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The time series is unfiltered in this plot.
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 2.5 for 1800-2007 and the "National Centers for Environmental Prediction near-real-time" (also an ICOADS product) for 2008 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, for example "-73"
is -0.73. Missing values are blank.
jan feb mar apr may jun jul aug sep oct nov dec
1817 -73 -101 -83
1818
1819
1820 -122 -31
1821
1822 -25 -23 -58 188 31 -153 199
1823 -106 155 25 -51 -86 -132
1824 208 -67 30
1825 90
1826 -269 -78 29
1827 -119 -167 -69 84 -76 15 146 -8 -120 99
1828 -75 55 -72 175 -55 -77 -17 107 13 75
1829 8 -39 -26 16 -67 -246 -196 -108 -185 -137 -44
1830 -189 -162 4 57 -123 41
1831 -8 77 57 38 -140 110 -12 -9
1832 13 -67 -22 -87 -4
1833 -24 13 -52 -88 -11 -214 0
1834 -25 -16 -68 2 -96 171 -39 73
1835 -348 -360 -46 89 36 202 -53 2
1836 -106 -131 -16 7 -79 -21 -40
1837 164 58 124 -75 -52 -86 -31
1838 149 70 -144 -23 61 -56 116 93
1839 -60
1840 2 -81 -119 -134
1841 -22 -161 -68 -13 218 22 -4 63 339
1842 10 -148
1843 -15 -101
1844 -34 25 -193 -259
1845 14 -45 -187 23 -78 -6 -103 -29 8 20 35 17
1846 -195 78 12 -134 -6 -18 9 -118 -18 87 76
1847 33 -86 38 -93 -111 -144 -77 -120 13 89 17
1848 -67 -66 -135 -37 -116 -81 -31 -5 -12 27 -37 -3
1849 -8 -5 2 -17 -14 0 -9 -44 1 26 7 -6
1850 15 14 -15 -18 29 31 31 20 37 -2 25 18
1851 0 -13 -17 -20 -34 10 32 25 29 -7 -5 22
1852 -2 6 -17 1 3 24 33 31 3 24 31 -6
1853 21 17 16 -14 -19 -25 33 0 23 33 40 14
1854 1 9 20 11 28 26 4 -1 11 47 34 28
1855 -6 -2 4 13 18 -13 6 6 19 9 15 -2
1856 -17 19 -2 -19 17 19 9 14 60 44 13 30
1857 -2 -19 -58 -29 -14 -16 31 11 16 28 -16 -3
1858 -9 -11 -6 -27 -15 21 3 22 41 41 37 -7
1859 17 -8 3 -12 53 42 39 48 3 -4 8 6
1860 -46 -17 -24 12 -20 8 6 28 32 20 -29 -24
1861 -28 -40 9 -25 -24 -15 31 15 13 28 17 6
1862 -10 -7 0 11 49 8 46 82 41 58 -10 -10
1863 -37 -1 -25 -30 13 20 -1 23 54 44 1 -18
1864 -36 -69 -27 -28 -9 -6 27 -1 35 -1 26 -18
1865 -15 13 10 43 39 33 19 50 60 15 46 15
1866 20 4 38 54 12 26 17 59 33 10 25 -47
1867 -14 27 24 3 57 38 31 78 29 34 23 32
1868 15 30 25 10 42 20 7 19 61 33 47 -1
1869 -14 -26 28 21 52 4 25 54 35 26 15 23
1870 1 30 2 -7 1 5 -3 7 29 25 -62 -3
1871 -28 -3 10 8 29 -3 39 37 29 50 1 18
1872 -18 9 -34 -21 -2 23 8 37 11 6 -14 -20
1873 -20 -16 -4 23 25 -8 -21 26 51 22 3 0
1874 -9 -18 -5 -41 16 2 6 -12 15 -18 -24 3
1875 0 17 -13 -34 -22 -8 19 -36 4 27 43 40
1876 27 15 38 25 17 13 6 -4 -23 7 21 6
1877 -3 -26 -23 14 15 28 43 40 61 56 14 43
1878 85 66 34 53 59 61 54 32 13 34 42 7
1879 -4 11 -17 -8 0 12 -1 17 -4 -20 9 -12
1880 -19 8 4 -13 6 -14 -41 -6 -9 4 4 10
1881 -6 2 24 27 30 9 38 35 41 25 38 17
1882 0 1 -1 20 -2 -37 -27 2 4 1 1 -11
1883 -2 -36 -17 -27 6 -6 -6 -9 0 -8 -28 -26
1884 -38 -17 -33 -23 3 9 5 6 31 8 10 8
1885 9 16 0 6 7 -15 -5 -7 22 54 30 21
1886 13 6 18 19 33 6 8 9 24 0 -2 -19
1887 -7 0 -8 -21 -17 -38 -14 -16 12 13 35 11
1888 18 6 45 30 28 4 39 26 35 42 46 47
1889 56 38 37 40 30 18 31 24 30 6 -14 -12
1890 -15 -27 -13 -23 -19 -42 -18 -31 -37 -28 -39 -24
1891 -15 -4 -1 11 13 7 6 1 -8 16 13 11
1892 -5 -1 6 -19 -18 -25 -16 -36 -28 -28 -46 5
1893 -15 -40 -33 -25 -24 -27 -7 -6 -12 -9 -10 -16
1894 -30 -23 -25 -31 -25 -20 -27 -28 -11 -1 -11 -6
1895 3 12 13 -1 5 -12 -5 20 32 36 34 35
1896 25 15 20 22 8 5 5 18 26 42 60 54
1897 54 37 33 41 34 19 40 38 41 49 28 6
1898 -3 -23 -20 -20 -9 -20 -30 -40 -4 5 17 -2
1899 -19 -30 -27 -23 -2 -19 -18 12 3 16 23 47
1900 22 28 24 30 23 19 24 12 3 29 22 44
1901 21 12 33 25 0 -7 -9 15 5 9 36 24
1902 -6 2 -13 13 14 14 44 36 15 23 27 29
1903 30 21 0 8 15 23 17 32 9 23 -2 -18
1904 -31 -40 -29 -41 -22 -29 -11 -7 12 3 11 23
1905 7 19 -2 -10 21 -1 -17 9 11 30 33 16
1906 15 33 19 -1 11 -3 -9 -1 9 -6 9 5
1907 -9 2 -19 -12 -16 -5 -6 -4 0 10 24 16
1908 16 -1 -26 -18 -15 -36 -31 -14 0 7 -6 -5
1909 -4 2 9 -8 -2 -17 -1 1 8 -3 4 4
1910 7 1 -3 -8 5 12 21 5 11 5 4 4
1911 -4 -4 -11 -24 -16 -20 -10 -15 -17 3 8 6
1912 27 16 1 21 0 19 15 21 42 31 23 11
1913 4 9 -3 -17 -1 14 16 13 15 15 29 40
1914 30 18 5 7 -2 -5 -5 14 20 11 39 32
1915 30 35 39 19 29 15 23 15 19 6 9 19
1916 26 3 7 -9 7 -16 0 -9 -18 -17 -16 -29
1917 -17 -2 -30 -23 -14 -5 -1 -1 -19 -22 -4 -6
1918 -1 -26 -22 -41 -18 -24 -20 6 4 30 64 58
1919 52 67 30 15 17 -7 -5 7 3 2 5 15
1920 14 7 22 -17 -25 -19 -20 -14 -6 -1 4 15
1921 19 -3 -23 -16 -12 -24 -9 -7 4 -8 0 29
1922 12 16 1 -12 4 -11 -17 -4 -5 3 11 6
1923 7 -8 -21 -15 -10 -5 -1 -10 6 22 25 33
1924 28 43 35 26 16 -8 6 -11 4 -4 -1 -5
1925 -14 -25 -17 -13 -4 -12 19 13 14 10 35 41
1926 40 43 36 35 30 31 38 23 29 17 23 24
1927 12 29 13 -2 -9 5 -1 -4 25 22 32 57
1928 38 40 17 7 11 2 -15 -11 -4 -4 9 21
1929 19 17 19 9 -8 -13 -8 -2 5 15 12 21
1930 10 16 9 6 -18 -16 -21 4 11 33 41 36
1931 52 48 60 48 49 29 42 12 24 23 18 17
1932 2 1 20 18 17 9 -12 12 3 -9 8 9
1933 8 17 17 -7 2 -15 -10 -23 -12 -18 -8 2
1934 -7 -5 -23 -17 -27 -33 -17 5 0 7 2 4
1935 7 3 0 -14 4 -7 -14 7 2 3 15 24
1936 23 24 26 20 10 -17 -11 7 8 13 13 20
1937 10 15 24 13 10 6 -10 -8 -3 3 19 31
1938 19 28 8 -17 -20 -39 -27 -23 -19 -11 -13 -7
1939 -4 -17 -23 -7 -6 -7 -7 -9 -12 -36 -7 22
1940 41 44 40 27 36 17 10 24 35 30 35 33
1941 51 53 55 36 32 50 39 59 25 46 33 37
1942 39 31 11 15 9 0 -22 -21 -10 -14 -18 -16
1943 -17 -19 -28 -43 -17 -17 -17 -7 -1 -15 -18 -24
1944 -30 -17 -9 3 -7 -1 27 13 14 -2 -4 6
1945 31 16 -20 -1 -6 14 -6 9 4 -14 -12 6
1946 9 30 26 9 -16 -2 -22 -1 -19 -15 -8 22
1947 19 25 31 -3 1 11 0 -6 -2 0 -5 6
1948 3 30 13 9 -5 -5 -4 -7 -15 -13 -12 3
1949 -37 -14 -18 -18 -20 -10 -3 -3 -19 -21 -36 -30
1950 -20 -34 -25 -29 -38 -39 -41 -41 -38 -33 -37 -44
1951 -36 -35 -32 -23 -10 -19 1 -6 13 23 25 13
1952 -1 -3 2 6 -1 -16 -25 -31 -12 -20 -26 -2
1953 9 3 6 1 -2 11 6 7 1 -6 6 4
1954 -6 -2 -7 -11 -15 -13 -24 -5 -25 -24 -33 -35
1955 -15 -35 -32 -42 -46 -44 -29 -22 -14 -30 -37 -34
1956 -28 -29 -24 -27 -31 -25 -32 -18 -24 -32 -22 -11
1957 -18 -8 3 7 23 24 13 13 11 16 18 24
1958 28 46 29 28 18 8 14 7 3 -4 -2 -1
1959 14 14 13 14 10 4 -9 -8 -8 0 5 2
1960 6 0 15 9 15 -2 -5 -6 -1 -5 -5 13
1961 7 12 -6 -4 -14 -15 -29 -26 -25 -27 -18 -10
1962 -15 -17 -8 -14 -15 -2 -7 3 -14 -11 -2 -7
1963 8 12 16 20 15 17 22 27 23 29 33 37
1964 47 36 25 13 -3 -3 10 1 -1 -8 -11 -19
1965 -20 2 7 19 26 17 15 28 32 33 38 41
1966 33 38 34 23 20 23 31 18 17 15 13 8
1967 3 -8 -12 3 2 -5 -18 -33 -25 -28 -32 -6
1968 -15 -7 -8 -11 -14 10 17 19 17 27 23 24
1969 34 38 44 50 49 39 33 21 29 44 39 39
1970 41 30 36 20 21 7 13 -4 -5 -13 -16 -25
1971 -23 -23 -23 -14 -10 -18 -21 -13 3 -13 -18 -25
1972 -14 5 -11 3 5 17 24 40 41 59 52 49
1973 44 28 19 11 10 9 12 8 9 0 -11 -19
1974 -47 -40 -33 -29 -13 -6 5 6 -8 -19 -14 -22
1975 -23 -20 -24 -17 -25 -22 -12 -18 -31 -29 -36 -43
1976 -43 -31 -31 -21 -7 4 6 16 24 34 37 11
1977 16 7 -1 -4 10 15 9 9 10 14 22 20
1978 25 12 12 1 0 5 7 4 -11 -2 -4 0
1979 9 7 16 19 19 18 12 4 10 12 15 19
1980 16 13 14 19 30 20 17 21 26 28 26 14
1981 4 -2 3 -3 7 1 13 12 21 41 29 20
1982 15 15 10 18 24 31 26 35 44 47 48 54
1983 44 55 55 46 44 56 51 47 33 19 7 17
1984 14 14 28 15 8 -1 13 10 24 15 7 -7
1985 -7 0 -8 -8 -13 -13 7 15 8 1 14 10
1986 0 12 2 6 11 16 31 21 22 26 36 25
1987 22 20 36 30 58 59 51 54 54 69 67 49
1988 42 35 37 31 21 7 10 19 20 4 4 -6
1989 -18 -15 -20 -25 -20 -21 2 -5 3 12 4 11
1990 -1 18 5 5 6 6 5 8 7 14 8 10
1991 17 7 7 -2 17 27 25 26 21 21 22 27
1992 19 19 10 23 34 23 31 27 29 29 13 2
1993 -3 2 6 16 28 29 34 24 31 29 37 33
1994 28 19 16 15 14 14 -3 -1 5 22 14 17
1995 21 28 21 23 26 32 27 19 19 5 14 14
1996 5 8 12 4 2 16 29 17 23 23 15 1
1997 -6 -17 -11 2 18 23 36 40 46 57 73 75
1998 66 70 63 38 34 20 12 9 16 1 -13 -13
1999 -27 -26 -22 -28 -23 -30 -1 -12 -11 -15 -23 -19
2000 -21 -15 -20 -24 -23 -33 -18 -3 2 -3 -1 -20
2001 -9 -20 -6 2 7 -8 -5 -3 -5 -2 -13 -8
2002 1 -3 6 12 12 20 17 8 15 21 33 50
2003 38 36 25 17 5 0 15 20 14 28 27 23
2004 21 15 9 6 -9 -13 -16 -7 20 18 23 33
2005 29 20 27 15 23 -1 -5 0 -1 -3 -10 -3
2006 -2 3 1 -1 11 9 4 7 19 23 31 36
2007 28 21 11 12 8 17 15 9 -1 -11 -19 -8
2008 -12 -17 -20 -16 -16 -19 -11 6 15 12 10 -1
2009 1 -4 2 -2 14 11 18 32 38 33 35 41
2010 40 42 46 43 40 22 3 -9 -12 -6 -7 -4
2011 -18 -10