The very warm decade - 1730's

[Optimus Prime]

Up until the 1990's, the 1730's was the warmest decade in the Central England Temperature series. It measures 9.85 °C compared to 9.25 °C for the 1701 - 1730 reference period. The sharpest increase in warming was measured in January (4.5 °C vs 3.1 °C , +1.4 °C rise against 1701 - 1730). November showed the lowest level of warming at +0.1 °C (6.5 °c vs 6.4 °C). The warmest month relative to average is January 1733 at 6.9 °C (+3.8 °C). The warmest month registers 18.3 °C in July, also in 1733; 1733 is the warmest year of that decade at 10.5 °C. Looking at the temperature series, 1733 was to be the warmest year until 1834 when 10.51 °C would be recorded (and subsequently equaled in 1922). It would then take until 1959 to finally exceed this (10.52 °C)

 

That period compares quite well to the 1990's where the decadal average comes in at 10.1 °C. The  decade of the 1730's is 0.6 °C above its 30 year average reference period. Comparatively, the current warmest decade (2000 - 2009) is 0.61 °C warmer than it's reference period (1971-2000).

The preceding decade was exceptionally cold; the 1740's averaged 8.86 °C or broadly equivalent to 2010.

The warming spike of that decade can be clearly seen on the Met Office annual anomaly chart;

The rolling 10-year average for the 1730's is actually a little higher than the next warmest decade, the 1940's (prior to the 1990's)

Some interesting information can be found here;

Britain's Little Ice Age: When Was It And What Happened?

WWW.HISTORYEXTRA.COM

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The Thames turned to ice, gales flattened communities, and famine killed peasants in their thousands. Brian Fagan describes the climatic calamities that beset Britain from the 14th to 19th centuries as it shivered...

 

Edited June 5, 2021 by Optimus Prime

[Optimus Prime]

Detailed analysis of the weather experienced in the 1700's.

[Timmytour]

From September 1729 to August 1739 there were 21 months that registered mean CETs that fall in the all time warmest 10% for the months concerned, and just one that features in the coldest 10%

In a similar time-frame, from June 2011 to May 2021, the same figures are 38 in the warmest and 2 in the coldest.

Given the time that has elapsed and the warming that has undergone since, I'd say the period in the 18th Century stacks up pretty well!

Which makes me wonder how it all changed so dramatically?  The numbers of cold months in the same period following  August 1739 was 20, while warm months only mustered 5.

What produced such a difference?   Could it have been to do with the plinian eruption of Mount Tarumae in Hokkaido, Japan. in August of 1739  with the relative frequency and severity of subsequent volcanic eruptions keeping temperatures subdued for some time?  

Could it happen again?

[Derecho]

18 minutes ago, Timmytour said:

From September 1729 to August 1739 there were 21 months that registered mean CETs that fall in the all time warmest 10% for the months concerned, and just one that features in the coldest 10%

In a similar time-frame, from June 2011 to May 2021, the same figures are 38 in the warmest and 2 in the coldest.

Given the time that has elapsed and the warming that has undergone since, I'd say the period in the 18th Century stacks up pretty well!

Which makes me wonder how it all changed so dramatically?  The numbers of cold months in the same period following  August 1739 was 20, while warm months only mustered 5.

What produced such a difference?   Could it have been to do with the plinian eruption of Mount Tarumae in Hokkaido, Japan. in August of 1739  with the relative frequency and severity of subsequent volcanic eruptions keeping temperatures subdued for some time?  

Could it happen again?

For my MSc dissertation, I looked at variations in winter atmospheric circulation from the 17th century to the present day. The 1730s were notable for their big increase in SW winds which would explain the mild winters. Late 1739 however saw a shift to frequent northerlies before 1740 saw abnormally high SLP and a high number of easterly winds.

January 1740 probably saw a beast from the east at some point and so did October 1740. By the following winter, cold pooling off the continent must have begun abnormally early as it had a CET in the 5s.

Interestingly the following December was dominated by cyclonic days and variable winds. Low pressure bumping into cold air masses, some big snow events must have occurred during that month.

The 1740s had much more frequent easterly winds and were very dry. 1750s were a bit more normal. 1760s and 1770s had a higher incidence of northerlies. The 1780s to mid 1810s then saw the most abnormal atmospheric circulation with easterlies at times more frequent then westerlies, probably due to Icelandic volcanic activity. The mid-late 1810s saw a jump in westerlies after Tambora, with the late 1830s-1850s seeing more meridional patterns again.

The switch from 1739 to 1740 I think may have been triggered by an undocumented volcanic eruption. Or there are variations in atmospheric circulation that may be greater then what we are currently used to.

[virtualsphere]

4 hours ago, Quicksilver1989 said:

For my MSc dissertation, I looked at variations in winter atmospheric circulation from the 17th century to the present day...

Slightly off topic here but I'm curious as to when you did your dissertation and what data you used?  I feel like there was a notable absence of easterly winds in the years up to around 2008/09, replaced by an increased frequency in easterlies in the 2010s, and it seems there has been an absence of northerlies in recent years until last winter - but it could just be my perception.  Other than the volcanic activity, did you find any likely drivers for longer term changes in circulation patterns which particularly affected the CET?

[Derecho]

16 minutes ago, virtualsphere said:

Slightly off topic here but I'm curious as to when you did your dissertation and what data you used?  I feel like there was a notable absence of easterly winds in the years up to around 2008/09, replaced by an increased frequency in easterlies in the 2010s, and it seems there has been an absence of northerlies in recent years until last winter - but it could just be my perception.  Other than the volcanic activity, did you find any likely drivers for longer term changes in circulation patterns which particularly affected the CET?

It involved looking at weather diaries in the UK back to the 1720s up to 2014 when I was doing the MSc project. I absolutely loved it but it would have needed more years of work to be a great piece of research, it needed to be more than a year. 

I think Ocean Circulation may have also been a factor but variables such as SLP become increasingly sparse when we get to that long ago.

I see atmospheric circulation like an elastic band, there is a mean state but how much that elastic band can be stretched and the extent to which it can before it snaps is an unknown.

[virtualsphere]

1 hour ago, Quicksilver1989 said:

It involved looking at weather diaries in the UK back to the 1720s up to 2014 when I was doing the MSc project. I absolutely loved it but it would have needed more years of work to be a great piece of research, it needed to be more than a year. 

I think Ocean Circulation may have also been a factor but variables such as SLP become increasingly sparse when we get to that long ago.

I see atmospheric circulation like an elastic band, there is a mean state but how much that elastic band can be stretched and the extent to which it can before it snaps is an unknown.

Thanks, that sounds like a really fascinating project.  I wondered about the data as getting historical records back that far seems challenging, and because the timescales for the data we have are so short in climate terms there are probably a lot of interesting natural cycles like this that we haven't yet paid much attention to.  I've been wondering whether there's a dataset for average wind direction / speed, or average SLP in the UK over a specific period (e.g. a month, year etc).