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Roger J Smith

The "new normals" for 1991-2020 (CET)

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Posted (edited)

This thread will track the emerging next set of 30-year normals to replace the 1981-2010 CET values, which are shown below, followed by what we have to date (1991-2019 for Jan to July and 1991-2018 for Aug-Dec and annual). The July 2019 value is projected from current tracking as 17.5 and this will be adjusted in edits later this month. 

What follows the list of almost completed 1991-2020 averages will be final values that would occur for ranges of plausible values in 2020 (for Jan-July) or average of 2019-20 for Aug-Dec and annual. The thread will be maintained and edited so that these ranges shrink down to 2020 values by January, and we welcome in the new normals one by one during 2020 (subject to official verification when close to the rounding boundaries). 

_______ Jan _ Feb _ Mar _ Apr _ May _ Jun _ Jul _ Aug _ Sep _ Oct _ Nov _ Dec __ YEAR

1981-2010 _ 4.4 _ 4.4 _ 6.6 _ 8.5 _11.7 _14.4 _16.7 _16.4 _14.0 _10.7 _7.1 _ 4.6 ___ 10.0

1991-2019*_ 4.6 _ 4.8 _ 6.7 _ 8.9 _11.9 _14.7 _16.8 _16.5 _14.1 _11.0 _7.4 _ 4.9 ___ 10.2

* 1991-2018 Aug-Dec and annual

JAN will end up 4.6 if Jan 2020 is 3.0 to 5.9. It will end up 4.7 for 6.0 to higher than record max, and 4.5 for zero to 2.9 in Jan 2020 (4.4 for a neg value).

FEB will end up 4.8 if Feb 2020 is 2.2 to 5.1. It would end up 4.9 for any value 5.2 to current max 7.9 or even 8.1, and 4.7 for anything -1 to 2.1.

MAR will end up 6.7 if Mar 2020 is 4.2 to 7.1. It would end up 6.8 for any value 7.2 to record 10.0, and would drop to 6.6 for a cold 1.3 to 4.1 (last seen 2013).

APR will end up 8.9 if Apr 2020 is 7.4 to 10.3. It would end up 9.0 for any value 10.4 to beyond current record max, and would drop to 8.8 at 7.3 or lower.

MAY will end up 11.9 if May 2020 is 11 to 14, only 1833 was warmer than that (for 12.0 avg). Any plausible value 10.9 or below would yield 11.8 as new value.

JUN will end up 14.7 if June 2020 is 14.1 to 17.0. A very warm 17.1+ would change it to 14.8, and a cool 14.0 or lower would drop it to 14.6.

JUL will end up 16.8 (assuming 2019 close to 17.5) if July 2020 is 14.6 to 17.5. Warmer (17.6-20.5) would yield 16.9. Unlikely to be below 14.6 (to drop back to 16.7).

AUG will end up 16.5 if 2019 and 2020 average 16.3 to 17.8. It has only just rounded past 16.45 through 2018 and will drop back to 16.4 (the current value) for any average below 16.3 as far down as 14.8. It could go to 16.6 if we see two very warm Augusts (average 17.9 to 19.3).

SEP will end up 14.2 if 2019 and 2020 average 13.8 to 15.3. From 13.7 down to 12.3, the new September average would be 14.1.

OCT will end up 11.0 if 2019 and 2020 average 10.8 to 12.3, otherwise (10.7 or colder to 9.3) the new normal is 10.9.

NOV will end up 7.4 for any average 6.5 to 7.9. It would go to 7.5 for two mild Novembers that average 8.0 to 9.4, and down to 7.3 for two cold ones (avg 5.0 to 6.4).

DEC will end up 4.9 for any average 3.6 to 5.05, from 5.1 to 6.5 it would end up 5.0, and for 6.6 or higher, 5.1 C. 

and the ANNUAL seems locked in to 10.2, the current value to two decimals is 10.19. Some persistently warm anomalies now to Dec 2020 could push it to 10.3, but it would require about half the months to adjust upward. I see little chance of it falling back below 10.15. 

All of these stats will be updated by edit going forward. 

Edited by Roger J Smith

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Roger, do you have the Minimum and Maximum temps, as it is often mentioned that temps overnight  have risen quicker than Maximum temps.

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I have not been tracking that aspect, J10, maybe somebody reading this could provide some insights. I also had that perception about max rising a bit slower than min during this half century of warming. May be more applicable to warmer half of the year. 

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Posted (edited)

Here are the averages from London for 1989-2018, so the 1991-2020 averages should be very similar.

image.png.dd48bf52686533a7761c8032d1934a

Slightly warmer, wetter and cloudier than the 1981-2010 averages.

Edited by B87

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Posted (edited)

A brief glance at the annual data (lower graphs on the right) seems to suggest that the opposite is true, i.e. maxima are increasing more rapidly than minima.

https://www.metoffice.gov.uk/hadobs/hadcet/cet_info_max.html

https://www.metoffice.gov.uk/hadobs/hadcet/cet_info_min.html

Will do some quantitative analysis if I can find the time.

Edited by Relativistic

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Interesting that July, August and September have each only increased by 1C.

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Posted (edited)
27 minutes ago, J10 said:

Roger, do you have the Minimum and Maximum temps, as it is often mentioned that temps overnight  have risen quicker than Maximum temps.

In the UK it is the other way round at the official MetO observing network - maximum temperatures have generally increased faster than minimum temperatures.  I get a sense that this shift occurred in the 1990s and 2000s, associated with a decrease in cloud cover, and that we may see the maxima and minima both go up by a similar amount from 1981-2010 to 1991-2020.  That said, in many of the expanding populated areas of the UK the mean minimum temperature has risen more quickly due to the urban heat island effect.

Edit: I see Relativistic beat me to it!

Edited by Thundery wintry showers

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Posted (edited)

Trends.xlsxLooking into this further, Relativistic and Ian are both correct.

Max Temps have risen by an additional 0.1c (roughly) compared to Min Temps per decade.

At least though I have learnt something from my incorrect assumption.

MeanTempJAN  FEB  MAR APR  MAY  JUNE   JULY  AUG    SEP   OCT   NOV  DEC YEAR   INC
1961-1990 3.81  3.76  5.68  7.89  11.16  14.16  16.05  15.77  13.60  10.62  6.55  4.65    9.51
1971-2000 4.20  4.24  6.27  8.07  11.31  14.07  16.48  16.21  13.71  10.41  6.87  5.06    9.77      0.26
1981-2010 4.44  4.39  6.58  8.52  11.66  14.48  16.71  16.41  14.03  10.69  7.14  4.63  10.00      0.23
1991-2020 4.60  4.84  6.74  8.90  11.88  14.67  16.82  16.45  14.18  10.96  7.42  4.94  10.22      0.22

Min Temp JAN  FEB  MAR APR MAY  JUNE  JULY AUG  SEP  OCT  NOV DEC YEAR  INC
1961-1990 1.21  0.96  2.26  3.96  6.75    9.73  11.68 11.46   9.64  7.20  3.64  2.04  5.91
1971-2000 1.56  1.32  2.90  4.08  6.78    9.69  11.94 11.71   9.75  7.00  3.94  2.46  6.12     0.22
1981-2010 1.75  1.38  3.08  4.30  7.13  10.02  12.17 11.95 10.02  7.29  4.24  1.96  6.30     0.18
1991-2020 1.91  1.79  3.09  4.57  7.33  10.11  12.18 12.04 10.12  7.55  4.48  2.20  6.48     0.17

Max Temp JAN  FEB  MAR  APR  MAY  JUNE  JULY  AUG   SEP   OCT   NOV  DEC YEAR  INC
1961-1990 6.44  6.56  9.08  11.82 15.56 18.57  20.41  20.08  17.56 14.02   9.45   7.29  13.11
1971-2000 6.86  7.13  9.63  12.06 15.81 18.41  20.98  20.71 17.68  13.80   9.80   7.69  13.41   0.30
1981-2010 7.15  7.36 10.07 12.72 16.16 18.91  21.23  20.85 18.05  14.08 10.06   7.32  13.70   0.29
1991-2020 7.31  7.86 10.38 13.22 16.40 19.22  21.45  20.86 18.25  14.37 10.36   7.68  13.97   0.27

 

 

Edited by J10

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Thanks for adding those details. Interesting. 

Meanwhile, the July CET was in fact 17.5 so no edits required to the tracking. It will take a warmer July than this year to produce a new normal of 16.9, otherwise it's likely to remain 16.8. 

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