Historic variations in sea levels. Part 1: From the Holocene to Romans

by Tony Brown

The IPCC AR4 projected sea level rise in 2100 to range from 18-59 cm, depending on  the emission scenario.  More recent projections are for a 1 m sea level rise in 2100 [here and here].  Apart from the issue of uncertainty and reliability of these future sea level projections, how do these magnitudes of sea level rise compare with historic variations in sea level rise?

Historic variations in sea levels is in three parts. Part 1 covers the Holocene to Roman times. Part 2 traces sea level changes to the Medieval Warm Period. Part 3-the modern age from 1700 to today.

This post is an abridged version of a longer document (Part 1), replete with references and additional diagrams and pictures.

The IPCC on historic sea level rise

The IPCC AR4 statement on historic sea level rise from AD0 is cited below:

Yes, there is strong evidence that global sea level gradually rose in the 20th century and is currently rising at an increased rate, after a period of little change between AD 0 and AD 1900. Sea level is projected to rise at an even greater rate in this century.

The two major causes of global sea level rise are thermal expansion of the oceans (water expands as it warms) and the loss of land-based ice due to increased melting…

 Global sea level rose by about 120 m during the several millennia that followed the end of the last ice age (approximately 21,000 years ago), and stabilised between 3,000 and 2,000 years ago. Sea level indicators suggest that global sea level did not change significantly from then until the late 19th century. The instrumental record of modern sea level change shows evidence for onset of sea level rise during the 19th century. Estimates for the 20th century show that global average sea level rose at a rate of about 1.7 mm yr–1.”

The IPCC provides no references for this FAQ on “Is sea level rising?”

The Figure below  from the Wikimedia Commons shows sea level rise since the end of the last glacial episode.  Because of the large magnitude of the change, the scale on the y-axis makes it impossible to resolve the magnitude of changes for the last 8,000 years.  An expansion of this diagram   for the past 9000 years enables examination of the sea level rise on the scale of meters.  The uncertainty of the estimates at individual locations plus the range across different locations at any particular time can be associated with an uncertainty of several meters, which is larger than the magnitude of projected sea level rise that is under consideration.

Challenges in reconstructing and interpreting historical sea levels

Apart from the uncertainties in actually determining sea level change, the physical interpretation of sea level change needs to take into account deposition and erosion, land movement-often through post glacial rebound- and tectonic activity, in addition to climate change.

These historic changes in land level-dramatic or gradual- will have been taken into account in academic studies (although there is not unanimity over the rate of change). However all these factors demonstrate that accurate sea level reconstruction is problematic.

In private email correspondence that he has given me permission to reproduce, Dr Simon Holgate of Proudman Oceanographic Observatory refers to sea level reconstructions back to 200AD-which covers several warm periods such as the Roman Optimum and MWP- and remarks:

“It seems plausible that sea level would be higher in a warmer period (how warm and how much of the Earth was actually affected by the warm period is debated) but it isn’t clear how sea level would respond. So maybe it was higher than today, or maybe it wasn’t. We have no observations and we just don’t know. For me, there is far too much uncertainty in the ‘reconstructions’ of sea level for them to be very useful…Overall  I would say that the evidence from the (Roman) fish tanks etc suggests that there has been no real change in the average height of sea level over the last c. 2000 years prior to the mid to late 1800s.”

It is important to fix in our minds therefore that sea level change is not necessarily as a result of their being less or more water (through glacier melt and thermal expansion) but that much of what we might observe is as a result of changes in the height of the land relative to the sea.

 Doggerland

We commence our watery journey with this short excerpt from the book ‘The Little Ice Age’ by Brian Fagan, Professor of Archaeology at the University of California.

“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.”

Prof. Bryony Coles has been examining the archaeology of “Doggerland”, which now lies under the North Sea. Its highest point is the submerged Dogger Bank where prehistoric artefacts are occasionally found by fishermen and geologists. At the height of the last Ice Age, Doggerland was dry and stretched from the present east coast of Britain and the present coasts of The Netherlands, Denmark and North Germany. Thus, the so-called land-bridge, was a place where people settled as the ice-sheets wasted and north Western Europe became habitable once more. But, as the ice-sheets retreated further and sea levels rose, the North Sea encroached on the land, eventually separating the British Peninsula from the mainland.”

It is a sobering thought that where once our ancestors hunted, fish now take their place, and graphically illustrates that sea level rise is by no means a modern phenomenon in the context of human history.

St. Michaels Mount

Let us now move from Doggerland on the east coast of Britain, through several thousand years to the Roman period on the Western coast of Britain. Where better to examine sea level fluctuations than a place especially susceptible to them -a tidal island known as St Michaels Mount in Cornwall.

From the Wikipedia:

“St Michael’s Mount (Cornish: Karrek Loos y’n Koos) is a tidal island located 366 m (400 yd) off the Mount’s Bay coast of Cornwall, United Kingdom. It is a civil parish and is united with the town of Marazion by a man-made causeway of granite setts, passable between mid-tide and low water. The island exhibits a combination of slate and granite. Its Cornish language name — literally, “the grey rock in the wood” — may represent a folk memory of a time before Mount’s Bay was flooded. Remains of trees have been seen at low tides following storms on the beach at Perranuthnoe, but radiocarbon dating established the submerging of the hazel wood at about 1700 BC.

The ancient Cornish name for the mount certainly suggests it was once dry wooded land.  In his Report on Cornwall’, Sir Henry de la Beche remarked that:

‘Submarine forests are so common that it is difficult not to find traces of them in the district at the mouths of all the numerous valleys which open upon the sea and are in any manner silted up’.

The folk memory of woods and a rock is supported by modern observational evidence which confirms that the woods existed, with radio carbon dating suggesting they were submerged around 1700BC.

Sir Gavin de Beer, F.R.S., a former Director of the Natural History Museum, wrote in his book Reflections of A Darwinian, published in 1962, that scientific methods of analysing the traces of old tree trunks still found in Mount’s Bay had indicated that the forest was submerged by the sea at least 1,500 years before Pytheas came there on his voyage of exploration in about 325 B.C

Modern science does not confirm precise dating, but the legend talks of a Kingdom stretching from Penwith in Cornwall to the Scilly isles. Page 3 of this study from 2006 seems to confirm a series of inundations, suggesting some truth in the older legends, and that the earlier Romans-or their predecessors- may have viewed the Scillies as one land mass rather than the series of islands it has subsequently become:

“From the beginning of the Holocene period, as the ice sheets melted and sea level rose, the submergence of low-lying areas led to the formation of one main island by about 3,000 BC. This included the present islands of St Mary’s, Bryher, St Martin’s, Tresco, Samson and the Eastern Isles, with three smaller tracts of land around St Agnes, Annet and the Western Rocks (Ratcliffe and Johns 2003, 4). Charles Thomas’ model for sea level change in Scilly suggests that at around 1000 BC Mean Sea Level (MSL) was 7.25m lower than today, with the modern 5m marine contour roughly representing the coastline at that time (Thomas 1985, 17–64). The main island may have survived until the end of the Roman period but further rises in sea level, and perhaps a final inundation during the early second millennium AD, resulted in the eventual submergence of the ‘flats’ in the middle of the land mass and formation of the present pattern of islands. Final separation of the islands might not have been complete until the early sixteenth century.”

Interestingly, this last account places the inundation at around the period that Lyonesse was said to be drowned- around 3000BC.

It is said (by the local tourist board) that King Arthur’s castle is located at nearby Tintagel on the North Cornish coast.  So the area-whether or not as part of some legendary Arthurian Kingdom-was undoubtedly inundated by rising sea levels, and here we can find some definitive scientific information about the subsequent rise to prominence of St Michaels Mount, following its transition from an inland place in a forest to a port.

So to summarise, over historic- rather than geological time, St Michaels Mount- which was originally some distance from the sea -became flooded following several periods of dramatic sea level rise. The first during the Doggerland era and then also at some point around 3000 BC or so, of which the folk memory of Lyonesse still lingers, and possibly again 1000 years later. Whether the levels fell in the interim period is outside the scope of this study, but we do know that by 350BC at the latest St Michaels Mount was a thriving port for the export of tin, which during the ebb tide was carried over in wagons i.e. by that time it was a tidal island.

To put in context that sea level fluctuations are often about the characteristics of land rise or fall, we refer again to the earlier study (original article here) from Durham University.  According to this academic study, Cornwall, together with the adjacent counties of Devon and Somerset, is one of those areas of falling land which (apart from any other reasons such as thermal expansion and glacial melting) is thereby causing rising sea levels. The land is falling at 0.5mm/yr which comes to some 1 meter over 2000 years.

In a personal email to the author Simon Holgate of Proudman Observatory amplified this study:

“With respect to Newlyn, (close to St Michaels Mount)  it is probably the highest quality tide gauge record in the world. The land is the region is subsiding by about 1 mm per year due to the effects of the last glaciation. You can see the data for yourself here.  Once we’ve taken the “glacial isostatic adjustment” into account we’re left with about 1.4 mm/yr, which is typical of Europe and slightly less than the global average of 1.8 mm/yr over that time period.”

So taking this into account we should reasonably assume that the sea level we see now is going to be around 1 meter greater than was current in 350BC for reasons of the land sinking and quite apart from any genuine sea level rise. Is that increase verified by the observations we can make?

No. Today St Michaels Mount is still not navigable for large parts of the tidal cycle as was also observed in historic times. There are better places nearby to have acted as a historic tin port, for the Mount is dangerous when the wind is from the wrong direction.

St Michaels Mount remains a tidal island today, although the studies seem to indicate that after 2000 years it should now be surrounded by sea at all stages of the tide due to land movement alone-irrespective of the notion of modern sea level rise. The tide window today for a fairly deep draught ship who had travelled some distance and who would be unwilling to hove to in treacherous waters is still fairly small-a matter of a few hours in each tidal cycle.

If the port was bustling 2000 years ago it is reasonable to suppose that tidal access was less limited then than it is today-or was at least as good. Consequently the evidence suggests that in 350BC there was probably a little more water than exists today in order for it to be a worthwhile place to ship cargo from, and therefore current ocean volume (glacier melt and thermal expansion) is less now than then, to take into account the known land changes. There was speculation that in Phoenician times the island was still connected to the mainland by a spine of land (Bloch et al) but that can not be authenticated by recent archaeological evidence, and as other accounts clearly describe it as a tidal island.

A broader perspective on historic sea level changes in the UK

Thus far we have concentrated on one small part of one small country, albeit the tidal island is an interesting proxy. Britain, as one of the world’s largest islands, is a good place to examine sea level changes, helped by the wealth of visual evidence and written records created through a long period of continual habitation.  At this stage of the study, therefore we will look elsewhere in the UK for evidence of likely sea levels in the Roman period.  Specific examples are provided below

From this article:

 “ In Northumberland, researchers found sediments from 7,000 years ago five metres below, and others from 4,000 years ago at 1 metre above the present sea level. This indicates that the sea level rose above present levels from around 7,500 years ago to 4,500 years ago, and then dropped and is continuing to fall. Sea-levels in most of Scotland peaked even higher about 4,500 years ago and have been falling ever since because the land has risen.”

To put these changes into a human perspective, the remains of a drowned Mesolithic village was found on what is now the sea bed off the Isle of Wight on Britain’s South coast. [link]

“A few Archaeologists originally found Mesolithic flint tools within a 1km stretch of seabed over a decade ago. This was the first time such pieces were found in their original location underwater around the British coast. Ten years on, continued searching has recently resulted in much more startling finds.  Elements of a substantial wooden structure ( found in 2009) built about 8,000 years ago by our Mesolithic ancestors. Some of the recovered timbers have very clear, distinct and sophisticated cut marks, so we know they have been worked on by humans capable of craftsmanship. These could be part of a collapsed structure, or perhaps a platform built close to a waterway.

According to the BBC ‘Britain’s Drowned World’ TV programme carried out by ‘Time Team’, the inundation was caused by a prolonged sea level rise at 2cm per year (around 10 times the current rate) and exacerbated over a 15 year period by a 7 degree Fahrenheit temperature rise.

A discovery of a fort formerly on te shore is discussed here:

Pevensey in Sussex (South Eastern Coast) was one of the ‘forts of the Saxon shore’-built by the Romans in the 3rd century to keep out the Saxon invaders. The castle -still visible-now lies a mile or two inland but was very important at the time of the Romans.

The need for this fort is graphically described here:

“The North Sea had a nasty little jump between 350 and 550AD, flooding the coasts of northern Europe with an extra 2 feet of water and sending its inhabitants — folk known as Angles and Saxons — fleeing (although “conquering” might be the better word) into ill-prepared Roman territories. At the start of this rise, the areas we know as the Fens were a well-settled part of Roman Britain ruled from the town of Duroliponte (Cambridge) by its native people, the Christianized Romano-Celtic Iceni. Then the sea level rose, and history’s curtain went down for two centuries.”

The Roman castle evolved into a Saxon fort and then a medieval castle. When it was built it commanded the entrance to a harbour and was surrounded by the sea on three sides. [link]

Thanet, on the South East coast of England, yields further evidence:

“Rectangular and curvilinear enclosures have been recorded at Dumpton Gap and Broadstairs on the east coast of the island (both of which may indicate small subsistence farming communities) whose incomes were bolstered by the extraction of salt from sea-water, as evidence linked to this activity has been found at both of these sites. The industry was probably curtailed by the early 3rd century at these sites, however, due to the rising sea-levels. Burials have also been recorded at both sites.”

“At Faxfleet a Roman site was probably abandoned in the 4th century AD as a result of rising sea levels.”

 “A Roman road was built northwards from South Ferriby towards the Humber during the 1st and 2nd century ad but this became buried by estuarine sediment within around 200 years of its construction indicating rising sea levels” (also see further references on Page 114 of this link)

This next item refers to an academic studymade to the east of London:

“These indicate a sequence of oscillations of relative sea levels to land mass as the sea has advanced and regressed over the last 10,000 years. The mean relative sea level curve shows an overall trend of a steadily rising sea level with time (see Devoy 1977: 714 fig 2) with levels in our period of +0.4m above present (OD) (Newlyn). For our period the Thames IV transgression phase equates to the middle of the third century AD (c 1750 yr bp), when sea levels at Tilbury were approximately +0.4m above present OD ordnance datum (Newlyn) (Devoy 1977; D’Olier 1972: 127).”

And finally, from this article:

“There appears to have been a general abandonment of settlements across the region during the late Roman Iron Age and the Migration period, probably due to rising sea-levels and storm-tides in the 4th century. Settlement recommences in the 7th or 8th centuries, often in areas that had been previously favoured as settlements sites in the Roman Iron Age.

Historical sea level references from elsewhere in the Northern Hemisphere

Still in the Roman era we now travel further afield to ascertain the characteristics of sea levels in other countries.

The first study is by Lambeck et al. in the scientific journal (Earth and Planetary Science Letters) entitled “Sea level change from Roman times in Mediterranean,” which illustrates some of the complexities of this subject:

“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.”

From a second study by the same author:

“During the detailed excavations of ancient Caesarea, Israel, East Mediterranean, 64 coastal water wells have been examined that date from the early Roman period (with the oldest occurring in the 1st century AD), up to the end of the Crusader period (mid-13th century AD). The depths of these coastal water wells establish the position of the ancient water table and therefore the position of sea level for the first century AD up to 1300 AD. The connection between the coastal water table and changes in sea level has been established from modern observations in several wells on time scales of days and months and this is used to reconstruct sea level during historical time. The results indicate that during the Byzantine period, sea level at Caesarea was higher by about 30 cm than today. The Late Moslem and Crusader data shows greater fluctuations but the data sets are also much smaller than for the earlier periods.”

This next study is of a Roman market:

“After rapid submersion of the Roman market, crustal uplift explains the death of the marine organisms. These radiocarbon dates are compatible with epigraphic data, which mention the Roman market for the last time in A.D. 394. This implies a rapid relative sea-level rise during the fourth century A.D.”

“.. According to the new data, submersion of Pozzuoli was not a unique event, but included three maximum threshold oscillations between the fifth and fifteenth centuries A.D. (1) During the first phase, marine transgression of the Roman market ended ca. A.D. 400–530 after its last restoration in A.D. 394.”

This of an earlier Egyptian harbour;

“Archaeological investigations along a carbonate / conglomerate terrace located 600 m landward of the Red Sea coast in Egypt have uncovered the existence of an ancient (~4 kya) Egyptian harbor, a site from which seafaring ships departed for trade routes along the African Red Sea coast. Nearly 10 years of excavations at Mersa / Wadi Gawasis, a Middle Kingdom Egyptian site, have documented evidence for occupation on the top and at the base of the terrace, including temporary shelters, rock-cut caves, ceremonial structures, and industrial areas for metal working.

Ground penetrating radar, sediment coring, malacological and foraminiferal studies, radiocarbon dates, and rheological models demonstrate that the wadi bed adjacent to the terrace was once an open, protected bay. The base of the corraline / conglomerate terrace consists of a narrow coral-beach rock platform (dated at ~3500 BP) presently buried by anthropogenic, eolian, and colluvial sediments. Ubiquitous medium-fine wadi sediments underlie and extend beyond the beach rock. Malachological analyses, foraminifera distributions, radiocarbon dates, and sedimentological data indicate that these sediments were deposited in a protected tidal lagoon receiving infrequent freshwater inputs. Wave-cut notches along the seaward shoreline confirm a site-specific rheological model for the northern the Red Sea that indicates a sea-level highstand (~1 m above present MHW) during or immediately prior to occupation. Late during the period of occupation, the lagoon began to close as equatorial siphoning forced a regional sea-level fall while at the same time, riverine discharge through the wadi processes were infilling the bay at rates on the order of .25 cm/year.”

Some details on Ostia Antica from the Wikipedia:

“Ostia Antica is a large archeological site, close to the modern town of Ostia, that was the location of the harbour city of ancient Rome, which is approximately 30 kilometres (19 mi) to the northeast. “Ostia” in Latin means “mouth”. At the mouth of the River Tiber, Ostia was Rome’s seaport, but, due to silting and a drop in sea level, the site now lies 3 kilometres (2 mi) from the sea.[1] The site is noted for the excellent preservation of its ancient buildings, magnificent frescoes and impressive mosaics.”

The following references are provided from this site covering our period of study are from the Middle East, Holland, Britain, Greece, Egypt,  and Germany.

“In the ancient port Caesarea, south of Haifa, stands a wall which must have been built between the time of Herod and the 2nd century. (A. Negev , personal communication , 1962). The top of this wall, now 1.50 m above the present sea level, is perforated with the typical holes made by the Lithophaga. The wall stands vertical and shows no sign of tilting. Near this wall are the remains of two aqueducts which once supplied Caesarea with water. Of the two, the older one was built near the present shore line; the parallel and newer aquaduct, situated further inland, must have been constructed when the sea was threatening and ultimately destroying the first one (REIFENBERG, 1951, pp. 27-28). It is most probable that the original aqueduct was constructed during Herod’s reign or shortly after, and that it was situated at that time quite far inland. It is estimated that it was destroyed towards the middle of the first millennium A.D. and the sea, therefore, must have been temporarily 1-2 m higher than it is now ((Fig.4C) “.

“Not only are the aquaducts of Caesaria (REIFENBERG, 1951) and the columns at Puteoli still in the original positions of construction (two things which would be almost impossible if there had been a tectonic movements of 3 m vertical amplitude since their erection) but many other old buildings in the reputedly unstable Mediterranean area are still vertical, a sign that the instability in many places was not great enough to cause a tilt. At the old shore the Etang of Vendres, near the mouth of the Aude, are the ruins of a Roman Therme of the 1st or 2nd century A.D. (locally called the temple of Venus). There the walls have been washed out by waves so that they now have a deep double notch about 1.80 m above present sea level (Fig. 4C). The remaining walls of the “temple” are not tilted at all.”

“Unfortunately these methods can only give estimates of within time intervals of several hundred years and differences of heights of half metres at best. Still, it is clear that the sea level at the Frisian coast according to 14C peat determination was higher ((Fig. 4C) in the middle of the first millennium A.D. than it is today and much higher than it was in the first millennium B.C. (Fig. 4F). The maximum in the middle of the first millennium A.D. is also supported by 14C data in the stable Recife area of Brazil (VAN ANDEL and LABOREL, 1964) (Fig. 4D).

“Similarly the studies of GODWIN (1943), (archaeological , palynological and ecological) show for the middle of the first millennium A.D. (Fig. 4C) a definite rise of 1 m in the Fenlands of East Anglia over the present day sea level there, and a subsequent fall of several metres below today’s level in the 11th century A.D. (Fig. 4B).”

“Between 1200 and 7 B.C. (Fig. 4C) we have evidence of an high sea level: Ramses II succeeded in connecting the Niles to the Red Sea by a canal (1200 B.C.) (Fig. 4G) (MUIR, 1924) which re-used later by Trajan and still later by the Arabs, as mentioned before (650 A.D.) (Fig. 4C).”

“In Schleswig (Haitabu area) a cutba river is indicative of a sudden rise of the sea level (1000 B.C.) (Fig. 4G) (K(STER, 1960).”

 Alternate interpretations

From the above analysis, there appears to be solid evidence that, after taking land changes into account, sea levels in Roman times were rather higher than today, as measured in a variety of locations. At this point any author after having proven their hypothesis (to their own satisfaction) would be wise to quit whilst they’re ahead and not face up to contradictory information. However that would lead to a charge of cherry picking, so it must be said that my assertions to date seem to be refuted by this 2010 article that comes from much the same part of the world as earlier studies. It appeared in a variety of places including Science Daily.

Science Daily featured a mix of selected quotes from the press release of a new study on sea levels, with which they combine into their own narrative.  Some excerpts:

“The sea level in Israel has been rising and falling over the past 2,500 years, with a one-meter difference between the highest and lowest levels, most of the time below the present-day level.

“These revealed that the sea level during the Crusader period — just 800 years ago — was some 50-90 centimeters lower than the present sea level. Findings from the same period at Caesarea and Atlit reinforced this conclusion. When additional sites were examined from periods before and after the Crusader period, it was revealed that there have been significant fluctuations in sea level: During the Hellenistic period, the sea level was about 1.6 meters lower than its present level; during the Roman era the level was almost similar to today’s; the level began to drop again during the ancient Muslim period, and continued dropping to reach the same level as it was during the Crusader period; but within about 500 years it rose again, and reached some 25 centimeters lower than today’s level at the beginning of the 18th century.”

So the conclusion would be reached from reading the article that although the sea level was almost as high as today in Roman times it subsequently dropped, rose again to some 25cm, lower than today and as we all ‘know’ has surged to new levels in the last century.

The original study is found here. It appears that inexplicably a significant portion of this study was omitted, which throws a rather different light on the Science Daily story.  The original study states:

“The Caesarea results indicate that about 2000 years BP sea levels was at its present elevation, (note; not ‘almost similar to today’s) 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 40cm, plus or minus 15cm.”

That the Science Daily version can have a rather different inference than the study and that some key parts have been omitted can be seen in the attribution by SD;  The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Haifa. (Their link then originally lead to the University’s home page in Hebrew)

Let Dr Sivan himself have the last word which can put the Science Daily reporting of this section into its proper context now we know the complete story:

“Over the past century, we have witnessed the sea level in Israel fluctuating with almost 19 centimeters between the highest and lowest levels. Over the past 50 years Israel’s mean sea level rise is 5.5 centimeters, but there have also been periods when it rose by 10 centimeters 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,” Dr. Sivan concludes.

This observation is interesting as the use of the word ‘fluctuating’ can be matched to an earlier reference in other studies to ‘oscillating’ whereby is implied that over the last few thousand years or so sea levels have moved up and down around a central average by up to 30 cm or so.

Summary: Part I

So notwithstanding the statements of the IPCC AR4 who assert a sea level status quo from ancient until modern times, there are many studies that point to a picture of relatively static sea levels after the initial Holocene rise. These then show that some 3000 years ago there was a further inundation (think Lyonesse in Cornwall) and in early Roman times levels were somewhere around current levels. Levels then rose significantly through the Roman period peaking around the 700 AD Byzantine period at levels higher than today, which concludes at this period of study for Part 1.

511 responses to “Historic variations in sea levels. Part 1: From the Holocene to Romans

  1. I’m venturing to guess that something’s missing from the end of this post?

    • Latimer Alder

      Do you think the second paragraph of the whole thing

      ‘Historic variations in sea levels is in three parts. Part 1 covers the Holocene to Roman times. Part 2 traces sea level changes to the Medieval Warm Period. Part 3-the modern age from 1700 to today’

      will give you the clue you are looking for? Especially when taken together with the final clause

      ‘which concludes at this period of study for Part 1′?
      .

    • Latimer –

      The post was altered after it was first put up – to correct for an editing problem at the end.

      Other than that, you’re 100% correct, as usual.

    • Latimer Alder

      Thanks for the clarification.

    • Perhaps my vision continues to be distorted by eternal optimism, but I see encouraging signs that NASA employees, editors of PhysOrg.com and some politicians are beginning to see the connection between:

      a.) Hiding and manipulating data on the Sun – Earth’s heat source,
      b.) The world-wide fable of CO2-induced global warming,
      c.) Disintegration of the USA space program,
      d.) Disintegrating world’s economy, and
      e.) Loss of our national sovereignty

      Those are not a mere coincidence!

      It is all follows from a 1972 decision by world leaders to use “Global Climate Change” as the common enemy to unite nations, end nationalism, and avoid mutual destruction by nuclear annihilation.

      Many skeptics endorse those noble goals, but not the abuse of scientific information as a propaganda tool that could lead us to a tyrannical world government.

      NASA scientists and the editors of PhysOrg.com are starting to see the connection [1].

      1. “Dark fireworks on the sun,” by NASA’s own
      Dr. Tony Phiilips [PhysOrg.com 12 July 2011]

      http://www.physorg.com/news/2011-07-dark-fireworks-sun.html

      With kind regards,
      Oliver K. Manuel
      Former NASA Principal
      Investigator for Apollo

    • No one knows how far into the earth that water extends. The idea that the ocean basins “contain” the oceans is likely incorrect. The visible oceans likely simply reflect the spots at which the global water table is higher than the land.

      It is quite possible that the oceans of the earth contain significantly less water than the rocks under. Water is heavy and seeks the lowest level. As the boiling point of water increases with pressure, it is quite possible that water extends far within the earth itself, in volumes only hinted at by the oceans.

      Without a measure of the volume of water moving between the deep oceans and the rocks under, it is unlikely that estimates of the scale of the heat transfer are accurate, along with the effects on climate and sea levels.

    • Dear Dr. Curry:

      With all due respect, the sea level graph posted on this thread cannot be right for it disagrees with observations. A rise in sea level of 135 meters since the Last Glacial Maximum is an impossibility for the following basic calculations:

      Our record shows that sea level 125,000 years ago, prior to the onset of the last glacial period, was slightly higher than today’s, say by approximately three (3) meters. Based on the sea level graph posted on this thread, sea level at the end of the lat glacial period was -135 meters. Therefore, the last glacial period dropped sea level by approximately 138 meters. This is equivalent to depositing 4.9E19 kilograms of ice on the continents (138 x 5.1E14 x 0.7 x 1000), where 5.1 E14 is the surface area of the earth, m²; 0.7 is the area ratio between surface water and total surface area of the earth; and 1000 is the density of water in Kg/m³.

      Ice deposited on continents originated from surface water, and generally, the deposited ice and surface water are not in direct contact, and there can be no ice formation on continents, or sea level drop, without surface water cooling. This is true now as we speak and then. Therefore, based on the graph, the heat removed from surface water during the last glacial period must have equaled to at least the latent heat of ice formation, or 4.9E19 x 333,600=1.6E25 Joules, where 333,600 is the ice latent heat of fusion, Joules/Kg. This heat removed from surface water is sufficient to: cool all of the hydrosphere by 3 ºC; cool the top 700 meters of ocean by 16.9 ºC; or cool the top 200 meters, or surface water, by 59 ºC. Mass of the hydrosphere is assumed 1.41 E21 Kg, and hydrosphere specific heat is about 3,900 Joules/(Kg ºC ). The calculated cooling based on the graph disagrees with Antarctic ice core data, and this substantial surface or ocean cooling has not been confirmed by researchers.

    • How much did the sea level rise since the last glacial maximum, in your opinion?

      It should be noted that sea level during glacial periods is the “normal” level. Most of the time, at least for the last few million years, the sea level was at least ~100 m lower (continental shelfs). Only during relatively very short interglacials, sea level rises ~100-150 m.

    • Dear Edim,

      Most of the time In the last 400,000 years, the normal sea level was about equal to that of glacial periods, roughly five meters (5.0 meters) below the present sea level. It rose to about the present sea level briefly during interglacial periods then dropped back to glacial period levels. 20,000 years ago, around the Last Glacial Maximum, sea level was approximately -5.2 meters. These figures are calculated based on thermodynamics. For more, please see my book posted on http://www.global-heat.net. Thermodynamics does not require a reference point on land and can calculate sea level accurately. All other methods require a reference point on land and a fixed reference point is hard to find. Consequently, the observed past sea level varies all over the place.

    • Hmm. Five meters is way too underestimated for glacial period levels. There is too much evidence from different fields and sciences that it’s much much more. Very likely more than 100 m.

      But it’s good that you’re sceptical. That’s what moves science forward.

    • Dear Edim,

      Thank you for your comments. Please take the 100+ meters of sea level rise since the Last Glacial Maximum with a grain of salt. Recent publications challenge this high sea level rise. Please see this recent paper: sea level 81,000 years ago was 1 meter higher while CO2 was lower. Science, Volume 327, 1ssue 5967. You can find free summary of the paper on the web, key words: sea level 81,000, Mallorca caves, ancient sea –levels rewrite ice age transition.

      The procedure used in the paper is correct and the source of samples, Mallorca caves, Spain, is geologically stable. You will find that the average sea level during the last glacial period was around -7.0 meters, reasonably close to the calculated one of -5.2 meters.

    • Dear Nabil,

      I take everything with a grain of salt. If I have pepper, I take it too. I like it spicy.

      Regarding sea levels during glacial periods, I think it was much lower. When I have time, I will maybe look into it. Isn’t there so much evidence for -~120 m?

    • Dear Edim,

      Back in 2007 when calculations showed that sea level during the Last Glacial Maximum ( 16,000 BC in Table-1, page 58 of my book) was -5.2 meters, all published paper available at the time, or I was aware of, suggested -100 to -150 meters instead, which can not be justified mathematically. I’m not a scientist or researcher but I can read, evaluate; and I go by numbers. Regretfully, the numbers are not there to justify -100 to -150 meters.

      One way to judge a published paper is to evaluate the procedure with which sea level is determined. I found that a lot of researchers were using a mobile bench mark or reference point for their data, and then correct sea level for the errors resulting from point’s motion. Others, which were the majority, used computer models to estimate ice sheet size and eustatic sea level changes. Apparently the models overestimated sea level.

    • “On the paraglacial coast of Northern Ireland the late Holocene sea level history involves a rise from a lowstand at 13ka to cross the present level by around 7kaBP reaching a few metres above present by 5ka BP and a Subsequent fall to present sea level. `Raised’ or `stranded’ beaches associated with the late Holocene highstand are distributed widely around the Northern Ireland Coast ”

      http://eprints.ulster.ac.uk/1464/

      The world is full of “stranded beaches” showing that sea level was higher than today.

    • Latimer Alder

      South Devon too.

      I remember going on a school geography ‘O’ level field trip about 40 years ago and examining them. Direct immediate evidence that sea levels were once higher.

      No statistics or cherry picking or correlations or models or speculation or peer-review needed. You can touch them and see them in situ as you walk along today’s beaches. And collect the old seashells.

  2. Please help me understand this issue in practical terms. As I understand the situation:
    1. There has been a lower level of temperature rise than was predicted/modeled based upon CO2 changes since the year 2000- virtually no temp change?
    2. There is very poor data available to reliably determine historic sea levels around the world
    3. Since we have been measuring sea level in a “scientific” manner it has been rising at a rate of around 1mm per decade
    4. The world’s oceans do not show any significant temperature rise
    5. Worldwide ice levels are very consistent with where they were 5 years ago
    If we see some evidence that sea levels are rising by 10 mm per decade vs. 1 mm per decade then 1 meter by 2100 might be an appropriate fear, but why is it a fear now with no such evidence?

    • Most references say 3 mm/year which is 30 times what you have. Where do you get your 1 mm/decade from? Seems like an error.

    • Rob Starkey

      Jim- Thanks for catching my error. The correct answer based upon 1991 to 2011 information is a 25 mm per decade rate of sea level rise. One inch per decade seems to be something to which we can adapt.

    • Rob Starkey

      And one inch per decade does not equal one meter by 2100

    • Correct. If sea level rise remains constant, it will be about one quarter meter by 2100. However, note that RealClimate’s topic today is on whether sea level rise is accelerating, which is the real question.

    • Rob Starkey

      The Real Climate topic seems to be an attempt to generate fear as a case for action. At the end of the day isn’t real, actual data the best information upon which to base our conclusions/decisions?

      Since the actual measurements demonstrate sea level is rising by 1 inch per decade, if we are going to believe someone’s claim that it will rise at a different rate in the future- doesn’t the person making the claim have to have a rock solid case to support the claim that the rate will change? Shouldn’t they be able to state when the rate change will occur and what it will become in order to be believed?

      When I read some of these studies that initially speculate about the ocean floor falling due to compression due to the additional weight of the water from melted ice, and then read papers by others that then take the 1st studies speculation, make it an undisputed fact and then do a long term analysis based upon these assumptions….I shake my head in disbelief

    • “At the end of the day isn’t real, actual data
      the best information upon which to base our conclusions/decisions? ”

      You may want to reread the topic, which agrees with that statement and is entirely about the actual data. The controversy is that the acceleration (or lack thereof) depends on the starting date for your measurements. For example, their figure 2 shows that if we look at the data from 1950-present, sea level rise has been accelerating by 0.03mm/yr^2. However, if we look at the data from 1930-present, sea level rise has only been accelerating by about 0.007mm/yr^2, while if we look at the data over the last hundred years, we see an acceleration of about 0.02mm/yr^2. Note that in all choices of dataset (based on the Church&White reconstruction), the data shows that sea level rise is accelerating. However, the observed rate of acceleration depends greatly on the choice of years, which is what the article is trying to understand.

      Note that your stated position of sticking with the observed data suggests that we should base our conclusions/decisions on the observed data, which says that sea level rise is accelerating (perhaps averaging over starting dates, to avoid cherrypicking the data). Alternatively, you could try to criticize the quality of the Church & White Sea Level reconstruction as insufficient for drawing conclusions, but that is not what I am hearing from your post.

    • mps – perhaps you disagree with me, but I do not think there can be found in observations now any hint of the prediction of ~1 meter by 2100. If there is a resumption of La Nina later this fall, that will say nothing about the prediction of ~1 meter. Say the rate drops in half. Bob will trumpet 1/2 inch per decade, which have no more relevance than his 1 inch per decade.

      Per Hansen, a significant percentage of the ~1 meter will happen after ~ mid century.

    • Rob Starkey

      mps– You are incorrect.

      When you look at the observed data it shows a quite consistant trend. If you measure from the early 1990′s to today you will see that the rate of increase is about 25 mm per year. Everything else written by scientists from Hansen to Curry is speculation as to what may have happened in the past or might happen in the future.

      imo, if someone claims that the rate of sea level rise will change to a higher rate in the future they need to state when they think it will go up, and whet the new rate of increase will be. For the last 20 years (the most reliable data possibly available) it has been going up at an unexpectedly slow rate of 25mm per year. If we see that the rate is changing we should try to understand why. For now at a rate of 1 inch per decade it certainly is nothing to worry about enough to implement mitigation

    • 25 mm per year? You mean 2.5 mm?

    • Rob Starkey

      Yes a typo–25mm per decade not per year

    • “When you look at the observed data it shows a quite consistant trend. If you measure from the early 1990′s to today you will see that the rate of increase is about 25 mm per year. ”

      20 years is too short to measure acceleration trends (look at the 2 sigma bars in the RC Figure 2). The data for any time period long enough to measure acceleration trends shows a positive acceleration.

      “imo, if someone claims that the rate of sea level rise will change to a higher rate in the future they need to state when they think it will go up, and whet the new rate of increase will be.”

      As above, the empirical data shows that the rate of sea level rise has been changing to higher rates over any period of time long enough to have statistical validity. If you want to claim that it will stop accelerating, you need to state when it will stop going up and what the final rate of increase will be.

      Alternatively, are you saying that the Church and White data is wrong? If so, you need to claim that, and say why. You can’t just silently discard all empirical data that disagrees with your conclusion, especially when you are saying that empirical results should be driving our behavior.

    • Latimer Alder

      @mps

      ’20 years is too short to measure acceleration trends (look at the 2 sigma bars in the RC Figure 2). The data for any time period long enough to measure acceleration trends shows a positive acceleration’

      Fair enough. Please show me some some data that you believe is long enough to measure acceleration trends and advise what the acceleration you see actually is.

    • Latimer Alder

      @mps

      PS

      I;d also like to know how you determine ‘how long’ is long enough to measure any acceleration (or not). You clearly believe 20 years is too short, but how long is long enough…and why?

      Is it 50 years, 100 years, 200 years?

    • “If you want to claim that it will stop accelerating, you need to state when it will stop going up and what the final rate of increase will be.”

      mps,

      If I may, this sl time series since 1993 shows a peak (+45 mm) in the beginning of 2010:
      http://sealevel.colorado.edu/

      I claim that, that was the maximum for the next few decades, maybe even much longer (until next interglacial maybe, considering the glacial is kind of long overdue). Don’t forget, the temperature (and sl) trend for the last 10,000 years is negative, going down slowly from the interglacial peak.

      So, I claim it’s already stopped accelerating (if there was any acceleration at all, of course it depends on magnitude and time scale) and that the rate of 3.1 mm/year (according to CU) will decrease steadily
      Whatch that sl time series develop and fasten your seat belt!

    • @Latimer Adler
      “I;d also like to know how you determine ‘how long’ is long enough to measure any acceleration (or not). You clearly believe 20 years is too short, but how long is long enough…and why?

      Is it 50 years, 100 years, 200 years?”
      I am going by the 2 sigma bars from the RC graph. If we use 50 years of data, the 2 sigma range for acceleration on the graph goes from about .005mm/yr^2 to .05mm/yr^2, which is still extraordinarily wide (although “no acceleration” is outside of the 2 sigma range). If you go with 100 years of data, the 2 sigma range seems to be between about .02mm/yr^2 and .03mm/yr^2, which makes for a reasonably tight measurement.

      “Fair enough. Please show me some some data that you believe is long enough to measure acceleration trends and advise what the acceleration you see actually is.”
      By the above, I’d say 100 years seems long enough (there are some caveats in the RC article that shouldn’t be ignored, but I agree with there ultimate conclusion that we can regard the numbers as robust). 50 years by itself isn’t convincing, but the fact that the midpoint of its range is similar, is certainly reassuring. The acceleration trend I see in the Church and White reconstruction is between about .02mm/yr^2 and .03mm/yr^2.

      @Edim
      As above, conclusions about acceleration from a 15 year time series aren’t very compelling because the error bars are too great, so I don’t believe that overturns a conclusion based on much longer data (and presumably is consistent with the margin of error of your much shorter data).

      BTW, I appreciate how thoughtful and civil everyone is being around a comment based on a RC topic. I am trying to appropriately qualify my use of the data.

    • Latimer Alder

      @mps

      I can only conclude that you and others have all been torturing the data until you get whichever result you want. Whether accelerating, decelerating or doing neither.

      I cannot take seriously a claim of an acceleration trend of +.0.025 mm/y2
      when the daily tidal range I have just been sailing on (Solent UK) is about 4500 mm..and even that varies by 1400 mm within a fortnight.

      Even if it were possible to measure sealevel to the sorts of accuracy that would be needed to measure the numbers, you claim to be able to see an acceleration 1,500,000 times less than the natural variation from the tides. And that takes no account of weather-driven events.

      And given that even the predicted sealevel rise is so small overall (500 mm in 100 years) I see no point in worrying about sealevel ever again.

      Unless somebody can really come up with some concrete reasons to worry. Not just hypothetical scare stories like the 50 ,million climate refugees that never were.

  3. What exactly is meant by ‘ancient’ times? Camels first evolved in North America. Before going extinct 75 million years ago, camels migrated from N. America to Asia and Africa 6 million years ago by crossing the Bering Strait.

    • I think you might want to reword that statement since logically it makes no sense. Now either:

      The camel went extinct in North America 75 million years ago, which means it couldn’t cross the Bearing Strait 6 million years ago from N. America to Asia (unless they are Zombie camels).

      Or

      The camel didn’t go extinct in North America 75 million ago and was still around to cross the Bearing Strait 6 million years to Asia.

    • Ok–Before going extinct [in North America] 75 million years ago, camels migrated from N. America to Asia and Africa 6 million years ago by crossing the Bering Strait.

      There were elephants in North America as well, and horses… oh my!

    • Hippo’s in the UK

      “Fossilised remains of two ancient hippos have been discovered in Norfolk by scientists at the Natural History Museum and Queen Mary, University of London.”

      http://www.nhm.ac.uk/about-us/news/2004/july/news_5293.html

    • Were they on display when found?
      ;^)

    • Latimer Alder

      Have they signed as the new centre-back pairing for Norwich City?

    • Craig Goodrich

      Will they vote Labor in the next election?

    • tempterrain

      No it still doesn’t make any sense. If an animal goes extinct then that means there aren’t any left. And if there aren’t any left they can’t migrate!

      Incidentally Camels have evolved in the last 25 million years so wouldn’t have existed, in any recognisable form, 75 million years ago.

    • I know I was hoping that he would catch that point. Also it is listed in the Encyclopedia Britannica that the camel could have been alive in North America as late as 11,700 years ago:
      http://www.britannica.com/EBchecked/topic/90806/Camelops?anchor=ref132044

      So obviously the camel did not go extinct in North America 75 million years ago.

    • They migrated before they were extinct and became the camel you recognize today.

    • I think you’re just off by a factor of a thousand or so – maybe ten thousand.

      Or maybe the mental short circuit is vocabulary-based:
      6 million years ago is not “before” 75 million years ago. Look up the word “ago”.

    • P.S.
      75 mya is during the Cretaceous. If any camels existed in N.A. then, they were cleverly disguised as dinosaurs.

    • True, true the camel died out in N. America during the last ice age–75 thousand not million years ago–but, those who made it to S. America now speak llama-nese.

    • They’ve found camel bones in paleo-indian sites in North America (along with horse btw). So that would put them there within about 20,000 years.

    • Ah, Wag, the dinosaurs only went extinct between about 65 and 70 million years ago. Camels in North America vanish around the end of the Pleistocene, which was around 10 thousand years ago. In South America camelids – llama, alpaca – are still present.

  4. Thanks, Professor Curry, for continuing the effort to unravel the climate warming story.

    Perhaps blinded by optimism, I see indications today that the entire fabric is coming apart at the seams!

    With kind regards,
    Oliver K. Manuel
    Former NASA Principal
    Investigator for Apollo

    • tempterrain

      Unravel? It strikes me as just the opposite. I could understand Judith encouraging climate sceptics with her continued comments of doubt and uncertainty if she believed that climate sensitivity to CO2 increase was low, say less than degree.

      But she doesn’t.

      She places it in the likely range of 1 – 6 degC. With a significant possibility that it may be higher.

      Does anyone have any plausible explanation?

    • Well actually this post is not about climate sensitivity, it is about sea level rise which may or may not be related to global temperature.

      If anything, this post would argue for; co2 increases not being a meaningful indicator of sea level rise , large natural variations that we do not understand, or high climate sensitivity due to solar (?) effects. If you read the referenced material, it is difficult to draw a conclusion. Clearly we do not know enough at this point.

      Roy Weiler

    • tempterrain

      Its all about climate sensitivity. If the climate warms:
      The polar ice is going to melt and sea levels are going rise.

      Anyone care to disagree?

    • Why don’t you let Fred make the comments for your side? He’s way better at it and he sounds so much more intelligent.

    • So you should be happy for me to carry on then? :-)

    • No, bathos can be painful.

    • tt –
      Actually, it’s not quite that simple. But that IS the standard alarmist line for public consumption. Do you believe it?

    • John Vetterling

      I will disagree. This is the kind of simplistic argument that adds nothing. If the tropics warm by .5 degrees while the poles cool by the same amount you wold have a net warming of about .3 (since the tropics are about 3x more area) but the ice might freeze and the sees might go down (all other factors being equal).

      Conversely, if the poles were to warm by .5 while the tropics cooled by the same amount the climate would cool but the ice might melt.

      that’s the problem with complex systems. They defy simplistic reasoning.

    • John Vetterling

      Actually that’s an overly simplistic view in itself. Advance and retreat of glaciers/ice caps is a complex, non-linear, process that’s is affected by several other factors such a cloud cover, precipitation, wind, and sea temps for the arctic. Temperature is actually a very minor factor since most of those locations are below 0C most of the year. It doesn’t matter if its -2 or -1, ice still wont melt.

      The most dominant factors appear to be precipitation, which adds to snow pack, and cloud cover, which reduces sublimation to to solar heat gain.

      I believe USGS still has some really good reference material if you are interested.

    • In the paleo record, which period(s) saw ice retreat while the globe was cooling?

    • John Vetterling

      1. Paleo records tell you nothing about global cooling or warming. they are a very selective sample at a specific point on the globe.

      2. Dendritic samples don’t tell you about ice because if there’s ice there wasn’t dendro.

      3. Ice cores tell you something about ice, but then if there was melting there wouldn’t be ice.

      A lot of people are trying to torture interpretations from data that the data just doesn’t support.

      On top of that, from a thermodynamic standpoint, statements about average global temp have no physical meaning. In theory there is an average heat content. But average temp is meaningless. You can calculate it, but what does it really mean in a thermodynamic sense?

      It has no meaning for radiative heat transfer since that is proportional to T^4 not T^1. It has no meaning for heat absorption since that is not a function of area; it is a function of air density (which itself is a function of pressure and temp) water content and other chemical factors.

      What does it really mean?

    • tempterrain

      John Vetterling,

      I sounds to me like you are engaged in deliberately over-complicating the issue. There is always a degree of averaging involved in any measurement and, of course, temperature is no exception.

      Yes, you are right that the concept of world temperature average, and even regional temperature averages, do have their limitations. The average temperature over the land is different than the average over the ocean for example. Nevertheless the average temperature over the land has increased by more than over the ocean. Similarly, the average temperature in the Arctic has increased more than in the tropics.

      So are these facts useless? I would argue they are well worth knowing . But maybe you disagree?

    • Please define polar ice melting.

    • tempterrain | July 12, 2011 at 9:58 pm | Reply
      Anyone care to disagree?

      What you, Gore and Hansen neglect to mention is time scales. Even if the earth was to warm to 22C, which is the paleo maximum over the past 600 million years when CO2 levels were 10 to 20 times present levels, the time it would take to melt the ice caps is on the scale of 10 thousand years. This would raise sea levels less than 100 meters according to Wikipedia.

      So, over 10 thousand years we would see worst case 100 meters of rise. This works out to be less than 1 cm per year. Less than 1 meter per century is the worst that we can expect from the ice caps melting, with CO2 levels 10 to 20 times higher than present.

      1 meter per century is well within the ability of humans to adapt. The biggest problem is not people, who have shown throughout the ages a willingness to move to greener pastures. By far the biggest obstacle to adaptation is the governments of the world. While governments are quick to promote free trade in goods and services, they have very strict controls on the movements of people looking to improve their lives.

    • 1 meter per century is well within the ability of humans to adapt.
      1. The graph in J. Curry’s post shows a lot of centuries with more than 2 meter rise.
      2. Sea level rise won’t stop in 2100. What about sea level in 2500 or 3000? “Adaption” would mean giving up a lot of coastal regions.

      BTW:
      If we are interested in sea level rise, there are more meaningful time periods than the last 8000 years. For example times, when temperatures were 2-3°C higher compared to our time.

    • tempterrain

      Ferd,

      Well I think it might happen slightly faster than you say. But we’ll leave that question aside for now.
      Am I right in thinking you accept that CO2 and other GHG’s are going to cause serious warming, but you feel that no mitigation is either desirable or possible and full adaptation is the best and cheapest option?

    • Temp:

      That really depends on which pole you are referring too. Clearly the south pole is, so far, not melting. You could make the argument that the Western peninsula is melting, but that really is a small fraction of the whole. The North pole has little impact on sea level as it is floating on water (you might get a change due to changes in salinity). You could be referring to Greenland, but with respect to Greenland the melt levels do not seem to be outside of normal variability. We are still discovering new Viking settlements and farmland that were, until recently, covered in ice. So there must have been less in the past.
      So what climate sensitivity is affecting which pole or poles to make the sea level rise? Please be more specific.

      Roy Weiler

    • tempterrain

      ” You could be referring to Greenland, but with respect to Greenland the melt levels do not seem to be outside of normal variability. ”
      Roy Weiler,

      Do you have a reference to support your statement about normal variability of Greenland ice melts?

      It is interesting to look at the Eemian period. The last interglacial about 130,000 years ago.

      http://en.wikipedia.org/wiki/Eemian

      Then temperatures were 1-2 deg warmer on average. But maybe John Vetterling would dispute the significance of that statement? So the temperatures were warmer by an amount comparable to what we have so far experienced and are like to experience in the coming decades.

      So what about sea levels? They were 13 -20 ft higher than today. So it seems that the polar ice caps must have been smaller although some sea level rise does occur due to thermal expansion also.

      http://www.ncbi.nlm.nih.gov/pubmed/16556837

    • http://www.nipccreport.org/articles/2011/jul/6jul2011a3.html

      “During the past century of general mass loss, they found that “periods of warming were observed from 1918 (the end of the Little Ice Age) to 1935 of 0.12°C per year and 1978 to 2004 of 0.07°C per year,” and they say that “the warmest average 10-year period within the last 106 years was the period from 1936-1946 (-1.8°C),” while the second warmest period was from 1995-2004 (-2.0°C). In addition, they note that “also on West Greenland the period 1936-1946 was the warmest period within the last 106 years (Cappelen, 2004).””

    • tempterrain

      Bruce,

      The report is from a contrarian website (NIPCC) with zero scientific credentials.

    • tt –
      The report is from a contrarian website (NIPCC) with zero scientific credentials.

      IOW – anything that disagrees with or refutes your viewpoint has zero scientific merit – which is either anti-scientific or ignorant.

    • tempterrain, how about NOAA?

      Four stations go back to the 1800s. 3 out of the 4 have 1929 as warmest Sep-Aug

      Upernavik 1929
      Ilulissat 1929
      Nuuk 1929
      Tasiilaq 2003

      http://www.arctic.noaa.gov/reportcard/greenland.html

      Interestingly enough, 1983,1984,1884,1918 were the coldest years of the 18xx stations.

    • I’m not sure there is much of a data base on melt rates but if you associate melt rates with temperature then it has been warmer:

      http://www.ncdc.noaa.gov/paleo/globalwarming/holocene.html

      and it has warmed faster:

      http://www.agu.org/pubs/crossref/2006/2006GL026510.shtml

    • Just as a semi-interesting addition, the 1920 – 1930 period referenced in the second paper linked corresponds to the change in the AMO going from negative to positive. A situation very similar to the recent past.

    • Temp:
      The other posters have provided links to support my supposition. So I will dispense with that.
      Your link to the Eemian period indicates the following:
      “Changes in the earth’s orbital parameters from today (greater obliquity and eccentricity, and perihelion), known as the Milankovitch cycle, probably led to greater seasonal temperature variations in the Northern Hemisphere”
      As a consequence it makes it difficult to relate that time frame to our own.

      I am not sure where your proof lies?

      If you spend some time looking at the evidence for the Vikings conquest and withdrawal from Greenland, many of other questions you ask will be answered.
      Just the facts please, or reasonable scientific studies.

    • tempterrain

      Roy Weiler,

      “reasonable scientific studies” eh? Well I guess you are raising the point that the so-called MWP when Vikings did indeed settle successfully, at least for a time, in Greenland was global. It could have been the result of changing ocean currents which would make it more of a local effect.

      OK you go first with your “reasonable studies”. You haven’t given any references yet.

      Incidentally , science is evidence rather than proof based. We leave ‘proofs’ to mathematicians.

    • tempterrain

      Another paper which you might care to take a look at, which I hope you would agree comes into the category of a “reasonable scientific study” is:

      http://www.pnas.org/content/early/2010/08/09/1003336107

      “The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century.”

      Which is somewhat at variance with your claim about the lack of warming in the Antarctic.

    • “As in many other parts of the world, the Medieval Climate Anomaly in the Pacific Basin was generally a time of rising temperatures comparable to the period of recent warming in which we are living today. Evidence is patchy but generally compelling. Good studies of China, employing various techniques (Qian and Zhu 2002; Yang and others 2002), typically indicate that, between 570 and 1310, warming in the Huanghe and Yangtze Valleys occurred at the rate of 0.04[degrees]C per century (Ge and others 2003). In New Zealand the Medieval Climate Anomaly lasted from 1050 to 1350 or from 1290 to 1430 (Williams and others 2004, 2005); in California, from 950 to 1220 (H.-C. Li and others 2000). The sudden onset of cool conditions marking the end of the Medieval Climate Anomaly occurred about 1200 in the Canadian Rockies (Luckman and Wilson 2005). Fish-catch proxies of sea-surface paleo temperatures off Southern California show that temperatures were low around 800, had reached a maximum for the Medieval Climate Anomaly about 1000, and had again reached a minimum about 1400 (Baumgartner, Soutar, and Ferreira-Bartrina 1992).”

      http://goliath.ecnext.com/coms2/gi_0199-7024384/The-A-D-1300-Event.html

    • Okay; How about this old text, that clearly tells us what we can all expect,…
      in a little while.
      Please read, II Peter 3:10-13.
      What a difference a Day makes.
      Global flooding; is so-over.
      And by the way, thanks for asking.

    • Roy

      Why are you so worried about a 1 inch per decade rise in sea level? Since actual measurements show this as the rate of rise over the last 20 years wouldn’t you agree that this is the rate we should be discussing, and isn’t it a non problem?

    • I am not concerned about sea level rise at all, I am merely commenting on the post. It is clear the sea level rise was much greater coming out of the last ice age. This planet has often experienced sea level rises and falls of over 160 meters. One inch per decade is hardly cause for alarm. In fact this post makes the idea of a recent one inch per decade rise completely absurd for comparison to historical norms.
      As a consequence, I am not sure of your disagreement with my response? Is it because I indicated we are not sure of how to get from A to B? In other words we do not even know enough to guess at this point?

      Roy Weiler

    • tempterrain

      I would say that my disagreement is over your self confessed lack of concern for sea level rise. You yourself are unlikely to be personally affected so your lack of concern isn’t without a certain logic,

      Yes, 160 metre rises have occurred previously occurred but then the world’s population slightly lower than it currently is!

      If you are suggesting we should have zero effort on mitigation and concentrate totally on adaptation you should at least make some case that total adaptation is cheaper. Current economic thinking is that it won’t be, although of course some measures of adaptation are already inevitable.

    • tt –
      you should at least make some case that total adaptation is cheaper. Current economic thinking is that it won’t be, although of course some measures of adaptation are already inevitable.

      We’ve been through this discussion. Before anyone can determine the relative costs of adaptation/mitigation, one needs to have a handle on the costs of mitigation. Which neither you nor anyone else has even come close to defining.

      By law in the US, installing a 2-plank footbridge in a park requires an environmental impact statement – including cost) – such that a simple 2-plank bridge (material cost ~ $30 can take 2 years and $20,000 or more. Why do you think “mitigation” is so cheap?

    • tempterrain

      I could ask why you think adaptation is so cheap? I don’t believe that we should necessarily looking out for ‘cheap’ but the most effective solution. I don’t believe there are any credible scientific/economic studies which go against the old adage that ‘prevention is better than a cure’.

    • tempterrain

      Yes I’d settle for 1 inch per decade. But that’s just a figure you’ve made up though. Its likely to be much more than that this century and more again net century.

    • Rob Starkey

      temprerrian– No 1 inch per decade is not a made up number but it is the actual measured rate of sea level rise over the last 20 years. Please compare it to what the various models predicted. Now what is your worry?

      http://wattsupwiththat.com/2011/07/03/the-ups-and-downs-of-sea-level/

    • tempterrain

      Yes I could point you to climate models of sea level rise, but people like Max (manacker) start to get their knickers into a twist at the mention of these. He also starts frothing at the mouth and uttering phrases like “garbage in garbage out” etc.

      I’d just point you to the empirical evidence of the Eemian period. Temperature the same as what we can expect in a few decades. Sea levels several metres higher.

      http://en.wikipedia.org/wiki/Eemian

    • tt-
      1) This isn’t the Eemian period – for which the actual conditions “on the ground” are presently unknown (and likely to stay that way).

      2) What – other than your excessive level of fear – makes you think that the conditions you predict will actually occur? Evidence please.

      3) What – other than your excessive level of fear – makes you think that the human race is so utterly helpless as to be incapable of handling those conditions? Evidence please.

      If you have no evidence, then you are dabbling in either spiritualism or paranormal “science” (i.e. – fortune telling)

    • Tempterrain

      Based on satellite altimetry, the period 1993-2003 showed a linear average rate of sea level rise of 3.1 mm/year, according to IPCC (tide gauges showed around half this rate of rise)

      Satellite altimetry for the most recent period 2004-2011 (through March) shows a linear average rate of rise of 0.76 mm/year..

      So taking the average trend over this 17.25 year period, we arrive at 2.12 cm/decade = 0.83 inch/decade (not too far off your 1 inch/decade).

      If this average rate continued over the rest of the 21st century, we would see a rise of 21.2 cm over the entire century (slightly higher than the lower end of the IPCC projection).

      If the most recent trend of 0.76 cm per decade were to continue, we would only see a rise of 7.6 cm over the entire century.

      I would guess that the first estimate would be more likely, based on the past record and assuming that the current lack of warming ends and we return to a long-term trend of slight warming.

      This would be a rate of sea level rise as was observed by tide gauges for the first half of the 20th century

      You seem to think it is likely to end up being even higher, but I have not seen any data to substantiate that estimate.

      Maybe you have some estimates, possibly tying these to projected temperature trends. If so, I would be interested in seeing them.

      Max

    • Latimer Alder

      Martin me old mucker

      Does it not occur to you that a range as wide as 1 to 6 C is pretty full of doubt and uncertainty anyway? And useless for all practical purposes.

    • Latimer Alder

      @martin

      Nor that after thirty years of ‘professional’ climatology, the most critical component of the whole AGW argument is still so elusive that such a wide range can be quoted by a leading climatologist with a straight face.

      In those thirty years CO2 levels have increased by about 15%, we have had goodIsh) worldwide temperature measurements. so ideal conditions for a real observationally based experiment.

      .And yet there is still such a broad range of guesses.Seems to me that maybe good old Arrhenius got it right way back when in 1907. We can sleep easy in our beds..absent any convincing data to the contrary.

    • tempterrain

      Judith puts the chances of AGW being higher than 6 deg as about 1 in 6. That’s the same odds as in Russian roulette, isn’t it. So before you pull that trigger do you tell yourself that you doubt the bullet is in the right cylinder, there’s too much uncertainty to be worried?

    • Rattus Norvegicus

      One should note that this is considerably more “alarmist” that the IPCC estimates.

    • Yes it is. I just can’t follow her line of thought at all. It seems like there may be two Judith Currys: one climate scientist and another who has political objections to the implications of that science.

      I’m reminded of the case of Marcus Ross who’s both a young earth creationist and an old world evolutionist

      http://scienceantiscience.blogspot.com/2007/02/two-faces-of-dr-ross.html

    • Again, you discount the costs of mitigation. Adaptation is a more moderate course.

    • tempterrain

      Reference for this assertion?

    • Latimer Alder

      And the relevance of Russian roulette to the discussion is?

      BTW – we all survived far worse risks than 1 in 6 during the Cold War. For a time in the 50 and 60s there was a very real possibility that civilisation was going to end imminently in a far more spectacular, dramatc and painful manner than anything even the most ardent CAGWists can dream up

      By comparison with several thousand nuclear weapons detonating simultaneously, deaths of hundreds of millions of people, a nuclear winter lasting several years and the immediate and complete breakdown of all the necessities of life (food, power, water), then a gentle and predictable rise in sea level of 3 mm per year (1 inch per decade, 1 foot per century) seems pretty containable and pretty trivial. We just slowly evacuate the wet bits to the vast amounts of dry land still around and put more bricks on the seawalls where we wish to stay. Big deal.Annoying but not impossible.

      Maybe that is why all the climatic shroud-waving fails to gain traction with people over, say, 50. They’ve been there, done that, survived far worse and really can;t quite see what all the panic is about.

      And trivial and spurious comparisons with Russian roulette do not help your cause.

    • Cooling the earth is very, very simple. Shoot a bunch of SO2 into the stratosphere. Or wait for 1 or 2 volcanoes to go off.

      Or sell China more coal.

      Warming the earth seems quit difficult. but considering the coming LIA, it is a skill we should acquire. Or many people will starve.

    • tempterrain | July 12, 2011 at 9:55 pm | Reply
      Judith puts the chances of AGW being higher than 6 deg as about 1 in 6.

      The paelo maximum over the past 600 million years, with CO2 levels 10-20 times higher than present is 22C. About 7.5C higher than present.

      The paleo record suggests that climate is chaotic with an attractors at 11C and 22C. As such, it is quite possible the current temperatures are quite unstable at 14.5C, and wild swings between 11C and 22C are likely, quite independent of anything we might do. Such swings have happened many times before due to natural causes, so it would be unreasonable to assume they are not just as likely today.

    • But the mitigation gun is fully loaded. If you are forced to play, which gun do you pick up?

  5. I provided a couple of interesting links a few threads back on sea level changes in the Roman period. Near Rome, salt making flats retreated several times as sea levels rose. The port the Romans built where they invaded Britain is now 2 miles inland…

  6. There is another famous Mont-Saint-Michel in Normandy. It too is a tidal Island. It has been used a strategic position since Roman times and is now a huge tourist destination due to it’s medieval atmosphere and unique location. The difference between the high tide and low tide high water marks today is about 14 m there. 30 cm would only be a 2% difference. If you look at maps from a couple centuries ago the islands border has not decreased when you compare it with today on google maps. The dutch have had systems in place since Roman times as well. People that live on the coast already know from centuries of experience about the tides and the dangers.

    • For Mont St Michel, there was I believe a huge flooding/tsunami in the years 700 or so AD ; prior to that the Mont was not a tidal island, but a litlle mount as Mont Dol, its current neighbor, which you can see today !

  7. 14,000 years ago, the sea level was about 100 meters less than the current level. Whenever I think of this, and the people who think an inch in 150 years is significant and human-caused, the legend of King Canute comes to mind.

  8. Because of the large magnitude of the change, the scale on the y-axis makes it impossible to resolve the magnitude of changes for the last 8,000 years.

    Classic denier reasoning. “This graph on wikipedia doesn’t prove sea level is stable — so rather than look at the original data used to make the graph, or any of the other peer-reviewed literature, I’m just going to proclaim that the historic sea level is “impossible to resolve.”

    The post goes on in like manner. I’m at a loss for why Dr Curry lends space to this unscientific garbage. Every post Tony writes damages her credibility without advancing our knowledge of the subject one whit.

    • Latimer Alder

      @robert

      You didn’t read very far.

      Firstly JC says nothign about the sea level being ‘stable’ or not, Secondly her very next sentences directly address your point.

      ‘An expansion of this diagram for the past 9000 years enables examination of the sea level rise on the scale of meters. The uncertainty of the estimates at individual locations plus the range across different locations at any particular time can be associated with an uncertainty of several meters, which is larger than the magnitude of projected sea level rise that is under consideration’

      Do try to keep up.

    • tempterrain

      Robert,

      Well at least he hasn’t mentioned Nils Axel-Morner but he’s basically saying the same thing.

      Sea levels have been relative stable for the last few centuries. We’ve seen 20 cm rise in the 20th century. Currently sea level is rising by 3mm/yr according so we may only, if we’re lucky, see a modest rise of about a half metre this century which may not be disastrous were it to stop there.

      However, if the warming is as high as Judith thinks it may be you don’t have to be a climate scientist to know that a lot of Greenland and Antarctic ice is going to slowly melt and the water in the ocean is going to expand. The real problems will be in the centuries to follow.

    • Latimer Alder

      But that is the point. Even under the most alarmist predictions, the ice would only slowly and predictably melt. Slow and predictable we can plan for and have time to do something about – as we have done for centuries. It is rapid and unpredictable (eg Tsunamis, Hurricanes, New Vesuvius) where we get big problems.

    • Latimer Alder

      typo..New Orleans, Vesuvius, not New Vesuvius. sorry

    • Predictable? No – not really. If the polar and Greenland ice sheets start to become unstable there is every possibility they will lurch suddenly into the ocean.

      A simple analogy would be to watch melting snow on a roof. The first sign of it melting would be drips of water in the guttering. It all looks quite predictable but then suddenly the whole lot slides over the edge in one go.

    • Most of the greenland ice sheet sits below sea level because of the weight of the ice. And it is surrounded by mountains.

      No lurching.

    • tempterrain

      Yes there are mountains on the edge of Greenland but not sufficiently continuous to hold a lake if the ice melted.

      Most of it below sea level? No this is not correct.

    • This link has renditions of Greenland with and without ice.” I can’t remember the portion below sea level, but it’s a chunk.

    • John Carpenter

      Interesting graphic, but it doesn’t look to me like there is much space for the ice to ‘squeeze’ through… looks like a bowl with not much chance for slip sliding away. What’s your thought?

    • In the sense of a big chunk falling into the ocean? I don’t think so, but what if Osama grows a brain and pushes it… Wait, he’s dead.

      But that’s not that reassuring. My understanding is Greenland is slated to get more precipitation. The ice sheet is very tall and there is a substantial percentage above the snow line. So it will get a lot of precipitation up there, and it will be well defended from melting; offsetting melting around the base. So I think the snow line is fairly important. Anything sliding below the snow line would be bad because it would be tough get back the defensible platform.

      There a bunch of glaciers squeezing through the mountains right now.

    • John Carpenter

      Aren’t the glaciers squeezing through the mountains a normal event? I agree there will not likely be a chunk sliding off the edge anytime soon by the looks of it.

    • Craig Goodrich

      OK, we started with the Horrible Vision of half the Greenland ice sheet slipping into the ocean. When it was poiinted out that this was impossible because Greenland is sort of dished, we switched to the Horrible Vision “… not sufficiently continuous to hold a lake if the ice melted.”

      But with a persistent rise in ambient temperature of more than 5 deg C, it would take over three thousand years to melt the Greenland ice sheet, so there’s no hurry about replacing all those dreadful power plants which actually produce power with Rube Goldberg monstrosities that don’t.

      I can hardly wait for the next Horrible Vision, Temp.

    • Topographic map of Greenland.

      Blue in middle is below sea level. Red and orangw are mountains. Greenis just above sea level and likely to be sinking …

      http://en.wikipedia.org/wiki/File:Topographic_map_of_Greenland_bedrock.jpg

    • Latimer Alder

      @tempterrain

      Any references or precedents for such an event as you fearfully describe?

      Is the underlying physical geography of either landmass analogous to a steeply sloping roof? Hint: seems unlikely that it is at an angle of 45% or more. And roofs in snowy areas are designed specifically to allow snow to slip off.

      Is freshly fallen snow a good analogue for a compacted ice sheet present for tens of thousands of years or longer? Do glaciers already behave this way. – snapping in the middle rather than eroding around the edges? .

      Or are you just trying to scare yourself?

    • Actually there is a precedent, though whether this supports tempterrains point is highly debatable, but in 6000 BC there was a huge tsunami that devastated the east coast of Britain caused by a landslip in Norway.

      http://en.wikipedia.org/wiki/North_Sea

    • Latimer Alder

      I don;t think that an underwater earthquake is at all a good precedent for half of the Greenland icesheet suddenly falling into the sea.

      And we needn’t look as far back as 6000 BC to understand the devastating power of tsunamis…there have been two (both earthquake driven) in the last decade.

    • Latimer, the 6000 BC tsunami was due to a landslip, not an earthquake as such.

    • Latimer Alder

      @agnostic

      Here’s what the referenced article says:

      ‘a series of underwater landslides, in which a piece of the Norwegian continental shelf slid into the Norwegian Sea’

      If there is a real distinction other than semantics between that and an earthquake, I;m happy to stand corrected.

      But neither of them have anything to do with the propensity of large (many miles in diameter) chunks of the Greenland Ice Sheet suddenly slipping into the oggin and melting.

    • Greenland has a large number of glaciers. The are dumping a very large amount of ice into the ocean. That ice dump is being offset by ice formation above the snow line. Anything that reduces the area of the ice sheet that is above the snow line will reduce the offset.

      As the base shrinks, the two ice domes, 3000 meters and 3200 meters tall, will lose some of their support. Ice could slide below the snow line, and the offset would be reduced.

      Of course, it is possible that temperature is not correlated with melting. In that case I would predict the two domes will take on a pronounced mushroom shape and double in height. These massive ice mushroom heads would stabilize sea level for centuries.

    • JCH –
      Of course, it is possible that temperature is not correlated with melting. In that case I would predict the two domes will take on a pronounced mushroom shape and double in height. These massive ice mushroom heads would stabilize sea level for centuries.

      Not sure where you got that from, but I’ll assume you’re joking.

      Unless you’ve forgotten that “Ice” is not a solid, but a high viscosity fluid. And glaciers flow due to gravity and the pressure of the “upstream” ice.
      Ice mushroom heads are not a supportable concept except in (bad) science fiction.

    • Latimer Alder

      @jch

      ‘As the base shrinks, the two ice domes, 3000 meters and 3200 meters tall, will lose some of their support’

      Is the base shrinking? Where can I read about it?

      If not, then the rest of your remarks are irrelevant.

      If it is these things might be 10K feet tall, but they are also several hundred miles across. Doesn’t sound like a mile or two round the edges will make a huge difference. And even if the ice were uniformly retreating at a foot a day (sufficiently fast for us to know all about it), it would still take 100 years to move just under 7 miles.

      I think you have your sense of proportion and of relative magnitudes somewhat uncalibrated.

    • The ice sheet 660,235 sq mi.

    • Latimer Alder

      To put 660,000 square miles into perspective, that is about the total size of Alaska, twice the size of Texas, about eight times that of the whole UK and over three times the size of France.

      The Greenland ice sheet is big! It isn’t going to melt overnight.

    • The calving fronts of some glaciers are reaching the interior mouth of the mountain valley through which the glaciers are traveling to the sea.

      This graphic illustrates the amount of perimeter decay around the domes.

      The largest chunk of ice to slide into the sea is thought to be 100 square miles: an iceberg. The smallest is whatever, say a square foot. Greenland produces a large number of icebergs.

      Obviously Greenland is a tough place to melt ice. It defends itself well. When it is hot, ice recedes to its most defensible positions, and Greenland is one of them. You confusing me perhaps with TT and his 1/2 chunk all at once. I have already said that is not likely to happen. I think the paleo record indicates it has not happened in the past. The issue is can melting on Greenland accelerate enough for it to make a large enough contribution to other sources of SLR to make the ~1 meter prediction by 2100 plausible.

      I will describe what I think would be necessary as dome calving.

    • ch

      This is a extractr from my article ‘Historic variations in Arctic ice’
      http://wattsupwiththat.com/2009/06/20/historic-variation-in-arctic-ice/

      There seems to have been substantial changes in Greenland glacier flow and coverage as can be seen from these contemporary accounts dating back to the 1860′s. Generally glaciers are thought to have been in general retreat since the 1750′s

      ““156 DR. EAE, 1853-54— ANDERSON, 1855.

      Cape Parry was passed at midnight, and we came across some heavy ice, being the first met with since leaving the straits. On the 30th it was so close as to compel us to haul in shore, affording a great contrast with the state of the ice at the same period two years ago, when the pack was 30 miles from the land.”

      This is an extract from 1868 concerning a British expedition to Greenland, a land which was then an almost unknown quantity but whose coast it will be remembered Scoresby junior had found to be clear of ice in 1820, had subsequently iced up again, then found by Captain Graah in 1828 to be clear again. Apparently conditions had changed once more;

      “We lived for the greater portion of a whole summer at Jakohshavn,
      a little Danish post, 69° 13′ n., close to which is the great Jakohshavn
      ice-fjord, which annually pours an immense quantity of icebergs into
      Disco Bay. In early times this inlet was quite open for boats ; and
      Nunatak (a word meaning a ” land surrounded by ice “) was once an
      Eskimo settlement. There is (or was in 1867 ) an old man (Manyus)
      living at Jakohshavn whose grandfather was born there. The Tessi-
      usak, an inlet of Jakohshavn ice-fjord, could then be entered by
      boats. Now-a-days Jakohshavn ice-fjord is so choked up by bergs
      that it is impossible to go up in boats, and such a thing is never
      thought of. The Tessiusak must be reached by a laborious journey
      over land ; and Nunatak is now only an island surrounded by the in-
      land ice, at a distance — a place where no man lives, or has, in the
      memory of any one now living, reached.

      Both along its shore and that of the main fjord are numerous remains of dwellings long unin-habitable, owing to it being now impossible to gain access to them by sea. The inland ice is now encroaching on the land. At one time it seems to have covered many portions of the country now bare. In a few places glaciers have disappeared. I believe that this has been mainly owing to the inlet having got shoaled by the deposit of glacier-clay through the rivers already described. I have little doubt that — Graah’s dictum to the contrary, notwithstanding — a
      great inlet once stretched across Greenland not far from this place, as represented on the old maps, but that it has also now got choked up with consolidated bergs.

      In former times the natives used to describe pieces of timber drifting out of this inlet, and even tell of people coming across ; and stories yet linger among them of the former occurrence of such proofs of the openness of the inlet.”

      tonyb

    • John Vetterling

      This begs the question of who the real deniers are.

      Those who deny questionable statistical results based on very imprecise measurements or those who deny 100 years of geology and archaeology.

      These is no empirical evidence that sea levels have been stable; there is a mountain of evidence to the contrary. Flaky statistics notwithstanding.

    • Robert,

      This is post-modern posting.

      Crtiique is its own justification.

      No need to parse the contents!

  9. Robert
    Robert

    So are you agreeing or disagreeing that sea levels have been higher than today during the period under study? If you disagree why don’t you post some sensible information to back up your case?

    tonyb

  10. From the above analysis, there appears to be solid evidence that, after taking land changes into account, sea levels in Roman times were rather higher than today, as measured in a variety of locations.

    A few things: first, quoting cherry-picked sources you don’t understand is not “analysis.” “Analysis” is something very different. To do it effectively in the case of sea level, you would first need to study science and become literate in the general methods and tools of science, then study the subject in detail, rather than dumpster diving for quotes.

    Second, if you’re going to cherry-pick sources, make sure they support you:

    “there has been no real change in the average height of sea level over the last c. 2000 years prior to the mid to late 1800s”

    “the change in eustatic sea level since the Roman Period is -0.13±0.09 m”

    “The sea level in Israel has been rising and falling over the past 2,500 years, with a one-meter difference between the highest and lowest levels, most of the time below the present-day level.

    “The results indicate that during the Byzantine period, sea level at Caesarea was higher by about 30 cm than today.

    So much for the ” solid evidence that, after taking land changes into account, sea levels in Roman times were rather higher than today.

    What Tony has proved, again, is that interpreting science is hard if you’re scientifically illiterate. In a classic example of “cargo cult science,” Tony believes he is analyzing, when in fact he is merely quoting and making assertions unsupported by those very quotations. WUWT pioneered this sort of fake “critique,” proving that you could peddle this sort of nonsense to people without a scientific background and a possessing a strong ideological filter, and they wouldn’t know the difference. But anyone with a whit of training in science knows, and Dr Judith Curry certainly should know, which is why I find the “WUWTication” of her blog so baffling.

    • Robert,
      You are far too erudite to be spending your time with such boorish philistines.

    • “dumpster diving for quotes”? What do you have against these sources for the quotes. Which are from the “dumpster”?

    • The IPCC AR4 Chapter 5 (linked provided in the main post) provides a rather pathetic assessment without references. Using that as the “standard”, Tonyb’s essay provides historical evidence and anecdotes supporting that in some locations, there was substantial variations in sea level over this period, including higher sea levels than the current time. This topic needs a good assessment. Tonyb’s essay is an interesting contribution. If you know of other assessments of sea level variations during this period, I would appreciate your references.

      Sorting this issue out is important, particularly in context of the regional/global relationships being developed and used that regress temperature change to sea level change.

    • Dr Curry:
      I know that you are predominately focused upon uncertainties in the IPCC reports, this post seems to indicate that uncertainties are not necessarily the problem. In fact, they would seem to argue that the IPCC is just plain wrong. I am having difficulty in understanding how you can claim the only point of contention is uncertainty in the face of such analysis.
      What I would ask humbly, as a layperson, is where is this analysis wrong? Have I missed an important step in understanding that the IPCC should be considered right, and this wrong?
      Higher sea levels with less CO2 seems to be an important step in determining if the current situation is ‘unprecedented’.

      Roy Weiler

    • Roy you have to look at all the evidence. Not one PDF. And you have to assess that evidence. Not all evidence is credible. Personally, I tend to take a complilation of quotes from a variety of source as evidence of NOTHING. It makes me curious, it does not make me doubt the IPCC, but I’m curious to see the science. Quotes from books and quotes from the IPCC are NOT THE SCIENCE. they are advertisements for the science. The real science happens when an individual gets his or her hands on the data and produces results.

      So, I’m relatively unimpressed by anything the IPCC writes ( its a secondary source) or anything tony writes. hes asecondary source.

    • I agree with you Mr. Mosher, the picture is not clear. My intent is to indicate that there is not enough evidence one way or the other to ‘settle’ this debate. At the least, I think we need 30 more years of data before any conclusions can be ‘argued’, let alone understood. Even then, we will only be scratching the surface.

    • Actually, I view synthesis and assessment as very important elements of climate science and the surrounding debate, owing the complexity of the subject. Tonyb does an excellent job of synthesizing a wide range of information on his target topics.

      As for the IPCC, they assess without doing a thorough synthesis, lots of “expert opinion.”

      Much of what i have been talking about here is trying to develop better strategies for assessment

    • Not all data is credible either. Real science is when you collect the data yourself rather than use someone else’s.

    • Newton recognized that all of us rely on the work of those that have gone before. Collecting the data is part of the process. Analyzing the results another. Experimental design suggests that both should be independent of the other, to minimize the chance of bias.

      Instead “science” these days is focused on the end result. Knowing what results are desired, the researchers work backwards to find data and methods that support the conclusion, then announce in a paper that they have proven what they set out to prove.

      This is not science, it is the Columbus effect. Having set out to find India, then when you find something, it must be India.

    • yes. I was just trying to show that a term like “real science” is not a good choice of words and I realize sometimes doing a complex task yourself is impossible and modularity, layering, hierarchy, and abstraction are required for something complex.

      Chinese proverb
      I hear and I forget. I see and I remember. I do and I understand.

      Mr. Mosher is incorrect about real science. If the data you get is from another source that makes his real science also a 2ndary source.

      Albert Einstein is reported to have said(paraphrased by someone else): No amount of experimentation can ever prove me right; a single experiment can prove me wrong.. If Tony finds something historical that goes against the data collected then he showing a conflict that means one thing or the other is wrong, it they agree then its supported. I expect that lack of understanding from certain people here but not Mosher.

    • Roy – the IPCC is just plain wrong about what?

    • Specifically here we are talking about sea level rise, or did I miss the intent of the post?

    • They have a prediction of up to 59 cm, which subsequent studies indicate is an underestimate, but the IPCC strongly hinted that it was likely an underestimate.

      I’ve never been able to grasp the point of one of Tony B’s articles. Maybe you can help me out.

    • Lets say 600mm over the next 89 years.

      6.7mm year. Has it ever come close since 1980 for even 5 years?

      Sea level rise is steady (tide gauges) for dropping (satellite).

      They are so desperate they are claim the bottom of the ocean is dropping .3mm a year so they have to add .3mm as a bogus fudge factor to try and squeeze a tiny bit of sea level rise out of the datq.

      And they failed.

    • I guess its hard if there were no veterinarian’s setting off fires here.

      I never been able to grasp the point of one of JCH’s replies. Maybe someone can help me out?

    • JCH –
      It’s information. It’s also largely based on archaeology which is, in itself, a science. Which is, in turn, generally ignored by the climate community – to their detriment. If Mann had paid any attention to them, the Hockey Stick would have taken another shape. And I “might” not have become a sceptic. But don’t take that last too seriously. :-)

    • JCH:
      As you pointed out, the true value in the future is very uncertain. What I get from Tony B’s post is that they are severely overestimating the value. He may be wrong and the IPCC may be wrong. Truly it remains to be seen. Looking into the past from a archaeological point of view seems to indicate the IPCC overestimated.
      As I indicated earlier, I am not really sure. On the other hand in my opinion, the archaeological conclusion seems more robust then the paleoclimatological conclusion.
      Please feel free to disagree with that opinion :)

      Roy Weiler

    • I’ve never been able to grasp the point of one of Tony B’s articles. Maybe you can help me out.

      Everything Tony has done, back to his days of ineffectually complaining about the surface temperature record, seems to follow the same pattern:

      * He presents some science he doesn’t understand.
      * He confuses his inability to understand it with it being uncertain and unreliable.
      * He attacks scientists without understanding how they deal with complex data, uncertain measurements, local variability, or other things that make doing science a profession requiring a skill set.

      Basically, the logic of all Tony’s arguments is the logic of a 400-pound man covered in Doritos crumbs who thinks running a mile in four minutes is impossible because he himself can’t do it.

    • Robert –
      Did your mother raise any other foolish children?

      The fact that Tony writes articles that you don’t understand is insufficient reason for you to complain about them. It’s reason only for you to try to understand them. Go back to your mommy and get some help. At least I assume she’ll care enough to help you.

    • Roy, my take on this is that the story surrounding historical sea level rise is very incomplete. My current interest in this is assessing the relationship between temperature change and sea level change, such as used in the Kemp et al. article. I suspect that those relationships are not useful on sub-millenial time scales.

    • Joe Lalonde

      Judith,

      You still miss the point that everyday and every year is different due to planetary physical changes such as slowdown and distant changes to the sun, etc.

    • I suspect your suspicion is suspect.

    • Dr. Curry:
      I agree with you that it is incomplete, but I do not see the way forward that will make it more complete or reduce the error bars on that understanding. Without accurate measurements this is all moot. Even under the IPCC’s worst scenario it seems likely we can give this 30 more years worth of study. At that point we would have more conclusive reporting of real measurements to tell us if our current guesses are even close to correct.
      We are humans, with all the benefits thereof. If this is truly shown to be a problem, REALLY shown to be a problem in 30 years, we will deal with it. My biggest problem unrelated to this post is, we know that temperature extremes cause severe weather. A warmed planet would have lesser extremes, and thereby likely less severe weather. I have not seen anything to indicate otherwise.

      Roy Weiler

    • “My current interest in this is assessing the relationship between temperature change and sea level change, such as used in the Kemp et al. article. I suspect that those relationships are not useful on sub-millenial time scales.”

      Judy – I find that statement puzzling, because it seems to me that temperature/sea level relationships are very informative on almost any scale longer than 5-10 years. Sea level rise reflects two major components – steric changes due temperature change (and to a smaller extent salinity change), and eustatic changes due to melting of land ice.
      The steric changes are quite rapid in response to temperature, particularly in the upper ocean. Ultimate equilibration involving the deep ocean is much slower, but if we are looking at ocean responses, it isn’t necessary to reach equilibrium to correlate sea level rises with temperature rises. Currently, these correlations are further reinforced by ocean heat content measurements, where again, upper ocean changes are informative without the need to await deep ocean equilibrium. (There is a rough analogy here with the concept of transient climate response as a non-equilibrium indicator of climate sensitivity, and also with the type of energy balance studies performed by Forster and Gregory, and discussed in these threads recently.)

      The eustatic component is somewhat trickier because ice can melt from warming in the distant past if the ice is not yet in equilibrium with the distant temperature change. Here, however, we can look at changing rates of ice loss as a function of temperature change – e.g., through the GRACE measurements. The recent paper by Rignot et al on Acceleration of the Greenland and Antarctic Ice Sheet Contribution to Sea Level Rise – GRL 2011 is an example of informative data. More and longer series of measurements will add to the strength of evidence of this type, but I believe it would be an overstatement to suggest that we would need to wait one thousand years before drawing confident conclusions.

    • Fred, my point is that the thermal expansion of water tends to be a minor component in local sea level rise. At the magnitude of centimeters, definition of global sea level rise doesn’t make a lot of sense, given the other factors that determine sea level rise and the time lags involved in glacial melt.

    • David L. Hagen

      Fred & Judith
      Ground water irrigation and subsidance
      Modern pumping up groundwater for irrigation is a major factor affecting sea level that is different from temperature and different from pre-mid 20th century sea level change. That in turn can cause serious local subsidence. See:

      Global depletion of groundwater resources Wada, Y., L. P. H. van Beek, C. M. van Kempen, J. W. T. M. Reckman,
      S. Vasak, and M. F. P. Bierkens (2010), Global depletion of groundwater
      resources, Geophys. Res. Lett., 37, L20402, doi:10.1029/
      2010GL044571.

      We estimate the contribution of groundwater depletion to sea level rise to be 0.8 (±0.1) mm a−1, which is 25 (±3) % of the current rate of sea level rise of 3.1 mm a−1 reported in the last IPPC report [Bindoff et al., 2007] and of the same order of magnitude as the contribution from glaciers and ice caps (without Greenland andAntarctica).

      Global sea-level rise is recognised, but flooding from anthropogenic land subsidence is ignored around northern Manila Bay, Philippines Kelvin S. Rodolfo and Fernando P. Siringan
      . . .”Land subsidence resulting from excessive extraction of groundwater is particularly acute in East Asian countries. . . . excessive groundwater extraction is lowering the land surface by several centimetres to more than a decimetre per year. . . .” Disasters, 2006, 30(1): 118−139

    • The IPCC AR4 Chapter 5 (linked provided in the main post) provides a rather pathetic assessment without references.

      This seems like a rather silly criticism. The quote is from the FAQ section, which is presumably reference-light by design because it’s aimed at an entry-level enquiry. If references are desired look at your chosen subject in the full report.

      The relevant section in Chapter 5 (5.5.2.4) cites [Sivan et al., 2004], [Lambeck et al. 2004], [Donnelly et al. 2004] and [Gehrels et al. 2004]. Chapter 6 also has a small section on paleo-sea level with numerous references. Regarding changes over the past 2,000 years [Peltier, 2002], [Peltier et al., 2002] and [Lambeck, 2002] are most relevant.

      Regarding other assessments, a visual guide to quantified estimates over the past 2,000 years is provided in the recent Kemp et al. 2011 paper (http://www.pnas.org/content/early/2011/06/13/1015619108.full.pdf?with-ds=yes), Figure 3. It features some of the papers cited by Tonyb (Lambeck 2004, Sivan 2004) and several others.

    • We discussed Kemp et al. on this thread
      http://judithcurry.com/2011/06/22/sea-level-hockey-stick/

      Section 5.5.2.4 has only this text that is of relevance:

      Geological observations indicate that during the last 2,000 years (i.e., before the recent rise recorded by tide gauges), sea level change was small, with an average rate of only 0.0 to 0.2 mm yr–1 (see Section 6.4.3). The use of proxy sea level data from archaeological sources is well established in the Mediterranean. Oscillations in sea level from 2,000 to 100 yr before present did not exceed ±0.25 m, based on the Roman-Byzantine-Crusader well data (Sivan et al., 2004). Many Roman and Greek constructions are relatable to the level of the sea. Based on sea level data derived from Roman fish ponds, which are considered to be a particularly reliable source of such information, together with nearby tide gauge records, Lambeck et al. (2004) concluded that the onset of the modern sea level rise occurred between 1850 and 1950. Donnelly et al. (2004) and Gehrels et al. (2004), employing geological data from Connecticut, Maine and Nova Scotia salt-marshes together with nearby tide gauge records, demonstrated that the sea level rise observed during the 20th century was in excess of that averaged over the previous several centuries.

      Very skimpy.

    • “Very skimpy.”

      A generous critical assessment. I’d raise it to “misleading”, given the copious historical literature documenting far alrger excursions in sea level.

    • Certainly it’s skimpy, though it does manage to cover the quantified evidence available – i.e. it’s skimpy because there isn’t a large amount of good evidence available specifically on the last couple of thousand years. My point was that it is misleading to insinuate the IPCC don’t provide references on the topic.

      I’m not really referencing the actual Kemp 2011 study, but rather Figure 3 in the paper which contains graphs showing some of the information discussed by Tonyb + other published evidence all contained in a very useful format.

      Written historical evidence is great as a starting point for a study but without detailed quantification it shouldn’t be regarded in the same light as papers like Lambeck 2004 and Sivan 2004.

    • Yes, tonyb’s article is a blog post that provides an historical perspective, not a refereed journal article. The paucity of information in the IPCC is arguably consistent with the amount of information available, but inconsistent with the high confidence statements made by the IPCC on the subject of sea level.

    • Could you be more specific about these high confidence statements? I can’t see anything about pre-19th Century sea level in the Chapter 5 Executive Summary or the overall Summary for Policymakers.

    • expert opinion tends to over estimate confidence levels because experts conclude they know all there is to know on the subject. the science is settled. of course if that was true then there would be no further need for scientists. it would all be written in books for all to read. then the next generation comes along and to make names for themselves, rewrite the records and over time the past becomes murkier and murkier.

    • Except they were done in only in the east coast of North America. Physical geography is not important?

      Starting points are useful if you want to go somewhere.

    • North America?. Figure 3 in Kemp 2011 shows historical sea level evidence from several locations around the planet (though admittedly mainly in the North Atlantic-Mediterranean region.

    • Judith

      Do you agree that the best avaliable data regarding sea level change is since 1991 and actual sea level rise since that time shows a rate of approximately 25mm per decade?

    • Ooops. IPCC lied.

      IPCC: “Oscillations in sea level from 2,000 to 100 yr before present did not exceed ±0.25 m, based on the Roman-Byzantine-Crusader well data (Sivan et al., 2004)”

      Sivan: “The depths of these coastal water wells establish the position of the ancient water table and therefore the position of sea level for the first century AD up to 1300 AD”

      Sivan: “The results indicate that during the Byzantine period, sea level at Caesarea was higher by about 30 cm than today. The Late Moslem and Crusader data shows greater fluctuations but the data sets are also
      much smaller than for the earlier periods. The consistency of the data indicates that the near-coastal well data from Caesarea provides a reliable indicator of sea-level change, with an accuracy of about 10–15 cm.”

      http://people.rses.anu.edu.au/lambeck_k/pdf/237.pdf

    • Rule #1. ALWAYS assume the IPCC altered or lied about its references.

    • Latimer Alder

      Rule #2. When an alarmist asserts something to be true ALWAYS CHALLENGE THEM for their source. If they can provide one, always read it carefully and see if it actually says what they claim.

      80% of their claims fall at the first hurdle and 50% of the remainder at the second.

      As sceptics we have let them occupy the high ground of truth by simple assertion and by wishful thinking, It’s time to challenge everything and see if it is really built on firm foundations.

    • most of the time below the present-day level does not mean <all of the time.

    • Robert:
      Can you at the least read some of the referenced papers before commenting. Then perhaps, we would have something to discuss.

    • Robert –
      This would be funny if it weren’t so pathetic.

      1) you would first need to study science and become literate in the general methods and tools of science, then study the subject in detail

      All of which you have shown absolutely no indication of ever having done yourself.

      2) You accuse Tony of “cherry-picking” – and then you cherry-pick” the quotes you use while ignoring his answer to your asinine “cherry-picking” nonsense.

      3) Tony believes he is analyzing, when in fact he is merely quoting and making assertions unsupported by those very quotations.

      In fact, Tony is quoting those who have done the research and presenting their findings. This is what the IPCC claims to have done – but has obviously failed to do.

      Earlier, on a different thread, I mentioned waspish incivility . Thank you for demonstrating that lovely character trait for us.

    • “What Tony has proved, again, is that interpreting science is hard if you’re scientifically illiterate.” Robert

      ====

      Well, you’d certainly seem to be qualified to expound on scientific illiteracy. (And general churlishness as well)

      I’m not entirely wild about Tony’s article. It seems to me to pay entirely too little attention to local and regional tectonic forces including, but hardly limited to, glacial isostacy. For example, the proclivity of our ancestors to build towns, forts and harbors on unconsolidated sediments that should probably be expected to consolidate and sink over time.

      But it appears to me to be every bit as well researched as typical peer reviewed “climate science” Regretably, that is not an especially high standard as far as I can see.

  11. Grinstad projects Sea level rise of 1 meter within 100 years on a 3 deg C rise. However, on reviewing historic cooling periods, Easterbrook projects three levels of cooling by 2030/40 depending on solar activity developments.
    Craig Loehle projects similar cooling:
    TREND ANALYSIS OF SATELLITE GLOBAL TEMPERATURE DATA

    ENERGY & ENVIRONMENT VOLUME 20 No. 7 2009
    Nils-Axel Mörner project global cooling by mid century.

    Differing scientific models and climate sensitivity from natural cycles or anthropogenic CO2. The coming decades will reveal which are more accurate.

  12. “The Older Peron transgression was one of a series of gradually diminishing marine transgressions during the middle Holocene. It was followed by the Younger Peron, Abrolhos, and Rottnest transgressions. During the Younger Peron transgression (c. 4000–3400 BCE), sea level peaked at 3 meters above the twentieth-century level; during the Abrolhos (c. 2600–2100 BCE), 1.5 meters; and during the Rottnest (c. 1600–1000 BCE), 1 meter.”

    http://en.wikipedia.org/wiki/Older_Peron

    • Am I alone in objecting to the use of the word “transgression” to refer to flooding? If a fancy word is needed why not an “alluvion” or “inundation” or “incursion” or even “sea level rise”? “Transgression” puts me in mind of “Transgressing the Boundaries: Towards a Transformative Hermeneutics of Quantum Gravity” ie, The Sokal Hoax. Maybe I’m getting old but this kind of overblown terminology seems to me symptomatic of “post normal science”(and yes, I used “terminology” and “symptomatic” with ironical intent).

    • Latimer Alder

      I am just wondering if the Older Person Transgression is the latest PC term for what we used to call a Dirty Old Man?

    • Am I alone in objecting to the use of the word “transgression” to refer to flooding? JT

      =====

      Probably not alone, but in a minority. “Transgression” is a pretty much standard term in geology to refer to positive sea level changes that last for significant periods of time.

      Geologists care because in general marine deposits are easier to analyze, discuss, and correlate over distances than are terrestrial deposits.

  13. Question: What if global warming were to continue for the next 100 years? But, what if–as throughout the 10,000 years of the Holocene–future global warming had nothing to do with humans at all–would it still be a disaster?

    Answer: To put global warming into historical perspective, the Minoan, Roman, and medieval warm periods have one thing in common. The current global temperatures are 5°F cooler than these previous warm periods. Even given the most alarmist predictions based on a `doubling of atmospheric CO2,’ as Walter Starck observed, `The net result…is most likely to be positive.”

  14. Since satellite altimetry measurements starting in 1993, estimates of global mean sea level have achieved far greater coverage than in earlier recent and historical times, although even today, coverage is not yet ideal. Over that interval, the satellite-determined sea level trend has averaged about 3.1 mm/year with periodic ups and downs (correlated to some extent with fluctuations in global temperature and ocean heat content trends). Tide gauge measurements have yielded lower values, and the discrepancies are not yet fully resolved.

    Without full coverage, any attempt to estimate global sea levels from regional data risks large errors in the magnitude and even the direction of a trend. Regional sea level varies according to changes involving the water itself (temperature, salinity, ocean currents, tides, and winds), as well as changes in the adjacent land due to erosion, buildup, and isostatic adjustment. On a percentage basis, changes between glacial and warmer climates involving hundreds of meters are probably less subject to these deviations from the mean than changes measured in centimeters over the course of the past few thousand years.

    The estimate of a potential 1 meter rise by 2100 is itself subject to large uncertainties. It depends both on the trajectory of future temperature trends as well as the degree to which current sea level is not yet in equilibrium with current climate. Probably the principal basis for projecting a possible rise of this magnitude is the expectation that rates will rise substantially above the average of the past few decades on the basis of a continued acceleration in the rate of net ice loss from the Greenland and Antarctic Ice Sheets. The increased ice loss reflects a combination of runoff from warming as well as an increase in the velocity of ice sheet slippage toward the ocean.

    The 1 meter projection is on the high end even with that acceleration as a factor but is probably not outside the range of plausibility. It might be more informative to estimate a range and confidence intervals for projected rises rather than a single value. My expectation is that 1 meter would fall close to, if not above the high end of a 90% confidence interval. A rise of only 10 centimeters or less would be equally likely to fall below the lower bound, but I haven’t seen this estimated and would be interested to know whether it has been attempted since the earlier AR4 estimates.

    • Fred

      I appears you are making inaccurate claims once again. Since 1991 the actual rise in sea level has been at a rate of 25 mm per decade or one tenth of what you write.

      http://wattsupwiththat.com/2011/07/03/the-ups-and-downs-of-sea-level/

    • Rob – How is 25 mm/decade one tenth of 31 mm/decade?

    • Rob Starkey

      Fred

      I agree I was wrong in that regard, but got confused because of your comment about 1 meter rise by 2100, which the data does not support as happening

    • Fred, sea level is dropping (and no higher than it was in 2004) according to at least one satellite.

      http://stevengoddard.wordpress.com/2011/07/12/gavin-asks-is-sea-level-rise-accelerating/

      US Tide Guages and many in the world show no acceleration in sea level rise — and maybe a small deceleration.

      “Without sea-level acceleration, the 20th-century sea-level trend of 1.7 mm/y would produce a rise of only approximately
      0.15 m from 2010 to 2100; therefore, sea-level acceleration is a critical component of projected sea-level rise. To determine
      this acceleration, we analyze monthly-averaged records for 57 U.S. tide gauges in the Permanent Service for Mean Sea
      Level (PSMSL) data base that have lengths of 60–156 years. Least-squares quadratic analysis of each of the 57 records
      are performed to quantify accelerations, and 25 gauge records having data spanning from 1930 to 2010 are analyzed. In
      both cases we obtain small average sea-level decelerations. To compare these results with worldwide data, we extend the
      analysis of Douglas (1992) by an additional 25 years and analyze revised data of Church and White (2006) from 1930 to
      2007 and also obtain small sea-level decelerations similar to those we obtain from U.S. gauge records.”

      http://www.jcronline.org/doi/pdf/10.2112/JCOASTRES-D-10-00157.1

    • Bruce – If you visit the satellite sea level link I cited in my above comment, you’ll find that the site Steve Goddard refers to estimates the trend at a rise of 3.22 mm/year – similar to the other satellite-derived trends. What Goddard did was to truncate a small portion of the data in a way that fails to reveal that short term ups and downs are a constant feature of these trends even as the overall average is that of a rise. I expect that if you want to pursue this in more detail, you can contact the AVISO group to learn how they calculate trend rates.

      The U.S. tide gauge estimates are a poor means of judging global mean sea level for a variety of reasons, some of them discussed at the same website I linked to earlier. However, tide gauge and altimetry trends still need to be better reconciled, particularly since altimetry will be the main source of global and regional coverage in the future.

    • It’s also important to distinguish between a trend that may or may not be “decelerating” and one than is declining. Deceleration refers to a rate of rise that is lower than previously, but still upward, just as acceleration refers to an increase in the rate of rise. That is also a subject of some controversy because it depends on what year is chosen as the starting point.

    • Sea level has been rising for 10,000 years.

      If there is a deceleration in sea level rise it means CO2 is causing the earth to cool.

    • 1) 7 years is no a small portion.

      2) Even with the GIA fudge factor added in (which spuriously adds a lot), here are the 3rd measurement (there are only 3 in 2011) for the last 9 years.

      6.1mm over 8 years = 1.3mm per year

      2011.0673 30.809
      2010.0628 31.337
      2009.0583 39.251
      2008.0810 34.438
      2007.0765 31.094
      2006.0720 25.011
      2005.0675 23.163
      2004.0630 27.604
      2003.0586 24.719

    • Bruce- I think the numbers you listed show why you can’t compute a trend simply by arbitrarily selecting a starting point and subtracting it from the most recent data point. You subtracted 2003 from 2011, but a very different “trend” emerges if you subtract 2005 from 2009. Neither is legitimate. At this point, the trend values of about 3.1 mm/year are a reasonable description of what the multiple satellites have found over an interval of about 18 years. The critical question relates to how this will change over coming decades.

      Incidentally, the glacial isostatic adjustment is not a “fudge factor”, but rather a means of calculating changes in the height of the water column in the face of a sinking sea floor. How this affects ocean/land relationships can’t be summarized in a single formula because it depends on geography. In some cases, the adjustment would have little effect on calculating the relationship of sea level to coastal land. In other regions, it might mean that a rise of several centimeters in ocean height above sea floor will leave the coast at the same height above the adjacent sea as it was a few thousand years ago, despite the extra water.

    • The last 7 years 6.1mm and then subract the bogus .3mm per year = 2.1mm resulting in 4mm over 7 years.

      Less than .6mm per year.

    • John Q. Lurker

      It sounds like you don’t know what a “trend” is. A trend takes all values into account, not just the first and the last. The least-squares linear trend for your 9 figures is 10 mm/8 years, or 1.25 mm/year, not 1.3 mm/year. 1.3 is close enough to make me wonder if actually you do know, but I think you used 8 years/6.1 mm=1.3 years/mm (which is the inverse of what you intended). I think so because you get your 0.6 mm/year again by only taking the first and last values into account.

      If I’m right that you don’t understand “trend,” what I’ve just written won’t help you. You’ll have to look into the matter yourself. But the general idea is to fit the data to a mathematical function (e.g., linear, exponential, others) by assuming that the deviations from the function are errors, and then choosing the parameters that minimize the error.

    • I understand what trend means. But the IPCC predicted a 590mm rise by 2100. 5.9mm per year is needed to get to 590mm. (More if you start in 2007 when AR4 came out.

      If sea level goes down, then the 590mm rise has to start from the new lower level. The new lower level IS IMPORTANT in FALSIFYING the IPCC scare prediction.

      If you look at the data I supplied, even with the bogus .3mm adjustment, there has never been a 5,9mm rise.

      There was one 4.8mm … the rest were drops or very small rises.

    • “Incidentally, the glacial isostatic adjustment is not a “fudge factor”, but rather a means of calculating changes in the height of the water column in the face of a sinking sea floor.” Fred Moolten

      =====

      That’s correct. The fudge that is being referred to is the decision by the folks at CU to apply a blanket GIA adjustment of -0.3mm to satellite data. The adjustment isn’t entirely without justification, but that doesn’t mean that it is appropriate.

      GIA adjustment is necessary and appropriate for tidal gauge measurements that are made relative to a local reference that is rising or sinking along with the coastline. GIA adjustments probably should not be made for satellite measurements that are relative to the geoid. What the CU “GIA adjustment” seems to do is convert satellite derived sea level that is conceptually consistent with tidal gauge measurements to a sort of sea volume index that is not consistent with tidal gauge sea level.

      I don’t expect you to either understand my miserable explanation or to take my word for it. But put it on your list of things to look into someday. I expect that when you have the time and inclination to analyze the situation, you’ll come to the conclusion that GIA is needed for tidal gauge data, but should not be applied to satellite data. And if it is applied because sea volume is important to you, the resulting value should not be called “sea level”.

    • Even within the terms given the quoted trend is wrong. To properly calculate the trend load the text file into a spreadsheet, create a scatter plot from the desired time series and get a linear regression. The real trend from the CU data from 2003 to (beginning of) 2011 is 2.2mm/yr.

      While your selection process may have been objective it produced a bias. To give you an idea of what I’m saying the annual means for 2003 and 2004 are actually 19.75 and 22.7 respectively.

    • There is some evidence satellite sea level is an artifact of bad calibrations.

      They are so desperate they came up with GIA to explain why the sea is farther away from the satellite recently.

    • World tide gauges show a light deceleration as well.

      And by deceleration they mean that CO2 is causing less sea level rise each year that before CO2.

      Which implies to me that the world is cooling and only UHI or something similar is causing temperatures to appear to have risen in the 1990s.

    • simon abingdon

      Just for perspective 3.22mm/year = 3.22 metres/millenium.

    • It’s truncated because it’s only from one satellite.

      There’s a couple of other problems:

      - It doesn’t include the 0.3mm/yr GIA correction, which is curious because ‘Include GIA’ is the default setting.
      - The reported trend is wrong, though that appears to be an error in the AVISO software. I think this is because they have two time series points for each year but don’t correct for that when outputting the slope.

      The real trend over this period is about ~2mm/yr.

    • GIA = desperate cry for help. HELP!!! Sea level is dropping!

    • Correction: the reported trend (0.7mm/yr) is not a result of software error as I thought. It’s a result of picking a particular satellite (Envisat) with a trend that doesn’t match any others.

      The AVISO multi-satellite reference data produces a 2.7mm/yr trend over the 2004-present time period.

    • Aviso has had many satellites producing data, but only 3 are functioning now. Envisat is one of the three.

      All are plunging.

      http://stevengoddard.wordpress.com/2011/06/19/hiding-the-decline-in-sea-level/

    • The graph from 1993 to present has quite a linear characteristic over 18 or so years. The recent data is even a down tick. 2100 is a long way off I can’t say there is anything that should alarm us.

    • Basically, the trend is increasing but no one has any idea why. AGWers will say its the ice caps but there isn.t that much water in them, so it’s probably the position of our orbit and the moons, and throw in some plate tectonic movement and there ya go!

    • Fred,

      What is this statement based on?

      Tide gauge measurements have yielded lower values, and the discrepancies are not yet fully resolved.

      As far as I’m aware this isn’t the case. Indeed there was a paper out a couple of years ago titled: ‘Is coastal mean sea level rising faster than the global mean?’ That was aimed mainly at Holgate 2004′s findings of a 4mm/yr SLR in tide gauges over 1993-2002, higher than satellite altimetry. Their answer was no, both have worked out to the same trend over a longer period.

    • Paul – I’m unfamiliar with the paper you mention. My evidence suggesting that tide gauge measurements have yielded values lower on average than the altimetry values comes from data such as Tide Gauge Sea Level. Unfortunately, most of the estimates are not synchronous so exact comparison is not possible. The Church and White tide gauge measurements closely approximated the 3.1 of so altimetry rise rates, but most other measurements have been lower – and typically involve earlier intervals. Do you have a reference for the 4 mm/year tide gauge estimate?

    • Fred, the ~4mm/yr comes from Holgate 2004 (the scientist quoted in this thread by Tonyb). Unfortunately I can’t find the paper online anywhere. The results are featured in IPCC AR4 though and a graph is shown in Holgate 2007 (http://www.joelschwartz.com/pdfs/Holgate.pdf).

      The paper comparing coastal tide gauges and open ocean data is here: ftp://soest.hawaii.edu/coastal/Climate%20Articles/Cazenave%20coastal%20sea%20level%20and%20altimetry%202009.pdf

      Another tide gauge record Jevrejeva et al. 2008 (http://www.psmsl.org/products/reconstructions/jevrejevaetal2008.php) also features a high SLR over the 90s at ~3.4mm/yr with the data ending in 2001. Church & White 2011 and the Prandi 2009 paper I linked are the only papers I can find that produce reliable tide gauge-based estimates beyond 2002 and they still show good agreement with satellite data where they coexist in time.

    • Thanks – The paper by Prandi et al is informative because of the 1993-2007 interval evaluated, and the good concurrence between tide gauge and altimetry data during that interval (although with much greater variability in the tide gauge record). Church and White show slightly smaller tide gauge rises, but the disparity isn’t great.

    • No problem. The interesting thing for me in that paper was the plot of coastal data from satellite altimetry, which appears to be a reasonable match to the variability in tide gauges. It suggests that most of the strong variability seen in tide gauge records is actually physical rather than an artifact of measurement.

    • CO2 Science on Holgate 2007

      “As a result of this finding, Holgate presented the nine-station-derived wavering black line in the figure below as a reasonable representation of the 1904-2003 mean global sea level history of the world, and based on that history calculated that the mean rate of global sea level rise was “larger in the early part of the last century (2.03 ± 0.35 mm/yr 1904-1953), in comparison with the latter part (1.45 ± 0.34 mm/yr 1954-2003).””

      Boom.

    • I’m well aware of Holgate 2007 findings (i’ve privided a link to the actual paper). As stated in the passage it uses only 9 tide gauge stations to build a record, compared to 177 in Holgate 2004. Where they overlap the 2004 paper should really be the preferred reference.

      The point of Holgate 2007 was that an acceleration over the 20th Century is not evident from available tide gauge data.

    • I’ll add some emphasis to ‘where they coexist in time.’ Church & White 2011 shows a high SLR across the satellite period but your link also shows their 20th Century average is in good agreement with all the other records.

      I should note that other periods over the last 100 years have featured ~3mm/yr SLR even though averaging to about 1.7mm/yr.

    • David L. Hagen

      Sea level expert Nils-Axel Mörner weighs in with a 22 pg review:
      THE GREAT SEA-LEVEL HUMBUG: THERE IS NO ALARMING SEA LEVEL RISE! SPPI May 26, 2011

      , the real observational facts demonstrate that sea level
      has remained virtually stable for the last 40-50 years. . . .
      The spectrum of proposed rates of present-day sea level changes
      ranges from 0.0 mm/year, according to observational facts from a
      number of key sites all over the world, to 3.2 mm/year, according to
      calibrated satellite altimetry. . . .
      If the uplifting and subsiding sites (green areas) are excluded, we are left with a number of sites (red area) where the rise in sea level ranges between 0.0 and 2.0 mm/year . . .
      Values in the order of 1 mm/year represent minor centennial rises (and falls). This agrees with estimates of a possible sea level rise by year 2100 of 5 ±15 cm (Mörner 2004) and 10 ±10 cm (INQUA 2000), but differs significantly from the value proposed by IPCC of 37 ±19 cm (IPCC 2007). . . .
      Recently retired as director of the Paleogeophysics and Geodynamics Department at Stockholm University, Mörner is past president (1999-2003) of the INQUA Commission on Sea Level Changes and Coastal Evolution, and leader of the Maldives Sea Level Project.

  15. Of rested case, lads and gentiles, I dutifully present…drum roll…the Nobel life of Randy Man Minus Wife:
    Tobacco farmer Gore’s six-fireplace palace: http://directorblue.blogspot.com/2010/05/exclusive-estimate-carbon-footprint-of.html
    And “BIO-solar” jet ski launch (and bachelor) pad yacht: http://www.youtube.com/watch?v=19PAXEzx1Uo

    Oh, this post is ’bout leveled seas.

    I see.

    Well then:

    http://i.min.us/idFxzI.jpg

    • C’mon, Nik.

      Al is jes’ a nuther good ol’ Tennessee boy that done real good by doin’ good.

      Never mind that he’s got a carbon footprint the size of Murfreesboro, Cookville and McMinnville combined (plus everything in between).

  16. TonyB

    Thanks for an interesting “Part 1″.

    It appears clear that the simplistic idea of constant sea level prior to the Industrial Revolution is ill-founded..

    It also appears that claims of a recent “acceleration” in the rate of sea level rise may simply be part of a longer-term oscillation.

    On a shorter-term basis, the decadal rate of sea level rise has bounced all over the place since the modern tide gauge record started (as studies by Dr. Holgate have shown).

    With this in mind, I would not place much confidence in any multi-decadal forecasts of sea level rise, let alone scare mongering predictions of inundations of several meters in the next “10 or 100 years”.

    Looking forward to “Part 2″.

    Max

  17. Judith,

    Don’t you know anyone who has some sort of scientific qualification to lecture us on the subject of sea levels?

    Someone who may know what they are actually talking about?

    • The problem with that request is that the AGW movement has lowered the IQ levels of its believers. That leaves you unable to hear evidence counter to your beliefs.

    • hunter –
      That leaves you unable to hear evidence counter to your beliefs.

      Would this qualify as “agnotic”?

    • I’m quite happy to hear any qualified evidence to counter my beliefs. Not just on AGW but everything else scientific too. For instance, currently I do believe AIDs is caused by the HIV virus. I could be wrong , but if my opinion is going to be changed its not going to by reading this sort of stuff on the net:

      http://www.jesus-is-savior.com/Evils%20in%20Government/AIDS%20and%20Population%20Elimination/hiv_not_the_cause_of_aids.htm

      anymore than reading similiar unqualified rubbish is going to change my opinion on the threat of AGW.

    • tt-
      My best friend is a liberal/progressive hemophiliac sceptic with HIV. No AIDS. AIDS may be caused by HIV – but the link is no more absolute than that between smoking and lung cancer. IOW, some get it and some don’t. If you figure out how to determine who will and who won’t, let us all know. We’d all appreciate the information.

    • andrew adams

      Not everyone who has HIV gets AIDS. But has there ever been a recorded case of someone who has AIDS but not HIV?

    • aa –
      No clue. Never had reason to delve that deeply into the subject. But it IS a good question. Let me know if you find the answer.

    • Are you next going to talk about evolution and tobacco?

    • tempterrain

      Sure, some people just don’t seem to get flu, even though they are in close contact with people who have it. So they may carry the virus and just don’t go down with the disease. But we digress.

      The point is that Tony B is a crank who thinks the Antarctic ice core records are all wrong. He thinks that CO2 levels were higher in the 19th century than they are now. Of course, that doesn’t necessarily make him wrong on the sea level issue but it does raise cause for concern about his scientific credibility.

      I doubt if Judith would be allowed to have unqualified guys lecture her students. She really ought to apply the same criteria when inviting guest authors on her blog.

    • Latimer Alder

      Where in his essay above does TB discuss Antarctic ice core records? I see no mention of such.

      PS Newton was an alchemist first and physicist only second. Do you discount his work on mechanics because he never found the Philosopher’s Stone? And Arrhenius – founder of greenhouse theory – was a believer in Eugenics. Does his earlier work on electrochemistry fail because of his later views? BTW he won the Nobel Prize for Chemistry in 1903.

      Perhaps you are so used to providing ad hom attacks on people that your sense of perspective has been affected.

    • Joe Lalonde

      Newton’s work fails the history of the planet test of going back billions of years. Totally different pressures, gravity, densities, sun distance, etc.

    • Latimer Alder

      And if and when you actually explain where you believe his work is wrong, we will all read it with great attention. But while all you do is make veiled hints,about your own theories, you are destined to be rightly ignored.

      Put up or shut up is the vulgar way of expressing it.

    • Joe,
      My bet is you missed a call from your pharmacy about a refill.

    • tempterrain

      Are you comparing Tony Brown to Newton? I hope not! Newton lived in an age when Science was just starting out. There was no published work to explain to Newton just how difficult it is to change one element into another.

      TonyB does his best to keep his more extreme scientific views away from Judith, but I think you’ll find that what I’m saying is correct. If I hadn’t been he would have on to it himself by now.

    • tt –
      Tony’s views are his own – and one of your business. He has his reasons, which I have no doubt, are far better than yours which are apparently based only on fear, arrogance and intolerance. If his views don’t match yours, then you REALLY need to take a long look at yours to make sure that they’re even a vague shadow of reality. So far I’ve seen no indication that you’re capable of that kind of introspection. Which means that your judgment wrt science or anything related to science is more than suspect. This comment of yours reminds of nothing so much as a 5 year-old tattling on an older brother. Or perhaps a nosy neighborhood gossip trying to make trouble for others.. Either is truly unbecoming in someone who claims any knowledge or grounding in science.

      Grow up, be a mensch – and stop whining about others.

    • If I’m doing any “whining”, as you put it, its more directed towards Judith than it is towards Tony Brown or any of the other dodgy authors she’s invited to start off new postings on her blog.

      As Robert puts it “Every post Tony writes damages her credibility without advancing our knowledge of the subject one whit.”

      Are Tony’s views just his own and none of my business? That would perhaps be a valid argument if he weren’t so keen to enlighten the world with what they were. Ideally they should be just his own and none of anyone else’s business either!

    • Latimer Alder

      @martin

      Suggest that you limit yourself to remarks roughly about the subject under discussion, rather than bloviating about your interpretation of views that you think others contributors might express if we were discussing something completely different.

      You do yourself no favours with your constant whingeing about others while making few positive contributions yourself. Grow up or butt out.

      Otherwise you;ll be joining Joe and a few others on people’s scroll-by lists.

    • tempterrain

      Bloviating eh? My spell checker has put a wiggly red line under that word! But Ok I’ve checked and it is an Americanism mean to speak overly long and pompously on an issue.

      I do usually try to use plain English. So how about this?

      Yes, by and large, the AGW denier community is made up of right wing bigots, religious creationists, conspiracy theorists and cranks. It’s well worth sounding out opinions on non AGW issues.

      Is that concise enough for you?

    • tt –
      Yes, by and large, the AGW denier community is made up of right wing bigots, religious creationists, conspiracy theorists and cranks.

      That’s pretty much inaccurate except in your own little fantasy world. But conversely the believer community, as evidenced on this blog and others, is largely made up of left wing bigots, the anti-religious intolerant left, left wing conspiracy theorists and the ignorant. There are a few who are intelligent enough lace their own shoelaces, which is an admission that you’re apparently not intelligent enough to make about those who consistently eat your lunch in discourse.

      If I had the time right now it would be interesting, but probably unproductive to deconstruct your comment word by word. Another time.

    • Latimer Alder

      @martin

      Don;t forget to send me a postcard and bring me back a stick of rock from your excursion to Planet Barmy.

    • Those are other issues on other threads. If you find a mistake in Tony’s post then maybe you will have a useful comment for once.

    • Where is Ictus?

    • Why don’t you just tell us?

    • I don’t know.

    • tt,
      No, you are not happy to hear counter evidence.
      You typically come back with ridiculous arguments by authority or start talking about how we skeptics will all be dead when our wickedness is made plain.
      Face it: You are trapped in a pseudo-religious thought pattern and filter out anything that gets in its way.

    • I looked into HIV/AIDS controversy 10 years ago. The more I read about it, the more sceptical I became. I am still a HIV/AIDS sceptic, but haven’t looked into it lately.

    • If somebody wants to learn about the controversy, maybe the best way to get started is the movie House of Numbers.
      http://www.houseofnumbers.com/site/

      Also, there was an article in Harper’s:
      http://www.harpers.org/archive/2006/03/0080961

      Then, there was a famous BMJ debate.

      It’s very controversial, more than AGW.

    • Thanks for letting me learn about this controversy, which was thoroughly debunked over the time of 20 years and which may now be thought to be in one line with the controversies about a flat-earth and creationism.

    • Edim,
      If it is so important to you, then please post about it at sites dedicated to discussing it.
      It is completely inappropriate to talk about your concerns regarding a health issue like that at a site like this.

    • You’re right Hunter. Sorry everyone.

    • tempterrain

      “Completely inappropriate”? Why? I’m not sure I agree.
      Of course, it is a logical fallacy to say that because a person may have some crazy ideas about subject X, then therefore any ideas they may have on subject Y must be crazy too. But it’s enough to make you wonder isn’t it? Its certainly worth knowing.

    • This is a site about climate, but also about uncertainty, ignorance, and doubt.

      HIV “skepticism” and evolution “skepticism” are quite as relevant to the problems of uncertainty and ignorance as is climate change “skepticism.”

      Those that wish to exalt “skepticism” and condemn consensus have to deal with the problem of irrational beliefs that do not contribute to knowledge and are not subject to correction with evidence. It may be easier for climate change “skeptics” to examine this problem in discourse if we relate it to examples from outside the climate change debate.

    • tempterrain

      Conspiracies about 911 , UFOs at Roswell, New World order etc? Do you believe in any them? And you’re sceptical of the link between AIDs and HIV , global warming and CO2 emissions?

    • Not interested in conspiracies at all.

      Only in progress of science, dogma in science, scientific paradigms, groupthink, herd mentality…

      I agree with Feynman that science is the belief in the ignorance of experts. I used to believe in knowledge of experts, like most people do.

      Now, my belief in the ignorance of experts is robust. It’s getting stronger the more I look into their knowledge.

    • One example of what I am interested in:

      “When Sky and Telescope devotes almost five full pages to a new book, you may be sure that something important has happened. The book is H. Arp’s Quasars, Redshifts, and Controversies.

      We know that we have perhaps overplayed the shakiness of the redshiftdistance hypothesis and the fizzling of the Big Bang, but our whole cosmological outlook is at stake. Now, rather than review again the scientific pros and cons (you can read Arp’s book for that), we will be content here with a few comments about how science has failed to work well in Arp’s case.

      G. Burbidge, who reviews the book, recalls how the politics of science works in the following quotation:

      “…the important factors for a successful career are your sponsors (where and with whom did you get your Ph.D); field of research (popular or unpopular); and diplomatic skills (always speak quietly with great conviction, and, when in doubt, agree with the wisest person present, who by definition must come from one of the the very few [recognized] institutions). Look upon new ideas with great disapproval and never discover a phenomenon for which no explanation exists, and certainly not one for which an explanation within the framework of known physics does not appear to be possible.”
      Arp played this game for 29 years at the Mount Wilson and Palomar Observatories. He compiled the marvelous Atlas of Peculiar Galaxies, and was once rated among the top 20 astronomers. But he kept finding Anomalies — apparently-associated celestial objects with different redshifts. More and more he began to believe and (perhaps recklessly) assert that some redshifts are not cosmological; that is, a measure of recessional velocity and distance. Soon, his rating dropped from the “upper 20″ to “under 200″. The final (and disgraceful) blow came about four years ago, when he received an unsigned letter stating that his work was without value and that he could have no more telescope time! Arp now lives in West Germany. (Burbidge, Geoffrey; “Quasars, Redshifts, and Controversies,” Sky and Telescope, 75:38, 1988.)

      Comment. More political details may be found in Arp’s book. Is Arp a martyrin-the-making? You bet he is! Burbidge, an admitted Arp sympathizer, suggests that the “Arp Effect” is only the tip of the iceberg. In closing his review, he invokes the ghost of Alfred Wegener, who had the temerity to suggest that continents could drift.”
      http://www.science-frontiers.com/sf056/sf056a02.htm

      There are thousends of such iceberg tips. I am interested in that. I think the issue is very important for science, probably the most important.

    • tempterrain

      I’ve heard Feynmann quoted, or misquoted?, in a similar fashion but it would be a mistake to think that Feymann felt that the experts were generally wrong.

      Feymann wrote his famous “Feymann’s Lectures on Physics” in the 1960′s – I’ve still got them on my bookshelves – and in them he includes the work of all the famous Physicists, Newton, Plank, Bohr, Einstein, Heisenburg etc

      Never once does he say these famous names were other than experts, and deserving our full respect, and never once does he say they were ignorant – at least not in the way you imply.

    • Tt, Feynman didn’t mean experts were ignorant about everything, he meant they were ignorant about somethings.

      Check out his speech called “The Unscientific Age”
      http://www.i2o.uva.nl/BGB/KIN/Feynman-unscientific.doc

    • Tempterrain

      As usual you are full of nothing but ad homs and red herrings. As someone apparently more observant than you observed, I take studies and synthesise them in much the same way as the IPCC (but on a smaller and cheaper scale obviously)

      If you disagree with my paper then you are disagreeing with scores of reports from numerous scientists and other qualified experts. Thats fine, but then it is incumbent on you to respond to the challenge I made earlier and do the IPCC’s work for them by supplying good solid evidence that sea levels were, in effect, static for 1800 years or more from AD0 to 1800. This will be useful for Part 2 of the study.

      if you can’t supply these then why not just cut out the conspiracies, red herrings and the affront to your extremely narrow view that climate science uniquely knows all the answers, and just read and learn from those who are willing to engage? Did you read those excellent studies that Daid Hagen posted? Have you actually read the scores of reports in my full paper?

      Perhaps you can take up some of your grumbles with Professor Brian Fagan and get his books removed?

      tonyb

    • Latimer Alder

      Tony …and other folks

      Looks like Josh the Cartoonist has been thinking along the same lines.

      Check out

      http://bishophill.squarespace.com/blog/2011/7/14/beware-trolls-bearing-gifts-josh-112.html

    • tempterrain

      Forget sidetracks about HIV virus/AIDS from the “jesus-is-savior site” and stay on topic.

      The first part of Tony’s study has to do with sea level changes in the historical and recent geological past.

      TonyB references his material well. Check out these references.

      Then, for more recent sea level trends, check out reports by sea level experts, such as Holgate 2007.

      Then learn to stay on topic rather that bloviating about totally unrelated subjects.

      Max

    • “TonyB references his material well. Check out these references.”

      The references say exactly the opposite of what he claims they say.

      Your ideological convictions appear to have comprised your ability to examine evidence honestly.

    • Robert –
      The references say exactly the opposite of what he claims they say.

      Only to those who don’t understand them. Learn to read. It’s not that hard.

    • Latimer Alder

      @Robert

      OK

      Please provide at least three examples of where his references

      ‘show the exact opposite of what he claims they say’

      I am a layman in these matters so you will have to explain each one on detail for me.

      1. The actual reference
      2. Tonyb’s interpretation of that reference
      3. Your discussion of why the reference in fact shows the exact opposite,

      I have no dog in this fight – apart from a passing knowledge of some of the English coastline he refers to from long ago holidays in Cornwall -, so persuade me and the rest here that you are right and that tonyb is wrong.

      Deal?

    • Where is Ictus? What could it look like now?

    • As I suggested in the last thread, “gnotic” might be more appropriate.

    • TT, it’s not a lecture. Why don’t you start by explaining what you don’t like about the information? You’re not being forced to read this post (I hope)

    • A commenter here who seems to have an excellent grasp on SLR science is Paul S. I think he jumped in shortly after TT did.

    • Well, I’m blushing, but really I’m not all that knowledgeable on the subject. I actually think the original post is quite a nice write-up with the caveat that presented evidence should be considered with appropriate weighting according to the precision of the study, rather than assumed to all have equal relevance.

      As Dr. Holgate notes at the top one of the most convincing and well-constrained sources of evidence comes from Roman fish tanks studied in Lambeck 2004, which concludes in the abstract:

      When corrected for [glacial isostatic adjustment], using geologically constrained model predictions, the change in eustatic sea level since the Roman Period is -0.13±0.09 m. A comparison with tide-gauge records from nearby locations and with geologically constrained model predictions of the glacio-isostatic contributions establishes that the onset of modern sea-level rise occurred in recent time at ~100±53 years before present

      I think the line about the Roman period is badly written. From reading more of the paper it appears that it is the Roman period which is -0.13m below present, not the other way around.

      Tonyb’s stated conclusion sea levels in Roman times were rather higher than today, as measured in a variety of locations. was a little confusing since it doesn’t really gel with the best evidence presented though this may be because his definition of Roman times is somewhat extended to include 500AD.

    • Paul –
      From reading more of the paper it appears that it is the Roman period which is -0.13m below present, not the other way around.

      For what it’s worth, that’s the way I read it.

      his definition of Roman times is somewhat extended to include 500AD.

      The Western Roman Empire ended in 476 AD. Which is close enough, given the other historical uncertainties. That, of course, does not mean that the infrastructure (fish tanks in this case) crumbled to dust on that precise date. It’s only (?) a political divide.

      FWIW, the Eastern (Byzantine) Roman Empire endured until 1453 AD.

    • Tonyb’s stated conclusion sea levels in Roman times were rather higher than today, as measured in a variety of locations. was a little confusing

      Paul, you’re so kind. Props to you for that.

    • you mean like the IPCC, who have very little to say on the subject?

    • The IPCC claims are misleading.

  18. For those interested in 20th century sea rise here is a paper that claims it really hasn’t varied for the last 80 years:

    http://www.sciencemag.org/content/320/5873/212.abstract

    • steven –
      You might want to take another look at that paper. I don’t think it shows what you think it does.

      I’ll be interested in the Chief’s take on it, though.

    • I meant the rate of rise hasn’t really varied. I personally have problems with it since it doesn’t seem to take into account ground water but thought it was interesting anyway.

    • Sorry – I misunderstood your intent.

      Yeah – groundwater is a consideration. Especially at the rate it’s disappearing (from the ground) in the Western US.

    • Yup – I just picked the Western US because I have a lot of direct experience there. Didn’t mean to slight anyone.

    • You are also not considering sediment run-off into the oceans from major rivers and dust blowing from deserts. The Amazon alone sends sediment hundreds of miles out into the oceans. This again serves to displace water and increase sea levels.

    • Sediments and deforestation both increase SLR. Another potential source of error that I find interesting is possible changes in the earth’s circumference. I find it odd that a globe with both liquid and solid matter constantly changing between states would be assumed to remain perfectly stable in size.

    • “∼10,800 cubic kilometers of water has been impounded on land to date”

      Yet one acquifer has taken water that would have sate there and put it in the climate system: “As of 2005, the total depletion since pre-development amounted to 253 million acre-feet (312 cubic km)”

      http://en.wikipedia.org/wiki/Ogallala_Aquifer

      We may be storing water in dams but we are pulling it out of unreplenishable acquifers as well.

      http://www.eoearth.org/article/Aquifer_depletion

    • Steven,

      I think what you’ve written is slightly ambiguous. The paper is saying sea level rise has been offset by the building of water impoundments (reservoirs, dams etc) and would have otherwise been higher than measured.

    • Yes, that is exactly what it is saying. On the other hand they are also saying the rate hasn’t varied. I find the lack of a varying rate more interesting then an extra half mm or so as an average sea level rise. As I stated above there is the problem that they didn’t include groundwater usage. If you take what they have done and add in the effects of the added water from groundwater mining you would end up with a steadily decreasing rate of SLR since ground water mining has been increasing steadily over the century.

    • A paper about to come out includes Wada in the model.

    • Happen to know the name? I’d like to keep an eye open for it. Thanks!

    • Lol, if I thought you would like this, I would have said so in the first place, but oh well. Give me second to duck:

      Perrette, M., Rahmstorf, S., and Vermeer, M.

      Semi-empirical sea-level projections for the RCP scenarios

      They’ve included Chao et al for quite some time.

      If you want to get a foreshadowing, they refer to the paper in their reply to Houston and Dean.

    • Thanks again, I’m sure it will be an interesting read. I can’t wait to see how something that would account for 25% of the recent sea level rise will only affect projections by a few percent but with Rahmstorf I’m sure it has something to do with half of Greenland falling into the ocean :) . Have a great night.

    • Let’s be fair, Steven, half of Greenland falling into the ocean constitutes a dynamic change in the ice sheet (I think,) and that ain’t in their model (I think.)

    • JCH,
      Which half of Greenland is falling into the ocean?

    • Latimer Alder

      Top half or bottom half?

    • Tsk Latimer, it’s most unusual that I’d have to point out the obvious to you twice in a week. The bottom half of Greenland fell into the sea aaaages ago. It’s what the top half sits on.

    • Yeah. And the top half keeps growing as new snow falls (Johannessen et al. 2005, Zwally et al. 2006).

      Besides, Rahmstorf is going to have to find a way for all that ice to fall uphill, so it looks like he has his work cut out for him to paint a disaster scenario (but, hey, these guys have been pretty creative in the past, so who knows how they will try to scare us).

      Max

  19. JCH, I’m familiar with the terminology in AR4 you are referring to regarding the estimates to be possibly low. This was based upon flow rates of the then recent short term trends in Greenland and Antarctica flow rates. I seem to remember a correction to the isostatic adjustment since then which indicates less ice loss from Antarctica then previously thought and the flow rates in Greenland are very disputed. This paper even indicates it slows as melting increases
    http://www.ice2sea.eu/Documents/Papers_published/026_Shepherd_nature09740_published.pdf

    “According to our data set, which covers a
    range of melting conditions23 that is small in comparison to predicted
    changes over the next century22, increases in surface melting lead to
    a reduction in rates of summertime ice flow in the lower ablation zone
    of southwest Greenland.ubchann”

    • Steven – I don’t think current rates of SLR matter much at all versus the one-meter prediction by 2100. Up a bit or down a bit is not of much concern to me. If the current decade fails to be warmer than the last decade, that would place one meter in a bit of a pickle. Global temperature in 2013 or 2014 is my benchmark. That’s my layman’s perspective. It has to keep getting hotter, roughly decade to decade, to melt one meter’s worth of ice by 2100. Intuitively, I think at least 65% of that one meter is 2nd half of the century, so there is no point thinking it can be seen now.

    • Latimer Alder

      Excellent.

      We can revisit the horrors (if any) of sealevel rise in 40 years or so and see if we need to do anything then. It would be premature to worry about it beforehand when there are real and pressing problems to solve right now, Like feeding an expanding population.

  20. Sea level rise doomsday scenarios are among the catastrophists’ memes that never really caught on like a whopper about the extinction of the polar bears.

  21. Holgate, S.J. 2007. On the decadal rates of sea level change during the twentieth century. Geophysical Research Letters 34: 10.1029/2006GL028492.

    As a result of this finding, Holgate presented the nine-station-derived wavering black line in the figure below as a reasonable representation of the 1904-2003 mean global sea level history of the world, and based on that history calculated that the mean rate of global sea level rise was “larger in the early part of the last century (2.03 ± 0.35 mm/yr 1904-1953), in comparison with the latter part (1.45 ± 0.34 mm/yr 1954-2003).”

    http://www.co2science.org/articles/V10/N4/C1.php

  22. tonyb –
    Once again, thank you for an interesting and informative read. Since I have an active present interest in the time period in question, I found it especially interesting and am looking forward to Part 2.

    But I do sometimes wonder how many people actually read the material – or even the thread title.

    • John Vetterling

      I’d like to echo that.
      For all the peer review that supposedly goes into the IPCC, its interesting to see some of the things that aren’t so well documented.

    • Jim

      Thanks for that. I think certain people-on both sides-have made up their minds as soon as they see an author or read the first few paragraphs to see if it fits their particular view point.

      I’m not sure that most people read ALLl the links which are chosen to tell a narrative of the activity I am describing. However, they do encouragecomment and allow people to spin off into their own sea level related interests. :)
      tonyb

  23. Sea Level was 5m above current levels 4.2ka BP

    Sea Level Sunda Shelf (great color maps)

    “The rise of sea levels during the Holocene
    between 10 ka BP and modern times, based on
    the research of Geyh et al. (1979), Hesp et al.
    (1998), and Tjia et al. (1983), may be
    summarized as follows. Between 10 and 6 ka
    BP, the sea level rose from –51 m to 0 m.
    Between 6 and 4.2 ka BP, the sea level rose
    from 0 m to +5 m, the mid-Holocene
    highstand. After this highstand, the sea level
    fell gradually and reached the modern level at
    about 1 ka BP.”

    http://research.rmutp.ac.th/paper/cu/VorisSupplement.pdf

  24. “Paleosea-level data for the Pacific Islands suggest that sea level in the region fell, possibly in two stages, between 680 and 475 cal yr B.P. (A.D. 1270–1475). This was associated with a ∼1.5°C fall in temperature (determined from oxygen-isotope analysis) and an observed increase in El Niño frequency. For a long time, it has been clear that these changes—characterized as the “A.D. 1300 event”—brought about environmental and cultural changes on Pacific Islands. These are documented here systematically for the first time. Temperature fall, sea-level fall, and possibly short-lived precipitation increase are the principal effects of the A.D. 1300 event. Temperature fall stressed ecosystems, but its effects are difficult to separate from those of the others. Sea-level fall saw dramatic falls of nearshore coral-reef productivity and the formation of (habitable) reef islands (motu). Precipitation rise increased upland erosion and lowland sedimentation. The human outcomes of these environmental changes are organized in three groups: conflict, settlement-pattern changes, and the end of long-distance voyaging. Conflict increased during/after the A.D. 1300 event because of an abrupt fall in the food resource base. This also caused large coastal settlements on many islands to be abandoned in favor of caves and/or smaller fortified hilltop settlements. Successful long-distance voyages ceased during/after the A.D. 1300 event, as did interisland exchange within many archipelagoes. The regional (rather than local) extent of the A.D. 1300 event is demonstrated. Questions remain as to its synchronicity and duration. © 2000 John Wiley & Sons, Inc.”

    http://onlinelibrary.wiley.com/doi/10.1002/1520-6548(200010)15:7%3C715::AID-GEA4%3E3.0.CO;2-L/abstract;jsessionid=C345A0BD435A816EBB4B15ABC78D182C.d03t04

    • “Evidence shows that sea levels rose slowly during the Medieval Climate Anomaly before falling as much as 135 centimeters (typically 70-80 centimeters) during the A.D. 1300 Event (Figure 1B). During the ensuing Little Ice Age, sea levels appear to have remained below their present levels before they began to rise again around A.D. 1800-1850. ”

      http://goliath.ecnext.com/coms2/gi_0199-7024384/The-A-D-1300-Event.html

    • Bruce

      Thanks for the reference. Thats a good link which replicates several others I came across whilst gathering together research materia which talked of rises and falls of the magnitude you describe. Whether that can be explained by periods of much warmer than today or much cooler than today affecting glacial meltr/attrition amd thermal expansion/reduction remains to be seen.
      tonyb

    • Sea-Level Changes during the Last 2000 Years at Point Barrow, Alaska

      “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 highwater levels; the ocean partially floods Birnirk.”

      http://www.sciencemag.org/content/150/3700/1165.abstract

      1965 … well before the IPCC.

    • Thanks for spotting this

    • Is there anything useful like the Nunn paper in the IPCC?

  25. Fred,
    By the way, your arguing for slr and ocean warming offsets your argument for OA.

  26. “More recent projections are for a 1 m sea level rise in 2100 [here and here].”

    It appears that this paper depends on an accelerating sea level rise and they claim that they have shown such an acceleration using historical data.
    Here is a link to the Grinsted et al paper.
    http://tinyurl.com/6jb8ucj

    Go to page 5 and look at Figure 4.

    Here they claim that their model is validated because their model is accelerating and they claim that the data is accelerating. But the problem is that the satellite data is not accelerating. It is decelerating. Note that while their paper came out in 2009, they only used satellite data through 2006. This is likely because the rate of sea level rise started to decelerate after 2005 and has been doing so to the present. I took all of the data available on the University of Colorado sea level site and split it into two equal halves. The rate of rise for the first half was 3.3 mm/year. The rate of rise for the second half was 2.1 mm/year. So the rate of rise for the second half comes out to be about 8.3 inches in 100 years. If I extended the deceleration curve in the same way as Grinstead extended his acceleration curve, the data would actually turn around at some point in the next 100 years and sea level would beging to drop. I don’t consider that likely – I’m just pointing out the foolishness of Grinstead’s assumption of continuing acceleration.

  27. It seems to me that if people were to take core samples from the walls of the Cosquer Cave in france from the entrance up to the current surface they would discover quickly the time line of the rate of sea level increase over time. We know, because people were in the cave tens of thousands of years ago and that the entrance is now over a hundred meters under the sea when access to the cave ended. It is a natural clock calibrated against sea level. It needs to be tested. It will also tell us if the sea level is still rising.

  28. Re: Mediterranean sea. Prolonged seiche? A long, relatively narrow sea basin could pile up water at one end under the influence of predominant winds toward that shore. Just speculation on my part.

    I think I recall an ENSO/PDO reference to changes in the trade winds that affected sea heights in the western Pacific, and reversal when the trade winds weakened.

  29. Judith, a few days ago a saw a reference to an in-press paper in your area of expertise, tropical cyclones, which might be of interest. I’m posting in this thread because I haven’t seen it mentioned and there are no relevant recent threads. Ryan Maue of Florida State finds that, contrary to many doomsayers (most of them not climate scientists), global accumulated cyclone energy has decreased dramatically since 2006.

    A Cato Institute article – http://www.cato.org/pub_display.php?pub_id=13296 – quotes from Maue’s paper. Here is the abstract and some of the conclusions:

    Tropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40-years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the global frequency of tropical cyclones has reached a historical low. Here evidence is presented demonstrating that considerable variability in tropical cyclone ACE is associated with the evolution of the character of observed large-scale climate mechanisms including the El Ni&ntidle;o Southern Oscillation and Pacific Decadal Oscillation. In contrast to record quiet North Pacific tropical cyclone activity in 2010, the North Atlantic basin remained very active by contributing almost one-third of the overall calendar year global ACE. …

    It is still a fundamental research question as to what are the atmosphere and ocean mechanisms responsible for the observed annual global [tropical cyclone] frequency of ~87 storms (Frank and Young, 2007)… . [I]t is critical to have the best possible diagnosis of periods of global TC inactivity and incorporate the recent pentad of historical lows into the context of natural and anthropogenically forced climate variability (Knutson et al., 2010). Furthermore, research must better explain the role of tropical cyclones in the climate system especially during this current period of record inactivity.
    ________________________________________
    Reference:
    Maue, R.N., 2011. Recent historically low global tropical cyclone activity. Geophysical Research Letters, doi:2011GL047711R, in press.

    There is more detail at http://www.coaps.fsu.edu/~maue/tropical/ .

    • “In contrast to record quiet North Pacific tropical cyclone activity in 2010, the North Atlantic basin remained very active by contributing almost one-third of the overall calendar year global ACE. …”

      Which is interesting, given that the north Atlantic gained a lot more ocean heat content than other basins during the global warming period. And is now losing ocean heat content faster than the other basins now we have entered the global cooling period.

    • Thanks for the link. I heard Ryan Maue give a seminar on this about a month ago. I will be doing a new hurricane around the end of Aug.

    • I hope your August article is the only aspect of a tropical cyclone we in the Gulf Coast will have to deal with….

  30. Judith/TB
    In the middle of the article there is this:

    WHAT IS THE REF FOR THIS:

    “ In Northumberland, researchers found sediments from 7,000 years ago five metres below, and others from 4,000 years ago at 1 metre above the present sea level. This indicates that the sea level rose above present levels from around 7,500 years ago to 4,500 years ago, and then dropped and is continuing to fall. Sea-levels in most of Scotland peaked even higher about 4,500 years ago and have been falling ever since because the land has risen.”

    The missing reference from the essay can be found here

  31. Tony,

    Interesting that not a single drop of molecular vapor is lost to space by current science standards.
    Any object hitting this atmosphere has to generate a “splashing” effect of some sort to the atmosphere. Yet we have not lost a single drop.
    Hmmmm.

    Loosing material into space is a very slow long process that can take thousands of years to measure the loss of material in mm.

  32. Fred Moolten | July 12, 2011 at 8:00 pm | Reply
    the satellite-determined sea level trend has averaged about 3.1 mm/year

    JASON/TOPEX is not the only satellite platform Fred.
    The European effort shows a considerably lower rate of rise than the Colorado based effort. About 1.2mm/year.
    http://www.aviso.oceanobs.com/fileadmin/images/news/indic/msl/MSL_Serie_EN_Global_IB_RWT_GIA_Adjust.gif

    The rapid sea level fall in the last two years is in line with my own calcs for the loss of ocean heat content. This is consistent with the sun being responsible for late C20th thermal expansion of the ocean, not co2.

    • Any Rapid Sea Level Fall in the last two years is in line with the massive Arctic Ocean Effect Snow that fell on land because of the Record Low Arctic Sea Ice Extents that occurred. This did raise the Albedo of the earth. Much of the Snow did fall in the oceans and likely directly cooled some of the water.

    • “Arctic Ocean Effect Snow”

      Which data shows that in your mind?

      If “Much of the snow did fall in the oceans” albedo changes would be miniscule.

    • AVISO shows a 3.22 mm/year rising trend over the interval from its start to the present. One can always select a short interval that deviates from the longer term trend, but that is true in both up and down directions. The problem arises when one selects a starting point for the purpose of demonstrating a deviation, because that can easily mischaracterize the data.

      On your other point, although it’s OT here, back radiation from GHGs and solar absorbed energy are well mixed in the ocean, and one can’t dissect out the contribution of one or the other as the almost exclusive source of ocean warming. This can easily be shown by looking at the Earth’s energy budget. If back radiation did not contribute substantially to ocean temperature, its energy would have to go somewhere else. The only major outlet would be latent energy transport via evaporation, but observational data on the hydrologic cycle (e.g., precipitation rates) show that this outlet can only account for a rather small fraction of back radiated energy.

    • AVISO is a mix of 6 satellites of which only 3 are now operating. And plunging.

      The satellites did not all run concurrently.

    • Fred Moolten

      You wrote:

      AVISO shows a 3.22 mm/year rising trend over the interval from its start to the present. One can always select a short interval that deviates from the longer term trend, but that is true in both up and down directions. The problem arises when one selects a starting point for the purpose of demonstrating a deviation, because that can easily mischaracterize the data.

      Indeed.

      If one checks the tide gauge record for the 20th century (Holgate 2007) one sees two significant things:
      http://farm4.static.flickr.com/3206/3144596227_545227fbae_b.jpg

      1. That the overall trend over the 20th century was one of slight deceleration of the sea level change rate.

      2. That the decadal rate of change in mm/year varied from a decadal highs of +5.3 mm/year (1974-1984), +4.7 mm/year (1933-1943) and +4.4 mm/year (1951-1961) to decadal lows of –1.3 mm/year (1984-1994), -1.2 mm/year (1961-1971) and -0.5 mm/year (1920-1930).

      So it seems a bit disingenuous for IPCC to cite a decadal rate of rise of +3.1 mm/year for the period 1993-2003 (measured by a totally different methodology and covering a totally different scope) and first comparing it with a cobbled-together record for a longer period (1961-2003). And then stating (bold face by me):

      Global 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.

      .

      If one looks at the record it should be pretty clear to anyone. The period 1961-2003, which IPCC compared with the shorter period 1993-2003, includes the decade 1961-1971, during which sea level actually declined by –1.2 mm/year.

      This directly reflects what you wrote:

      The problem arises when one selects a starting point for the purpose of demonstrating a deviation, because that can easily mischaracterize the data.

      Just another bit of IPCC “smoke and mirrors”, as I am sure you will agree.

      Max

    • The question as to whether there has been a recent (i.e., post-1993) acceleration in sea level rise remains unsettled, but there is some supporting evidence. It comes mainly from the satellite altimetry data which are similar in estimated rises of about 3 to 3.2 mm/year, in combination with recent tide gauge data (Prandi et al, Church and White, and others) that yield similar estimates despite tide gauge estimates of lower rates during earlier times. Paul S discussed some these data above in the thread, and I also provided links. I’m not sure what this has to do with the IPCC, since much of the data are from years since 2007.

      There has also been extensive discussion of short term deviations from the longer trends – in both the up and down direction. Past records show that any “trend” of less than 10 years will often misrepresent trends calculated over a longer interval. However, altimetry trends for the past 10 years calculated by linear regression (not subtraction of one end point from another) come fairly close to that of the entire altimetry interval.

    • From 2002/2003 on the figure 3 to 3.2mm is incorrect.

      I suspect the 1990s satellite data is hopelessly contaminated.

      Things are so bad they had to come up with the .3mm GIA to try and get the values back to the bogus 1990s ones.

    • Fred Moolten

      It’s correct, as you say, that satellite altimetry showed a higher rate of rise in the decade after 1993 than the tide gauge record.

      IPCC reported a linear rate of rise of 3.1 mm/year on average over the period 1993 to 2003, while the tide gauge record showed around half this rate of increase.

      Since then the linear rate of rise from satellite altimetry has slowed down considerably, i.e. 0.76 mm/year from 2004 to 2011.
      http://stevengoddard.wordpress.com/2011/05/27/sea-level-plummeting-lowest-level-since-at-least-2004/

      The two methods also measure two entirely different things (apples and oranges): the sea level at several shorelines (where we land mammals live) and the entire ocean (except those areas near shorelines or the poles, which cannot be measured by satellite).

      For this reason, a comparison of one time period using one method and covering one scope with another time period using another method and covering another scope in order to show an acceleration between the two periods is meaningless, even if one excludes the large margin of error of satellite altimetry.

      In addition, the longer-term record shows major decadal oscillations (as pointed out earlier), and the current downward swing since 2004 as well as the apparent upward swing from 1993-2003 may well be a reflection of these decadal oscillations in the rate of sea level change.

      At any rate, to project any kind of recent acceleration from the past record would be fraught with a very high level of uncertainty.

      Max

    • “IPCC reported a linear rate of rise of 3.1 mm/year on average over the period 1993 to 2003, while the tide gauge record showed around half this rate of increase.”

      I believe tide gauge records starting on or after 1993 have been generally concordant with the altimetry data. Prandi et al and Church and White report tide gauge estimates close to 3 mm/year as cited in other comments. Perhaps other records with a global purview report a different value, but most tide gauge records with lower values also include data from earlier intervals.. Nevertheless, I do agree with you that the issue of recent acceleration is not yet settled. For that purpose, we need data for at least another decade, because short term ups and downs are likely to give a false picture of longer trends.

    • Fred Moolten

      You wrote:

      Nevertheless, I do agree with you that the issue of recent acceleration is not yet settled. For that purpose, we need data for at least another decade, because short term ups and downs are likely to give a false picture of longer trends.

      Looks like our interpretations of the data agree, Fred.

      It’s also correct, as you say, that satellite altimetry showed a higher rate of rise in the decade after 1993 than the tide gauge record.

      IPCC reported a linear rate of rise of 3.1 mm/year on average over the period 1993 to 2003, while the tide gauge record showed around half this rate of increase.

      Since then the linear rate of rise from satellite altimetry has slowed down considerably, i.e. 0.76 mm/year from 2004 to 2011.
      http://stevengoddard.wordpress.com/2011/05/27/sea-level-plummeting-lowest-level-since-at-least-2004/

      I would not place too much significance on this latest “blip” (just like the earlier 1993-2003 “blip”).

      The two methods also measure two entirely different things (apples and oranges): the sea level at several shorelines (where we land mammals live) versus the entire ocean (except those areas near shorelines or the poles, which cannot be measured by satellite).

      For this reason, a comparison of one time period using one method and covering one scope with another time period using another method and covering another scope in order to show an acceleration between the two periods is meaningless, even if one excludes the large margin of error of satellite altimetry.

      In addition, the longer-term record shows major decadal oscillations (as pointed out earlier), and the current downward swing since 2004 as well as the apparent upward swing from 1993-2003 may well be a reflection of these decadal oscillations in the rate of sea level change.

      At any rate, to project any kind of recent acceleration from the past record would be fraught with a very high level of uncertainty.

      Max

  33. JCH, to be fair anyone taking the short term trends of melting in Greenland and extrapolating them into the future is doing everyone a disservice. It is as if they had never heard of the AMO. You would have to compare the melting to a similar point in the AMO oscillation. If you doubt the validity of my argument look at the temperature pattern created by the AMO as it cycles through its phases in the linked paper.

    http://www.meteo.psu.edu/~mann/shared/articles/KnightetalGRL05.pdf

  34. Judith
    The 2009 NIPCC report provides a 22 page review of sea level:
    Section 4.5 Sea Level pp 184 – 206
    Ch. 4 Observations: Glaciers, Sea Ice, Precipitation, and Sea Level, Climate Change Reconsidered, NIPCC 2009

    NIPCC further provides summaries of 15 more recent papers on sea level.

    • David

      Some exellent papers

      tonyb

    • tempterrain

      TonyB,

      I’ve tried to explain to you before, so I’m probably wasting my time doing it again, but the term “paper”, in the scientific sense, does imply something slightly more substantial and worthwhile than a sheet of dried and compressed wood pulp!

      The paper used by the NIPCC may indeed be of excellent quality, but what’s written on it is just a load of crap I’m afraid. The best thing is to put it all in the recycling bin and start again.

  35. Chapter 5 of AR4 from the IPCC dismisses nearly 2000 years of sea level history by asserting;

    “Yes, there is strong evidence that global sea level gradually rose in the 20th century and is currently rising at an increased rate, after a period of little change between AD 0 and AD 1900. Sea level is projected to rise at an even greater rate in this century.”

    There are no references to support this assertion. Most of my articles try to put modern day climate into its historic context and as the IPCC position on sea levels until 1800 is neither scientific nor evidential in its claim, so my article tries to explore the historic context that the IPCC omits.

    It had not really occurred to me before, until after writing the article, that we have two hockey sticks-one following the land temperature record developed by Michael Mann- and the second following sea levels as defined by Chapter 5, starting from around 1800. As some scientists make a direct link between temperatures and resultant sea levels (which whilst logical remains uncertain) it seems to follow that if the Mann Hockey stick is correct it requires a static sea level until an uptick in modern times to support its findings, and vice versa. The uptick representing the warming ‘caused’ by man. Consequently my article contradicts the view of history that some here hold and inadvertently questions two pillars of climate science.

    I have no idea as yet whether during the MWP the sea level was higher or lower than the Roman period, so papers on the 1800 year ‘missing gap’-particularly those that support the IPCC view of ‘little change,’ are welcome for consideration for Part 2 of this series.

    In the meantime I would point out the above article is a summary of a very much longer paper citing many more studies of the Holocene to Roman period, together with graphs and charts etc.
    Its available at the start of the article above or from here;

    http://curryja.files.wordpress.com/2011/07/document.pdf

    tonyb

    • Tony,

      First a suggestion: You should add your name to the document. When it’s linked from any other source than this thread, it doesn’t indicate the author. The only and misleading hint is curryja in the url.

      Your collection of information is interesting. I don’t know what it implies concerning future sea level, risks of climate change or quality of work of IPCC, not necessarily much on any of those, but it’s interesting on it’s own right.

      The most surprising observation is that there are several indications of rather rapid variations of sea level with a change of the order of 1 m. That’s surprising in view of all the evidence of how much it requires to induce a change that large. One obvious possibility is that the global sea level has not changed so much, but the observations tell either about a local relative sea level variation due to some deformation of the Earth crust or are simply misinterpreted and the apparent change is due to something totally different.

      There are also variations in the relative level of Mediterranean sea compared to Atlantic ocean due to the differing and varying saltiness, but my guess is that this effect cannot be very large. (I have not tried to estimate, how large it could be, neither do I know any reference for that.)

    • Steven Goddard found a mysterious bulge of satellite sea level rise near Australia equating to 20mm per year.

      http://stevengoddard.wordpress.com/2011/06/19/satellite-sea-level-data-is-crap/

      Maybe the satellite sea level rise is just a measurement of plate tectonics.

    • Changes in the temperature and salinity profiles may have significant effects on the sea level at least locally, but to some extent also globally. Keeping the heat content of the oceans constant the sea level will fall, when surface water cools and deep water warms, because the thermal expansion gets stronger with increasing temperature. For the coldest ocean water the coefficient is essentially zero.

      Thus a major change in thermohaline circulation might influence rapidly both the surface temperature and the sea level.

    • However, when tide gauges show no rise and satellite shows 20mm per year rise … “Sea Level Data is Crap”.

    • Alexander Harvey

      Pekka,

      My understanding of this is that the isopycnics are curved when plotted against temperature and salinity. Hence water bodies of the same density but with different temperatures and salinities will when mixed become denser (for that is the nature of the curvature). The importance of this distinction is that it is bodies of the same density that can and do come into contact with each other and this form of mixing does occur.

      I believe that it is this ability to increase density by the admixture of bodies of equal density that acts to drive aspects of the circulation.

      The effect is quite strong, mixing bodies of equal density but extreme but still physical differences in T and S could result in a densification greater than 1%.

      For reasons like the one you have highlighted I find it difficult to see what conclusions people are drawing from a rise in sealevel. For the relationship between the volume of water, the amount of water, and the altitude of the surface is complex and I wonder if we are each have quite different notions as to how to interprete the information with which we are presented.

      My understanding is that without any change in total thermal energy, total salt content, total water content, or ocean boundary profile, the sealevel could vary considerably, (by a few metres) purely by changing the T & S gradients.

      Hopefully this is somehow accounted for and it is merely my ignorance that makes me uneasy in such matters.

      Alex

    • Alex,
      A Google search of the equation of state of seawater provides links to papers that describe the EOS-80 equation of state that has been used widely in actual calculations and also links that tell about a rather new refined equation of state TEOS-10. From the newsclips and the IOC-webpage linked below my conclusion is that the difference between if EOS-80 and TEOS-10 becomes significant, when the analysis is detailed enough to go to the details of chemical constitution of the salinity. There are also several net calculators based on EOS-80 and some simplified approximate equations of state.

      http://www.ioc-unesco.org/index.php?option=com_content&task=view&id=144&Itemid=112

      Looking at available graphs the dependence on salinity appears to be close to linear over the range that almost all seawater has. Thus reducing salinity differences would have only a small effect while changes in the temperature distribution would influence the sea level much more. Taking the full equation of state into account must be an essential part of all calculations that aim to explain the presently observed regional variations, but I have no idea on, how much effort has been put in determining the influence of temperature gradients in historical sea level variations.

    • The pressure is also a significant factor. One calculator that can be used to calculate more variables and in more different ways is this one from Johns Hopkins Univ. Ocean Remote Sensing Group. This is, however just a calculator without any graphics.

      http://fermi.jhuapl.edu/denscalc.html

      One text with quite a lot of information, but not exatly in a form I was looking for is this lecture notes from UCSD.

      http://sam.ucsd.edu/sio210/lect_2/lecture_2.html

      I have also seen curves representing thermal expansion coefficients under varying conditions, but don’t remember where.

      The simplified equation of state presented here might be of help for improving understanding, while it’s probably not good enough for serious research.

      http://mason.gmu.edu/~bklinger/seawater.pdf

      There is really a lot of material available on this front.

    • Alexander Harvey

      Pekka,

      We are slightly at cross purposes, the distinction is was drawing was in the nature of how the mixing and densification occurs.

      I feel that, by and large, bodies of different density are seperated, bodies along an isopycnic on the T-S plane do come into contact and give rise to densification which I believe drives some of the dynamics.

      Yes the curvature is in T not S but the existence of gradients in S is necessary for such mising to occur.

      Gradients in both S & T can represent “plausible” mixing that could occur giving rise to densification. Whereas a gradient in T alone with warmer water above cooler would not easily mix.

      The existence of bodies of water with the same density but different T-S represents a opportunity for mixing and densification.

      Any tendency to increase such an opportunity should give result in an increase in volume and any tendency towards reducing duch opportunities should reduce that volume even without any net change in energy water, or salt.

      I agree that ultimately it is the reduction of temperature gradients that really matters, but whereas they give rise to a possibility for densification they do not give rise to a plausible opportunity.

      I believe that in the body of the ocean it is primarily bodies of similar density that mix.

      My viewpoint is that any tendency for the distribution of salt along a surface of equal pressure to become less homogenous would tend to correlate with sea level rise and any tendency for that layer to homogenise would be compatable with a sea level reduction.

      I hope I am more clear now. I am restriciting myself to those things that could affect the sea level that present real opportunities to achieve densification.

      I will add that there seems to be two schools of thought or at least to presentations as to what gives rise to the ocean circulation. I think it is the convection circulation that is most well known. My understanding is that it is the result of the mixing process not the cause.

      Here is a quote:

      “Notice that the deep circulation is driven by mixing, not by the sinking of cold water at high latitudes. Munk and Wunsch (1998) point out we have known for 100 years that deep convection by itself leads to a deep, stagnant, pool of cold water. In this case, the there is no deep circulation.”

      From here:

      http://oceanworld.tamu.edu/resources/ocng_textbook/chapter13/chapter13_02.htm

      From this, it becomes my understanding that it is the production of such opportunities for mixing resulting in densification that drives the circulation. That it is the mixing which is thought to occur moslty adjacent to strong currents, over ridges and around mounts that causes localised densification giving rise to a general upwelling elsewhere that forces water to the surface that drives the overturning and results in the sinking of water in the North Atlantic.

      Now that is what the textbook tells me. That this seems completely at odds with almost everything else I read puzzles me deeply. For instance it does not support the view that the overturning would be stopped by freshening in the North Atlantic for that would not remove the primary driver. It is noticably at odds with much of the text in the link you kindly provided.

      There seems to be quite a bit of divergence between what some oceanographers think and the rest of the community. Here is another quote:

      “The term thermohaline circulation was once widely used, but it has disappeared almost entirely from the oceanographic literature (Toggweiler and Russell, 2008). It is no longer used because it is now clear that the flow is not density driven, and because the concept has not been clearly defined (Wunsch, 2002b).”

      If they have moved on in their understanding, it seems that the many have not. I certainly used to believe in the density driven thermohaline circulation. The online textbook is from 2005 updated 2008 so is fairly recent. Rahmstorf (1995) view on salinity changes is discussed but is countered by the argument summed up as:

      “Because the meridional overturning circulation is pulled by mixing and not pushed by deep convection, the transport of heat into the north Atlantic may not be as sensitive to surface salinity as described above.”

      I am not surprised by my being puzzled. A circulation that is internally “strictly geostrophic” (another quote) as the textbook indicates and driven by localised mixing is a little counter-intuitive and not as easily understood as density driven motion. But if that is the way it is, that is the way it is, and unless and until it is generally described in terms of a mixing driver as opposed to a density driver I will continue to feel like I am marching against the crowd.

      Alex

  36. Thanks steven for the link.

    A signature of persistent natural thermohaline circulation cycles in observed climate. Knight et al, 2005
    http://bit.ly/nfQr92

    …associated “Atlantic Multidecadal Ocillation” (AMO) change would partially offset expected Northern Hemisphere warming. This effect needs to be taken into account in producing more realistic predictions of future climate change.

    This means that the IPCC’s projection of 0.2 deg C per decade warming is wrong.
    http://bit.ly/b9eKXz

    And the oscillation pattern in the global mean temperature shown in the graph below is due to oceanic thermohaline circulation (THC).
    http://bit.ly/ePQnJj

    As a result, based on the data so far, the global warming rate is only 0.06 deg C per decade!
    http://bit.ly/oI8dws

    Congratulation skeptics!
    http://bit.ly/qAXJ60

  37. The sea level rise rate decreased by 40% from 3.79 to 2.26 mm/year.
    http://bit.ly/fMb7bw

  38. Who knew? Relatively short-term patterns or periods/regional sea level, is not the same thing as historical sea level trend/global sea level.

    The science re. global sea level has moved along a fair bit since the last IPCC report. The relevant question is how sea level rise in the current climate state (different sea level sensitivity) will respond on a long-term time scale to climate change; and how that will affect different regions.

    • Can you please specify what climate change? Is it the Orwelian one or the real one?

      What is your prediction? Which way is the climate going to change? Do you want the climate to STOP changing?

    • She means it’s because of Big Tobacco, or was that last week?

  39. So in paragraph 1 you say A is not B.

    But in paragraph 2 you say the important question is what is future B and how does that affect future A.

    I think its safer to say that what are most important are the “relatively short-term pattern or periods/regional sea levels” (A) and if we can get any future prediction that would be of any use. However, these local short term events are much more drastic than the rather meaningless global one.

  40. St. Michael’s Mount:

    The future: In the early 18th century the causeway was accessible for six hours at low tide. Now it is accessible for four. In 40 years time it may be accessible for under an hour and eventually the Mount could become a true island. As the causeway becomes unusable, the harbour will increase in importance but this too will be increasingly vulnerable to flooding. – National Trust

    • National Trust marketing, it’s not very insightful. The harbour is going to benefit, so?

    • JCH

      Simply not true. I was there last week researching the article and National Trust History tends to the romantic.

      tonyb

    • Anybody can say something is not true. Show me that it is not true.

      Whether the levels fell in the interim period is outside the scope of this study, but we do know that by 350BC at the latest St Michaels Mount was a thriving port for the export of tin, which during the ebb tide was carried over in wagons i.e. by that time it was a tidal island.

      How do we know St. Michaels was a thriving tin port by 350 BC? Who decided the winner among all the guesses?

    • ICTIS DISENTANGLED, AND THE BRITISH TIN TRADE

      Summary. Recent writers here, on routes by sea to ancient Britain, have revived the quest for Ictis, recorded as a port for the trade in its tin. Apart from Caesar’s De Bello Gallico, nearly all the relevant sources are in Greek, and one of the few in Latin is from previous Greek. The relevant archaeology, marine technology and natural sciences, should still be advantaged by attention to these texts, in their wording and their contexts and chronology. They comprise three groups: Pytheas and Timaeus, before and after 300 BC, Polybius and Posidonius, before and after 100, Diodorus in the middle first century and Strabo near its end. Pliny, after the middle first century AD, quotes Timaeus. Each of the three groups throws light on the trade, Diodorus almost certainly, and nearly always Strabo, reflecting what had been shed by writers before them. It is Diodorus, expected here to be using Posidonius, who tells us of Ictis. But the various dates of the evidence altogether, when compared with the archaeological and scientific findings, let routes for the trade be distinguished not only in geography, but also in the chronology of their use. This essay takes account of all relevant work done hitherto, but advances beyond it wherever this is seen to be feasible. It disentangles the location of Ictis from persistent error, though doing so cannot yet fix it with final probability; but putting all the ancient sources for the trade to a critical scrutiny, with exact translations, enhances their accord with archaeology.

      This guy can sell a paper. Does anybody know his result?

    • JCH

      Do read the FULL article where I deal with this at great length-one of the reasons that a summary was necessary.

      tonyb

  41. Where’s the voice of reason? There is no end to the calls for government involvement to speedily rebuild the lives of those who build their homes in floodplains below sea level. We cannot even begin to quantify the effects on the economy brought about by the unrelenting calls from the Left for government to address the harsh problems of nonexistent victims based on fearmongers’ worst case scenarios concerning nonexistent sea level rise.

  42. Can we infer change in mean global temperature from change in mean global sea level, or vice versa? This question inevitably arises when one or the other is evaluated. Over a relatively short term horizon of a few recent centuries or less, the relationship appears fairly solid, and even stronger since the advent of direct tide gauge measurements and the even more recent satellite altimetry starting in 1993. This record is characterized by many transient fluctuations of a decade or less but trends are nevertheless apparent as discussed in many above comments.

    As one moves into more distant history, and into the realm of paleoclimatology, the uncertainties grow. Clearly, major deviations in temperature such as those distinguishing glacial and interglacial intervals can be shown correlated with major changes in sea level of the order of 100 meters or more. Changes of the order of meters, or of 1 or 2 degrees C are more problematic because of past reliance on proxy measures. In the case of sea level, the measurement of oxygen isotope changes in benthic foraminifera have provided a powerful tool for both sea level and temperature analysis, but margins of error are still significant. Substantial regional deviations further complicate attempts to arrive at overall mean values, particularly as one moves backwards in time.

    Some of this is illustrated by a number of studies showing the trajectory of sea level rise since the Last Glacial Maximum. In general, the evidence indicates that current sea levels are more or less the highest for any extended interval during the Holocene – for one example, see example Holocene Sea Level History. Other studies are referenced in Holocene Sea Level together with a graphic illustration of the changes over time. What is striking are both the regional differences and the uncertainties, which during the early Holocene were characterized by differences among data points as large as 12 meters.

    Another informative effort involves comparisons between the current Holocene interglacial and past interglacials. One such effort – Holocene and Last Interglacial Sea Level Rises – finds that an interglacial temperature about 2 C above the present was correlated with mean sea levels 4-6 meters higher than current ones after averaging over the course of regional and temporal variations, with a major contribution from the Greenland ice sheet. This analysis is subject to the same uncertainties as described above, but is not inconsistent with projections for future sea level trends during the remainder of this century. Further comparisons of this type will be helpful in narrowing the uncertainties about past temperature/sea level relationships during interglacials comparable to the current one.

  43. “the evidence indicates that current sea levels are more or less the highest for any extended interval during the Holocene”

    Except for the 3 x 500 year intervals I referenced here:
    Bruce | July 12, 2011 at 7:50 pm

    And the 5 meter above today referenced here:
    Bruce | July 12, 2011 at 11:03 pm

    And probably a lot more studies if you looked for them

    • Bruce – That is one reason why I cited the oxygen isotope method as more powerful than earlier less informative techniques, although for regional sea levels, a variety of methods are applicable. However, if you visit the referenced content I linked to on sea level rises during the Holocene, it appears that most studies utilizing modern techniques have shown current sea levels not to have been clearly exceeded earlier. The data also show considerable regional variation, which is why one can’t infer mean global sea levels from studies in any one or a few regions. In any case, interested readers should visit all the referenced material to form their own conclusions.

    • Reading the conclusion … I see nothing that tells anyone much about the Holocene at all that passes the smell test.

      MIS-11 had 2 insolation maximums. Holocene 1.

      “On the one hand, the apparent 2.0–2.5 kyr discrepancy”

      Oh … only off by 2500 years? Please!

      As for the Red Sea? There are humans around this time which kind of makes the comparison weird.

    • And Fred, a graphic on Wikipedia that shows significant data points above todays sea level ruins your argument

    • Readers should visit the graphic to judge for themselves. You may have misunderstood the difference between a global trend and the data points that form it from individual locations that can differ considerably among.themselves (e.g., Malacca vs Santa Catarina).

    • “The black curve is based on minimizing the sum of squares error weighted distance between this curve and the plotted data. It was constructed by adjusting a number of specified tie points, typically placed every 1 kyr and forced to go to 0 at the modern day. A small number of extreme outliers were dropped. It should be noted that some authors propose the existence of significant short-term fluctuations in sea level such that the sea level curve might oscillate up and down about this ~1 kyr mean state. Others dispute this and argue that sea level change has been a smooth and gradual process for essentially the entire length of the Holocene.”

      Santa Catarina was one of the sites showing high sea level on the graph

      Now wonder!!!!

      “The best defined relative sea-level curves for the Brazilian coast, such as the Salvador (State of Bahia) curve, exhibit three Holocene maxima with progressively decreasing heights dated at about 5100, 3600 and 2500 years B.P. Although the maximum reached a height of 3 to 5 m in different sectors of the Brazilian coast, previous workers (Martin et al., 1988) postulated that for the coast of ParanáState (Southern Brazil) it would have been less than 2.5 m and that the other maxima would likewise also have been lower than in other sectors.

      Re-evaluation of available evidence, including new data on Vermetidae, indicated an ancient sea level of 2.9 ± 0.5 m above the present at 3500 ± 60 years B.P., approximately coincidental with the second Holocene maximum in Paraná. If the relative differences in height between the maxima that are observed elsewhere along the Brazilian coast hold for the Paranácoast as well, then it is possible that the first maximum may have been 4 m above the present sea-level in this state.”

      http://www.sciencedirect.com/science/article/pii/003101829500055Q

    • And Fred, remember, the whole purpose of the IPCC is to lie and hide or alter any data that ruins their “unprecedented” this or that narrative.

      Its been warmer.

      Sea level has been higher. A lot higher.

    • Bruce – It seems to me you still may be missing the point that sea level changes at individual locations have varied in either direction from the past mean or current levels, and that it is the composite picture that indicates that current mean sea levels have probably not been exceeded earlier in the Holocene for any extended interval. This now comes from multiple sources, and may or may not be completely accurate but is probably reasonably close to historical reality. It also may be less important an issue than perhaps you consider it to be.

      Again, rather than continue to discuss this at cross purposes, my suggestion is for interested readers to visit the linked sources for themselves to form their own judgments.

      I notice that you say that it’s “the whole purpose or the IPCC to lie”. I won’t vouch for the accuracy of all IPCC statements about sea level, because I haven’t recently reviewed them, but it seems to me that you are viewing all information you encounter through a lens distorted by an antipathy that makes it hard for you to be objective. I may be wrong in this, but if that is my perception, it’s probably seen the same way by at least a few others who would react the same way to broad accusations of lying as opposed to a more dispassionate attempt to see whether certain statements on climate are accurate or inaccurate without impugning the motives of those who make them.

    • Fred, try to be objective once. I have presented evidence of 1 meter above current, 1.5 meter, 3 meter and 5 meter and more including significant drops during the LIA and 30cm above current.

      Read my references.

      The 30cm one is quite annoying because the IPCC lied about the value and lied about the lenght of time the paper covered.

      You have presented ,,, a graph.

    • sea level changes at individual locations have varied in either direction from the past mean or current levels, and that it is the composite picture that indicates that current mean sea levels have probably not been exceeded earlier in the Holocene for any extended interval. This now comes from multiple sources, and may or may not be completely accurate but is probably reasonably close to historical reality.

      It’s exactly the same nonsense we used to hear constantly about the temperature record — deniers would point to one station or a tiny region with no warming or cooling and say, hey, the earth’s not warming. Michael Crichton did it, famously, in “State of Fear.”

      Now the temperature record is a dying argument, but the same boring ignorance is being recycled in discussions of sea level, polar bear populations, coral health, agricultural productivity, and any other effect that is impossible to understand without looking carefully at the whole data set.

      It’s really just cherry-picking writ large.

      It’s

    • Yup – your the same boring ignorance is being recycled

    • “Yup – your the same boring ignorance is being recycled”

      With the grammatical error. Priceless.

    • It’s the thought that counts, Robert. But then – you don’t.

  44. “Climatologist Robert Balling points out that the sea level as been rising about 1.5 mm/yr for the last 8000 years; some say as much as 20,000 years. If this rate of increase were to continue for 100 years more, it would amount to about 6 inches. Given the Dutch ingenuity with holding back the sea, I think we can adjust for a 6 inch rise. A 6 inch high “tidal wave” dribbling into Lower Manhattan suddenly isn’t so scary, either. We can also marvel at the roaring successes of Al Gore’s fantasies, which are void of such mundane scientific evidence.” (Michael R. Fox, Ph.D., February 25, 2007)

  45. Bruce has brought up a very pertinent point:

    when tide gauges show no rise and satellite shows 20mm per year rise … “Sea Level Data is Crap”.

    The scientists gathering the satellite altimetry data apparently have the same reservations about the reliability of this method:
    http://www.cosis.net/abstracts/EGU04/05276/EGU04-J-05276.pdf

    The currently accepted value is 2.5±0.5 mm/year.
    However, every few years we learn about mishaps or drifts in the altimeter instruments, errors in the data processing or instabilities in the ancillary data that result in rates of change that easily exceed the formal error estimate, if not the rate estimate itself.

    In all these cases the intercomparision with external sources, mainly contemporary altimeter satellites, like ERS-1 and ERS-2, were pivotal to the uncovering and correction of the problems. With the missions of Jason-1 and Envisat now on the way for a few years, more differences between the missions pop-up. Neither of these missions currently fit the established rates. It seems that the more missions are added to the melting pot, the more uncertain the altimetric sea level change results become.

    To measure the increase/decrease of stationary snow mass on top of a polar glacier by satellite altimetry makes sense to me. To try to measure sea level in a heaving sea to an accuracy of fractions of a millimeter makes very little sense, especially when we have a tide gauge record that goes back to the early 19th century and that measures what we (as land mammals) are really interested in, i.e. the sea level at various coast lines.

    Max

    • Yes, Max, I very much agree about the limitations of taking altimetry readings to within a fraction of a mm. This is also why I think that geological and archeological evidence is important, accepting of course that it provides a local story. They all add up though.

    • 2003 altimetry techniques have been supplanted at least in part by GRACE technology for quantifying ice mass loss. This is a different from but complementary to altimetry measurements of sea level itself, which are also improved over earlier intervals. Reasonable concurrence between altimetry and tide gauge measurements over intervals starting since the inception of altimetry also reinforces confidence in the trend estimates.

      I agree that individual measurements to a fraction of a millimeter are subject to inaccuracy, but if your logic is that altimetry measurements therefore make very little sense, I don’t agree, and I doubt that the authors of the report you cited would agree (but you can contact them).

    • “The most prominent result of this analysis is a reduction by about a factor of two in the estimate of current rates of ice loss for Greenland and Antarctica compared to previous GRACE estimates based on the a priori GIA model, due partly to clear evidence for ice accumulation in the interior of Greenland (accompanied by ice loss around the margins of Greenland). Parts of West Antarctica also show rapid loss and others rapid gain of ice mass, while East Antarctica seems relatively stable. The current (2002-2008) global non-steric (not due to ocean warming and water expansion) sea level rise attributable to ice mass loss is estimated in the study to be only 0.54 mm/yr (about 2 inches per century). This suggests that almost none of the sea level rise is due to glacial ice loss, as is widely assumed.”

      http://www.nipccreport.org/articles/2010/sep/22sep2010a2.html

    • Fred –
      Satellite altimetry makes sense if and only if the instrument is properly calibrated and ground truth checked – AND if the data processing software properly handles the instrument data.

      GRACE has had enough past problems to render the implementation of some of those requirements questionable. But the questions can ONLY be answered by an independent validation process – which is not likely to be allowed.

      BTDT – this kind of validation activity was specifically my playground for most of 40 years.

    • Calibrations for altimetry and GRACE mass changes are frequently updated, and at least the GRACE site has provided information on these in the past. To the best of my knowledge, there is no current reason to see these instruments as grossly inaccurate. As I mentioned, they complement each other, and tide gauge sea level measurements since 1993 have provided further confirmation that the measured sea level trends are not seriously in error. Recent ocean heat content measurements have further reinforced these conclusions (although the intervals of good OHC data are short), and so the ranges of error seem to be fairly narrow.

    • GRACE has only been up their since 2002. It can’t tell you much about 1993. Since recent data shows sea level dropping or a return to historically small rises, maybe they fixed the bad data from the 1990s.

    • Uh, Fred – you may be right – or not. But the sat data has to be ground truth checked if it’s to be properly validated. Do you have any data on that process? I haven’ found any indication that it was done. Maybe I’m looking in all the wrong places?

    • OK – my bad – I WAS looking in the wrong place. HAd my search terms wrong.

    • They calibrate to tide gauges but state this can only detect a change in bias and not an absolute bias

      http://sealevel.colorado.edu/content/calibration

    • This paper wasn’t too complimentary to the accuracy of GRACE

      http://onlinelibrary.wiley.com/doi/10.1111/j.1365-246X.2010.04508.x/abstract

    • The article was behind a paywall so I was unable to read it. I had never heard of the Geophysics Journal International.

      However, as far as I can tell from the abstract alone, the article addressed the use of GRACE for ocean mass measurements, whereas I was referring to its use to measure ice sheet loss, where it seems to have a better established track record. Satellite altimetry doesn’t measure ocean mass, but only looks at ocean height, and so it would be useful for additional methods to complement altimetry to correlate sea level changes with ocean mass changes. Whether GRACE is ready to undertake that task accurately is something I’m not familiar with.

    • I would add that thermal expansion of sea water raises sea levels but doesn’t increase ocean mass, whereas melting of land ice adds to the mass. A method that compares mass changes with sea level changes would be helpful in making the distinction between the two processes more accurate than it is currently..

    • Fred, just for fun, do you think it might be possible to measure ocean thermal expansion, as a global warming artefact, in another way. I find pretty persuasive arguments questioning the validity of sea level changes, especially as the only thing that matters is whether the sea level is rising or falling relative the bit of coast you have concerns about. It is purely and adaption/prognosis issue.

      However, it might be possible to measure sea level expansion by measuring perturbances to the earths angular momentum. If sea level is rising, or more accurately, the ocean is expanding thermally, it will shift a lot of weight outwards, thereby slowing down our day by a tiny tiny fraction. But, over time, that very slight change might be detectable. At least our ability to detect such changes to that level of accuracy is within our capabilities.

      Anyone want to have a go at working out the affect on a single rotation of the earth for an over night and instantaneous 1m increase in average sea level?

      In my view, it’s no less absurd than some of the other forms of measurement currently being used.

    • Agnostic – Length of day changes have been observed as a result of mass shifting, but I don’t have the exact reference at hand at the moment.

    • I’m afraid GRACE is only as accurate as the models of the post glacial rebound in the case of ice sheet measurements and there seems to be some concern as to how well these reflect the real world.

      http://www.jpl.nasa.gov/news/news.cfm?release=2010-298

      http://www.reportingclimatescience.com/this-issue/oceans-and-polar/ice-sheet-loss-estimates-reduced.html

  46. Global Warming: A Guide For The Perplexed
    by Marcelo Gleiser
    Theoretical Physicist
    Appleton Professor of Natural Philosophy Dartmouth College

    http://www.npr.org/blogs/13.7/2011/07/13/137705149/global-warming-a-guide-for-the-perplexed

    …facts.

    1.The Earth is a finite system, which receives most of its energy from the Sun. A small amount of heating also comes from radioactive decay and release from the interior.
    2.The Sun emits radiation mostly in the visible spectrum, peaking at about 500 nm, closely corresponding to yellow light. Some of the radiation is reflected back into space, and some is absorbed and then reemitted back into space as lower-energy infrared radiation. Warming occurs when a larger fraction of the absorbed radiation is trapped near the surface. Think of your car, parked under the sun. With windows closed it gets much hotter inside.
    3.The trapping of heat is caused mainly by what are called greenhouse gases: water vapor, carbon dioxide, methane, and ozone are the main ones. Without these gases in the atmosphere, the average temperature would be approximately 59 ºF lower.
    4.During the past 100 years, the average global temperature has increased by 1 degree Fahrenheit. Global sea levels have risen 4 to 8 inches.
    5.These numbers are not disputed. What is disputed is the cause behind the increase: natural vs. anthropogenic (i.e., caused by human activity)…

    • And your point is…….?

    • Dear Deogenes:

      There are no heat trapping gases. Had they existed ,there would be practical applications for them by now: we can trap clean solar energy and solve the energy/environment crisis that we are in cheaply using these gases; but they do not exist. And as long as we keep thinking with fictional concepts that have no practical or experimental grounds, such as this heat trapping gas concept, we will get nowhere with climate science. Gases absorb heat differently, but there are no heat trapping gases, sorry!

  47. So, Judith and Tony, would a good summary of the point of this paper be :

    In AR4, the IPCC asserted that global sea level had been relatively stable and invariant from around 0 AD to the mid-1800s and then started rising at a much accelerated (and unprecedented) rate to the present However, the IPCC ignored or glossed over extensive archaeological and other data that indicates there have local sea level changes of up to approximately 1 meter during this time frame and that in at least some locations, these data indicate local sea levels which were higher in the past millenium then currently. These data also suggest that at some locations, local sea level changed at rates must faster than the estimated rates for current global sea level change. Because of these discrepancies, the IPCC needs to do a much more thorough evaluation of sea level changes over the past two millenium and the causes for those changes (whether they be local, regional, or global) to be able to support its degree of confidence regarding the unprecedented nature of sea level rise in the 20th and into the 21st century.

    • BobN

      Excellent summary. I think t that I would add in the difificulty of trying to compute a ‘global’ average when no such thing exists, as levels may be rising in some areas and falling in others and to try to average this all out is rather meaningless

      tonyb.

    • Tony – an average is meaningless for individuals in any particular location, but not meaningless as part of an effort to determine how much ocean volume has changed over time, and to correlate that with influx of water from melting of land ice plus expansion of water in response to increases in temperature.

      I do agree with you that sea level changes at a small number of locations are poor indicators of what is happening to ocean volume overall. There are large differences among the different oceans and probably between the two hemispheres.

    • Meaningless is perhaps not the perfect word here. Perhaps its better to say it overwhelms/hides/floods the more relevant/interesting and granular local situations.

    • Fred and Kermit

      Let’s agree that its a poor indicator AND then add in all the derivatives of ‘meaningless’ that Kermit has created.
      tonyb

    • Maybe tony or someone has a better way to phrase it.

      All this averaging by climatologist is troubling to me. You can’t just average everything and then say something like, “well, we took the height of every mountain in the world(or whatever) and then averaged it”. And then say, “so, over the last 20 years (or 100 years) I have made this graph and its going down(or up)” and then fit in how its caused by CO2 AGW.

    • BobN –
      the IPCC ignored or glossed over extensive archaeological and other data that indicates there have local sea level changes of up to approximately 1 meter during this time frame and that in at least some locations, these data indicate local sea levels which were higher in the past millenium then currently

      The IPCC and climate science in general, has made a habit of ignoring the other sciences, archaeology in particular, in pursuit of their predetermined conclusions (pre-conceptual science). SLR is not the only subject in question.

    • I wonder if you and BobN have ever read an IPCC report.

      Sea level science spans many fields, including climate science, archaeology, and other disciplines. Historical, social, geological and archaeological records are a feature in addition to the science reported by the IPCC.

      BTW, sea level science has moved along since the last IPCC report, but Sivan’s work was used for archaeological indicators in AR4. ;-)

    • Sea level science is now so advanced that the history of two thousand years of global sea level can now be determined from the study of two marshes in N. Carolina.
      /sarc

  48. Fred Moolten brought up something that is an important point – rather than concerning ourselves with only the holocene, it is worth looking further back – to previous interglacial periods. In previous interglacials, sea levels are estimated as between 3 and 20 meters higher than present, thought to be associated with “global average” temperatures 2C or more higher than at present (eg. http://pubs.usgs.gov/fs/fs2-00/, http://www.nature.com/ngeo/journal/v1/n1/full/ngeo.2007.28.html).

    Given that previous interglacials were not influenced significantly by humans, are we really able to say that the current trends in sea levels or in temperatures are the result of human activities? Of course, this may still mean that a few of us may end up with wet feet over the next century – but paleo-studies may be telling us that there is nothing we can do about it other than find homes at higher elevations…

    • “Given that previous interglacials were not influenced significantly by humans, are we really able to say that the current trends in sea levels or in temperatures are the result of human activities?”

      Yes.

  49. Nils-Axel Mörner (Open Letter to President Mohamed Nasheed of the Maldives):

    “And let us, for Heaven’s sake, lift the terrible psychological burden that you and your predecessor have placed upon the shoulders of all people in the Maldives, who are now living with the imagined threat that flooding will soon drive them from their homes, a wholly false notion that is nothing but an armchair fiction artificially constructed by mere computer modelling constantly proven wrong by meticulous real-world observations.

    “Your cabinet meeting under the water is nothing but a misdirected gimmick or PR stunt. Al Gore is a master in such cheep techniques. But such misconduct is dishonest, unproductive and certainly most un-scientific.”

    Stockholm, Sweden, October 20, 2009.

  50. This study also discusses a sudden 1 metre rise in sea levels during the period under study.

    http://www2.hull.ac.uk/news_and_events-1/news_archive/2009_news_archive/july/pre-historic_vessel_provides_c.aspx

    30cms seems a common oscillation (in this context) but the increasing number of claims of up to 1 metre will be interesting to examine in Part 2 of ‘Historic Variations’ to see if they also occurred during the MWP.

    tonyb

  51. If there is one thing we have learned, if you are to keep the global warming hoax alive, you must personalize the Global Climate scare-stories—e.g., first you give an ice shelf a name; then, when you hear that if calved-off Antarctica to just float away and silently die alone and forgotten, it’s like hearing that a member of the family has been run over by a drunk driver in a SUV.

    “… the doyen of sea level scientists, Niklas Axel-Mörner… determined the sea level curve over the past 5,000 years based on evidence of morphology, stratigraphy, biology and archaeology supported by extensive C14 dating, and found that ‘All over the Maldives there is evidence of a sub-recent sea level some 20 cm higher than the present one. In the 1970s, sea level fell to its present position’… Our politicians (and some scientists) should base their opinions on real observations instead of alarming us with nightmares of catastrophic sea level rise based on false models of ice caps.” (Cliff Ollier)

    “Serial sovereign defaults and further severe global economic recession seem unavoidable. In these conditions, the ongoing obsession over AGW is looking more and more like a mental disorder, not unlike the mass manias of the Middle Ages… [where] angry mobs may be only too willing to accord full credit to false prophets.” (Walter Starck)

  52. “I think t that I would add in the difificulty of trying to compute a ‘global’ average when no such thing exists, as levels may be rising in some areas and falling in others and to try to average this all out is rather meaningless” tonyb

    Tell me, did you come up with that all by yourself? Since it is making the rounds on all the usual sites, I’m thinking not.

    I’m wondering if you want to argue it on the basis of math, observation or physics.

    Briefly, it is not mathematically or observationally meaningless or pointless as a measure of climate change (along with other data); and as a measure of the estimated volume of water in the ocean (increasing due to ice melt and ocean warming), it has a literal physical meaning and tells us something about danger to coastal and delta regions for risk planning.

    Risk planning is needed because coastal environments are very sensitive to changes in sea level, and especially to sea level extremes. We all know that changes have happened in the past and settlements have coped by moving away: but modern ability to adapt is limited because society has built a lot of infrastructure in coastal areas and climate change may cause highly accelerated sea level rise with the possibility of extremes. Many nations do not have the resources to cope with extreme sea level changes.

    It’s really not helpful when nonsense like yours goes uncorrected.

    • tweet tweet – I am blowing the BS whistle on this. Modern ability to adapt is better now than it ever was.

    • Tell that to Venice Martha. I think the BS whistle was definately called for.

    • “Risk planning is needed because coastal environments are very sensitive to changes in sea level, and especially to sea level extremes. ”

      As someone who lives near a harbor with tide changes of 15 feet (4572mm) and waves up to 6 feet (1828mm) in height if the wind is really, really strong and blowing the right way … I would suggest the harbor master and others who live near it or on it can deal with the normal sea level rise of 200mm per century.

      If you can deal with a 6400mm change in one day, you can deal with 2mm per year.

    • Latimer Alder

      Just back from a day’s sailing in the Solent (near Southampton UK). There are good tides there of about 15 feet and very strong currents.

      i am firmly convinced that those who fret so much about miniscsule changes in sea level have never been anywhere near the sea in their lives.

      If the tides were suddenly to put on extra three feet, that would undoubtedly cause problems. But spread over four or five human generations I do not believe that this will ever get much beyond an annoying fact of life thet we can deal with as apart of normal coastline operations.. Certainly not to a full blown crisis.

      PS – had to leave the boat at Ryde IOW because the entire harbour dries out at low water.

    • The AGW claim that wetlands and other coastal regions are highly sensitive to changes in sea level seems to be yet another AGW truism that would be worth a critical review.
      I will bet that upon review, this claim turns out be just another meaningless, bit of fear mongering.

    • Whats funny is that North Carolina (the site of Mann’s latest hockey stick) has been hit by hundreds of hurricanes and cyclones over the last few hundred years. I think the coastal regions couldn’t care less if the sea level rise is 1.7mm or 2mm.

    • What is funnier is that the internet geniuses who believe Mann think coastlines are some sort of static barrier just waiting for the sea to inundate it.
      I guess the only thing funnier than the believers buying that is that Mann and pals seriously propose it.
      The idea that they are grabbing a 1.7mm or 2.0mm signal out of a system that fluctuates meters per day, much less making a trend out of it, is rotfl hilarious.
      BTW, we spent a lovely afternoon at Atlantic Beach in NC just over a week ago. It was so nice, not too hot, with a fresh breeze. It is a tremendous beach, especially when compared to our skinny beaches here in Texas.

  53. Latimer Alder

    ‘modern ability to adapt is limited because society has built a lot of infrastructure in coastal areas’

    I often hear this idea. But it seems to me that our abilities to adapt are are far greater than they were in the past, We can almost literally move mountains nowadays that we couldn’t do 200 years ago. True, we have built infrastructure close to the sea…but we can easily do so again in a new location. I think of the derelict Isle of Dog sin London…25 years ago a wasteland and now one of the great financial centres of the world. From zero to a lot in a generation.

    Please give at least three concrete examples of where you think our ability to adapt is less now than it was in say, 1661.when the Great Fire of London razed the City.

  54. Chief Hydrologist

    The oceans are never still. For instance – we can get differences in sea level of a metre near Darwin in changes in trade wind intensity. Along with an 8m tidal range. So we are fiddling about with mm’s – 0.55mm/year for water storages, 0.3mm/year for sea bed levels. When we have a fundamental disjunct between ocean temps – http://i51.tinypic.com/dr4hop.jpg – and a near linear rise in sea level. I suspect torturing of data and intend contacting the International Court for Crimes Against innocent Data (ICCAID).

    I am not inclined to worry about a few millimetre/year – the oceans are cooling for a decade or three at least, coastlines adjust and 2100 is a long way away. As an engineer and environmental scientist – I have a very hands on philosophy. I have built coatal defenses and advised on coastal setbacks. The latter is much more environmentally friendly for the luverly turltes and other creatures – a planned retreat if neccessary, putting critical infrastructure (hospitals etc) out of harms way, ensuring through natural disaster planning that people have escape paths, etc. It is not rocket science – and it is not something that is primarily driven by ‘global warming’.

    Cheap and carbon free energy is a decade or 2 away – and we could do much in the meantime if there was any co-operation and good will. Instead – as my newspaer said this morning – there is a global battle against comfortable elites who have decided that there has been enough economic progress in the world.

  55. Martha said;

    “Tell me, did you come up with that all by yourself? Since it is making the rounds on all the usual sites, I’m thinking not.”

    I am surprised that you don’t know that sea level change is variable for a variety of reasons that I covered at length in the full paper.
    However I am glad to see that you are at last questioing the IPCC

    http://ipcc.ch/ipccreports/tar/wg1/433.htm

    More reading here;
    http://www.psmsl.org/train_and_info/faqs/#6
    and here;
    http://www.insidescience.org/research/1.1766

    tonyb

  56. Based on all evidence presented by Tony, IPCC and others one of the essential observations is that there has not been any strong trend in the sea level between years 1 and 1900. There is more difference in claims on the variability over this period. The Technical Summary of AR4 WG1 tells that the variations have not exceeded ±0.25m. Tony tells about local observations of larger variations, but we know that sea level does not vary uniformly but regional differences are great as discussed also in the Box TS.4 Sea level of the Technical Summary and as shown over shorter periods in the Figures 5.15 and 5.16 of WG1.

    Tony has presented much more detailed information than AR4, but what is the proper extent WG1 should have discussed these matters? There is not very much peer reviewed literature to report on to support more extensive texts.

    If the statements of IPCC are not fully justified – and based on the text of Tony and the above discussion this is only a conjecture – what would that mean for the conclusions on climate change and it’s risks. It would evidently mean that the estimates on the variation of sea level are mostly too conservative, and the actual risk is larger than estimated in AR4, not less.

    The discussion on everything related to climate change is sometimes funny. People have taken sides, and they are countering whatever the other side says even when the logical conclusion of the words of the other side work to support their other views.

    For some the main issue is to prove that IPCC is incompetent or malevolent. For that they build up claims of what it should be and search evidence that it’s different, i.e. they use strawman argumentation. Tony’s post has such implications in some of it’s sentences. There is nothing wrong in collecting and presenting the data that Tony has written about, but his conclusions on the related chapters of the WG1 report remain unjustified, because they have been approached from a too narrow point of view and neglecting almost all the valid reasons that are most important, when the IPCC authors choose, what to tell and how.

    • Pekka

      Thanks for your thoughtful comments. My main purpose in writing my historic articles is to demonstrate that there is often greater variability or uncertainity than is often believed, whether it is sea levels, land temperatures or actice ice. Akso that some of the information that is presented to us has doubtful provenance such as SSTs.

      Climate science is still in its infancy and is sometimes making bold assertions that can’t be made at this time. Few things are unprecedented but I doubt our policy makers know that and perhaps might start to take a different view point if they did.

      I do not believe the IPCC is incompetent, malevolent or deliberately involved in a hoax or scam but are sometimes presenting a narrow viewpoint.

      tonyb

    • Tony,

      One error is prevalent when science is presented or criticized – overemphasizing the significance of the particular point presented by the author. That’s a common bias of scientists who write publications and that’s done both intentionally and because the scientist often have a sincere belief that their own research is of more importance that it really is.

      I think that this has been even stronger than average in some of the paleoclimatological papers and I believe that this is at least as strongly present in the criticism of paleoclimatological multiproxy analysis by the skeptical side. Similar problems occur also in other climate science, but not necessarily much more than in other fields of science.

      I would have liked your post more, if you would have changed just a few words avoiding implications, which you didn’t actually even try to support. It’s a fact that AR4 discusses only very briefly the historical sea level variations. That’s by itself is a good reason to look at this evidence more thoroughly. It doesn’t require implying that IPCC has erred in it’s choices or that IPCC would have presented too strong claims. For such implications you should have given much more emphasis on those papers that IPCC did refer to in AR4 and also in TAR as IPCC leaves by out material that has been discussed in earlier reports to keep the length of the text from growing even more.

      Avoiding carefully confrontational sentences is very helpful in getting better acceptance from those, who are not on the same side that they perceive the writer to be. We have seen several comments criticizing your post solely based on such prejudices or your earlier writings. If you are not happy with that, you must be really careful in wording. That will help in time, but the prejudices will persist long. If you don’t care, whether you can get wider acceptance, but prefer applauses from the convinced skeptics, then your choice of formulation will of course be different.

    • Pekka – where is the Isle of Ictis? From the historic descriptions of Ictis, how could it look today?

    • Pekka, have you criticized the IPCC for its lies?

    • The obsession on lies is ridiculous.

    • I have a philosophy on using the word lies and liar similar to the one you appear to have. If you call a liar a liar they don’t really care since they already know they are a liar and are only concerned if you can prove it. If you call an honest person a liar they will think you a fool since you have already proven yourself wrong once and they will become entrenched in their views. One other factor to take into account is the possibility that you may be wrong on both the argument and the ethics of the other person. There is a lot less crow to eat if the argument isn’t personal and I’ve heard crow is most palatable in small bites.

    • Pekka, would you criticize the IPCC for this:

      IPCC: “Oscillations in sea level from 2,000 to 100 yr before present did not exceed ±0.25 m, based on the Roman-Byzantine-Crusader well data (Sivan et al., 2004)”

      Sivan: “The depths of these coastal water wells establish the position of the ancient water table and therefore the position of sea level for the first century AD up to 1300 AD

      Sivan: “The results indicate that during the Byzantine period, sea level at Caesarea was higher by about 30 cm than today. The Late Moslem and Crusader data shows greater fluctuations but the data sets are also
      much smaller than for the earlier periods. The consistency of the data indicates that the near-coastal well data from Caesarea provides a reliable indicator of sea-level change, with an accuracy of about 10–15 cm.

      http://people.rses.anu.edu.au/lambeck_k/pdf/237.pdf

    • Why would I comment on anything you write? Arguing on some cherry picked and mostly misinterpreted claims is pointless.

    • The answer is (as I suspected) Pekka will never criticize the IPCC, no matter how blatant the IPCC misrepresents papers.

    • Cherry picked???????????

      Direct quote from IPCC: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-5-2-4.html

      Countered by direct quotes from the actual Sivan paper?

      http://people.rses.anu.edu.au/lambeck_k/pdf/237.pdf

      And you claim this is cherry picked?????????????

      Wow. You sure sure know how to dig yourself a deeper hole.

    • Rob Starkey

      Bruce

      Actually you are mistaken. Pekka has pointed out flaws in what the IPCC has concluded many thimes in the past and is generally very reasonable in his position

    • Not this time. This case looks like fraud to me.

    • The Sivan 2004 paper also states:

      ‘Sea-level oscillations within 20±15 cm of present day sea level, as had been concluded in this research, have great local and regional importance, both for locating sea level at different cultural periods and for understanding the role and rate of the tectonic component in each archaeological site.

      I think some of the confusion may stem from usage of different conventions for what counts as *today*.

      The paper also states:

      Furthermore, the observations are consistent with the eustatic model assumption of constant ocean volume for much of the past two millenia.

      What’s being stated here is that their results, showing regional oscillation with no particular trend, are consistent with largely unchanging global sea level over the past two thousand years.

      The IPCC statement about sea level oscillation may indeed be a misinterpretation because I don’t think Sivan is proposing his results to be representative of global changes, which would be smaller.

    • Previous research referenced in the Sivan paper:

      “Geological, geomorphological, and archeological data of changes in sea level during the Holocene at the Mediterranean coast of Dor provide a eustatic curve of the region. This curve shows that sea level was approximately 2 meters below the present level 4000 years ago, rose to 1 meter below the present level 3000 years ago, and was 1 meter higher than the present level 1500 years ago. It then dropped to 1 meter below the present level about 800 years ago.”

      http://www.sciencemag.org/content/226/4676/831.abstract

    • Yes, they mention the paper in a discussion of other results from the region, then note:

      The high resolution and accurate data from the wells provide more reliable indicators of local sea-level change than those used in these other arguments.

    • Pekka

      I think you may have a somewhat idealised view of a blog article and how it will be received. In my experience the ‘average’ reader will come to an article with their own viewpoint on climate change–often a strong one-and will immediately determine that articles worth against four criteria, which in no particular order are;

      1) The web site it is carried on-some have much more credibility than others according to the readers personal stance on climate change.
      2) The author
      3) The subject
      4) The stance the article takes -if it matches with the readers viewpoint it will immediately gain much more acceptance than one that doesn’t.

      I try to be a moderate writer with no strident viewpoint and use historic references, together with academic studies and verifiable anecdotes, in an attempt to construct a strong narrative that follows a logical progression in an interesting manner.

      I have an offer for you. Assuming that Judith will allow me to present future articles here, can I suggest that prior to publication you edit it to ensure it has a neutral tone and that the evidence presented is verifiable as far as it can be? Provided it fits those modest criteria you will agree to have your name included as a co author, whether or not the end results agree with your personal viewpoint.

      At the least a joint article will thoroughly confuse readers, but who knows, they may see it as a genuine attempt to present a viewpoint that, whilst possibly challenging the status quo, does so in a measured fashion.

      tonyb

    • Tony,

      I know well that blogosphere has it’s own life and style. Adversarial style may bring more readers and the best article is wasted without readers, but when the content is interesting enough there is more to lose than to gain by emphasizing something else.

      I don’t think I would be interested in being a coauthor in any article, where my contribution is not essentially equal to that of other authors, or which would contain material that I don’t know thoroughly and agree on every detail. Commenting privately to indicate, where a see adversarial formulations, which rather take off than add to the value of the text as I see it is another matter and not excluded, but that would not make me a coauthor or indicate that I agree more generally on the content.

    • Pekka

      Fair enough.

      I’ll run my next article past you at the appropriate time. I hope to take some time off as an author during the summer but expect to start my next article in the autumn-
      tonyb

    • Pekka:
      People have taken sides, and they are countering whatever the other side says even when the logical conclusion of the words of the other side work to support their other views.

      I think there is a more simple and natural explanation for TonyB article. People have been told CO2 emissions are producing an unprecedented climate, and is getting worse. Such statement is rather peculiar. Particularly when you add it to the “end of the world because of the sins of man” moto. So, the natural answer is to look around and say: -Unprecedented, huh, where, how? And you find it very hard to see what’s wrong.

      And then they come with the funny argument: – If it is not unprecedented (bigger variability) is worse than we thought because it means climate is more sensible than we thought. But this is not serious of course. It only means they know quite less than they dreamed.

  57. –> “Tell me, did you come up with that all by yourself? Since it is making the rounds on all the usual sites, I’m thinking not. ’m wondering if you want to argue it on the basis of math, observation or physics.”

    You are having big problems here: Temperature is an intensive variable so an average global temperature is meaningless. Even if the temperature data was not corrupted, and even if a reductionist approach was reasonably practical, no one could ever argue that, for example, the accuracy of a discreet list of NY telephone numbers would be important in determining an average because the average NY telephone number is—meaningless! As a scientist your must first answer the key question: why is determining an average global temperature important?

    “The IPCC assessment reports do not contain any mathematical analysis based on the laws of physics to support their formulae or hypothesis. We are reduced to statistical correlation [like MBH98, aka 'the hockey stick graph which is a proven scientific hoax] between the CO2 content of the atmosphere [The data coming from the site of an active volcano and measured by a father and son team who have turned falsification of data into a cottage industry] and the average global temperature [which is an intensive variable which cannot be meaningfully averaged and has no meaning in the real world] …

    “According to the satellite data, since 1979 there has been no significant increase in global temperature. We have had 20 years of increasing temperature and 10 years of decreasing temperature, while the CO2 content has shown a uniform increase. Hence there is no correlation. If there was, I would ask the question: ‘Is the CO2 causing a temperature change or is the temperature change causing a CO2 change?’” (Barry Moore)

  58. Up above I linked to renditions of Greenland with and without ice.

    I also stated that I thought parts of the Greenland ice sheet are getting taller, and Max cited a study that confirms that parts of it are getting taller.

    This is an interesting graphic that shows the areas that are rising in height and the areas that are diminishing in height.

    Growing taller with a shrinking base.

    So to all the engineers out there, the Greenland ice sheet is a structure. It is buttressed in many places around its girth by mountains. Much of its base is below sea level, or in close proximity to sea level. During the melt season large amounts of water pond up on its surfaces, and run through its interior, and pool up underneath it. I have read that deformation eliminates most of these tunnels and gaps during the ice-formation season, so the meltwater has to reestablish its pathways to wherever each melt season. Eventually gaps could emerge between the mountains and the ice sheet, and ice from above the snow line could be in some trouble.

    How confident are you its heights will hold up? Because, without the heights, the Greenland ice sheet is going to melt faster than it has been to date.

    Got this far, here’s a SLR bone – new article.

    • “How confident are you its heights will hold up?”

      You think its going to tip over or something? tell us what the change is in percentages.

    • Latimer Alder

      I just looked at a map. The maximum height of Greenland ice is about 10,000 feet (2 miles) and the land is about 600 miles across.

      That gives an average gradient of 1:300. 1 foot in 100 yards. This is not a steep slope and I cannot imaine a general instability suddenly developing because the ice sheet is growing at 20cm (6 inches) per year. In 100 years it will grow by 50 feet! From 10,000 feet to 10,050 feet. A change of +0.5%.

      Do yo guys never do any basic sums before posting? Or have you no innate concept of relative sizes? 6 inches per annum is small. 10,000 feet is big.

  59. Title: “It’s the Sun, Stupid”

    “… solar activity since the mid-18th century, low sunspot activity matches up nicely with well-known Little Ice Age climatic events like George Washington’s Christmas-night 1776 crossing of the ice-strewn Delaware River and Napoleon Bonaparte’s retreat from Moscow in the horrifically-cold winter of 1812-1813.

    “The letter writer goes on to mention that not too long ago the Mississippi River froze solid above St. Louis, permitting westward wagon trains to cross in the winter and that you can still see old two-story houses in Wisconsin with second floor doors that allowed inhabitants to exit their homes in the middle of winter when snow depths reached 8-feet and more.

    “If sunspot activity continues to be so markedly low, then we should prepare for the possibility of a significant global cooling trend that could reduce agricultural yields and bring on the sort of food shortages that occurred during the Little Ice Age…”

    (Steven Milloy, Junk Science, November 29, 2007)

  60. Judith,

    I’d just like to draw your attention to the way TonyB has started to use your name to give credibility to his own ‘opinions’ on climate change, sea level etc.

    He’ll regularly use a link like http://curryja.files.wordpress.com/2011/0……

    rather than posting an article and referencing on his own site: http://climatereason.com/Links/

    Whatever the rights and wrongs of your criticisms of the IPCC, do you really feel it will do you any good to be giving free rein to people like Tony Brown? People who make claims, as you can see on the link above, like:

    “They [the IPCC] suppressed over 200,000 records of historic co2 readings made by a host of eminent scientists since 1830, showing that Co2 levels then were as high as today. Having read and researched the material and corresponded with Ernst Beck, I think his conclusions are essentially correct.”

    • tt,
      “People like Tony B”?
      Can you be more of a boorish little boot-lick?
      Were you one of those wimpy little hall monitors that everyone liked to laugh at when you were in school?
      If you were unable to achieve that distinction in school you are certainly achieving it now.
      People like you drone on endlessly as if your faith was not seen as the latest failure of Malthusian delusions and the laughing stock of critical thinking people.

    • tempterrain

      Isn’t it time for you to end your silly vendetta on Tony Brown, just because you personally disagree with his data on historical sea levels?

      The Ernst Beck stuff has absolutely nothing to do with the historical sea level information gathered and presented by Tony.

      Besides, Ernst Beck’s data did show a wide range of atmospheric CO2 readings over the 19th and early 20th century (prior to Mauna Loa), which do not correspond well with the Vostok ice core data used by IPCC.

      Is there any good reason to believe that all of these analyses were faulty or to completely ignore these records?

      If so, what is this reason?

      If the reason is simply “to make a nice, smooth graph that looks good”,(sort of like “hiding a decline”), I’d say that’s a poor reason – wouldn’t you?

      Max

  61. Well yes, Max, CO2 , sea levels, sea temperatures, AGW are all related. I doubt if Judith would get quite so many comments on sea level in the 19th century, and previously, if the view of conventional science wasn’t that CO2 emissions were too high, they are causing the planet to warm and sea level rise is a real future danger.

    But you’ve got to hand it to people like Tony Brown. His line of argument is that

    The increase in atmospheric CO2 levels isn’t caused by human activity, but even if it was, but which it isn’t, then it hasn’t caused the seas to warm because there hasn’t been any warming anyway. But even if if has, but which it hasn’t, then we just don’t know because the data isn’t good enough!

    And we are really expected to take this guy seriously?

    • TT, I really want to know. Where is Ictis? Based upon descriptions of how it looked then (a tidal island,) what are the possible ways it might look today?

    • St Michaels Mount, Cornwall, I’d say.
      http://www.roman-britain.org/places/ictis.htm

    • A pox on you. You are now no longer welcome in all the other places that claim to be Ictis.

    • JCH

      I have responded several times to you rearding Ictis. Please read the FULL article not just this summary. I go into ictis at such lemgths that I had to remove several references and even then it was so long it required this siummary!

      tonyb

    • tt,
      No one takes you seriously, so don’t sweat it.
      ;^)

    • tempterrain

      Can you find me the quotation of Tony Brown that states:

      The increase in atmospheric CO2 levels isn’t caused by human activity, but even if it was, but which it isn’t, then it hasn’t caused the seas to warm because there hasn’t been any warming anyway. But even if if has, but which it hasn’t, then we just don’t know because the data isn’t good enough!

      Or did you just make that up?

      Are we really expected to take YOU seriously?

      Max

    • tempterrain

      That’s my precis of the TB argument. Incidentally, I could have slipped in a clause saying:

      The increase in atmospheric CO2 levels , not that there has been any,

      Note that, unlike yourself, and which I’ve picked you up on previously, I don’t use quotation marks unless I’m actually quoting.

      So which part would you say was inaccurate?

    • TT

      Your precis of my arguent is so stupid it really doesn’t warrant any sort of reply let alone a serious one. However you make such a habit of misrepresenting and misquoting what I say that when time permits over the weekend I will respond.
      You make a very silly comment at 8.26 am and made a link to Judiths site which didnt work Perhaps you might like to repost it so I can begin to understand where you are coming from.

      My own site doesn’t carry any sort of comments-it is a repository for Instrumental temperature records and other related material including articles from myself and others.
      tonyb

  62. Some Germans get climate change:

    • Hockeyschlaeger!

      Umweltschutzer JA
      Klimaschuetzer NEIN

      Klimawandel wurde nicht von Menschen gemacht
      Damit halten sie nur die Menschen in Angst

      What a little cooling and little transparency can do! People are waking up.

    • Glad you liked it. I have sent it to my daughter, who minored in German. I expect to chastised by her, since this video talks of what is heretical for those freshly minted by Universities.

    • tempterrain

      Yes its odd that just about every university science department would agree with the IPCC rather than Rush Limbaugh. What is it with those universities? I thought the people there were supposed to be smart. If people like yourself can see that AGW is all a hoax why can’t they too? It’s just beyond belief -isn’t it?

    • tt,
      Do you still not get what skeptics are talking about?
      Are you aware of the history of science at all?

    • No, it’s not beyond belief, it IS belief – it’s all about belief.

  63. Excellent new article in Der Spiegel on sea level rise, check it out
    http://www.spiegel.de/international/world/0,1518,774706,00.html

    • Not very much consensus there. It appears truly unknowable at the moment.

    • tempterrain

      You’re implying:
      “truly unknowable” = no need to take any mitigating action just yet ?

    • Yes I am. As Dr. Curry has indicated, the uncertainties in some cases far outweigh the known. In other words the uncertainty bars are so large, we do not even know what we think we know.
      At a minimum 30 years of additional observations are needed to even be able to argue the merits of one action or another, or if such actions are even needed.

      Roy Weiler

    • Name one mitigation plan that you believe is workable and would actually impact the CO2 level sufficiently for you to believe it would impact the climate.

    • Preferably one that costs less than $1T/annum/1K “avoided warming” for the foreseeable future. Assuming that A-G Warming is still the target, and not the new “avoidance of all inputs to the climate system because it’s so dangerously violently chaotically touchy” meme. In which latter case we come full circle to Maurice Strong’s “dismantling of industrial society” as the only option.
      Which has, I hypothesize, been the plan all along.

    • tempterrain: “no need to take any mitigating action just yet ?”

      I am worried that the drop in sea level will make it harder for people with homes near the beach to actually walk to the beach since it will be so much further away. :)

    • Who will own the new land?

    • Judith

      This article poimts out that levels in some areas are rising whilst in others it is sinking as I tried to point out to Martha.

      An article on the merit of ‘global’ averages whether they are sea levels or temperaturres might be an interesting topic . A global figure hides many nuances such as uhi, areas that are cooling or faling sea levels.

      tonyb

      tonybdouble the average,” says Claus Böning from the Leibniz Institute. “Elsewhere, levels are even sinking, for example at some Pacific islands and in the Indian Ocean.” Ocean currents are largely responsible for these differences, he and colleague Franziska Schwarzkopf recently reported in the journal Geophysical Research Letters.

    • The geographic variations in the rate of change of sea level are shown also in the Figures 5.15 and 5.16 of the AR4/WG1. The downwards trend in the middle Indian Ocean is visible in those figures both over a period of 48 years from 1955 and over the shorter period 1993-2003. For the longer period the area of negative trend is very small, but it’s there.

    • tempterrain

      Yes it is, on the whole, a balanced and fair article. It’s a pity that Murdoch’s rag, the WSJ, can’t do the same when it comes to reporting on scientific issues.

      I did notice this though: “[Scientists] two years ago found coral reefs that are six meters above sea level today were under water 125,000 years ago. Sea levels must have been much higher at the time. And the climate was much warmer than it is today.”

      Right, except that the climate wasn’t much warmer. It was only slightly warmer then. About 2 degrees warmer which is what is generally considered to be our target maximum for AGW today.

  64. There is an obvious agreement centering on ~1 meter by 2100. The ever stubborn Holgate is apparently not publishing except in private emails to Tony B, so there is no way to evaluate his logic, but he is begrudgingly acknowledging up to one meter in the worst scenario. His colleagues continue to publish, and they’re saying ~1 meter is on the table. Hansen’s logic is here, starting at page 14.

    And the comment about the ice sheet not completely melting? What’s up with that? No ice sheet has to completely melt to reach ~1 meter by 2100. Not even close.

    • JCH

      IPCC has given us estimates on sea level rise by 2100, which are tied to CO2 and temperature projections, based on various “storylines and scenarios” as outlined in its AR4 WG1 SPM report.

      The top two “scenarios” assume a higher level of atmospheric CO2 than is contained in all the “possible inferred fossil fuels in place” on our planet according to a 2010 report of the World Energy Council (the maximum possible ever level remaining in our atmosphere when all fossil fuels are gone is around 1065 ppmv).

      [If you would like to see the backup for this statement, please let me know.]

      So we can automatically discard the two most extreme “scenarios”, (A2 and A1F1) leading to warming estimates averaging 3.4°C and 4.0°C, respectively.

      These are the same scenarios that project sea level rise of 0.23-0.51 meters and 0.26-0.59 meters, respectively.

      So we are left with scenarios B1, A1T, B2 and A1B, with estimated increase in sea level ranging from 0.18 to 0.48 meters.

      IPCC is not known for underestimating the impact of AGW on our climate, so these estimates are very likely on the high side, rather than understated (my opinion).

      The record shows that the rate of sea level rise fluctuates greatly on a decadal basis, from a high exceeding +5 mm/year to a low of –1.5 mm/year over the 20th century, so short-term records are fairly meaningless for making long-term forecasts.

      Since they started in 1993, satellite altimetry readings showed a linear rate of rise in sea level averaging around 3.1 mm per year from 1993-2003; since 2004 the linear rate of rise has slowed down to 0.7 mm per year to date. Over the entire 18+ year period since 1993, this represents an average annual rate of around 2.1 mm/year.

      If this rate were to continue, we would see a rise of 0.21 meters by 2100.

      My personal guess, based on all the data I have been able to see, would be that a rise of 0.2 to 0.4 meters by year 2100 would not be unreasonable. Anything exceeding 0.5 meters would be questionable and anything exceeding 1.0 meters would be unreasonable..

      But that is just my opinion, after having checked the data out there.

      Max

    • JCH

      Sorry about bold type. Somehow the formatting did not work,

    • First, I do not consider current rates of SLR, up a bit or down a bit, to have much at all to do with the prediction of ~1 meter by 2100. I find referring to them to be very odd. Do they indicate dynamic changes in ice sheet melting are now ruled out? Of course not.

      Here is a table of scenarios and SLR outcomes in 2100.

    • JCH

      Have seen the table you cite. Have a look at the “Der Spiegel” article and references cited by Judith.

      I like this quotation:

      Whereas James Hansen expects a five meter rise, his colleague Simon Holgate says that “I think that even in the highest emission scenario we won’t exceed a global average of one meter of sea level rise by 2100.”

      OK.

      Simon Holgate is a renowned sea level expert.

      Hansen is a NASA climate modeler turned AGW activist of “tipping points” and “coal death trains” fame.

      I’ll place my bet on Holgate, rather than Hansen, thank you.

      Max

    • tempterrain

      Except you won’t be around to collect your winnings! I agree that 5 metres looks too high from what we know at the moment – at least as far as the year 2100 is concerned.

      But if a few degrees of extra warmth produced this level of sea level rise in the Eemian period, then you’d have to ‘place your bet’ on a similar level happening again – eventually. The question is: How far into the future do we need to consider?

    • tempterrain

      We may actually AGREE!

      IF there did happen to be a long-term global warming of several degrees C, and this new higher temperature were to hold for several decades or centuries, then it is very possible that sea levels would rise, maybe even by meters above today’s levels.

      (Of course, you and I would be long gone before that could happen.)

      I just do not believe that the evidence is there to support the likelihood of such a major long-term temperature increase – at least not as a result of humans burning fossil fuels.

      (And that is probably where we do NOT agree.)

      Max

    • tempterrain

      JCH,

      You’ve mentioned the year 2100 twice. Any particular reason for that? Do you expect to be any more dead in the year 2200 or 2300 than in the year 2100?

    • TT – it’s just the way the scientists talk about it. I remember you once (IIRC, first day you were here) asked about what comes after 2100, and I have also asked that same question many times.

      They talk as though mankind steps through a doorway in 2100 and passes into a new dimension, like a sort of problem-free universe. So if it’s not that bad by 2100, peachy keen, man.

  65. The mysteries of how the reply function works on this blog continue to rival the mysteries of the climate.

  66. I think I understand how the nesting function works. Just follow the vertical lines on the left to connect the threads.
    Can I have a position on the IPCC now? A nice big pay cheque from George Soros, or the UN , would come in quite handy at the moment :-)

    • Check in with the guys at RC. They seem to have that well understood.
      Be sure and say ‘please’ real nice.

  67. #500 TonyB? (As per your WUWT comment ;-) )

  68. PeteH

    Please collect your large gift from the reception area :)

    tonyb

  69. Hm – blockquotes seems like a waste of time, but hey, two out of three ain’t bad. I just learned some stuff :)

  70. La Ni˜a

  71. Hm. How about ‘La Niña’ and ‘El Niño’

  72. More experiments..

  73. Añteros?

  74. Hey there, I think your site might be having browser compatibility issues.
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    but when opening in Internet Explorer, it has some overlapping.
    I just wanted to give you a quick heads up! Other then that, fantastic blog!

  75. We are a group of volunteers and opening a new scheme in our community.

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