Sunday, February 11, 2007

Shocking Facts about Sea Level Rise

The World Climate Report discusses the most recent journal article written about world wide sea levels.

Holgate's study utilises the 9 most accurate stations in the world which include New York (1856–2003), Key West (1913–2003), San Diego (1906–2003), Balboa (1908–1996), Honolulu (1905–2003), Cascais (1882–1993), Newlyn (1915–2004), Trieste (1905–2004), and Auckland (1903–2000) stating that

“Hence the tide gauge data presented here is of the very highest quality available. All these records are almost continuous and are far away from regions with high rates of vertical land movement due to GIA or tectonics.”

To start off with Holgate notes that

“All the stations in this study show a significant increase in sea level over the period 1904–2003 with an average increase of 174 mm during that time. This mean rate of 1.74 mm/yr is at the upper end of the range of estimates for the 20th century in the Intergovernmental Panel on Climate Change, Third Assessment Report.”

but as shown below in the graph,

Holgate states that

“the two highest decadal rates of change were recorded in the decades centred on 1980 (5.31 mm/yr) and 1939 (4.68 mm/yr) with the most negative decadal rates of change over the past 100 years during the decades centred on 1964 (-1.49 mm/yr) and 1987 (-1.33 mm/yr).”


“Despite the high decadal rates of change in the latter part of the 20th century, it is found that the first half of the record (1904–1953) has a higher rate of rise overall (2.03 ± 0.35 mm/yr) than the 1954–2003 period which had a rate of 1.45 ± 0.34 mm/yr.”

with the conclusion of

"a general deceleration in sea level rise during the
20th century."

The IPCC had this to say about seas level rises:

Global average sea level rose at an average rate of 1.8 [1.3 to 2.3] mm per year over 1961 to 2003. The rate was faster over 1993 to 2003, about 3.1 [2.4 to 3.8] mm per year. Whether the faster rate for 1993 to 2003 reflects decadal variability or an increase in the longer-term trend is unclear.

Although the IPCC would have us believe that sea level rise has been accelerating recently, they are not emphatic about it, and leave open the possibility that decadal variations may be responsible for the perceived rate increase. As shown by Holgate’s new research results that possibility looks like the leading contender.

From this article, we learn from the actual data that (a) sea level is generally rising, (b) the rate of rise decelerated during the 20th century, (c) the rate of sea level rise over the past two decades has been both positive and negative, (d) the rate of sea level rise has been quite small over the last few years, and (e) stations can witness an increase or decrease of sea level quite independently of one another.

At the very least, Holgate shows that the global warming – sea level linkage is far more complicated than typically presented to the public. Or the results show that what the public has been told about sea level rise is simply wrong.

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