Head for the hills folks! Sea levels are rising. But first read Ed Caryl’s latest essay on sea levels. It sure helps ignoring the climate catastrophe cultists for a few minutes and taking a sane look at the data.
A Level Look At Sea Level
By Ed Caryl
One of the tenets of the AGW crowd is the idea that sea level rise is going to be catastrophic in the next 100 or 200 years, drowning our coasts and harbors, and in the case of low-lying countries, like The Netherlands, whole countries. These are not the facts.
Figure 1 shows the sea level rise over the last 20,000 years. In the last 8 thousand, the curve looks flat. It looks like there has been no rise since civilization began, and that the recent rise of about 20 cm (Figure 2) since 1900 is “unprecedented.” That is not true. The sea level has risen and fallen several times in the last few thousand years.
In Figure 3, one can see that the sea level did not abruptly level off after the rather swift rise as the major continental glaciers melted, but slowly continued to rise, with one episode of falling between 3 and 4 thousand years ago.
A closer look at the last 2000 years is wanted. An article describing the sea level at Barrow Alaska was found. Here is the abstract in full:
Eustatic rises of sea level between A. D. 265 and 500 and between A. D. 1000 and 1100 caused the formation of raised beaches. After the first rise, sea level dropped about 2 meters below the present level, permitting Eskimo settlement of Birnirk about A. D. 500. The second rise of the ocean flooded Birnirk. At present, sea level is about 0.6 to 1.0 meter below the high water levels; the ocean partially floods Birnirk.”
The rises and falls at Barrow mirror the Roman Warm Period, the Dark Age Cool Period, the Medieval Warm Period, and the last fall in sea level in the Little Ice Age, with a slow rise since then. (See From Hockey Sticks to Boomerangs for the temperatures during this period.) But we are still below the high water levels seen at Barrow. These events are somewhat visible in the data points of figure 3, but the author of that chart has chosen to use a straight line to depict the sea level for the last two thousand years, not showing the natural variation.
The peak of the water levels in the fens was in the Iron Age; earlier Bronze and Neolithic settlements were covered by peat deposits, and have only been found recently. During the Roman period, waters levels fell once again, and settlements were possible on the new silt soils deposited near the coast. Though water levels rose once again in the early medieval period, by this time artificial banks protected the coastal settlements and the inland from further deposits of marine silts, though peats continued to develop in the freshwater wetlands of the interior fens.”
Then there are the Roman fish pens. Described at this site, but the story is all over the internet as proof of AGW caused sea level rise. It proves no such thing.
‘The Romans dug these fish pens into bedrock, and the water line in these well-preserved structures shows that the sea level along the Italian coast 2000 years ago was 1.35 metres below today’s levels. “They were used for only a very short time, so they make rather nice markers,’ says Lambeck.”
He then analysed how land elevations changed along the Italian coast due to both plate tectonics and the after-effects of the last ice age. In a paper to appear in Earth and Planetary Science Letters, he concludes that geological processes affecting land levels over the past two millennia accounted for 1.22 metres of the change, which means that the global sea level rose by 13 centimetres.”
The only problem with this story is that the sea level changed several times in the intervening years, both up and down. The fish pens are just one marker in time. They were used only for a short time because after that they were either above sea level and dry, or below sea level and unusable. Is there a chart of sea level over the last 2000 years? There is this one at CISRO, but the error bars are very long and it shows nothing useful. We only begin to get good data from tide gauges in the last 300 years.
A problem with measuring sea level is that isostatic rebound, post-glacial rebound, or glacial isostatic adjustment (GIA), is still happening. It affects tide gauge readings all over Europe, especially in Scandinavia. One way to correct for this is to use GPS readings to find the actual earth movement and subtract that from the tide gauge measurements. When this is done, the real sea level rise in recent years begins to dwindle. This quote is from the abstract of Geocentric sea-level trend estimates from GPS analyses at relevant tide gauges world-wide.
Sea level change in the era of the recording tide gauge. Int. Geophys.Ser., 75, pp. 37–64.] rules, whose estimate is 1.84±0.35 mm/yr after correction for the GIA effect [Peltier, W.R., 2001. Global glacial isostatic adjustment and modern instrumental records of relative sea level history. Int. Geophys. Ser., 75, pp. 65–95.]. We obtain a value of 1.31±0.30 mm/yr, a value which appears to resolve the ‘sea level enigma’ [Munk,W., 2002. Twentieth century sea level: an enigma. Proc. Natl. Acad. Sci. U.S.A., 99(10), pp. 6550–6555]. © 2007 Elsevier B.V. All rights reserved.
S. Jevrejeva et al (Figure 4) did another sea level reconstruction using several European tide gauges and correcting for GIA in 2008. This shows a steady rise of about 300±100 mm since 1800. This is about 1.5±0.5 mm/year. This is a steady rise since the end of the Little Ice Age, with no unusual rise after the increase in CO2. This natural rise began long before mankind began burning fossil fuel in earnest.
Is sea level rising? Yes, as it has been since the end of the little ice age 200 years ago. It will continue to rise. The remnant glaciers will continue to melt until the next cool cycle. But there is no catastrophe. At 1.31±0.30 mm/year, or 1.5±0.5 mm/year, if the trend is linear, it will be up 10 to 20 cm by 2110. The Dutch will need to put more blacktop in their dike roadways, which they normally do anyway, several times in the next 100 years. But if the current solar minimum continues for a few years we won’t need to worry about it. We will be in a cool cycle.
Anticipating questions, these are provided:
What about Bangladesh? The river silt has kept up with sea level rise so far, and will in the future, in fact, 250 years ago, much of Bangladesh was flooded all the time. To learn more look: here, here, here, and here.
What about the Pacific Islands, the Maldives, etc? Coral grows much faster than 2 mm/year, and has kept up with sea level rise so far, and it will in the future. Many of those islands are only there because of coral growth.
What about our harbors? Infrastructure is continuously wearing out, being torn down, and rebuilt. The docks of 1700 are no longer there. They have been replaced, 300 mm higher.