoe Storm for sub-zero probably.

Of course, this all relies on the macro circulation having altered significantly (which I am inclined to think it probably has), if it hasn't, the law of probability (SFs excellent baseline analysis aside) wold indicate a sub zero month is rather more likely, but still unlikely in the extreme whilst a sub 1 would be expected perhaps every 15-20 years - and if temps rise by 3 degrees this century then over the next 20 years move the goalpost to sub 2, then sub 3 before 2100 seeing 'Is the UK capable of a sub 4c month?'

[Stratos Ferric]

I think SF puts it rather well. A sub-zero month has the return value now of 'ain;t gonna happen'

I think a sub 1c month is perhaps in my estimation an 'I'll see one before 2050' level of return.

As likely as the Defoe Storm for sub-zero probably.

Of course, this all relies on the macro circulation having altered significantly (which I am inclined to think it probably has), if it hasn't, the law of probability (SFs excellent baseline analysis aside) wold indicate a sub zero month is rather more likely, but still unlikely in the extreme whilst a sub 1 would be expected perhaps every 15-20 years - and if temps rise by 3 degrees this century then over the next 20 years move the goalpost to sub 2, then sub 3 before 2100 seeing 'Is the UK capable of a sub 4c month?'

I was about to suggest, in response to your second sentence, that that was unlikely if we keep on warming in the next 5-10 years are we are now, and if thereafter there is no downward correction, but then you go on to make the same point yourself.

The one crumb of comfort is that the "by eye" baseline I suggest on the previous plot is rising more steeply than the general trend in the data. There is an argment that this might be counter-intuitive, that minina and maxima might be expected to change at the roughly the same rate. On this basis, applying the trend data, 1C is still - for now and just about - in bounds, but not for much longer.

The caveat here is that it is quite clearly perceivable now that recent winter half warming has been more a consequence of raised minima than maxima, and so consistent is the pattern becoming that it points to a fundamental change. Therefore, whilst it might be expected that minima would change at the overall trend rate, it needn't necessarily be the case, and it clearly isn't so in practice.

[Roger J Smith]

I might seem like the contrarian's contrarian here, but even if AGW was a complete reality and worth 1.5 or 2 C degrees, you could always envisage an actual circulation within that "new climate" where it could snow, turn cold, and stay cold.

Recent winters have demonstrated that snow can fall, lie on the ground for several days, and also that highs can form and drop temperatures to -8 or even -10 C. The fact that in most cases, the snowfall events and the cold high events have remained nicely separated has perhaps been the real reason why no month (or period of that length) has been notably cold in recent winters.

The dynamics themselves have not altered that much, so I would have to speculate that whatever the overall trend, unless it warms even more rapidly than in previous decades, there could always be a very cold month out of the blue, so to speak.

I know this will invite the usual chorus of protest, but surely the winter of 1739-40 must have seemed highly unusual at that time. The general experience of most people for over a decade previous would have been not greatly dissimilar to your own, and then came this very cold and snowy winter.

The winter of 1940 was also the first significantly cold winter since 1929, a fairly long absence, and there were very few cold winter months between 1895 and 1917, so this sort of thing has happened before on fairly comparable time and temperature scales. I don't have access to snowfall records so I can't comment on that, but surely in the past there must have been runs of several winters without much snowfall. When I did live in England from 1949 to 1957, I think I could be forgiven for not making detailed records, but when it snowed in February 1956 that made enough of an impression on me that I can still recall walking to school (in shorts) through that snowfall. Can't say that I recall my first Canadian snowfall though.

I'll make the prediction that there will be a sub 1.0 C month, and if you'll allow any 30-day period, a sub-freezing "month" some time in the next 5-10 years in the CET records. This winter was disappointing but you would have to say this, from such a mild zonal base established in Nov-Dec, the latter part of January and early February at least provided some resistance and one could imagine winters where this resistance would have been entirely absent, so "even larger teapot" whatever its actual realities is not totally dominant over the cold air masses yet. Since my bias is towards thinking of these shifts as natural and not AGW, I am more optimistic that things could shift in the other direction too. I think many would be astounded if some future decade showed a sharp decline in mean winter temps like the 1940s did over the 1930s, but I see no fundamental reason why this could not happen in some future decade (let's hope it's 2008-2017).

[Stratos Ferric]

I might seem like the contrarian's contrarian here, but even if AGW was a complete reality and worth 1.5 or 2 C degrees, you could always envisage an actual circulation within that "new climate" where it could snow, turn cold, and stay cold.

Recent winters have demonstrated that snow can fall, lie on the ground for several days, and also that highs can form and drop temperatures to -8 or even -10 C. The fact that in most cases, the snowfall events and the cold high events have remained nicely separated has perhaps been the real reason why no month (or period of that length) has been notably cold in recent winters.

The dynamics themselves have not altered that much, so I would have to speculate that whatever the overall trend, unless it warms even more rapidly than in previous decades, there could always be a very cold month out of the blue, so to speak.

...

I'll make the prediction that there will be a sub 1.0 C month, and if you'll allow any 30-day period, a sub-freezing "month" some time in the next 5-10 years in the CET records. This winter was disappointing but you would have to say this, from such a mild zonal base established in Nov-Dec, the latter part of January and early February at least provided some resistance and one could imagine winters where this resistance would have been entirely absent, so "even larger teapot" whatever its actual realities is not totally dominant over the cold air masses yet. Since my bias is towards thinking of these shifts as natural and not AGW, I am more optimistic that things could shift in the other direction too. I think many would be astounded if some future decade showed a sharp decline in mean winter temps like the 1940s did over the 1930s, but I see no fundamental reason why this could not happen in some future decade (let's hope it's 2008-2017).

I guess you haven't read many of my posts Roger, and certainly not the charts. I have mentioned several times in the mpast 6 months that whilst there have been occasional runs of winters without exceptional cold, none has been as consistently mild as the present sequence, nor so totally lacking in sustained cold of any form. Furthermore, those periods occurred as seasonal anomalies i.e. winter was warm but summer and the year was not consistently so. We now have year round warmth.

I'm not sure we have many instances of -10C here (Canada is a completely different kettle of snow and ice), nor do I agree that the basics haven't changed. They must have done, otherwise why are we consistently returning not just warm, but sustained warm weather?

There wil be ups and downs in future, but against a consistently warming trend the bottom of the wave will always be at an ever higher level for any given return period.

[Duncan McAlister]

I wonder how this July would look on SF's threshold chart <_<