London scoping - ukcip

Winter anomaly (%)
Summer anomaly (%)
Final Report
15
Figure 3.3 River Thames seasonal precipitation totals, 1883-2001
100
80
60
40
20
0
-20
-40
-60
-80
1881
-20
-40
-60
-80
1901 1921 1941 1961 1981 2001
0
20
100
80
60
40
1881 1901 1921 1941 1961 1981 2001
Nonetheless, the summers of 1995 and 1976 were still two of the three driest since the 1880’s,
with seasonal totals respectively –70% and –56% below the 1961 to 1990 average. The second
driest summer on record occurred in 1921 and had an anomaly of –62% (see Table 3.1).
Conversely, the wettest winters were 1914/15 (+ 112%), followed by the much celebrated
winters of 1989/90 (+94%) and 1994/95 (+73%) (see Marsh and Monkhouse, 1993; Marsh and
Turton, 1996). A further feature of recent winters has been the steady decline in snowfalls.
Since the 1960’s the frequency of snowfall in south east England has fallen from 45 days per
decade, to 39 in the 1970’s and 1980’s, to just 23 in the 1990’s (see also Wild et al, 1996;
2000). Average areal snowfall depths across the region have also declined in recent decades
(see Figure 3.4).
Figure 3.4 Snowfall depths in southeast England, 1959-1999. The composite was derived from
observations at Cambridge, Dover and Oxford.
Snow depth (cm)
20
15
10
Source: O’Hare and Wild (pers. comm.)
5
0
1959 1964 1969 1974 1979 1984 1989 1994 1999
Spring anomaly (%)
Autumn anomaly (%)
-20
-40
-60
-80
0
20
100
80
60
40
1881 1901 1921 1941 1961 1981 2001
-20
-40
-60
-80
0
100
80
60
40
20
1881 1901 1921 1941 1961 1981 2001