sea levels

I posted a comment yesterday which you removed, asking me to provide citations. Fair enough, here they are. The post read as follows and was sparked by a comment from De Ville to which I replied as follows;

“This is from the Michael Mann piece you linked to.

“If climate change is an elaborate hoax, then the ice sheets must be in on it; the sea level must be in on it; and the polar bears are likely in on it, although they are big losers.”

Me; 1) “What exactly do you believe sea level to be doing? Are you aware that (generally) it is lower today than during the MWP or Roman Optimum?”
Citations of Roman period;
1a) Jerry Mitrovica in the video referenced here by Jim Eager has homed in on the single Lambeck study of Roman Fish tanks which covers a period of generally lower waters prior to the rise in levels through the latter part of the Roman optimum. Lambeck also said this;

“Here, we present results for sea-level change in the central Mediterranean basin for the Roman Period using new archaeological evidence. These data provide a precise measure of local sea level of -1.35±0.07 m at 2000 years ago. Part of this change is the result of ongoing glacio-hydro isostatic adjustment of the crust subsequent to the last deglaciation. When corrected for this, using geologically constrained model predictions, the change in eustatic sea level since the Roman Period is -0.13±0.09 m.”

As can be seen isostatic adjustment makes a considerable difference to actual sea levels experienced at the time, so it is worth looking at the many other studies of the region and period which gives some additional data.

Citation 1b) This study (inexplicably misquoted by Science Daily a few months ago) covers numerous studies in the same area.

“The Caesarea results indicate that about 2000 years BP sea levels was at its present elevation, while during the Byzantine period it was at or above its present level by (about 30cm- plus or minus 15cm) During the Crusader period “(around 1300AD)”sea level may have been lower than today by about 40c, plus or minus 15cm.”

Citation 1c) Dr Sivan who compiled the study gives the proper context;

“Over the past century, we have witnessed the sea level in Israel fluctuating with almost 19 centimetres between the highest and lowest levels. Over the past 50 years Israel’s mean sea level rise is 5.5 centimetres, but there have also been periods when it rose by 10 centimetres over 10 years. That said, even acute ups and downs over short periods do not testify to long-term trends. An observation of the sea levels over hundreds and thousands of years shows that what seems a phenomenon today is as a matter of fact “nothing new under the sun,”

I have a further 20 studies of this period from a variety of authors in my own article ‘Historic variations in sea levels- Part 1 The Holocene to the Romans.’

Citations of Medieval Warm Period;

1d) there are many studies of sea level in this period and much physical evidence such as sea castles stranded as levels dropped following their construction.

A useful graph is shown here covering the period 200AD to 1999 (sea levels have very arguably risen some 15mm since that time-see later citation)

It is part of a more general article on sea levels here;

“Figure 1. Global sea level from 200 A.D. to 2000, as reconstructed from proxy records of sea level by Moberg et al. 2005. The thick black line is reconstructed sea level using tide gauges (Jevrejeva, 2006). The lightest gray shading shows the 5 – 95% uncertainty in the estimates, and the medium gray shading denotes the one standard deviation error estimate. The highest global sea level of the past 110,000 years likely occurred during the Medieval Warm Period of 1100 – 1200 A.D., when warm conditions similar to today’s climate caused the sea level to rise 5 – 8″ (12 – 21 cm) higher than present. Image credit: Grinsted, A., J.C. Moore, and S. Jevrejeva, 2009, “Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD”, Climate Dynamics, DOI 10.1007/s00382-008-0507-2, 06 January 2009

1e) We also have such luminaries as Prof Brian Fagan author of numerous books and Professor of Archaeology at the University of California. After conducting numerous studies he wrote in his book ‘The Little Ice Age’

“Ten thousand years ago the southern North sea was a marshy plain where elk and deer wandered…England was part of the continent until as recently as 6000 BC when rising sea levels caused by post ice age warming filled the North sea. By 3000 BC the ocean was at near modern levels. Sea levels fluctuated continually through late prehistoric and Roman times but rose significantly after 1000 AD. Over the next two centuries the North sea rose as much as 40-50 cms above today’s height in the low countries then slowly retreated again as temperature fell gradually in the north” (arctic)

2) Me; “Are you aware that the worldwide modern sea level record was cobbled together from only 23 tidal stations, only eight of which are older than 100 years.”

Citations: 2a)
Jerry Mitrovica

At around 9 mins 40 he shows the gauges, at around 35 mins he shows the location of the historic gauges I referred to which is exactly as I said. They can be more easily seen here

Citation 2b)
The reconstruction by IPCC using 23 tide gauges from 1900 -only 2 from the SH- and which include only seven that haven’t permanently moved -but ALL of those subject to considerable development around them necessitating temporary removal or cessation-is a poor piece of work. The latest existed only from 1933. A couple predate 1900. Missing information is interpolated. To then stick inaccurate satellite altimetry on top and try to pass it off as a highly accurate measure of the recent past is nonsensical.

The criteria and location of these gauges is shown here

As an aside, Tide gauges (like thermometers) were never intended to be highly accurate and varied enormously until very recent years with no standardisation. Here is one example;
Accurate to a fraction of an inch? I don’t think so, yet our entire sea level record is built on such as these

The controversy about the modern version of the sea level record is referred to by Jerry Mitrovica at around 45.54

Citation 2c)
I would refer you to Chapter 5 of AR4 which mentions this controversy (see 2b) as a brief note

Figure 5.13 on page 410 is the basis of many graphs used by Government and their agencies to promote scary sea level rises which are then eagerly picked up by the more sensationalist media and Al Gore.

There is a ‘missing’ section-reproduced below- of this report which is not generally seen as it is tucked away after many pages of references; It is 5A

It’s all worth reading-satellite inaccuracy is briefly mentioned but to keep on topic the tiny number of tidal gauges is shown as the very last graphs at 5A2
3) Me; “Are you aware that sea level has remained virtually static for the last four years or so and it would have to quadruple its previous rate of increase to reach the 1 metre rise suggested for the end of the century?”

Citation 3a) These are the official records (scroll down a little to see the graph)

It clearly shows sea levels are the same now as they were 4 or 5 years ago

Citation 3b) According to S. J. Holgate, a recognised world authority in geophysical research at the UK-based Proudman Oceanographic Laboratory in Liverpool, in his paper published in 2007, the following results represent the most comprehensive measurements of decadal sea-level change rates during the 20th century.

Between 1904 and 1953 global sea levels rose by 2.03 mm per year, whereas from 1954 to 2003 they rose by only 1.45 mm per year, giving an annual mean rate of 1.74 mm per year over the 100 years to 2003, or seven inches per century. Importantly, there was no increase in the rate of change over the whole century.

So, based on these peer reviewed and generally accepted numbers, 20th century sea levels rose at a 25% slower rate in the second half of the century than the first which, on any reasonable interpretation, contradicts the notion that global temperature increases during the last 50 years contributed to any sea level rise!”

This is graphically illustrated here.
Citation 3c)

Average rate of rise:
1904-1953: 2.03 ± 0.35 mm/year 1954-2003: 1.45 ± 0.34 mm/year

(virtually static since)

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