[summer '85]

Another year from the past but this one is absolutely bizarre, 1817. Months compared to 1781-1810 average

Jan:  4.5 (+1.6)
Feb: 6.4  (+2.5)
Mar: 5.5  (+0.9)
Apr: 7.6  (-0.2)
May: 8.7 (-2.8)
Jun: 15.1 (+0.6)
Jul: 14.1 (-2.0)
Aug: 13.6 (-2.2)
Sep: 13.2 (0.0)
Oct: 6.4 (-3.0)
Nov: 9.1 (+3.8)
Dec: 2.5 (-0.7)

The only instance of May being colder than November

The second half of May 1817 was nearly a degree colder than the first half of November 1817

May and October 1817 are the  third and second coldest months respectively ever recorded for each of those months .

November 1817 was the the 3rd warmest November ever recorded at the time

The first half of October 1817 was 1.5C colder than the second half of November 1817

The leap in CET between October and November 1817 is the largest ever record (+2.7)

The leap between May and June 1817 is the largest ever recorded (+6.4)

April 1817 was exceptionally dry, the driest on record until April 1938 but May was very wet, Autumn 1817 was until 1978 the driest autumn on record, whilst the summer is 8th wettest on record.

 There are few years as ridiculous as 1817

[StephenS]

Presumably some of these anomalies can be attributed to the lingering effects of the Mount Tamboura eruption, which resulted in 1816 being the 'year without a summer'? Certainly both years were very odd, weather-wise: what followed from that were crop failures, starvation, epidemics and large-scale civil unrest in various parts of Europe and North America.

[Dave W]

Diff between Nov and Dec is also very large..

[summer '85]

February  and October 1817 both have the same CET with 6.4, another oddity for that year.

There has never been a February warmer than the following October but this is the closest.

[Chris Alder]

A very strange year indeed though I'm not sure I like look of that summer!

[BUTTERFLY]

"Diff between Nov and Dec is also very large."

 Indeed, it was the 2nd largest fall (6.6 deg. C.) from November to December, after 1981 when it was 7.5 deg C.

[BUTTERFLY]

Also, 6 of the 12 months differed by 2 deg. C. or more from average, 2 above and 4 below; 2 of these were more than 3 deg. C. and followed each other, October 3 deg. C. below and November 3.8 deg. C. above. Has anything like this happened before?

November has been warmer than October in only 7 years from 1659 to 2006 (about 1 year in 50, last in 1939), mostly by 0.5 deg. C. or less. However in 1817 it was 2.7 deg. C warmer (October 6.4, November 9.1) and 1881 1.6 deg. C. (7.3, 8.9) warmer; in 1743 0.4 deg. C. (8.9, 9.3), 1852 0.1 deg. C. (7.8 deg. C., 7.9 deg. C), 1895 0.4 deg. C. &.1, 7.5), 1917 0.3 deg. C. (7.5, 7.8) and 1939 0.5 deg C. (8.2, 8.7).

1817 thus stands out in this respect as having a very cold October (2nd coldest at 6.4 deg. C., after 5.3 deg. C. in 1740) and the 5th mildest November (9.1 deg. C); only 1730 (9.2 deg. C.), 1743 (9.3 deg. C.) 1938 (9.4 deg. C.), 1818 (9.5 deg. C.) and 1994 (10.1 deg. C.) were warmer.

[summer '85]

CET trackometer for October and November 1817 respectively

1.    8.0       5.4
2.    5.8       7.8
3.    5.4       9.0
4.    5.9       9.3
5.    6.0       9.4
6.    6.1       9.6
7.    6.5       10.1
8.    6.8       10.2
9.    6.8       10.0
10.  7.0       10.1
11.  6.9       10.0    
12.  6.8       10.1
13.  6.8       9.9
14.  6.8       9.9
15.  6.7       10.1
16.  6.7       10.1
17.  6.5       10.2
18.  6.5       10.2
19.  6.5       10.0
20.  6.4       9.8
21.  6.4       9.7
22.  6.4       9.5
23.  6.4       9.4
24.  6.4       9.3
25.  6.4       9.1
26.  6.4       9.0
27.  6.4       9.0
28.  6.4       9.0
29.  6.3       9.0
30.  6.4       9.1
31.  6.4        -

---

[summer '85]

Temperatures at Tottenham for October and November

Oct               Nov
1. 56f, 30f      49f, 27f
2. 46f, 24f      57f, 41f
3. 50f, 32f      54f, 49f
4. 57f, 32f      55f, 45f
5. 56f, 33f      54f, 44f
6. 54f, 39f      55f, 49f
7. 54f, 43f      58f, 50f
8. 54f, 35f      55f, 44f
9. 53f, 39f      51f, 40f
10. 56f, 41f    55f, 44f
11. 50f, 36f    52f, 38f
12. 52f, 35f    55f, 38f
13. 52f, 32f    52f, 38f
14. 50f, 42f    54f, 49f
15. 48f, 37f    55f, 40f
16. 48f, 36f    54f, 39f
17. 48f, 37f    59f, 50f
18. 45f, 37f    57f, 35f
19. 45f, 42f    49f, 30f
20. 48f, 40f    46f, 38f
21. 52f, 39f    52f, 37f
22. 48f, 36f    47f, 37f
23. 50f, 40f    46f, 41f
24. 46f, 38f    49f, 32f
25. 50f, 37f    44f, 34f
26. 52f, 28f    52f, 40f
27. 49f, 32f    51f, 37f
28. 48f, 32f    49f, 40f
29. 49f, 27f    54f, 49f
30. 57f, 42f    54f, 52f
31. 52f, 28f

"The mean temperature of this period instead of falling some degrees as might have been expected from the season, is near 4F higher than that of last. But in October it had undergone a disproportionate of 12.5F for which the present warmth may be considered as a compensation"  Luke Howard.

[BUTTERFLY]

I thought I would post the figues for Armagh Observatory in Northern Ireland for each month and season of 1817 (winter 1816/1817 includes December 1816), with deviations (in brackets below) from the long term average 1838-2007 or 2008 as appropriate. i.e. to 2008 for January to October, to 2007 for November & December, and for the nearest 30 year period (1796-1825). The figures (in degrees Centigrade) are available at http://star.arm.ac.u...eprints/445.pdf

DEC 1816 2.2 (-2.4/-0.7) JAN 4.6 (+0.5/+1.6) FEB 5.8 (+1.2/+1.7) MAR 5.1 (-0.7/0.0) APR 7.2 (-0.7/-0.2) MAY 6.9 (-3.7/-3.3) JUNE 12.2 (-1.2/-0.7) JULY 13.8 (-1.0/-0.7) AUG 13.1 (-1.5/-1.2) SEP 11.3 (-1.2/-0.3) OCT 5.5
(-3.9/-2.9) NOV 6.5 (+0.3/+1.7) DEC 1.6 (-3.0/-1.3)

WINTER 1816/1817 4.1 (-0.3/+0.9) SPRING 1817 6.4 (-1.7/-1.2) SUMMER 1817 13.0 (-1.3/-0.9) AUTUMN 1817 7.7 (-1.7/-0.5) YEAR 1817 7.8 (-1.2/-0.5); this indicates that it was a period of frequent cold winters and autumns and somewhat cooler springs and summers than the overall period.

Where there are substantial differences (c. 1.0 deg. C.or greater) in the anomalies for 1796-2008 and 1796-1825, this indicates that these months were significantly warmer or colder during this period than the overall average; e.g. January averaged 1.1 deg. C. colder, September +0.9 deg. C. warmer, November 1.4 deg. C. warmer and December 1.7 deg. C. colder.

May was the coldest on record and October the joint coldest along with 1808 (At Armagh temperature records go back to January 1796, probably the longest continuous series of temperature records anywhere in the World). It was also colder than April, which has happened in only 6 of the 213 years from 1796-2008 (the last time was in 1955). October was also colder than November, which has happened in 5 years (last 1981). May was only 0.4 deg. C. warmer than November, the smallest differential between these 2 months apart from the 0.2 deg. C. in 1994 which had the warmest November on record (May 9.8 deg. C., November 9.6 deg. C.) and 0.3 deg. C. in 1899 (May 9.6 deg. C., November 9.3 deg. C.). The highest such differential was 10.3 deg. C. in 1809 when May (13.8 deg. C.) was the warmest on record and November was rather cold at 3.5 deg. C. (the coldest November was 1.7 deg. C. in 1807).

Interestingly, a year earlier, Armagh had its coldest ever September at 7.3 deg. C. (-5.2 deg. C. below average). The only other month with a lower deficit below average was January 1814 (-6.3 deg. C.). Generally, the coldest examples of individual winter months in the British Isles show much the largest negative deficits, compared with other months of the year, which are seldom much more than 3 deg. C. below average; at Armagh no coldest example of each month from May to October is more than 4 deg. C., apart from September 1816.

[summer '85]

A graph showing the CET values plotted through the year. The blue horiontal lines are the 30 year average (1781-1810) for each month. You can see the remarkable difference between October and November.

[mianfei]

summer said:

There has never been a February warmer than the following October but this is the closest.

From the CET record for another exceptionally odd year in 1779, it’s notable that February 1779 was 0.5˚C hotter than October 1778. That is the only February hotter than the preceding October. In fact, if we take the year from July 1778 to June 1779, October 1778 was the fourth coolest month and in fact cooler than every month from February 1779 until November. There have been eleven cooler Octobers in England since then, but none since 1919.

I had a look at the climate record for my hometown of Melbourne, Victoria for a comparison with the English climate record and it is interesting to note that in Melbourne there has never been an April as cool as the following August, with the closest approach being in 1995 with a maximum of 18.12˚C in April and 16.99˚C in August. For your information August 1995 was about as abnormally hot and dry in southern mainland Australia as it was in England, and the unusual weather led to many comments in newspapers such as the Sydney Morning Herald. A complete contrast came from Queensland’s Wet Tropics, where monthly rainfalls were what one would expect in the wet season from December to April, though this affected the sugar harvest it was not widely commented on.

In 1866, which but for man-made global warming would surely have been a 1-in-300 or 1-in-400 hot May in Melbourne, May in Melbourne had a minimum temperature of 9.0˚C and November of 8.6˚C, but the maximum in May was still 0.6˚C cooler than in November, so an analogue to England in 1817 just failed. By minimum temperature November 1866 was actually the fifth coolest month of the year in Melbourne.

It’s interesting to speculate whether the volcanic eruptions in Mount Tambora really caused the strange weather of 1817. It’s hard to say the wet May to August (sixth wettest), extremely dry April, September (equal twelfth driest) and October (equal fourteenth driest) fit in with that pattern. A very wet summer followed by a dry October has occurred in the EWP series since in 1830, 1879, 1931, 1946 and 1965, though a huge difference exists because September of all those years was much wetter. Maybe unpredictable weather does follow a volcanic eruption: the 1991 Australian Football League season to me is “two seasons in one” because of Melbourne’s and Adelaide’s bone-dry autumn giving way to a very wet June to September, with major consequences for the fortunes of competing clubs.

This post has been edited by mianfei: 12 May 2012 - 07:27