December CET

[The PIT]

Very interesting that we swung into a series of below average months, started having proper winters again since the sun has gone quiet.

I wouldn't be surprised in the coming winters we had few more very cold examples to add to the list.

[Gavin P]

Yes, it is a little bit funny to be fair, especially the "not a chance" comment to the <1º question.

That said, two years ago, how many of us would really have believed such a month (let alone a sub zero month) would happen again?

My view was always never say never. You only ever had to look at the warming that occured from 1900 to 1939 and then that sudden switch to cold in 1940 to see how quickly things can change.

Yes, the warming from 88-07 was greater than that of the early part of the 20th century, but even so, it always looked to me like a sudden flip back to cold was possible at some time. Again, if we flipped to mild so quickly in 1988, why not be able to flip again?

Edited December 27, 2010 by Gavin P

[eddie]

The change in our winter weather during those mild few years was mostly synoptic. It's not like we were getting perfect northerlies and still getting above average temperatures (although that day may come if the world warms 4C). The wind just never seemed to blow in the right direction for long enough to get a cold month.

There was always going to be another sub 1C month.

[Gavin P]

The change in our winter weather during those mild few years was mostly synoptic.

Well, there was an arugement tha said AGW was causing the synoptics by causing the sub tropical highs and thus the jet streams to push further and further north, locking us into a never ending south-westerly nightmare. This was essentially the "UK Warming/even larger teapot" theory in a nutshell.

For me it never really stacked up because the change happened so quickly and was so dramatic. In less than two years we went from the mega block of February 1986 to endless zonality of January 1988. AGW is a very long term thing with changes happening over decadal periods, not in a couple of years. But anyway, it was a theory I know Ian Brown and a few others signed up to.

Edited December 27, 2010 by Gavin P

[eddie]

Well, there was an arugement tha said AGW was causing the synoptics by causing the sub tropical highs and thus the jet streams to push further and further north, locking us into a never ending south-westerly nightmare. This was essentially the "UK Warming/even larger teapot" theory in a nutshell.

For me it never really stacked up because the change happened so quickly and was so dramatic. In less than two years we went from the mega block of February 1986 to endless zonality of January 1988. AGW is a very long term thing with changes happening over decadal periods, not in a couple of years. But anyway, it was a theory I know Ian Brown and a few others signed up to.

The null hypothesis for me was always that the never ending south-westerlies were just an unfortunate spell of weather. Nobody ever presented any strong evidence to say AGW had changed our weather patterns. There just seemed to be a lot of 'Well the jet stream hasn't been south for ages. What else is there to explain it apart from global warming?'

I should add that I do agree with the AGW theory although I'll save that for another thread.

[Thundery wintry showers]

I think there's a lot of truth behind the modern winter/global warming theory but such theories are always subject to the caveat that the atmosphere is very chaotic and just because a certain amount of global warming may accentuate a particular trend, it doesn't follow that further global warming will accentuate it further, or that the trend won't reverse in spite of global warming.

Indeed, while the warming at high latitudes probably contributes to more Icelandic cyclogenesis as a result of higher SSTs, it's possible that the recent warming in the Arctic and associated sea ice melt could have taken us to a point where that relationship switches and we see a bias towards more blocking at high latitudes and cold airmasses sweeping south with more regularity (some recent scientific papers point to this).

I always believed that a sub 1C month was still possible on the basis of the negative temperature anomaly of the 30 day period leading up to 23 March 2006, though I must admit I'd written off the possibility of sub zero CET months occurring within our lifetimes.

[North-Easterly Blast]

Well, there was an arugement tha said AGW was causing the synoptics by causing the sub tropical highs and thus the jet streams to push further and further north, locking us into a never ending south-westerly nightmare. This was essentially the "UK Warming/even larger teapot" theory in a nutshell.

For me it never really stacked up because the change happened so quickly and was so dramatic. In less than two years we went from the mega block of February 1986 to endless zonality of January 1988. AGW is a very long term thing with changes happening over decadal periods, not in a couple of years. But anyway, it was a theory I know Ian Brown and a few others signed up to.

You are dead right there Gavin. In the ten years prior to the 20 winterless years that began in 1988 we went from the severe 1978-79 winter and a number of winters in the 1980s that had notable cold spells to the mega mild dross and two of the warmest winters ever recorded in 1988-89 and 1989-90 - a pattern of which became the feature of most winters up to the end of the 2000s, although mainly to a lesser extent than 88-89 and 89-90. However, I will point out that the 1977-87 colder winter era was less notable than how mild the winters in the 1990s and 2000s were. 1977-78, 1982-83 and 1983-84 were all around average winters overall, or even a shade above, by historical standards. Also, 1979-80 and 1980-81 were a little milder than average overall. So, that is five winters over 11 years that still made average or even slightly above, and not below average at all - compared with only one or two winters between 1997 and 2008/09 that even made average rather than mild, and only a further two or three in the whole period from 1988 to 2008.

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

What is the biggest difference CET difference in two consecutive months?

[damianslaw]

What is the biggest difference CET difference in two consecutive months?

Don't have any stats but combos which spring to mind are -

Dec 86 and Jan 87

Mar 87 and Apr 87

Nov 09 and Dec 09

Aug 95 and Sep 95

[gmoran]

When talking about AGW, there are two components: the greenhouse effect (GHE), the effect of infra-red active gases on atmospheric radiative transfer, and; climate sensitivity, the feedbacks that amplify and dampen climate forcings, which are believed to be high (2.5'C or greater for a doubling of CO2).

The GHE is uncontroversial and well understood, as such it is climate sensitivity that lies at the core of disagreements around global warming. The majority (if not all) of the evidence that support high climate sensitivity are based on the inability of climate models to project the 20th century climate without high sensitivity - however there is also an assumption of low internal variability, as such the argument is somewhat "boot-strapped". In this viewpoint the cooling in the 50's, 60's and 70's is due to aerosols and the high rate of warming in the 80's and 90's is almost all due to anthropogenic forcing - leaving little room for other explanations for the pattern of warming in the 20th century (e.g. a long term warming trend plus high internal variability. Such arguments are termed detection and attribution.

The modern British climate of BBQ summers and mild winters was also presented as evidence supporting the detection and attribution arguments of AGW.

It is therefore plainly problematic to the AGW hypothesis of high climate sensitivity if we are entering a post modern climate of severe winters and late summer monsoons; particularly if there are wider synoptic changes that are consistent with high internal variability (e.g. the southward migration of the jet stream).

SF's posts assumed that the modern British climate would make severe winter weather events a rarity and less extreme. The progressing pattern of the last three years therefore must have come as an unpleasant surprise. The MetO must find themselves in a similar predicament, as in the summer in their contribution to the transport winter resilience report they stated that they did not believe the previous two summers indicated a trend, and that the chances of another severe winter would still only be 5% (once every twenty years ). I find the Potsdam institute paper that TWS mentioned unconvincing as it is plainly revisionist in nature - preferring the climate regime shift work of Swanson and Tsonis as some sort of explanation of current patterns.

[Albion Snowman]

With this less cold incursion likely to last to the end of 2010, could someone calculate what the temp would have to be between now and the end of the year for the CET to reach 0.0C please ? Hadley currently at -1.0C, but I would imagine this will rise noticeably over the next few days, not taking into account end of month corrections.

I really want this months to stay sub zero, but looking at the Beeb forecasts, 6-7C looks a distinct possibility over the next few days, with milder night time temps I would imagine due to cloud. I just want to see how "impossible" it would have to be!

[eddie]

Assuming no end of month adjustment, the period of the 27th-31st would have to average 5.2C for the month to end at 0.0C.

Since today's minumum was recorded at -3.2C it is likely that today will come in somewhere around 1C.

That will mean that last four days of the month will need to average about 5.8C to end at 0C. Looking at the GFS that seems virtually impossible.

[damianslaw]

Dec 2010 will be the coldest December since 1890 which is some statistic, I must admit I never thought I would see the day we beat Dec 1981. In terms of anomaly from the average, this month must be up there with the likes of feb 1947 and jan 63 and summer months like aug 95. Mr Data have any stats here?

More or less odds on our first sub-zero CET month since Feb 86, though I doubt we will beat Feb 86 but will be close. Unlike Feb 86 which saw persistant cold throughout but nothing particularly severe until the end of the month, this month has seen much more variety, much heavier snowfall,much colder maxes and mins, but also two thaws with milder weather between 10-16th and 27th - 31st, a bit more akin to Jan 85 and 79 months with severe cold and lots of snow interspersed with milder conditions. In this respect to many Dec 10 will seem more severe than Feb 86. I just think it superb we can be comparing a month to the likes of dec 81, feb 86 and dare I say it the infamous winter of 62/63, even more so only 11 months since last jan which I certainly didn't think we could better this winter. These are different times it seems, winter 06/07 and 07/08 seem like they belong to a bygone era - we have been very patient in the last 20 years and the patience has certainly been a virtue.

[jethro]

There's a whole section of the forum for climate change discussion, you'll all be welcome to carry on the conversations over there.

Please stay on topic in this thread.

[Paul T]

Assuming no end of month adjustment, the period of the 27th-31st would have to average 5.2C for the month to end at 0.0C.

Since today's minumum was recorded at -3.2C it is likely that today will come in somewhere around 1C.

That will mean that last four days of the month will need to average about 5.8C to end at 0C. Looking at the GFS that seems virtually impossible.

27th's min was -6.3oC. Max prob around 3 or 4 at best.

so, mean shall be -1.5oC.

-1.0oC to 28th

Last 4 days would have to hit a mean of around 7oC to hit zero.

predicted means will prob be:

28th: 3.5

29th 6.1

30th 6.4

31st 5.5

DEC will finish at -0.2 or -0.3 without adjustments.

So unfortunately it really was/will be an easy and simple breakdown from record breaking low temperatures to much milder temps by 28th - despite some serious inital denial by some in the model discussion.

Edited December 27, 2010 by Paul T

[eddie]

27th's min was -6.3oC. Max prob around 3 or 4 at best.

so, mean shall be -1.5oC.

-1.0oC to 28th

Last 4 days would have to hit a mean of around 7oC to hit zero.

predicted means will prob be:

28th: 3.5

29th 6.1

30th 6.4

31st 5.5

DEC will finish at -0.2 or -0.3 without adjustments.

So unfortunately it really was/will be an easy and simple breakdown from record breaking low temperatures to much milder temps by 28th - despite some serious inital denial by some in the model discussion.

You are correct. I mistook today's minimum for yesterdays mean.

[Optimus Prime]

Mines currently running at 0.1c. Easily beating 2009 at 3.4c. 1981 came in around 0.8c so that should be beaton.

[Weather-history]

What is the biggest difference CET difference in two consecutive months?

The biggest CET collapses from one month to the next

Jan 1983: 6.7

Feb 1983: 1.7

Feb 1883: 5.9

Mar 1883: 1.9

Mar 1780: 7.9

Apr 1780: 6.3

Apr 1755: 10.0

May 1755: 9.4

May 1833: 15.1

June 1833: 14.6

June 1676: 18.0

July 1676: 16.0

June 1858: 16.8

July 1858: 14.8

July 1737: 17.4

Aug 1737: 13.8

Aug 1807: 16.9

Sep 1807: 10.5

Sep 1740: 14.0

Oct 1740: 5.3

Oct 1921: 12.8

Nov 1921: 4.6

Nov 1981: 7.8

Dec 1981: 0.3

Dec 1828: 7.4

Jan 1829: 0.3

Biggest rises between one month and the next

Jan 1945: 0.4

Feb1945: 7.1

Feb 1895: -1.8

Mar 1895: 5.1

Mar 1865: 2.9

Apr 1865: 10.6

Apr 1743: 5.4

May 1743: 13.3

Apr 1808: 5.8

May 1808: 13.7

Apr 1809: 5.2

May 1809: 13.1

May 1676: 10.5

Jun 1676: 18.0

Jun 1749: 11.9

Jul 1749: 17.2

Jul 1802: 13.5

Aug 1802: 17.2

Aug 1865: 15.1

Sep 1865: 16.3

Sept 1807: 10.5

Oct 1807: 11.4

Oct 1817: 6.4

Nov 1817: 9.1

Nov 1862: 3.2

Dec 1862: 6.5

Dec 1874: -0.2

Jan 1875: 6.4

Edited December 28, 2010 by Mr_Data

[Roger J Smith]

I looked into the question of largest temperature changes month to month in the CET. Since I have a data base available, the command went forth to yield the largest month to month anomaly changes. I have listed these, with the absolute change in monthly mean in brackets

MONTH .... 352-yr mean .... Largest drop from previous month ..... Largest rise from previous month

JAN ...... 3.2 ..... 6.2 anom (7.1 abs) 7.4 Dec 1828 , 0.3 Jan 1829 ..... 7.5 anom (6.6 abs) -0.2 Dec 1874 , 6.4 Jan 1875

FEB ..... 3.9 ..... 5.7 anom (5.0 abs) 6.7 Jan 1983 , 1.7 Feb 1983 ..... 6.0 anom (6.7 abs) 0.4 Jan 1945 , 7.1 Feb 1945

MAR ..... 5.3 ..... 5.4 anom (4.0 abs) 5.9 Feb 1883 , 1.9 Mar 1883 ..... 5.5 anom (6.9 abs) -1.8 Feb 1895 , 5.1 Mar 1895

APR ..... 7.9 ..... 4.2 anom (1.6 abs) 7.9 Mar 1780 , 6.3 Apr 1780 ..... 5.1 anom (7.7 abs) 2.9 Mar 1865 , 10.6 Apr 1865

MAY .... 11.2 ..... 3.9 anom (0.6 abs) 10.0 Apr 1755 , 9.4 May 1755 .... 4.6 anom (7.9 abs) 5.2 Apr 1809 , 13.1 May 1809*

JUN .... 14.3 .... 3.6 anom (0.5 abs) 15.1 May 1833 , 14.6 Jun 1833 .... 4.4 anom (7.5 abs) 10.5 May 1676 , 18.0 June 1676

JUL ..... 16.0 ..... 3.7 anom (2.0 abs) 16.8 Jun 1858 , 14.8 Jul 1858 .... 3.8 anom (5.5 abs) 13.2 June 1852 , 18.7 July 1852

AUG .... 15.6 ..... 3.2 anom (3.6 abs) 19.7 Jul 2006 , 16.1 Aug 2006 .... 4.1 anom (3.7 abs) 13.5 July 1802 , 17.2 Aug 1802

SEP ... 13.3 .... 4.1 anom (6.4 abs) 16.9 Aug 1807 , 10.5 Sep 1807 .... 3.5 anom (1.2 abs) 15.1 Aug 1865 , 16.3 Sep 1865

OCT .... 9.7 ...... 5.1 anom (8.7 abs) 14.0 Sep 1740 , 5.3 Oct 1740 .... 4.5 anom (0.9 abs) 10.5 Sep 1807 , 11.4 Oct 1807

NOV .... 6.0 ...... 4.8 anom (8.5 abs) 11.4 Oct 1807 , 2.9 Nov 1807 .... 6.4 anom (2.7 abs) 6.4 Oct 1817 , 9.1 Nov 1817

DEC .... 4.1 ...... 5.6 anom (7.5 abs) 7.8 Nov 1981 , 0.3 Dec 1981 ..... 5.2 anom (3.3 abs) 3.2 Nov 1862 , 6.5 Dec 1862

Largest changes ..... 6.2 anom (8.7 abs) see above ......................... 7.5 anom (7.9 abs) see above

* same in Apr-May 1808 from 5.8 to 13.7

Looking at the years that had entries here, it's apparent that the climate was "wonky" in the early 19th century, especially 1807 which managed to score three times in a row. Of the 24 cases cited above (ignoring the tie as it was in consecutive years anyway), the frequency of "record monthly changes" looks like this in 25-yr intervals (the first of which starts in 1676, there were no cases 1659-1675.

In this table, x is an extreme temp drop and o is an extreme temp rise noted in that 25-year period.

1676-1700 o

1701-1725

1726-1750 x

1751-1775 x

1776-1800 x

1801-1825 ooxxoo

1826-1850 xx

1851-1875 ooxooo

1876-1900 xo

1901-1925

1926-1950 o

1951-1975

1976-2000 xx

2001-2010 x

The dominance of the 19th century in this "strange" statistic is quite striking.

The drop from say Oct 24-Nov 23 to Nov 24-Dec 24 is about on a par with the monthly extremes. But the actual drop from November to December 2010 cannot set a record at this point.

Edited December 28, 2010 by Roger J Smith

[Roger J Smith]

Looks like we have one or two differences, but most are the same.

[Paul T]

CET: -1.02 oC to the 27th.

Its a combined negative temperature total of -27.5oC / 27 days.

So, bearing that in mind, to reach zero it would have to rise a total of 27.5 oC in the next 4 days. i.e 6.9oC a day. Still not impossible, but as the min for the 28th is 1.9oC, then the mean will likely be 4.0. Therefore requiring 7.8oC for the final 3 days. unlikely.

-0.8oc to the 28th

It will drop to -0.3 before adjustments as said yesterday,

what will the adjustments hold? well, looking at January, some of the serious cold days were actually pegged back a little after changes, while some of the more average or slightly colder days were corrected colder. i believe the month was adjusted -0.4oC colder in total.

If i was a betting man i would say Dec may adjust -0.1 colder, as i believe some of the seriously cold days will be adjusted upwards slightly, while the mid month mild will be reduced down.

Edited December 28, 2010 by Paul T

[West is Best]

predicted means will prob be:

28th: 3.5

29th 6.1

30th 6.4

31st 5.5

DEC will finish at -0.2 or -0.3 without adjustments.

So unfortunately it really was/will be an easy and simple breakdown from record breaking low temperatures to much milder temps by 28th - despite some serious inital denial by some in the model discussion.

I doubt the means will be anything like that high Paul. The mild spell has been way over-hyped with daytime temps struggling.

I don't expect the -1.0C to rise by very much from here, probably to around -0.6C unadjusted and very close to the record coldest December by the time Hadley revises it downwards.

[Paul T]

I would much much prefer you to be correct, but im not usually far off... so lets see how it pans out.

Edited December 28, 2010 by Paul T

[BornFromTheVoid]

I doubt the means will be anything like that high Paul. The mild spell has been way over-hyped with daytime temps struggling.

I don't expect the -1.0C to rise by very much from here, probably to around -0.6C unadjusted and very close to the record coldest December by the time Hadley revises it downwards.

I'm with Paul on this. I think we'll either be at -0.2C or -0.3C by months end. Yesterdays maxima were forecast to be just around 2C but managed 3.7C. Todays were forecast to reach 5C and have already reached that figure across much of the CET zone. Doesn't seem too over hyped to me.

I do think the downward adjustment could still take us within 0.3C of the record though, which is remarkable in itself.

[TEITS]

I'm with Paul on this. I think we'll either be at -0.2C or -0.3C by months end. Yesterdays maxima were forecast to be just around 2C but managed 3.7C. Todays were forecast to reach 5C and have already reached that figure across much of the CET zone. Doesn't seem too over hyped to me.

I do think the downward adjustment could still take us within 0.3C of the record though, which is remarkable in itself.

I think what WIB is saying is some places within the CET zone only managed a max temp of 2C today.