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Introduction and analyses | Digital values
The index is the average SST anomaly equatorward of 20-degrees latitude (north and south) minus the average SST poleward of 20-degrees, and it captures the low-frequency part of the El Niño / Southern Oscillation phenomenon. Anomalies are with respect to the period 1950-79. The number of observations contributing is at least 1000 in each month and year beginning in 1850s.
The input data is the International Comprehensive Ocean-Atmosphere DataSet (ICOADS), version 2.0, for 1800-2005 and the National Centers for Environmental Prediction real-time marine data for 2006 to present.
The choice to calculate the index as the difference of two time series removes a spurious step-jump in SST observations at the onset of World War II that is associated with changes in measurement practices. (This jump is discussed in this link.) The difference also removes the common portion of the trend in SST.
Data:
Digital values:
The anomalies are in hundredths of a degree Celcius, with missing values left blank.
jan feb mar apr may jun jul aug sep oct nov dec
1817 -74 -100 -83
1818
1819
1820 -122 -30
1821
1822 -25 -22 -57 188 31 -154 199
1823 -106 155 25 -51 -86 -132
1824 207 -67 30
1825 89
1826 -269 -78 1
1827 -525 -230 -32 84 -79 15 -20
1828 -76 55 -74 134 -55 -76 -14 109 13 76
1829 7 -39 -26 16 -67 -245 -196 -108 -185 -137 -44
1830 -189 -162 4 57 -123 41
1831 -8 77 57 38 -140 110 -12 -8
1832 13 -67 -22 -87 -4
1833 -24 13 -51 -87 -11 -214 0
1834 -25 -17 -69 2 -96 171 -39 74
1835 -349 -360 -46 89 36 202 -53 2
1836 -106 -131 -17 7 -80 -21 -21
1837 237 175 125 -68 -51 -104 -31
1838 149 50 -144 -23 61 -55 116
1839 -59
1840 2 -81 -118 -133
1841 -25 -161 -68 -11 217 22 -4 63 371
1842 9 -148
1843 -14 -100
1844 -34 26 -193 -259
1845 13 -45 -188 23 -78 -6 -102 -29 8 20 35 18
1846 -196 78 12 -135 -7 -18 9 -118 -17 87 77
1847 32 -86 38 -114 -166 -158 -77 -120 13 89 17
1848 -67 -66 -135 -37 -116 -80 -31 -4 -12 27 -37 -2
1849 -8 -5 2 -17 -14 0 -9 -44 1 27 7 -6
1850 15 13 -15 -18 29 31 31 20 37 -1 25 19
1851 0 -13 -18 -20 -34 11 32 25 29 -7 -6 22
1852 -2 6 -17 1 3 24 34 31 3 24 31 -6
1853 21 17 16 -15 -19 -24 33 0 23 33 43 15
1854 1 8 20 11 28 26 4 -1 11 47 34 28
1855 -6 -2 4 13 17 -13 6 6 19 10 15 -2
1856 -17 19 -2 -20 17 19 10 14 60 45 13 31
1857 -2 -20 -58 -30 -15 -16 31 11 16 28 -16 -3
1858 -10 -11 -7 -27 -15 22 3 22 41 41 37 -6
1859 17 -8 3 -12 53 42 39 48 3 -4 8 7
1860 -47 -18 -24 12 -20 9 6 28 32 20 -29 -23
1861 -28 -41 9 -25 -25 -14 31 15 13 28 17 6
1862 -10 -7 0 11 49 9 46 82 41 58 -10 -10
1863 -37 -1 -26 -30 13 20 -1 23 54 45 1 -18
1864 -38 -69 -27 -29 -9 -5 27 0 35 -1 26 -17
1865 -15 13 9 44 38 33 19 50 60 15 46 15
1866 19 4 37 54 12 28 18 59 33 10 25 -46
1867 -14 26 21 1 56 32 31 78 29 34 22 32
1868 15 30 25 10 42 21 7 20 61 34 46 -1
1869 -14 -26 28 20 51 4 25 55 35 27 15 24
1870 0 30 0 -8 0 5 -1 4 30 25 -62 -3
1871 -28 -3 10 8 28 -8 39 36 26 48 2 19
1872 -19 9 -32 -20 -2 23 11 37 10 6 -13 -20
1873 -21 -19 -3 22 20 -7 -22 27 51 19 2 1
1874 -10 -20 -5 -39 8 -2 3 -15 15 -19 -26 3
1875 -1 17 -14 -37 -25 -11 20 -36 4 27 44 42
1876 28 15 40 23 13 11 7 -5 -22 6 21 9
1877 0 -28 -24 18 16 21 46 38 61 59 14 44
1878 88 71 37 51 61 63 51 33 13 30 34 8
1879 -15 13 -6 -5 1 3 5 4 -3 -15 8 -11
1880 -8 12 3 -14 -5 -2 -31 -8 -7 0 3 15
1881 -4 7 23 24 39 7 40 29 31 29 29 18
1882 0 -2 4 24 -1 -45 -24 1 8 1 -3 -15
1883 2 -28 -18 -26 9 -3 -10 -4 19 10 -23 -6
1884 -35 -11 -26 -9 9 18 13 8 21 23 9 21
1885 27 5 -5 1 11 -9 1 -1 37 33 2 17
1886 6 8 30 2 9 1 -12 9 21 -15 -1 -22
1887 -23 0 -18 -32 -15 -31 -21 -23 7 10 24 17
1888 11 10 49 30 18 2 34 29 36 53 43 46
1889 48 37 37 43 30 16 28 23 26 10 -14 -7
1890 -19 -28 -12 -18 -16 -37 -17 -35 -38 -28 -37 -27
1891 -19 -4 0 10 -1 14 -2 -2 1 9 12 6
1892 -6 -2 -4 -29 -16 -31 -15 -38 -25 -20 -48 4
1893 -18 -44 -44 -28 -33 -30 -11 -10 -15 -11 -10 -22
1894 -37 -30 -30 -33 -27 -18 -22 -25 -11 -2 -11 -7
1895 1 7 13 1 2 -14 -6 19 30 39 31 36
1896 26 13 21 19 4 5 6 17 27 46 62 52
1897 53 35 30 40 31 19 41 39 43 50 32 6
1898 -3 -22 -21 -20 -14 -22 -31 -41 -4 7 17 0
1899 -20 -29 -27 -23 -3 -19 -17 12 5 14 23 47
1900 25 29 23 30 20 20 26 14 4 28 23 45
1901 21 8 35 27 0 -2 -10 22 8 15 37 17
1902 -9 -1 -15 14 12 11 42 33 17 24 29 31
1903 26 12 -2 9 10 25 19 31 15 23 -11 -22
1904 -35 -41 -30 -43 -22 -27 -11 -5 13 4 10 19
1905 6 19 -3 -10 19 -2 -18 8 9 32 32 16
1906 13 32 19 -2 9 -1 -5 2 5 -4 11 5
1907 -15 -2 -19 -11 -14 -8 -6 -5 -2 19 24 16
1908 15 -1 -26 -18 -17 -36 -28 -16 -2 7 -8 -5
1909 -5 -3 4 -9 3 -15 1 0 6 -3 2 3
1910 7 5 -4 -9 11 13 22 5 14 4 3 4
1911 -5 -10 -13 -25 -14 -18 -16 -18 -18 8 8 8
1912 24 15 0 21 0 20 15 23 43 30 21 7
1913 5 11 -2 -15 -2 15 17 15 16 17 31 44
1914 28 16 1 7 -2 -6 -1 10 19 13 36 32
1915 30 34 39 17 28 16 23 14 18 5 8 20
1916 30 0 7 -9 7 -15 -2 -6 -19 -19 -17 -31
1917 -16 -4 -26 -24 -14 -6 1 -1 -14 -21 -4 -5
1918 2 -26 -22 -43 -21 -22 -18 8 3 29 62 60
1919 52 63 31 30 13 -5 -3 15 8 9 4 16
1920 3 2 6 -28 -28 -20 -19 -19 -8 2 8 15
1921 17 -6 -30 -19 -18 -26 -16 -1 5 -13 2 26
1922 11 7 -2 -14 2 -10 -13 -10 -7 -2 8 6
1923 3 -14 -26 -17 -10 -4 -1 -4 11 16 27 28
1924 27 38 29 24 11 -10 4 -7 9 4 0 -8
1925 -22 -36 -23 -11 -7 -12 15 18 10 13 34 31
1926 32 41 34 39 28 31 42 25 32 19 22 22
1927 5 25 8 1 -8 4 1 -1 25 20 32 49
1928 34 28 12 2 4 1 -11 -9 -4 -3 3 17
1929 11 12 13 6 -14 -9 -7 0 6 14 8 15
1930 3 8 5 -1 -23 -18 -24 6 5 31 37 33
1931 45 40 52 41 45 26 37 14 22 21 10 14
1932 -2 -9 8 11 7 5 -15 2 -8 -1 4 0
1933 8 17 17 -7 2 -15 -9 -23 -12 -17 -8 3
1934 -7 -5 -23 -17 -28 -33 -17 5 0 8 2 5
1935 7 3 0 -15 4 -7 -14 7 2 3 16 24
1936 23 24 26 20 10 -15 -11 8 8 14 13 21
1937 10 15 24 14 9 7 -10 -8 -3 3 19 30
1938 15 24 5 -19 -20 -42 -30 -24 -19 -13 -16 -8
1939 -6 -19 -26 -11 -7 -7 -10 -11 -19 -36 -17 26
1940 41 43 40 27 35 18 9 24 35 30 35 34
1941 54 51 61 45 38 51 39 64 29 40 30 30
1942 44 30 8 14 4 -2 -24 -17 -12 -24 -25 -14
1943 -19 -30 -34 -42 -13 -22 -29 -6 1 -12 -17 -24
1944 -36 -18 -13 6 -9 -2 14 4 17 -5 -6 -3
1945 14 12 -28 -15 -9 11 -2 11 0 -21 -14 -15
1946 4 27 14 -1 -20 -7 -19 -4 -19 -15 -13 22
1947 16 21 30 -5 -1 11 -3 -5 -2 0 -6 7
1948 2 28 11 12 -6 -4 -5 -8 -15 -12 -13 3
1949 -38 -14 -18 -19 -21 -10 -3 -4 -20 -21 -36 -30
1950 -21 -35 -26 -30 -39 -40 -42 -41 -38 -32 -37 -44
1951 -36 -35 -33 -24 -11 -20 -1 -7 13 23 25 13
1952 -1 -3 2 4 -1 -17 -26 -31 -12 -22 -26 0
1953 8 3 6 1 -3 11 7 8 0 -6 5 4
1954 -7 -2 -8 -13 -17 -14 -24 -6 -26 -24 -34 -35
1955 -15 -35 -33 -42 -47 -44 -29 -23 -15 -29 -36 -34
1956 -28 -30 -24 -28 -33 -26 -34 -18 -24 -33 -22 -10
1957 -18 -9 4 7 23 24 12 13 10 16 18 24
1958 28 45 27 27 17 7 12 6 3 -4 -2 -1
1959 14 13 11 14 10 4 -9 -9 -9 1 3 2
1960 4 0 15 9 14 -2 -5 -6 -1 -5 -5 13
1961 9 12 -2 -4 -16 -12 -29 -28 -29 -28 -16 -13
1962 -15 -20 -10 -12 -10 -2 -4 2 -16 -11 -1 -13
1963 7 12 16 21 12 14 23 25 27 25 32 32
1964 46 34 24 13 -3 -7 10 2 0 -7 -9 -16
1965 -20 2 7 19 25 16 15 26 31 34 36 40
1966 33 36 32 21 18 21 30 17 16 14 12 9
1967 3 -7 -11 3 3 -3 -19 -33 -27 -28 -30 -6
1968 -14 -6 -8 -11 -13 12 17 18 17 28 24 25
1969 33 39 44 52 52 41 33 21 29 44 38 41
1970 41 31 35 18 22 8 14 -1 -1 -11 -15 -23
1971 -21 -25 -23 -13 -10 -19 -21 -10 3 -12 -23 -28
1972 -8 10 -9 4 7 22 23 41 43 60 55 49
1973 44 30 21 16 12 10 16 11 11 -3 -11 -18
1974 -49 -39 -31 -26 -9 -4 7 4 -8 -19 -16 -22
1975 -25 -19 -26 -21 -25 -28 -12 -16 -29 -29 -37 -42
1976 -45 -29 -30 -23 -7 6 7 16 25 33 38 12
1977 19 9 1 -4 9 17 8 8 9 13 22 21
1978 26 14 14 2 0 5 9 5 -12 1 -3 0
1979 8 5 15 18 18 19 11 5 9 11 15 19
1980 15 12 13 17 28 20 16 21 25 27 25 15
1981 4 -3 2 -3 7 1 14 12 21 41 29 20
1982 14 14 10 18 23 31 26 34 44 47 48 54
1983 44 55 54 45 43 58 50 45 32 19 6 18
1984 14 12 27 15 8 -3 12 9 25 14 6 -6
1985 -8 0 -9 -9 -12 -12 9 16 7 1 13 10
1986 -2 11 0 5 9 16 31 22 22 26 36 24
1987 22 18 36 30 58 60 51 53 53 68 67 49
1988 42 34 37 30 22 7 10 18 22 4 4 -6
1989 -17 -15 -22 -26 -20 -20 2 -5 3 12 4 10
1990 -2 17 3 5 6 6 5 9 7 15 9 10
1991 15 5 5 -2 16 24 25 25 22 20 20 29
1992 17 18 9 22 34 23 32 28 28 27 13 1
1993 -4 1 3 14 26 30 32 24 30 26 36 34
1994 27 19 16 13 14 14 -1 0 4 20 13 17
1995 17 26 19 22 24 32 28 21 22 5 12 16
1996 6 6 11 4 2 16 29 17 23 22 12 -1
1997 -7 -19 -13 0 16 22 36 37 44 57 72 76
1998 63 71 57 33 30 21 9 11 12 0 -10 -15
1999 -24 -25 -25 -25 -25 -30 -2 -12 -11 -16 -19 -22
2000 -22 -17 -27 -27 -23 -35 -23 -2 1 -5 -1 -17
2001 -10 -22 -5 1 7 -9 -7 -4 -5 -5 -12 -9
2002 5 -4 7 12 12 15 15 6 17 20 30 49
2003 37 34 25 19 3 -1 10 18 12 26 23 20
2004 21 14 9 5 -13 -20 -21 -10 16 16 22 30
2005 27 19 26 12 20 0 -9 -3 -2 -4 -11 -8
2006 -8 -3 -1 -4 4 7 -1 7 17 17 26 35
2007 26 20 9 10 1 14 13