The most notable “cold-wet” outlier is January 1809, with CET of 2.0˚C, estimated Scotland temperature of -1.1˚C, estimated UK mean temperature of 0.9˚C, yet EWP of 134.3 millimetres. There exist other moderate “cold-wet” outliers (forming a semicircle between 100 and 110 millimetres and from 0˚ to 2˚C) in Januaries 1768, 1774, 1789, 1867, 1895, 1942, 1959, along with January 1979 – the coldest month over the contiguous US since before 1880, but very hot in southern Australia due to a super-monsoon and warm in the Far East:
The “warm-dry” outliers of 1898 and 1916 are distinctly different. 1916 was the mildest January on record (though in between a very cold November and snowy, dull March) but was probably the UK’s windiest month since 1871 with gales on 25 days – some destructive even when no rain fell. 1898 was a classic anticyclonic gloom month with little sunshine, but the red diamonds in the upper left (1989, 2005) were ten to fifteen hours sunnier than the mean, and the “winterless winter” of 1948/1949 was extremely sunny.
- record warm February 1779 with CET 7.9˚C and EWP of 13.5 millimetres
- February 1998 with CET 7.3˚C and EWP of 20.4 millimetres
- February 1790 with CET 6.6˚C and EWP of 20.9 millimetres
- February 1903 with CET 7.1˚C and EWP of 38.8 millimetres
- February 1846 with CET 6.4˚C and EWP of 37.1 millimetres
- February 1815 with CET 6.5˚C and EWP of 44.0 millimetres
- 1878/1879 (fourth coldest since 1766; CET 0.62˚C; EWP 250.0 millimetres)
- 1978/1979 (red diamond; CET 1.58˚C; EWP 335.2 millimetres one of only four winters since 1910 drier in Scotland)
- 1914/1915 (marginal outlier; CET 4.33˚C; EWP a then-record 423.0 millimetres)
- the amazing winter of 1778/1779 (record warm February is earliest surviving record warm month and MSLP was over 1,030 millibars)
- the second-driest winter in 1857/1858 (as noted earlier, December 1857 was warmer than 1934 or 1974 in Scotland and probably the UK as a whole, whilst its MSLP was comparable to February 1779)
- the winter of 1988/1989 with CET of 6.52˚C and EWP only 185.5 millimetres. In contrast to December 1857, this winter was warm all though central and northern Eurasia due to a highly positive NAO index
March:yellow diamonds the several very snowy Marches that occurred around a century ago during World War I. These were particularly disruptive in the emergency with cold delaying opening of the growing season in 1917, and causing human disruption during the snowy March 1916 – apart from 1947 the worst March of the twentieth century. That March 1916 and 1919 were exceptionally cold and wet is very clear from this graph.
It is extremely evident that the positive correlation seen for the previous four months has completely disappeared, and that the line looks exceptionally flat, with “outliers” being either warm (1938 and 1957), cold (1785) or wet (1947 and 1981).
It’s possible that the true shape of this curve is a triangle – one sees much more CET ranges in dry Marches (both March 1785 and March 1938 had EWP of under 20 millimetres and March-April EWP under 30 millimetres) – than in most wet Marches, though the two EWP outliers in 1947 and 1981 make claims of a “triangular”-shaped scatter plot look dubious and we can assume that in March EWP and CET show little correlation.
If we look at the red diamonds controlled by Australian greenhouse gas emissions, the conclusion is not really different. Despite the clear presence of several Marches (1990, 1997, 2011) that were both warm and very dry, the silver diamonds in the top left corner (1779, 1938 and 1961) and several cool, wet Marches during the 1970s and early 1980s suggest no fundamental change. However, before 1884 very cold, dry, easterly Marches occurred as not observed since in 1785, 1786, 1807, 1808, 1845 and 1883. Nevertheless, warm, wet, westerly Marches (1903, 1912, 1981) were not observed to oppose them as would be expected if the EWP/CET relationship had changed.
There exit numerous red diamonds in outlying parts of this graph – both hot and wet. Nevertheless, because the extreme hot outliers of 2007 and 2011 were both exceedingly dry, it is not likely that man-made global warming had altered the shape of the graph at all.
The “cold-dry” outliers of 1837 (coldest April on record) and 1771 (EWP 31.3 millimetes, CET 5.5˚C) are more striking than the “warm-wet” ones of 1792 and 1961 (CETs both 10.0˚C, EWPs 97.7 millimetres in 1792 and 98.1 millimetres in 1961) – the latter being the wettest April on record in southwestern Australia, which has seen huge rainfall declines due to its own greenhouse emissions.
The prime “cool-dry” outlier of 1876 (EWP 23.6 millimetres; CET 9.6˚C) featured two very cold days at the beginning but was the beginning of the summer when W.G. Grace hit the first two first-class triple centuries. From the context of a warming world, May 1991 – the third-driest on record but with CET 0.4˚C below the virgin mean of approximately 11.2˚C – is also notable although it was obviously a similar but more eastward Atlantic block to September 1986 which I discussed before.
In contrast to the numerous moderate “warm-wet” ouliers brought about by man-made global warming, there are two exceedingly marked “cold-dry” outliers from before 1974: the record-cold spring of 1837, which was 0.92˚C colder than the winter of 1833/1834, and the record-dry spring of 1785, the core of easily the driest fiscal year since 1750.
|Spring season||March EWP||Anomaly||April EWP||Anomaly||May EWP||Anomaly||March CET||March CET Anomaly||April CET||April CET anomaly||May CET||May CET anomaly|
|1785||18.8 mm||-40.0 mm||10.1 mm||-48.3 mm||25.9 mm||-38.4 mm||1.2˚C||-4.1˚C||8.4˚C||+0.4˚C||12.3˚C||+1.1˚C|
|1837||30.4 mm||-28.4 mm||50.4 mm||-8.0 mm||36.7 mm||-27.6 mm||2.3˚C||-3.0˚C||4.7˚C||-3.3˚C||9.9˚C||-1.3˚C|
Fiscal Year (July to June):
It is possible, though I have not checked, that the choice of the fiscal year over other possible twelve-month ranges affects the result by dividing over two years extreme hot and dry summers like 1826, 1868, 1911, 1921 and 1976. Such dry years as 1826 and 1921 were in fact hot as a whole, despite the association of dryness with cold during the winter, the quintessential “continental” year of 1780 was only 0.11˚ cooler than the 1766 to 1974 average despite an extremely cold January, and 1947 with its long, hot summer was 0.61˚C hotter despite its record cold February.
Compared to the individual months, outliers are more numerous for the whole fiscal year. The very cold year of 1813/1814 and the very dry year of 1784/1785, as well as the very wet anthropogenic years of 2000/2001, 2006/2007 and 2013/2014, especially stand out. The hot, dry anthropogenic years of 1975/1976 and 1991/1992 are also marked outliers, as is the extreme “cold-wet” outlier of 1878/1879, where a CET of 7.30˚C was recorded for the twelve months ending October 1879.