Changes in the Rate of Sea Level Rise

Changes in the Rate of Sea Level Rise

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Guest Post by Willis Eschenbach

There’s been some discussion of the rate of sea level rise lately, so I thought I’d take a look at some underlying data.

I started with a 2016 paper by the modern master of failed serial doomcasting, James Hansen. It has the frightening title of Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2°C global warming could be dangerous… yikes! Be very afraid!

In Figure 29 of that paper, Hansen claims to show that sea level rise has been accelerating, from 0.6 mm/year from 1900 to 1930, to 1.4 mm/year from 1930 to 1992, and 2.6 mm/year from 1993 to 2015.

hansen global sea level change.png

Now, as is far too common with this charming fellow, James Hansen is playing fast and loose with the facts. First, he’s taken the data of Church and White from 1900 to 1992 and multiplied it by 0.78. This has the effect of flattening the record and thus reducing the prior sea level trends … which of course makes it seem like there is more acceleration than might actually exist.

Next, he has cherry-picked the Church and White (C&W) data shown in blue. The C&W data actually goes from 1860 to 2009, and Hansen and his merry band have chopped off both the early and the late part of the data.

Finally, post-1991 he has spliced the satellite data (with a trend which differs from Hansen’s specially flattened tide gauge data) on to the end of the tide gauge data. They are measuring different things, and thus cannot be directly compared. This is the reason for the “knuckle” in Hansen’s Figure 29 at the year 1993.

In any case, as those who know me are aware, I prefer to go to the original data. I don’t believe anyone until I’ve run the numbers myself … and this is another example of why I do that. As my beloved grandmother used to say, “You can believe half of what you read, a quarter of what you hear … and an eighth of what you say” … and Hansen’s claims seemed unbelievable.

In this instance I went to the Church & White (2011) paper cited by Hansen above, entitled Sea-Level Rise from the Late 19th to the Early 21st Century.  (I guess C&W didn’t get the memo about how scientific papers now require terrifying titles.) I digitized the C&W Figure 5 and analyzed it. This is their Figure 5:

church and white 2011 fig 5.png

(Notice that because this data has not been subjected to the special Hansen flattening, the trends of the tide gauge and the satellite altimeter data are similar … but I digress.)

In particular, I wanted to look at the trends. Since Hansen had used a 31-year trend from 1900-1930, I looked at the same length trends. Here are all of the trailing 31-year trends, indexed by the final year of each trend, including of course the 1900-1930 trend referenced by Hansen et al.

thirty one year trends in sea level.png

I’m sure you can see the problem with making any general statements about whether or not there is any acceleration in the rate of sea level rise during the last hundred years or so …

You can also see why Hansen cherry-picked the 1900-1930 trend as his data to try to show acceleration … because if he’d used 1930-1960 instead, there wouldn’t be any acceleration to show.

Here’s my conclusion in all of this. Until we can say why the rate of sea level rise:

• decelerated from the start of the C&W record until 1930

• accelerated rapidly until 1960

• decelerated for the next ten years

• stayed about the same from 1970 to 2000

• and then started accelerating again,

… until that time, I say that making just about any statement about sea level acceleration is premature. However, one thing is clear:

There is no simple relationship between CO2 levels and the rate of sea level rise …


My best to all on a lovely spring day. Fog in the morning, sun in the afternoon, and now a foggy night. When the fog rolls in like this in the evening, on nights like tonight it sometimes traps the sound of the foghorn on the Bodega Bay breakwater six miles (ten km.) away, and carries that mournful wail up the hill to draw my mind away, away to the eternal sea …

w.

As Always: When you comment, please quote the exact words you are discussing so that we can all understand your exact subject. Misunderstandings are the bane of the intarwebs—please avoid them by being crystal clear about the topic of your comment.

Data: The digitized C&W data is below:

        Year Sea Level (mm)
1860 -189.26
1861 -188
1862 -181.91
1863 -190.25
1864 -183.17
1865 -195.65
1866 -173.16
1867 -165.84
1868 -165.97
1869 -178.11
1870 -185.01
1871 -188.48
1872 -176.14
1873 -183.09
1874 -186.54
1875 -194.25
1876 -173.47
1877 -157.7
1878 -142.53
1879 -160.14
1880 -156.5
1881 -151.98
1882 -167.18
1883 -163.06
1884 -142.54
1885 -143.86
1886 -145.98
1887 -150.93
1888 -149.59
1889 -148.08
1890 -146.2
1891 -147.32
1892 -144.44
1893 -140.21
1894 -148.15
1895 -138.29
1896 -144.3
1897 -140.22
1898 -130.42
1899 -123.61
1900 -128.64
1901 -128.78
1902 -124.68
1903 -117.49
1904 -125.51
1905 -131.25
1906 -124.66
1907 -126.68
1908 -128.87
1909 -125.03
1910 -125.02
1911 -116.97
1912 -119.44
1913 -118
1914 -111.49
1915 -103.77
1916 -105.22
1917 -109.45
1918 -111.33
1919 -110.29
1920 -108.7
1921 -106.76
1922 -107.55
1923 -106.2
1924 -113.18
1925 -111.98
1926 -105.11
1927 -105.62
1928 -109.52
1929 -108.45
1930 -105.16
1931 -105.19
1932 -100.24
1933 -95.73
1934 -99.6
1935 -95.54
1936 -97.99
1937 -93.5
1938 -90.97
1939 -85.54
1940 -90.15
1941 -78.75
1942 -78.74
1943 -78.26
1944 -84.11
1945 -82.05
1946 -75.11
1947 -71.97
1948 -66.46
1949 -67.77
1950 -65.8
1951 -56.29
1952 -58.63
1953 -54.39
1954 -56.98
1955 -55.69
1956 -60.77
1957 -47.21
1958 -46.93
1959 -46.46
1960 -44.06
1961 -37.11
1962 -40.57
1963 -42.94
1964 -50.72
1965 -39.43
1966 -44.65
1967 -43.95
1968 -43.36
1969 -36.39
1970 -38.3
1971 -33.01
1972 -24.35
1973 -29.12
1974 -18.55
1975 -19.64
1976 -20.5
1977 -22.17
1978 -16.03
1979 -20.79
1980 -15.65
1981 -3.64
1982 -7.17
1983 -0.27
1984 -0.67
1985 -10.31
1986 -10.55
1987 -9.99
1988 -6.51
1989 -1.08
1990 0.43
1991 2.78
1992 6.46
1993 2.45
1994 4.85
1995 8.76
1996 12.28
1997 22.09
1998 15.39
1999 20.05
2000 21.88
2001 26.62
2002 26.53
2003 34.82
2004 34.47
2005 34.04
2006 35
2007 37.88
2008 44.69
2009 52.43

Superforest,Climate Change

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