The coldest winters
Which are the coldest winters of the twentieth century? Here are the top ten.
1962-63 -0.3
1946-47 1.1
1939-40 1.5
1916-17 1.5
1978-79 1.6
1928-29 1.7
1941-42 2.2
1940-41 2.6
1981-82 2.6
1984-85 2.7
Are winters not as good as they used to be? Not lately they haven't, but it isn't clear that there is any trend until very recently.
Let's consider the distribution of severe winters, defined by two criteria.
1. Severe months with average temperature less than 2.0C. In the first half of the century, there were 14 severe months, and two occasions (Jan-Feb 1917 and 1929) when there were consecutive severe months. In the second half, there were actually a few more - 17 severe months, with two occasions (1963 and 1979) when there were two consecutive severe months, and only one occasion with three consecutive severe months (1916-1917). This difference however will be statistically insignificant.
2. Very severe months with average temperature beneath freezing. In the first half of the century, there were two very severe months (January 1940 and February 1947. In the second half, there were five (February 1956, January 1963, February 1963, January 1979, and February 1986 - and December 1981 came very close).
I think two things are happening. First, people's memories are distorted by the exceptionally severe winters of 1947 and 1962-63, in particular. Second, I think there is a recency effect where there haven't been many severe winter episodes in the last few years. Consider this table of the distribution of the number of severe winter months across the decades of the twentieth century:
1900s
1910s
1920s
1930s
1940s
1950s
1960s
1970s
1980s
1990s
1
4
2
1
6
4
5
2
5
1
Older people might be affected by the bump in the middle of the century (particularly the war years, which were exceptional) and compare that with the 90s. There is no overall trend, however: note the scarcity of severe months in the 0s and thirties. It is also possible that central heating means that we are less sensitive to cold weather when it happens.
Here are the severe months (mean less than 2.0C):
Feb 1902; Dec 1916, Jan 1917, Feb 1917, Feb 1919, Jan 1929, Feb 1929, Dec 1933, Jan 1940, Jan 1941, Jan 1942, Feb 1942, Jan 1945, Feb 1947, Dec 1950, Feb 1955, Feb 1956, Dec 1962, Jan 1963, Feb 1963, Feb 1968, Feb 1969, Jan 1979, Feb 1979, Dec 1981, Feb 1983, Jan 1985, Feb 1986, Jan 1987, Feb 1991
Here again are the very severe months (mean less than 0C):
January 1940, February 1947, February 1956, January 1963, February 1963, January 1979, February 1986.
It is true that although we have some recent hot months, you have to go back to February 1991 for a cold month. This difference is a clear suggestion of change.
Before the twentieth centuries, winters were better (if you like then cold and snowy). Remember the Little Ice Age? In the seventeenth and eighteenth centuries, winter knew how to be winter. Take the coldest winter of them all, the "Lorna Doone" winter of 1683-84, with a CET of -1.2. Or 1739-40, with a CET of -0.4.