PostScript | JPEG
The NCEP Climate Prediction Center, University of East Anglia, and the NCAR Climate and Global Dynamics Division all provide a Darwin SLP time series which begins in the 1800s and is updated monthly. A file of the difference, UEA minus NCEP is linked here. For all but a few months the differences are less than one or two tenths mb. In the following I use the UEA data.
Data (UEA only)
The following SLP anomalies (in tenths mb, for example, 10 is 1.0mb) are with respect to 1950-79. Monthly SLP anomalies exhibit significant month to month variability, but I have not filtered the following values.
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 1866 10 -1 9 4 -1 8 2 4 -1 1 0 6 1867 12 0 13 4 -1 1 -1 -2 -6 -9 18 7 1868 -2 5 10 9 16 14 5 9 6 8 18 5 1869 15 10 23 -25 -15 -13 -4 -13 -4 -14 -9 -11 1870 -23 -12 15 7 10 10 -2 -10 -2 5 7 17 1871 7 7 21 3 4 1 1 1 -3 -4 -5 0 1872 -30 -14 -18 24 -7 -23 -20 -11 -20 -15 -15 -26 1873 -25 9 11 8 23 44 24 10 31 5 2 -22 1874 -3 18 20 1 -6 11 3 3 -11 -19 0 -23 1875 -2 0 22 1 -2 -13 -1 3 -14 -29 3 -4 1876 -14 -11 -10 -11 1 -2 14 2 -3 5 -1 16 1877 6 13 0 16 3 26 19 13 19 21 16 15 1878 6 29 9 4 -2 1 -12 5 -17 -13 -5 -21 1879 -11 -11 -4 0 -2 -4 -12 -10 -8 -6 -10 -4 1880 -19 4 -7 7 -5 1 12 4 6 11 11 10 1881 7 9 18 20 1 2 14 15 12 22 -9 -7 1882 2 0 0 -8 -13 -1 3 6 -1 -11 8 -15 1883 12 2 17 -8 -3 2 0 -8 -1 -4 -16 -4 1884 12 10 0 19 4 2 3 -1 3 3 4 2 1885 12 0 11 12 21 12 13 6 13 20 25 -1 1886 16 -7 11 -2 -3 -1 -11 -14 -11 -7 -6 -28 1887 -5 -17 -3 -8 0 2 6 -1 3 7 8 9 1888 -8 7 24 12 4 9 10 9 6 17 11 16 1889 29 21 27 8 4 -11 0 3 -11 -4 -30 -28 1890 -22 0 -6 -5 0 -8 -4 -4 -14 -7 4 2 1891 -8 4 17 8 14 9 13 23 20 10 14 16 1892 2 17 -13 5 10 -5 3 -4 -7 -14 -6 -1 1893 -5 -7 14 -2 4 -5 -7 6 -4 -10 1 6 1894 -28 -3 0 2 10 6 10 -1 3 3 4 6 1895 -8 7 11 8 14 6 0 -1 -1 3 21 6 1896 -1 -3 4 -2 31 9 6 23 16 24 14 23 1897 16 10 24 15 17 2 10 6 -1 3 4 -15 1898 -1 -13 -34 -2 7 -1 3 -1 -11 -10 -19 -11 1899 -8 7 -13 -2 7 9 6 3 6 14 11 9 1900 16 17 24 15 7 -4 -7 -14 -4 0 4 13 1901 2 4 1 5 7 -1 3 6 10 0 11 3 1902 -4 17 7 9 21 9 10 9 16 17 21 13 1903 19 21 -16 -2 4 6 -14 3 -7 -3 -2 -18 1904 -4 -10 -3 -18 0 9 3 6 3 -7 15 6 1905 16 14 34 15 4 6 10 9 0 -3 21 13 1906 2 7 11 5 4 -1 -10 -1 -14 -7 -16 -4 1907 -11 -3 7 5 7 -8 -4 3 3 0 1 -14 1908 16 -10 -3 -12 4 6 0 -1 0 -3 -2 -1 1909 -4 14 -16 5 -3 -8 -7 -7 -7 -10 -6 -4 1910 -18 -13 -6 -12 4 -11 -10 -7 -14 0 -16 -14 1911 -8 -6 4 -8 11 16 6 9 3 14 11 3 1912 13 27 7 22 17 2 -10 6 -7 7 1 13 1913 -1 7 -6 2 17 9 10 3 13 14 15 9 1914 23 21 1 12 4 12 13 23 16 30 21 13 1915 23 14 31 19 11 -4 -10 -1 -14 -7 -2 -18 1916 -11 -3 1 5 -10 -18 -17 -4 -11 -14 -9 -31 1917 -1 11 -16 -8 -3 -11 -21 -18 -14 -7 -12 -21 1918 -8 -10 14 -2 0 2 10 9 23 7 4 9 1919 9 24 11 2 0 6 3 9 6 7 11 9 1920 -11 4 14 -5 0 -21 -17 -7 -7 -3 -2 -18 1921 -11 0 -6 9 -6 -18 -7 6 0 0 1 -11 1922 -8 -13 -6 2 -3 -8 -4 3 -4 0 1 -11 1923 -11 0 -10 -12 -6 -8 10 20 6 10 8 -1 1924 13 4 1 2 -3 -1 3 3 0 -10 -6 -14 1925 -8 -23 -23 -15 -3 -1 10 3 10 10 15 9 1926 2 21 21 9 4 6 0 3 -4 -7 8 -8 1927 -11 4 -6 -5 0 -4 -4 6 6 7 8 -1 1928 23 -6 -10 -2 11 6 0 6 0 -10 8 -8 1929 -32 -20 1 2 11 12 10 6 6 3 -6 -8 1930 -15 0 7 9 11 6 6 9 13 14 21 6 1931 2 21 11 2 7 2 3 -1 -7 10 1 -4 1932 -8 11 4 9 4 2 6 9 -4 -3 4 -8 1933 6 -10 -6 2 4 2 0 6 0 -7 -6 -8 1934 -4 11 -3 -5 7 -4 -4 9 3 3 -2 3 1935 -8 11 -13 2 14 6 0 9 -11 -7 4 9 1936 6 4 1 -2 -6 2 -4 -4 -4 3 8 -4 1937 -11 14 -13 -2 11 -1 6 -1 6 3 -6 -8 1938 -11 -6 7 -2 -10 -8 -10 -11 0 3 -9 -4 1939 -15 -6 -10 -2 4 2 0 -11 13 10 4 19 1940 -4 0 14 15 14 16 13 16 23 34 8 26 1941 16 33 13 13 4 14 25 19 8 14 5 16 1942 23 -1 12 10 -10 -5 3 -5 -8 -10 -4 -5 1943 1 -15 0 -5 0 8 -3 -6 -8 -8 -3 5 1944 10 3 2 9 8 8 11 9 5 8 3 -9 1945 3 0 -16 10 5 -5 5 -4 0 6 6 0 1946 1 -9 12 11 8 9 9 8 8 13 5 1 1947 13 -1 -4 3 16 3 3 -10 -4 1 -5 -5 1948 11 1 2 -3 0 4 -6 -4 3 -1 -11 5 1949 11 -8 -12 8 3 12 1 8 -1 -7 3 -20 1950 -15 -21 -9 -16 -9 -16 -8 -6 -2 -10 -22 -28 1951 -9 -13 -4 1 11 -11 4 6 6 9 8 17 1952 5 7 9 10 -5 2 1 0 2 -6 -10 12 1953 7 9 6 -4 23 2 10 4 13 3 7 9 1954 -13 9 3 -16 -7 0 -5 -8 0 2 4 -7 1955 21 -27 -7 -4 -14 -14 -12 -12 -10 -12 -11 4 1956 -14 -17 -5 -10 -17 -10 -17 -11 -5 -8 0 -16 1957 3 0 4 2 15 2 0 7 12 10 11 5 1958 23 7 7 -4 1 -7 -5 -10 -4 -9 4 11 1959 -1 23 -5 -4 -4 5 6 5 0 0 -10 -11 1960 3 3 -3 -8 -8 2 -4 -1 -14 2 0 0 1961 11 0 21 -1 4 6 2 5 2 -1 6 -3 1962 -11 10 10 4 -6 -6 -6 9 -7 -7 -4 2 1963 -2 16 -7 -6 -4 11 7 -2 9 18 18 19 1964 11 7 -3 -1 -3 -3 -8 -4 -14 -10 -8 5 1965 2 -6 -5 21 3 18 27 11 15 20 17 -5 1966 13 5 13 7 15 10 1 1 2 8 3 5 1967 -11 -7 -1 14 3 2 -1 2 10 4 2 7 1968 -21 -13 9 5 -12 0 -2 2 4 6 12 2 1969 -4 1 10 17 3 4 7 9 0 10 5 -2 1970 21 8 -2 8 -1 -4 10 -6 -17 -17 -13 -18 1971 -4 -19 -14 -13 -4 7 -4 -9 -11 -10 -4 -14 1972 -4 -13 -7 13 16 5 9 12 18 21 11 24 1973 11 19 0 -3 0 -13 -5 -11 -5 -9 -29 -6 1974 -22 -20 -19 -5 2 1 -2 -5 -9 -8 -9 -7 1975 3 5 -8 -15 -4 -9 -11 -13 -14 -16 -5 -16 1976 -11 -10 -18 6 12 2 13 15 11 -5 -10 -7 1977 -4 -8 7 -1 5 12 7 10 11 18 13 9 1978 20 25 21 8 -15 -12 -16 -7 -3 2 8 2 1979 -2 5 5 4 4 3 17 7 -2 5 4 13 1980 -3 -1 -2 4 5 2 3 8 8 2 4 1 1981 -11 -2 25 6 -3 -8 -11 -2 -4 6 -3 3 1982 3 6 1 8 11 16 16 21 24 20 24 21 1983 36 39 27 8 9 10 15 15 2 0 10 13 1984 9 -11 7 8 3 9 3 -4 -2 8 6 -21 1985 15 -10 -13 -18 -14 3 7 -2 -4 2 -3 4 1986 -15 5 10 0 8 -13 -1 -6 3 4 6 25 1987 9 10 33 22 18 8 19 17 16 7 2 6 1988 16 3 -6 8 0 16 -1 -1 -13 -14 -13 -6 1989 -8 4 -1 -17 -7 5 -8 7 -2 -6 0 16 1990 7 36 9 4 -5 1 -1 9 14 9 4 5 1991 1 1 21 6 18 10 5 14 14 6 14 13 1992 39 13 31 17 3 2 18 2 -7 7 8 1 1993 6 0 27 21 16 16 6 25 15 15 3 -2 1994 5 1 20 15 12 6 12 23 16 14 11 21 1995 8 14 -2 3 8 7 -2 6 1 -3 1 3 1996 -5 -2 0 -2 14 1 -4 0 -16 -6 -3 -16 1997 11 -16 12 26 11 24 14 25 28 27 27 14 1998 16 38 26 17 7 -1 -4 2 -2 -8 -13 -13 1999 -13 -2 -10 -6 13 7 3 13 5 -2 -7 -6 2000 5 1 0 -7 9 12 2 -4 1 -13 -22 -24 2001 10 -999 -999 -999 -999 -999 -999 -999 -999 -999 -999 -999