Extra - October 20, 2014
October Down The Ages
Warmer and Sunnier

By Philip Eden

October: the month the leaves change colour, apples and pears ripen, the clocks go back. Whatever the weather throws at us, it always has an autumnal flavour. On rare occasions the temperature climbs to the high 20sC, a reminder of summer past, but now the sun is low in the sky, the mornings are misty, and the evenings are dark. Equally rarely cold winds from the Arctic bring sleet and snow flurries, but the ground is generally too warm for the snow to settle and the cold snap never lasts more than three or four days.

Early in the 20th century climatologists became aware of a trend towards warmer and drier Octobers; indeed, a number of Octobers between 1957 and 1972 resembled a late-summer month rather than the traditional descent towards winter. This trend was abruptly checked with the exceptionally cold October of 1974, the coldest since 1905, but the recovery in temperature has resumed since 1998.

According the records for central England collected by the late Professor Gordon Manley, the mean October temperature between 1959 and 1900 was 9.4C, between 1901 and 1950 it was 49.8F (9.9C), and between 1951 and 2000 it was 10.5C. The warmest ten-year period was 2001-10 when the mean was 11.1C; looked at from another angle we can say that the warming between 1900 and 2014 is equivalent to a delay of 16 days in the onset of winter.

While October has grown warmer it also became drier until 1980. October was consistently the wettest month of the year, averaged geographically across England and Wales, until the beginning of the last century, but by contrast, between 1940 and 1980 it was routinely less wet than November, December and January. The mean rainfall from 1800 till 1940 was around 100mm, but from 1940-1980 it averaged 85mm. The driest ten-year period of all was 1969-78 with an average rainfall of 60mm. But since 1980 October has become rainier, and from 1998-2013 it was appreciably wetter with an average of 112mm of rain.

Sunshine records only extend back to 1876 and these show an erratic improvement in sunshine totals from about 95 hours from 1876-1900, 107 hours from 1976-2000 and 114 hours from 1999-2008.

Although there are huge fluctuations in October weather from year to year these figures show that there is a clear underlying trend towards warmer and sunnier months.

By Philip Eden

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