Fundamental questions on Isostasy and Mean Sea-Level

Guest post by Andi Cockroft

Firstly, let me declare that I am not a current student of Geology or Geophysics. I studied Mathematics, Computer Science and Geology at University way back in the 60’s and I have focused my entire working life in IT. To this day, I still run a small IT company in New Zealand.

I follow the workings of the climate models with interest, since much of my University life was spent on Numerical Analysis and Stochastical Processing – the pre-cursors to today’s modelling. Although back then, Computer power was measured in kilo-flops, and the first mainframe I worked on was 20K. A 1Mb mainframe was but a pipe-dream – our biggest was 128K.

On the other hand, my groundings in Geology were at a time when my Professor was still agnostic about plate tectonics (although my tutor was an avid proponent thankfully). It was a time when magnetic striping of the mid-Atlantic was known but not totally understood. It was also a time when isostacy (although an old theory) was finding new support.

So, I offer this post not as any particular expert in the field, but rather to stimulate discussion from those far more familiarity with the concepts than I – please feel free to correct my impressions and limited understanding of the various topics

All I am proposing here are some of the fundamental questions that bother me regarding Isostacy, melting or re-freezing ice-caps and the effect on global mean sea-level (GMSL).

Firstly, just what is GMSL? I don’t believe it can ever be measured against one specific location on the globe – for just about everywhere on this planet is in motion to some degree or other – north/south, east-west, up/down – although our impression is of a stable terra-firma, geologically speaking it isn’t – it is more like the skin of a rice-pudding floating on the more fluid layers below.

If you ever played with your rice-pudding as a child, let the skin form and then pressed on it with your spoon? Press on one place and the skin will rise in another. So the Earth responds to increasing or decreasing pressures (or mass) on its crust.

The earth’s crust (or lithosphere) “floats” on the more fluid asthenosphere. The thickness and relative buoyancy of that part of the lithosphere will determine just how high or low it will “float”. When the buoyancy is in balance, it is said to be in isostatic equilibrium. There are many places that still today are not in isostatic equilibrium.

image

In terms of mountain building, where for instance the Indian plate is hurtling northwards into the Eurasian plate giving rise to the Himalaya Mountains – the gravity measurements tell us that just like an iceberg, there is just as much if not more “Everest” below the crust as there is above it – the buoyancy of that extra material below is needed to support the weight of the Mountain Range above.

Imagine ice floating in a bath – add more weight on top and the ice will sink such that the Archimedes principle of displacement is yet again in equilibrium. Indeed, add too much weight and the whole iceberg will sink regardless – but that’s a diversion (think 2Km thick glacier!)

So back to the question – what is GMSL? To my way of understanding, it can only be measured against a theoretical spot, and must in this age of satellite and gps be measured relative to a reference datum and/or the calculated centre of the earth. Since the earth is not a true sphere – it is I believe referred to as an “oblate spheroid” – the averaging out of these measurements must be translated back into local datum to be able to measure against tide-gauges etc.

Then again, I have always maintained that Sea-Level is a local phenomenon – for many reasons.

Tides, temperature, winds, air-pressure as well as such phenomena such as ENSO etc

But given that statements implying GMSL was 300’ lower than today during the last ice-age, I ask the question – “but what was the real or relative sea-level back then in say New York State?” – in places under Kilometres of ice apparently. Certainly what is now the Great Lakes was inundated by huge ice flows.

That sheer weight of ice would have had the effect of pushing the underlying land-mass downward, to some extent counteracting the drop in GMSL – in fact (just in my imagination) – I believe that these areas would have been significantly below GMSL even with its 300’ decline.

Sorry I do not have the knowledge to do the calculation, but I hope here that group-science can answer the question.

There have been statements that New York was about 150 – 200 Kilometres inland during the last Ice Age 20,000 years ago – but would it have been? Wouldn’t Isostacy have taken the land-mass down with it?

One of the problems faced by modern day measurements of GMSL, is that Isostacy is still at work.

Remove the massive ice-flows from ice-age North America, and the continental land mass does not rebound instantly – it rebounds (uplifts) slowly – it is still rebounding today. As things equal themselves out over Geologic time, the land masses continue to rise, and as a counter, the ocean basins are actually falling. In other words, the oceans themselves gain a greater capacity to store water.

This expansion needs some accounting for, and this Global Isostacy Adjustment (GIA) is estimated at about the equivalent of 0.3 mm per year in GMSL, this at least partially offsets the predicted 3mm per year expansion of the oceans due to warming (that seems to have paused just now). Indeed, if thermal expansion of the oceans has paused, GIA will continue unabated and actually serve to lower observed GMSL.

All of this is a very roundabout way of me arguing that Sea Level is a local phenomenon, and calculating a GMSL whilst academically interesting serves no actual use. Certainly not in terms of Government and Policy decision-making.

imageIn England, long before Liverpool was ever heard of, the River Dee provided the main shipping for the North West. First Chester (used by the Romans), then further out to Burton and Neston and ultimately Parkgate were the main points of embarkation for Ireland. Visit Parkgate today, and the sea is many hundreds of metres away with a huge salt marsh in between.

In New Zealand, where I have lived this past quarter-century, there are many places where erosion is eating into the coast and houses are inexorably marching towards oblivion. In others, accretion of up to 1 metre per year is extending the land-mass ever seaward.

image

Yet Local Government in these areas is focused almost entirely on projected changes to GMSL rather than what is physically happening.

The local authority here is planning on Climate Change bringing inundation despite all the evidence that the sea is retreating !!!

imageHowever, I digress. Looking further at Geologic Changes, and back to Isostacy for a moment, where two tectonic plates collide, one usually will ride over whilst the other suffers subduction. This is where we will find seismically active areas (sadly Christchurch here and many more such as Japan, China etc). We will also likely find mountain-building – as mentioned earlier, the Indian plate is still moving northward (150mm or 6” pa), and the Himalayas are still rising (5mm or 0.2” pa) – in geological terms still very active.

At the same time, the subduction zone may well create significant volcanic activity – New Zealand has its fair share.

But just about anywhere plates collide will see some degree of uplift. Again using New Zealand as an example, the main mountain range in the South Island is the Southern Alps. Current measurements show an uplift rate of about 7mm per year.

How this translates into vertical movement at either east or west coast I have been unable to determine, but it has to be happening, and ongoing.

In Wellington, the biggest recorded earthquake was a magnitude 8.2 in 1855. This uplifted the east of the City between 2 and 3 metres. Today’s airport is built on this uplifted land, and the current business district sits on reclaimed marshland exposed at that time.

Wandering along Wellington’s Lambton Quay (where boats used to dock), reveals brass plaques set into the pavement showing the shoreline in 1840 – the current Quay is about 300 metres away.

Given the magnitude of that earthquake, I suspect Wellington’s rate of uplift over larger time-intervals will be outpacing GMSL, but I could be wrong. By thesis, Cole (2010) identifies a shift in vertical position around 1944 – this following two large earthquakes in the preceding years.

There is nothing to suggest that Wellington’s upward thrust (to the east of the Wellington Fault) has ceased, so the next “big one” will likely see further uplift and hence a relative drop in Sea Level.

Local effects of Plate collisions, Isostacy rebound (eg Great lakes) etc., all serve to modify the impact of GMSL .

If we are to believe recent reports, some of the small Island Nations such as the Maldives may in fact be growing rather than being swamped under an ever-rising tide. Explain that one – I understand coral growth may be at work here but I’ve not seen anything truly convincing yet.

In other places, we are seeing true inundation but usually accompanied by more rational explanation such as pumping ground water.

So is the observed increase in GMSL of 3mm pa actually causing any significantly observable effects?

I remember the Thames Barrier being built to protect London from inundation, but that was to protect against a storm surge – where a massive low pressure system in the North Sea causes a correspondingly massive increase in local Sea Level. This is of the order of metres, not 300mm per century.

And one final question. As Cole (2010) discovered, atmospheric pressure has been falling over time.

image

Ill-equipped as I am to perform the calculations, is this drop in barometric pressure yet one more factor affecting the calculation for GMSL?

As I said at the start, I do not have the skills necessary to answer these and many other questions posed above – just taking a leaf out of “justthefacts” methods – and asking from you the pundits to engage and answer via group-science. Be kind for I am not as used to this medium as Anthony and other major players.

153 thoughts on “Fundamental questions on Isostasy and Mean Sea-Level

  1. “And one final question. As Cole (2010) discovered, atmospheric pressure has been falling over time.”

    Automotive vacuum leaks. You will notice that atmospheric pressure was rather stable until about 1976 which is about the time the PCV was invented for cars. this generally includes a rubber hose that goes from the valve cover to the manifold vacuum. Those hoses spring leaks which eats up an enormous amount of atmosphere every year. In fact, if people were aware of the amount of atmosphere disappearing into automotive vacuum leaks every year, they would absolutely demand that their politicians do something about it.

    Another explanation is that things just pretty much suck these days compared to 1976.

  2. Interesting questions.
    You did post something I was not aware off, the atmospheric pressure declining over a long period of time. That fact alone demands more study.
    Thank you.

  3. The average of all sea level gauges produces a sea level rise of just under 2 mm/yr versus the 3 mms/yr we have been told. The sea level gauge values are effectively flat and declining in the most recent few years.

    Let’s think about the last few years when even the satellites are showing a decline. The recent La Ninas have produced more rainfall of which 25% falls on land and, thus, water accumulates on land and sea level therefore falls. That means even the ENSO and its rainfall patterns can upset the steady rise of sea level. Therefore, it must be a low number to start with and not be strictly related to warming.

    Keep it coming Andi. You have a great writing style.

  4. Thanks for cogent factual if non-formulaic reprise. Hadn’t realized that global atmospheric pressures show a century-long decline… the term for isostatic equilibrium is from Latin “isostasy,” thus no “c.”

  5. …thanks for comments to date

    Please forgive my olde-worlde spelling – I did actually have a classical English education, so many words tend to be spelt differently today. Isostacy is one such – I was brought up to spell such words this way rather than the more modern Isostasy.

    And thanks John Blake – but I think it’s actually from the Greek Isos and stasis – but you actually very correct – no ‘c’ in its derivative.

    Andi

  6. A quick comment on falling atmospheric pressure and sea-level. Ig atmospheric pressure is falling globally (which means we are losing gas to space) it should have no effect.

    The sort of low pressure rise you were talking about that the Thames barrier is supposed to protect against, is a localized low pressure area, the opposite of your pressing on your rice pudding skin … “sucking” the water up (with a consequent small fall everywhere else).

    But, if the atmosphere really is leaking away, that will be a very small reduction in pressure on the earth’s crust, allowing it to spring up just a tiny bit faster … but I would hate to be the one tasked with measuring that :-)

  7. Excellent questions and observations Andi , but unfortunately, you will not get the answers you are seeking . That is because no one knows the answers. That is why we AGW skeptics are winning this battle. No one, and no group of scientists can clearly saw without 100% doubt or clarity, that mankind is causing the planet to warm ( in my opinion the notion is plain silly ) .
    Your article is great , very thought out , and you are legitimately looking for answers, and have given the article a lot of deep thought.. That is how I became a skeptic. After thinking through all the potential variables, ( the sun for one example ) I had a hard time believing the IPCC, but when climategate emails revealed the conspiracy, I knew it was over, also, when Al Gore announced on CNN that the ” debate was over “….I said ” what debate ” ….I cannot recall a debate, I saw a lot of fluffy over the top statements by a lot of high paid politicians…
    Anyway, I will check back tomorrow to see if you get any answers to your comments, and good luck, and welcome to the group of non-believers in agw..
    Ian

  8. Look! An upside down hockey stick! The sky really is falling! Lookit the pressure dropping! Falling I say! And falling at an accelerated rate!

    WE’RE GOING TO RUN OUT OF AIR IF WE DON’T DO SOMETHING TO STOP THE SKY FROM FALLING!

    Ok, Ok, so it isn’t falling, it is leaking out to space. Either way we’re running out of air. All we need is something to tax that will prevent it and…. Ok, STFU dave… we’ve got enough taxes already.

  9. Philip Peake says:
    March 3, 2012 at 7:05 pm

    Hi Philip – yep, Thames Barrier very deffinitely for severe localised depression in North Sea – probably forming off Norfolk Coast and moving south the last big one I remember.

    As for losing atmosphere to space – just look at the graph – 1.2 millibar drop in a century – that’s huge. If indeed it is lost – we’d have nothing to breath within 100,000 years !!!

    But if we see Global Mean Atmospheric Pressure change over time – that is a mean over the globe and over each year – it is unlikely to be uniform over all water at all times – it’s not as though we had just a single container full of water with a single atmospheric pressure uniformly distributed.

    So my question still stands will it impact calculation of GMSL ?

    Cheers. Andi

  10. There have been statements that New York was about 150 – 200 Kilometres inland during the last Ice Age 20,000 years ago – but would it have been? Wouldn’t Isostacy have taken the land-mass down with it?

    A seemingly reasonable argument for the lower sea level during the last glacial advance can be supported by the under water drainage networks of the continental shelves.
    For example, on North America’s east coast, see

    http://pubs.usgs.gov/of/2004/1441/html/intro.html

    On the west coast, see
    (Figure 1):

    http://earthquake.usgs.gov/research/external/reports/06HQGR0149.pdf

    On land, in North America, the extent of glaciers and topographic features from the outflow of lakes on their southern margins have been studied. These suggest (to me) that the depression of the land mass is also very regional – that is, not depressed very far out from the terminus of the ice.

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

    Go to the part on “Geologic history”; click on map for a readable version.

  11. I read that for every millibar decrease in atmospheric pressure there is one centimetre rise in sea level ( under the low pressure area). According to tthe last figure the average pressure has fallen by 1.4 millibars so sea level would have increased by 1.4 centimetres; another factor ignored by the IPCC computer models.

  12. Thanks Andi for many Interesting questions.
    I was particularly interested in the revelation that pressure was declining at a measureable rate. All in all your post was a breath of common sense in an area studded with fanatical lunacy Your questions all demand more study.

  13. I was under the impression that the claim of “300’ lower than today” sea levels was based on evidence of ancient shorelines at the edge of the continental shelf, around 300 feet or more below today’s shorelines.

  14. Ian says
    That is because no one knows the answers.
    ———-
    Ian, just because the people here don’t know the answers does not mean no one knows the answers.

    I don’t know the answer either, but I bet I can find out, and there will be some science articles filled with math that will take me a week or 2 to digest.

    The thing is just cos you guys can think up obvious objections, does not mean they have not already been thought of and solutions found.

  15. After a quick perusal of Theresa Cole’s 2010 thesis, I noted the following items:

    1. Auckland’s historic annual mean atmospheric pressures at sea level (Figure 5.7 on page 116). This chart shows no observable trend in atmospheric pressure pressure between 1916 and 2007.

    2. Historic global annual mean atmospheric pressures at sea level (figure 5.8 on page 117, i.e. the chart shown in the post). This chart does show a drop in sea level air pressure.

    3. I further noted that the Historic global mean atmospheric pressure data were “derived from the Hadley Centre sea level pressure dataset.” Now given the fact that the Hadley Centre and its employees have been embroiled in a number of climate change data “fudging” incidences, why should I believe their data instead of the locally produced Auckland data?

    What I really want to see are collections of atmospheric pressure data from many (hundreds or thousands) locations around the globe. This type of data would either support or contradict the assertion that atmospheric pressure is decreasing. Relying on a heavily processed data set from a suspect data source will not cause me to jump up in a panic. Show me the raw data, then and only then will I decide what is more likely the truth.

  16. I don’t understand what kind of answer is expecting. When water warms it expands and when ice melts it flows into the sea. These processes follow physical laws.

    Temperatures and sea level changes can thrn be cross checked with each other to see if they are consistent with each other. Missing information can be measured to improve the accuracy.

    If the satellites are measuring changes in sea level they don’t actually need a reference point. That won’t stop them from defining a reference point if one is required.

    All this requires the collection of lots of information but it’s basically an auditing process.

    No one here has the time to do this properly so all you will get is lots of handwaving and the multiplication of confusion.

  17. Andi, the questions that you raise are good ones.

    The information needed to guide local coastal planning is Local Relative Sea Level, the global average (=eustatic) sea-level being an abstracted quantity.

    For a readable account of the sea-level change issue, I recommend Chapter 4 in Bob Carter’s book, Climate: the Counter Consensus.

    Kindle or printed copies are available, reviews and ordering details here:

    Cathy

  18. Re: As Cole (2010) discovered, atmospheric pressure has been falling over time.

    Perhaps a general slow warming of the atmosphere is causing the lower atmospheric pressure.

    Warmer air is lighter, colder air is heavier, and both change the air pressure as they pass through the neighborhood.

    From Wiki:
    “In general, high-pressure areas are associated with cooler, drier air as well as clearing skies due to their formation within areas of atmospheric subsidence, or areas of large-scale air descent. The strongest high-pressure areas are associated with arctic air masses during the winter, which modify and weaken once they move over relatively warmer water bodies.”

    If the pressure is going down, it might be getting warmer too.
    That could be one explanation.

  19. davidmhoffer says: “WE’RE GOING TO RUN OUT OF AIR IF WE DON’T DO SOMETHING TO STOP THE SKY FROM FALLING!”

    Wrong, David. All that missing air is being held under pressure in the inner tubes of vehicles and such bladders.

  20. A little bit off-topic, but look what Arctic ice is doing. Not too unexpected for the medium term future, but so soon ??

  21. Andi, nice paper. There is a paper on WUWT re comparing Texas with North East USA that has the numbers that you seek. It specified how much the great lakes was depressed and how much they have rebounded and how much more they have left. I am not clear how to find that paper here for you but somebody will.

    Where i live, Malaysia sea level was several metres higher in the recent past. Lots of sea caves in rice paddies.

  22. Roger Carr says:
    March 3, 2012 at 8:39 pm

    All that missing air is being held under pressure in the inner tubes of vehicles and such bladders.

    ————————————————————————————————————

    Why don’t we fill all tires with CO2 instead ? A good sequester for CO2 and perfect as a fire extinguisher if you ever have an engine fire… a rubber hose with a nozzle… that would be handy and dandy. And imagine the recycling fees on a tire full of toxic CO2 poison. The taxman and the UN warmers will love it.

  23. If global average atmospheric pressure is declining, then the mass of the atmosphere is declining. The only possible cause over these timescales is decreasing water vapor and condensed water (clouds).

    The main atmospheric pressure decline corresponds with the main period of late 20th C warming, the mid-70s to the mid-90s. Which indicates the two phenomena have a common cause. Although the relationship breaks down in the lead up to the 1998 super El Nino and subsequently.

    Decreasing atmospheric water vapor and clouds can either result from less surface evaporation (mainly ocean) or increased precipitation.

    In my view the common cause is decreasing anthropogenic aerosols over this period. While aerosols are known to act as condensation nuclei they are also known to decrease precipitation efficiency and prolong cloud lifetime (see link below, table 1).

    Decreasing aerosols will have decreased this effect, increasing precipitation and decreasing atmospheric mass.

    As I have previous explained decreasing anthropogenic aerosols was also a significant and in all likelyhood the primary cause of the late 20th C measured warming. Thus the common cause.

    http://hal-insu.archives-ouvertes.fr/docs/00/29/56/33/PDF/acp-5-715-2005.pdf

    The increasing precipitation efficiency resulting from decreased aerosols will have also contributed to rising sea levels during this period.

  24. crosspatch says:
    March 3, 2012 at 5:50 pm

    “And one final question. As Cole (2010) discovered, atmospheric pressure has been falling over time.”
    Automotive vacuum leaks. You will notice that atmospheric pressure was rather stable until about 1976 which is about the time the PCV was invented for cars. this generally includes a rubber hose that goes from the valve cover to the manifold vacuum. Those hoses spring leaks which eats up an enormous amount of atmosphere every year. In fact, if people were aware of the amount of atmosphere disappearing into automotive vacuum leaks every year, they would absolutely demand that their politicians do something about it.
    Another explanation is that things just pretty much suck these days compared to 1976.

    Crosspatch, in all the years that I’ve been reading this blog I have never read one that had me ROFLA (rolling on the floor laughing out loud). I almost fell of my chair! Thanks!

  25. An article in the Washington Post on early artifacts.

    http://www.washingtonpost.com/national/health-science/radical-theory-of-first-americans-places-stone-age-europeans-in-delmarva-20000-years-ago/2012/02/28/gIQA4mriiR_story.html?hpid=z5

    It tends to provide some physical evidence for a much lower sea level during the ice age. From the article: “Lowery also contacted the Cinmar’s captain, Thurston Shawn. The tusk and blade were so unusual that Shawn had made a point of marking the spot on his charts. It was 60 miles east of the Virginia cape, in 240 feet of water. At the end of the last ice age, when the oceans were low, that spot was land, on the coast.”

    Recovered in a scallop were a Mastadon tusk and an 8″ stone blade. So yes, there is at least some physical evidence or lower sea levels.

    Thanks for the article

  26. Could it be that water vapour is gradually precipitating out of the atmosphere to lower the pressure over time? If so the liquid water will still be applying mass to the crust but more localised in rivers and lakes and spread over the ocean.

  27. Anything is possible says: March 3, 2012 at 9:34 pm

    “No mention of the Geoid yet? That does a nice job of complicating things still further.”

    Yes, the geoid is the right way of defining GMSL.

  28. crosspatch says:
    March 3, 2012 at 5:50 pm

    Crosspatch,

    That is the dumbest and funniest thing I’ve seen on these pages in quite a while. Thanks for the belly laugh! I’m glad I had just cleared a swallow of gin and tonic, before I read that….. It doesn’t feel very good when it squirts out your nostrils!

    Thanks again! I needed that.

    MtK

  29. I recall at the time the Thames Barrier was built that the consensus [sorry] was, the north half of the island had been depressed by the ice caps, and was slowly tipping back towards equilibrium now that they have gone. Evidence was the white cliffs of Dover, being sort of ‘tear along the dotted line’. Also, the increasing weight of London itself (built on clay). Some places in Scotland still rise and fall with the weight of the tide.

  30. Mean sea level atmospheric pressure is 1013mb. Cole’s graph suggests around 1008mb. Seems strange.

  31. Andi,
    A thought provoking post – Thank You!
    Interesting, that Cole 20101 tidbit about decreasing atmospheric pressure. The following potential ’causes’ occur to me:
    1) Atmosphere gases are being lost to space, suggesting a weakening magnetic field for earth perhaps combined with a more active sun over the time period studied.
    2) Significant amounts of atmospheric gases (N2 and O2) were being extracted from the atmosphere by chemical reactions and ‘tied up’ in inorganic compounds on the planet, sufficient to reduce atmospheric pressure.
    3) Water vapor in the atmosphere is decreasing over time, cause(s) unknown.
    4) The Cole 2010 study is in error. Atmospheric pressure is not decreasing.
    5) Crosspatch 5:05 pm knows more than he is telling!

    Sincerely, Thanks for contributing!

    Mtk

  32. Warmer temperatures (UHI) might account for lower barometric pressure. Urbanized areas causing a “heat low” where rising air from urban sprawl creates more days with lower barometric pressure.

  33. If that air then cools and settles where there doesn’t happen to be a barometer, the corresponding increase in pressure somewhere else gets missed. The areas that are most likely to have a the most barometers are also the areas most likely to have UHI impact. So I guess it is also possible to have ULPI (urban low pressure islands).

  34. I’d bet that the decrease in atmospheric pressure is related to an actual loss of atmospheric gases to space via auroral fountains and such. This might just be caused by the decreasing strength of the magnetosphere over the last 150 years or so. At least that’s what I’m thinking.

  35. Hi Andi,

    Good article! I’ve had the same ‘problem’ with sea level measurements for a long time now. It seems to be assessed as if it’s a body of water inside a pan of specified size and known bottom. In reality, it’s on the surface of a globe, and the sea floor and ‘edges of the pan’ are constantly changing. Likely more important is that it’s rising over here while it’s falling over there, many thousands of volcanoes are adding to the sea floor, erosion moving sediments into the ocean, tides and currents depositing sediments in other areas, tectonic plate movement as you noted, and so on. Then you see earthquakes such as Japan’s, where subsequently significant areas that were above high tide level now no longer are, and a large area of the sea floor is known to have significantly shifted. All of these things and others I’m sure I’ve omitted or don’t even know about are constantly ‘playing’ with the shape of the ocean basins and edges.

    Look at some of the GRACE satellite renderings of the earth’s shape based on gravity – all of that must impact oceans also. It’s like the oceans are contained by silly putty walls and floor that’s constantly being warped, cracked, filled in, and so on, rather than something with a fixed shape.

    I fully admit that this has been my conceptual game when it comes to sea level, however, and I haven’t taken the time to educate myself on the state of the research in this area. As a result I’ve always sort of shrugged my concerns off and accepted that the scientists studying sea level likely have some reasonably idea of how to factor in some (most? a few?) of these factors. I took that attitude even tho I’ve seen some research that was far too easy to punch holes in simply based on evaluating basic scientific method compliance or lack thereof. Of course the shenanigans occurring with ‘climate science’ have made me a bit more leery of just trusting the scientists – especially if they are actively associated with AGW type research and are only looking at sea level issues in that context.

    Anyhow, that’s my two cents – I’m right there in the same boat with you just lookin’ and ponderin’ the sea level!

    To: davidmhoffer says: March 3, 2012 at 7:44 pm, and Roger Carr, thanks for the levity! (if I’ve missed anyone who added to the jokes, it’s because I haven’t read all the comments yet)

  36. re post by: crosspatch says: March 3, 2012 at 11:26 pm

    If that air then cools and settles where there doesn’t happen to be a barometer, the corresponding increase in pressure somewhere else gets missed. The areas that are most likely to have a the most barometers are also the areas most likely to have UHI impact. So I guess it is also possible to have ULPI (urban low pressure islands).

    Crosspatch, sorry I missed including you in the thanks for humor!

    Just try saying ULPI out loud, rapidly several times in a row, folks, I dare you!

  37. RE: John F. Hultquist says:
    March 3, 2012 at 7:50 pm
    “These suggest (to me) that the depression of the land mass is also very regional – that is, not depressed very far out from the terminus of the ice.”

    A really neat example of this is seen in the sheer sides of Scandinavian fiords. During the tens of thousands of years the last Ice Age lasted, ice poured out from a Scandinavian ice cap (like Greenland’s) in its interior, grinding away at the rock in valleys. At any given moment the ice in these valleys weighed roughly the same, however the total weight of ice and rock did not stay the same, because you have to subtract the weight of all the rock that was ground to powder and washed out to sea. Then, because the weight of the rock was less, there was a local isostatic rebound much like the rebound you see when the weight decreases due to the melting of ice. What this means is that the rock on either side of a valley glacier is rebounding upwards even as the center of the valley is worn away and moves downwards. The more it grinds away, the higher the sides of the valley rise. In a sense a glacier builds its own retaining walls, and an icecap builds its own restraining circle of mountains.

    An elegant paper on this topic is found at http://folk.uio.no/yuripo/papers/medvedev_geology_2008.pdf

    Scandanavian scientists seem to produce the best work on this stuff. I assume it is because they have only to look around at their local landscape to see examples of isostacy.

    As far back as the late 1700’s a Swedish geologist noted the sea seemed to be sinking in Scandinavia even as it seemed to rise in parts of Greenland. (The southern tip of Greenland was actually rising as the rest of Greenland sank, because the weight of ice towards the center pushes crust down, causing a plastic movement sideways beneath, causing a rise in the edges.)

    Further north in Greenland the weight of the ice coming down the valleys, due to the Little Ice Age, was depressing the land at the foot of the valley even before the ice went that far. To me this suggests there may be evidence of Viking ports in Greenland underwater. (Send me the grant money, and I’ll send hot-blooded young scientists in wetsuits up there to scuba dive, looking just off shore in Greenland’s fiords for Viking artifacts, as I work in a warm office staffed by beautiful blonds in Olso.)

  38. @Lazy teenager
    when water warms, it expands. are you sure about that ?

    when ice melts it flows into the sea. are you sure about that ?

  39. A change in atmospheric pressure of 1 mbar equals about 1 cm difference in SL. See this bit from the Jason2 Data Products Handbook

    5.10.1. Inverted Barometer Correction
    As atmospheric pressure increases and decreases, the sea surface tends to respond hydrostatically, falling or rising respectively. Generally, a 1-mbar increase in atmospheric pressure depresses the sea surface by about 1 cm. This effect is referred to as the inverse barometer (IB) effect.
    The instantaneous IB effect on sea surface height in millimeters (see parameter inv_bar_corr) is
    computed from the surface atmospheric pressure, Patm in mbar:
    inv_bar_corr = -9.948 ∗ (Patm – P)
    where P is the time varying mean of the global surface atmospheric pressure over the oceans.
    The scale factor 9.948 is based on the empirical value [Wunsch, 1972] of the IB response at mid
    latitudes. Some researchers use other values. Note that the surface atmospheric pressure is also
    proportional to the dry tropospheric correction, and so the parameter inv_bar_corr approximately
    changes by 4 to 5 mm as model_dry_tropo_corr changes by 1 mm (assuming a constant mean global surface pressure). The uncertainty of the ECMWF atmospheric pressure products is somewhat dependent on location. Typical errors vary from 1 mbar in the northern Atlantic Ocean to a few mbars in the southern Pacific Ocean. A 1-mbar error in pressure translates into a 10 mm error in the computation of the IB effect.
    Note that the time varying mean global pressure over the oceans, P, during the first eight years of
    the T/P mission had a mean value of approximately 1010.9 mbar, with an annual variation around
    this mean of approximately 0.6 mbar. However, the T/P data products provided a static inverse
    barometer correction referenced to a constant mean pressure of 1013.3 mbar.

    In regard to the Geoid, here’s one map. Note the scale.

  40. Erm, doesn’t The ideal gas law have something to say about falling pressure and it’s effect on the temperature of a gas? Anyhoo, I would have thought that with our vast knowledge and teraflops of computing power, we could have a damn good stab at working out the volume of water in the oceans instead of using a surrogate like global sea level.

  41. I guess there are more questions here that we’re unable to answer. Oh sure we have our hypotheses, but these are mere guesses, and nature shows over and over again that things are different.

    One problem for instance is that the theoretical ice volume that would have to match the sea level lowering (ca 130 meters) during the Last Glacial Maximum, can’t be matched on land, without violating some observations somewhere. It used to be on Siberia, until it was discovered that there was no ice at all. Meanwhile it has been revealed that Antarctica did not really have a lot more ice during the Last Glacial Maximum. So now we are looking at a gigantic American Ice Sheet of 4-6 kilometers thick, that must have accumulated in a mere 100,000 years, while the 3km thick and fast accumulating ice sheet of Greenland took at least 200,000 years. So where-ever you want to put that ice, you’re violating something one way or another.

    But do we know how mantle slab movements modify the sea level and what about a pulsating earth, the equatorial bulge growing and shrinking?

    http://beyondprophecy.blogspot.com/2010/05/equatorial-bulge-growing.html

    I think that we are not even in the infancy of understanding what’s going on with Earth, deep below our feet and what it did to sea levels in the past.

  42. In regard to the difference between satellite observations and tidal gauges see this map

    It shows the MSL trends from Oct 1992 to Jul 2011. Note the large red orange blob north and east of Australia. the sats indicate this area has experienced sea level rise of 9-12mm/yr for the entire nearly two decade period. Now consider this story

    http://www.theaustralian.com.au/national-affairs/sea-level-rises-are-slowing-tidal-gauge-records-show/story-fn59niix-1226099350056

    Tidal gauges that are pretty much cheek by jowl with the area the sats claim as having about the fastest rising SL on the planet show not much happening

  43. Andi,
    The upper surfaces of Middle Holocene marine beaches (around 6000 years old) in the Greymouth area on the West Coast of the South Island of NZ are 10 to 12 m above modern sea level. So the relatively recent coastal uplift rate is around 1 to 2 mm/yr. I suspect the uplift is episodic (associated with earthquakes). The same age of marine beach at Hokitika is at a max of about 6 to 8 m above sea level. There are ancient raised beaches at Point Elizabeth near Greymouth that are present on wave cut marine platforms up to 180 m above modern sea level. Uplift has clearly been happening for a long time, potentially more than 100,000 years.

    The coastal uplift rate is highly variable around the South Island. For instance long term uplift rates are relatively rapid in North Canterbury, but very slow around Banks Peninsula (despite the recent Christchurch earthquakes).

    In terms of the determination of long-term coastal uplift rates in New Zealand reliable information is scarce. This is because the ages of most of the indicators of ancient sea level are rather poorly constrained in most areas. There is literature on the subject but you will need to get into the relevant Research Journals and GNS reports to find it.

  44. Dear Andi,

    I have followed the Mörner vs. other scientists exchange. Unfortunately, it has been more repeated statements of opinions rather than a debate.
    Mörner maintains that the sea level hasn’t changed lately more than the last 100 years, while the other side maintains that it’s raising at an accelerated rate.
    The difference seems to be about the “adjustments” to the satellite measurements. The adjustments seem to have been introduced a few years ago and with them the acceleration in the sea level rise appeared. I have not seen a simple comparison between the old sea gauge based average sea level change and the modern satellite based one presented on the same chart, someone who have localized anything like that?
    I have not read more than the summaries of the scientific reports; the reports themselves are hidden behind paywalls. If one has an interest in reading literally hundreds of reports annually, it becomes too expensive, at least for me, to purchase them all. Typical price is $ 39.95. (Where did they learn pricing? At Wall Mart spring sales?) Hence, I try to keep informed by WUWT, CA, RC, research home pages, and so on – and with the occasional exchange of emails with scientists that care to answer my questions. (You spotted my Oxford comma?)

    Dr Gary Mitchum is a leading expert on the subject of sea level measurements. My short exchange of emails with him:

    “ Dear Dr Mitchum,
    I read on your website “The method of producing the tide gauge estimates of altimeter drift that we report here is described in detail by Mitchum (2000) and will not be discussed in full here.” and this is the reason that I email you.
    I have a question about altimeter drift in satellites for sea level change measurement.
    How comes that one use the sea level gauges to adjust the altimeters? Why not fix points on land in areas that are regarded as the most stable? The altitude of the satellite will then be determined by the fix points, and the sea level will be determined by the satellite. As long as the same altimeter is used, the physical drift in space as well as the instrument drift will be automatically be adjusted for. After all, it’s the change in sea level that so many people are interested in today.
    I feel certain this “solution” must have been considered by the scientists so I hope that you can help me with an answer and/or references.
    Best regards,
    Knut Witberg”

    Dr Mitchum kindly replied:
    “In fact, the tracking stations that determine the height of the satellite are on land. This determines what we call the orbit height. But the basic measurement of the altimeter is the time delay for the radar pulse from the satellite to the sea surface, and changing that to a range (i.e., the height above the sea surface) requires estimating the index of refraction along the entire atmospheric path. There are a number of measurements that must be made to do this, and all are possibly subject to drift or offset errors. Also, the orbit from the tracking stations (and now GPS as well) is relative some defined reference frame, which has possible drift and offset errors as well.

    So we need an independent set of measurements to monitor the stability of the altimeter measurements. That’s what the tide gauges are used for.
    Note carefully that we do not adjust the altimeter to agree with the tide gauges. We only look for unexplained drifts or offsets, and if any are found the various components of the altimetric system are all checked for possible errors. The tide gauge data are purposely kept independent.

    The method you propose would work if there were no errors in the reference frame used in defining the height of the satellite, and if we knew the index of refraction perfectly. Unfortunately, that is not the case, but on the positive side, a substantial body of work has shown that the tide gauge stability check can detect drifts at the level of a fraction of a millimeter per year and offsets of less than a few millimeters. Also, the errors associated with these stability checks are carefully propagated through to (most) estimates of sea level change.

    Best regards, Gary Mitchum”

    Dr Mitchums article on the subject can be found here: http://sealevel.colorado.edu/content/improved-calibration-satellite-altimetric-heights-using-tide-gauge-sea-levels-adjustment-lan

  45. Roger Carr says:
    March 3, 2012 at 8:39 pm
    davidmhoffer says: “WE’RE GOING TO RUN OUT OF AIR IF WE DON’T DO SOMETHING TO STOP THE SKY FROM FALLING!”>
    Wrong, David. All that missing air is being held under pressure in the inner tubes of vehicles and such bladders.>>>

    Nonsense. I did the calcs. If everyone on earth emptied their bladders at the same time, it would raise sea level by a fraction of a mm and air pressure change would be zero.

    Oh wait… you meant tires?

  46. Lawrie Ayres says:
    March 3, 2012 at 7:55 pm

    I read that for every millibar decrease in atmospheric pressure there is one centimetre rise in sea level ( under the low pressure area). According to tthe last figure the average pressure has fallen by 1.4 millibars so sea level would have increased by 1.4 centimetres; another factor ignored by the IPCC computer models.
    —–
    kbray in california says:
    March 3, 2012 at 8:37 pm

    Re: As Cole (2010) discovered, atmospheric pressure has been falling over time.

    Perhaps a general slow warming of the atmosphere is causing the lower atmospheric pressure.

    Warmer air is lighter, colder air is heavier, and both change the air pressure as they pass through the neighborhood.

    Lawrie:
    As you note, the decrease in pressure raises the sea only locally; it’s sucking water in from elsewhere. If the the pressure drop is everywhere, there is no elsewhere. No no go.
    kbray;
    warming air is only less dense (lighter) locally; it doesn’t decrease the total mass of the atmosphere, just pushes it around a bit. Not relevant. Also no go.

  47. Muller (?) disputes the rise altogether; much of the calibration of the world’s gauges and satellites is (incredibly) based on a Hong Kong benchmark, in a known rapid subsidence zone near the overbuilt harbour.

    The are deep deposition layers of incompetence and chicanery in the world’s data bases, in direct proportion to their relevance to policy (= gov’t-directed money flows).

  48. Thanks Andi, and one and all commenters. It is a pleasure to listen in on a discussion of physical science where confession to a degree of ignorance is not a confession of weakness, but a profession of curriosity. I live less than 2 meters above sealevel and less than 20 meters from it’s edge. Sounds precarious, but so far so good. I have heard many factors mentioned in the discussion including the very interesting information coming from the Grace satelite. I would like to contribute two points of interest. The first is that gravity works three-demensionally: it tends to pull the earth into a masswise perfect sphere. The second is that rock density plays a big role: rock density is highly dependent on silica content: rocks with high silica content have a density close to 2.5 gm/cm3. Rocks with low silica content have a density close to 4.0 gm/cm3. That is a huge difference, and the tendency for crustal rock to differentiate into high-silica and low silica rock minerals is well-known and reasonably well understood. The continents of earth are composed primarily of high silica rocks and the ocean floors of earth are composed primarily of low silica rocks. Even if there was no water on the earth, it is probable that continents would have formed and floated above the low-lying ocean basins. The difference in density between continental crust and oceanic crust is greater than the difference between water and air! It would seem that earth’s oceans are merely the cisterns into which earth’s water collects. One can only marvel at the concatenation of circumstances under which the earth formed. On Venus and Mars, different dynamics have predominated.

  49. Seriously, let’s put the pressure change back into perspective. Instead of plotting on a scale from 1007.0 to 1009.0, let’s do the exact same plot but with a scale of 0 to 2000. Right after it, plot the global temperature on a scale from 0 Kelvin to 500 Kelvin.

    Then take a look at two almost perfectly flat lines and ask what the fuss is about.

    This business of putting things under a microscope in order to declare a macroscopic trend is akin to a third rate 60’s era sci fi flick featuring ants as monsters. Hey, zoom out, their just freakin’ ants!

    We cannot even measure atmospheric pressure to tenths of a mb anymore than we can measure temperature to hundredths of a degree, let alone “average” the values across the globe and arrive at number with error bars that aren’t off the scale of what we’re supposedly measuring.

  50. Dave Wendt;
    the 1mbar : 1 cm ratio requires some justification. If that’s global, where is the water being moved to/from? Or is that a compressibility factor? I know water, especially saline, is slightly compressible, but that much?

    I wonder if there’s a biological angle. Buildup of biomass necessarily means withdrawing material from the atmosphere, in the form of CO2 and water vapour, plus (indirectly) some nitrogen. Over geo-time, it’s hardly negligible (see coal beds and limestone deposits, e.g.)

  51. crosspatch says: March 3, 2012 at 11:26 pm

    If that air then cools and settles where there doesn’t happen to be a barometer, the corresponding increase in pressure somewhere else gets missed.

    Sounds bass-ackwards to me; if air is cooling, compressing, and settling it’s pulling air from somewhere else, reducing that area’s pressure. Pressure is a result of vertical mass, not temperature per se.

  52. You really need to talk to Prof Nils Axil Morner, the world authority on sea levels but here is a bit to get on with.

    The planet is not a sphere, as you stated, in fact oblate sphereoid does not even cover it. The surface is very irregular and the surface of body drawn with surface gravity readings the same is the mean surface of ocean level. The ocean mean levels do not conform to a body of constant radius but to this gravitic body. For instance the Indian Ocean surface is some 140 meters below that of the mean Pacific or Atlantic. This mean surface level is daily changed by wind, atmospheric pressure, currents solar and lunar gravity and probably other inputs like evapouration, river input of frest water, salinity etc.

    Conplicated? you bet.

    Isostacy is another input and complication. Yes there are land level changes due to isostatic readjustment after the last ice age which are still ongoing, which will still cause minor earthquakes, and sea level rises in one place (sinking land), say SE England, are counteracted by sea level falls in another (rising land), Scotland in this case though not equally all over Scotland with the east coast rising less than the west coast.

    Prof, Morner has all this tied up but even his studies go unreported. His study of the Maldives, for the Maldives Government, concluded that they were experiencing sea level falls. Not what the Maldivian government wanted to hear so they refused to release the report to the public but had an underwater cabinet meeting to reinforce their demands for compensation (money) for climate change sea level rises. Your suspicion that corals grow to keep pace with sea level rises are correct as they aim to grow within their part of the surface waters with sufficient light. Corals love sea level rises but sea level falls will kill corals.

    This is by no means the whole story but I hope it helps and thanks for the post.

  53. Pluck thinks that without water there would still be continents. Probably not because water is vital for the low temperature, differential melting in subduction zones that produce the high silica, and lighter, rocks, that form the continents.

    • Response to John Marshall: Yes, water plays a very interesting role in the formation of minerals, and not only in subduction zones. The effects of water are fascinating, both flowing and stagnant, and when present in trace quantities or in excess. My point was that the density of crustal rock varies significantly. The continental rock tends to be light and bouyant and ancient. It rides atop heavy, fresh oceanic rock from which it is chemically distinct. You make a very good point, that water as component of minerals. Two thoughts along these lines: first, how much water is needed for water to have a significant effect; second, how deep does the water need to be to have significant effects as the critical point where water can no longer boil is roughly two kilometers.

  54. “So back to the question – what is GMSL? To my way of understanding, it can only be measured against a theoretical spot, and must in this age of satellite and gps be measured relative to a reference datum and/or the calculated centre of the earth. Since the earth is not a true sphere – it is I believe referred to as an “oblate spheroid” – the averaging out of these measurements must be translated back into local datum to be able to measure against tide-gauges etc.”

    This raises the question of precision. All measuring points, whether ‘fixed’ on the Earth’s surface or on a satellite, are in motion. So if the centre of the earth is the reference datum point can it be pinpointed to an exact location allowing measurements to a precision of a few mm? In addition satellites are moving through a gravitational field that is not consistent while experiencing the full heat of the sun, followed by the complete absence of the same, every 40mins, and when in the sun only one half of the satellite will get the suns heat.

    Recently, experiments at Cern indicated that the speed of light had been broken. This now looks to have been a problem with the equipment used to measure. The way in which the scientific community considered this assault on a central pillar of modern science was refreshing and at odds with the way any reasonable quizzing of CAGW is handled. So the speed of light still cannot be exceeded. As we all know how GPS works, wouldn’t a satellites speed close to a large body that has an inconsistent gravitational field mean that precision becomes very relative?

  55. crosspatch says:March 3, 2012 at 11:26 pm
    If that air then cools and settles where there doesn’t happen to be a barometer, the corresponding increase in pressure somewhere else gets missed. The areas that are most likely to have a the most barometers are also the areas most likely to have UHI impact. So I guess it is also possible to have ULPI (urban low pressure islands).

    So now Anthony has to gin up another volunteer army to go out and evaluate barometer siting. Gas up the car, Evan.

    As far as the 300′ of sea level rise/fall, the density of the asthenosphere is 3 to 4 times that of the ice piling up on the continents, so the ice won’t push the continent down nearly as much as its thickness. The plasticity of the asthenosphere will affect the rate at which the continents sink. Is 100,000 years enough to push them as far as they will go, or do the glaciers start melting before they’ve bottomed out? The continental shelves generally have a shallow slope, so it doesn’t take a lot of fall to move the shoreline quite a ways out.

    The glacial isostatic adjustment is totally bogus with regard to sea level. Any “rise” that isn’t really a rise but a deepening of the ocean is absolutely useless. Well, other than to keep from admitting that Baraq Obama was right when he said of his election that “this was the moment when the rise of the oceans began to slow… ” Bangladesh isn’t going to drown because the ocean got deeper.

    The barometric correction is another knob to twiddle to make things work out the way they want. Over the entire surface of the oceans, the barometric pressure differences should average out to zero, and the satellites do cover pretty much the whole thing. And how much of the ocean surface has barometer readings available?

    No global warming, no sea level rise, no tax increase. Desperate measures must be taken to counter this desperate situation.

  56. davidmhoffer; I’m showing my age. We don’t do tubes in tyres (tires) anymore, do we…

  57. Extremely interesting. I don’t usually think about geology, so this is mostly new to me.

    Should we be considering Urban Weight Islands as well as Urban Heat Islands? Over the last 50 years, vast quantities of iron, concrete and other heavy stuff have been extracted from inland areas and transferred to fast-growing cities, nearly all of which are on coasts.

  58. Layman thinking.
    I do not think a GLOBAL decline in pressure will do anything at all to the sea level. Local differences in air pressure just moves the surface water. However, a temperature change do have impact on the volume, thus changing the level.

  59. Great post and I think your “just the facts” approach will be productive. The drop in atmospheric pressure is more than interesting. If a shift in atmospheric CO2 of about .000001% a year warrants urgent global action, then surely the apparent loss of the whole atmosphere at the rate of .001% a year means we need to light our hair on fire immediately. I’m only half joking here. Where’s the outrage? More importantly, how do we make money off it?

    Returning to the main topic, I hope we can get some useful perspective on what sea level “means” for policy and politics. All politics is local and unfortunately I fear that the climate change-mongers will buy votes from the places where the sea level is falling as well as those where it’s rising. Because it needs “study” and “infrastructure preparation.”. And the mayor’s cousin needs a contract to build a sea wall…

  60. On the assumption that isostacy changes are gradual and consistent, local tide gauges should at least tell us whether long term sea level trends are changing?

  61. LazyTeenager says:
    March 3, 2012 at 8:34 pm

    If the satellites are measuring changes in sea level they don’t actually need a reference point. That won’t stop them from defining a reference point if one is required.

    Well that doesn’t make any sense. Firstly, your second sentence contradicts your first sentence. Secondly, if the satellites are using an earth reference to achieve mm accuracy how do you know if the earth reference is stationary (elevation wise)?

  62. Bill Illis says:
    March 3, 2012 at 6:35 pm

    The average of all sea level gauges produces a sea level rise of just under 2 mm/yr versus the 3 mms/yr we have been told. The sea level gauge values are effectively flat and declining in the most recent few years.

    Bill, this implies sub-mm measurement accuracy. I would expect it would take a decade or so just to see a signal so how can we be sure flat to declining sea level in just a few short years?

  63. Pluck says:
    March 4, 2012 at 2:17 am

    I have heard many factors mentioned in the discussion including the very interesting information coming from the Grace satelite.

    Pluck, have you noticed that nothing bad ever comes from the Grace satellite over the U.S.?

    • As interesting as the reults from Grace, in North America they place a mascon (mass concentration) in Mexico and in the Washington State, Oregon area. However, the GOCE satellite fails to confirm these features.

  64. Roger Carr says:
    March 4, 2012 at 3:54 am
    davidmhoffer; I’m showing my age. We don’t do tubes in tyres (tires) anymore, do we…>>>

    Well no we don’t, but we do fill them with compressed air. This off sets the aforementioned vacuum leaks in the engines. My guess is that this is where flat tires come from, vacuum leaks in engines that empty the tire.

    Swiffer should jump on this bandwagon…. no more vacuum cleaners, bad for the atmospheric pressure….

  65. Andi,
    Thanks for a most interesting article.
    If I may make one suggestion, I think you should stress more strongly that Global Mean Sea Level is like the Global Mean Temperatures. It is a human construct, an invented number, and has no physical existence. It cannot be measured anywhere, but is rather derived from combinations of other numbers of varying quality and precision.
    The effect of it supposedly increasing on any real physical location on earth is unknown.

    Even local sea level is a complex subject. e.g. the UK Mean Sea Level at Ordnance Datum Newlyn, was set by taking a tide gauge reading every 15 minutes and averaging. From 1915, to 1921. (the years, not the clock times :)

    As such, it is perfect as a proxy for ‘Climate Change’, ‘Global Warming’ or any other hobgoblin of the day.

  66. EternalOptimist says:
    March 4, 2012 at 1:02 am

    @Lazy teenager
    when water warms, it expands. are you sure about that ?

    when ice melts it flows into the sea. are you sure about that ?

    I smell a straw troll.

  67. To Andi Cockroft:
    Thank you for your clear and unambiguous presentation.
    I often complain here that the specialized language used by the “intellectual upper crust” far exceeds my learning from 6 years “at the university” where I studied Mathematics, Chemistry, Physics, Biology and Geology. I was especially pleased that you made an effort to explain language that may have been technical to most of those with lesser education. Again, Thank You!
    Now I am going back and try to understand what everyone else had to say.

  68. Slight correction

    “Certainly what is now the Great Lakes was inundated by huge ice flows”; “flows” > “floes”.

    I’ve jumped over all comments, so apologies if this has already been pointed out.

    IanM

  69. Sorry to do this, but it’s “isostasy”, not “isostacy”.
    I have found some other instances of “flow” instead of “floe”.

    IanM

  70. Sounds bass-ackwards to me; if air is cooling, compressing, and settling it’s pulling air from somewhere else, reducing that area’s pressure. Pressure is a result of vertical mass, not temperature per se.

    No, an area of high pressure is where you have air cooling and descending. That is why you have no clouds in a high pressure area. And I was NOT joking. In California, we experience “heat lows” in our desert. When you have air that is rising, you have a low pressure area. If the air is moist enough, you have condensation as that air rises and get rain.

    THAT was NOT humor. When you have increased urban heat, you have air rising and lower barometric pressure. The rising air pulls in surrounding cooler air which is also heated and rises. The city acts as a convection heater.

  71. Caleb says:
    March 4, 2012 at 12:31 am

    Caleb,
    Thanks for the link. I suppose this same set of processes went on at
    Gros Morne National Park, Newfoundland. Fjords rebound to become fresh water lakes.

  72. Phillip Peake informs us that gas escaping to outer space won’t matter much. Reminds me of Tony Hancock’s immortal line when the doctor refers to his blood sample (rather than the full donation) as a pinprick – ‘it might just be a pinprick to you but it’s bloody life or death to me mate’.

    How much of our air has got away already?
    Why has it gone away, and can we get it back?
    Can we complain to anyone about this?

    • Steve Fox: the atmosphere seems to be a great mystery to me. It doesn’t follow ordinary logic. Here, in our own small solar system, planets broadly similar to ours with hardly a breath of atmosphere, Mars, and a hundred times our atmosphere, Venus. Venus is often mentioned as a planet where global warming has gone wild: 860°F and a hundred thousand times more carbon dioxide. On Venus, is it so hot because there is so much carbon dioxide? or is there so much carbon dioxide because it is too hot to form carbonate minerals?

  73. Dirk;
    Yeah, that’s the guy. But not that doc.

    http://www.climatechangefacts.info/ClimateChangeDocuments/NilsAxelMornerinterview.pdf

    So, for example, those people in the IPCC [Intergovernmental Panel on Climate Change], choose Hong Kong, which has six tide gauges, and they choose the record of
    one, which gives 2.3 mm per year rise of sea level. Every geologist knows that that is a subsiding area. It’s the compaction of sediment; it is the only record which you shouldn’t use. And if that figure is correct, then Holland would not be subsiding, it would be uplifting. And that is just ridiculous. Not even ignorance could be responsible for a thing like that. So tide gauges, you have to treat very, very carefully.

  74. Andi Croft,

    “As I said at the start, I do not have the skills necessary to answer these and many other questions posed above – just taking a leaf out of “justthefacts” methods – and asking from you the pundits to engage and answer via group-science. Be kind for I am not as used to this medium as Anthony and other major players.”

    We appreciate your candor.

    There are the sorts of people who follow this blog who probably can answer some of the questions, you raise, [I can’t] and I’m sure the rest of us would be interested in the answers. So, I propose a method to help that process along; which is to revise this post and add what might be termed ‘anti-footnotes’ to it. At each point in your article where you raise a point that you can’t actually answer put a number, then at the bottom of the post for each number place a statement or question that defines the issue that some interested reader can then take home and work on. Answers can then be replies here in the comments, or have Anthony promote the ‘answer’ to a guest post if warranted. The advantage is that the ‘rest of us’ can keep track of what the original question really was in the first place, and where it originated in your article.

    I know I’m proposing extra work for a lot of other people, but here is a case where I have to admit I’m not qualified either.

    W^3

  75. As a fellow geologist of yore (though my education goes back to the mid-70s when plate tectonics was firmly accepted), I fell compelled to pick a nit about his statement “In Wellington, the biggest recorded earthquake was a magnitude 8.2 in 1855. This uplifted the east of the City between 2 and 3 metres.”

    Earthquakes do not cause the land to rise. The land rising (or sliding) very, very quickly along a fault causes the earthquake. Maybe it’s just me, but I think that saying an earthquake caused the land to rise, or slip, xxx meters is putting the cart before the horse. It’s like saying the shock wave caused the explosion.

    It’s a very, very tiny nit, but one that always bugs me.

  76. EternalOptimist says:
    March 4, 2012 at 1:02 am
    @Lazy teenager
    when water warms, it expands. are you sure about that ?
    when ice melts it flows into the sea. are you sure about that ?

    Both statements are false. 0-4C. evaporation.

  77. I checked the NOAA web-site and it seems they reset the tidal gauges every 20-30 years (I find that hard to believe). Also the mean sea level (MSL) needs to be “updated” every so often because it has a 19 year cycle. Is there a place to get unadjusted tidal gauge measurements?

    http://tidesandcurrents.noaa.gov/est/faq.shtml

  78. Sea-level rises and falls as Earth’s giant ice sheets shrink and grow. It has been thought that sea level around 81,000 years ago—well into the last glacial period—was 15 to 20 meters below that of today and, thus, that the ice sheets were more extensive. Dorale et al. (p. 860; see the Perspective by Edwards) now challenge this view. A speleothem that has been intermittently submerged in a cave on the island of Mallorca was dated to show that, historically, sea level was more than a meter above its present height. This data implies that temperatures were as high as or higher than now, even though the concentration of CO2 in the atmosphere was much lower.

    http://wattsupwiththat.com/2010/02/11/new-paper-in-science-sea-level-81000-years-ago-1-meter-higher-while-co2-was-lower/

  79. Terry Jackson says:
    March 3, 2012 at 9:29 pm
    An article in the Washington Post on early artifacts.

    http://www.washingtonpost.com/national/health-science/radical-theory-of-first-americans-places-stone-age-europeans-in-delmarva-20000-years-ago/2012/02/28/gIQA4mriiR_story.html?hpid=z5

    Recovered in a scallop were a Mastadon tusk and an 8″ stone blade.

    More evidence that humans were in North America much earlier than typically believed. How did they cross over the glaciers to reach the east coast if first settlement was indeed from Asia via land bridge?

  80. Its makers probably paddled from Europe and arrived in America thousands of years ahead of the western migration, making them the first Americans, argues Smithsonian Institution anthropologist Dennis Stanford.

    “I think it’s feasible,” said Tom Dillehay, a prominent archaeologist at Vanderbilt University. “The evidence is building up, and it certainly warrants discussion.”

    At the height of the last ice age, Stanford says, mysterious Stone Age European people known as the Solutreans paddled along an ice cap jutting into the North Atlantic. They lived like Inuits, harvesting seals and seabirds.

    The Solutreans eventually spread across North America, Stanford says, hauling their distinctive blades with them and giving birth to the later Clovis culture, which emerged some 13,000 years ago.

  81. ferd berple;
    This data implies that temperatures were as high as or higher than now, even though the concentration of CO2 in the atmosphere was much lower.>>>>

    No, what it shows is that sea levels were higher at that place on earth at that time scale. Why is conjecture.

  82. The shoreline of French Guiana is in some trouble from sediment redistribution, due to natural and anthropogenic causes, the main cause being the 18.6 lunar cycle and secondary causes including dredging. I especially like Figure 1 which shows a 10 cm rise and fall in the MSL. One question is “does the mean sea level return to its original value taking into account the lunar/solar cycles only, or are there longer cycles that we don’t know about”. When you’re talking about mm per year over decades after removal of a +/- 10 cm 18.6 cycle I think that is a fair question.

    http://www.lthe.fr/PagePerso/gratiot/publi/gratiot_et_al_NGeo08.pdf

  83. I’ve finally finished reading all comments (and the articles). Both were interesting and informative. I try to read everything at WUWT and CA because it is like a continuing university education in a subject that I knew little about before. Thank you, Andi, Anthony, and Steve (and others).

    IanM

  84. “Wandering along Wellington’s Lambton Quay (where boats used to dock), reveals brass plaques set into the pavement showing the shoreline in 1840 – the current Quay is about 300 metres away.”

    I was in Wellington last month and toured the downtown waterfront. The area from the water to the base of the hill on which the Beehive sits is composed of fill. It was produced by human effort, not a sea level change. I suspect that is true of most if not all of the flat areas adjoining the harbor.

  85. I have only read some of the comments, so apologies if I repeat anyones thoughts

    I did my first degree (geology) in the 70’s – so I know what you mean regarding stubborn professors, even though plate tectonics was pretty well accepted (Oh no – concensus science again! LOL), there were still some diehards!!
    The primary issue, IMO, is that there needs to be a suitable datum as a start point. This datum needs to be used as reference across all the areas/oceans of sea level measurement.

    I don’t know, but I should imagine that a number of satellites could cross reference several fixed points within their ‘view’, suitably overlapped with other satellites and should, with care be able to produce a 3D GPS based image of those fixed points. I have no idea of the actual GPS satellite accuracy, but if they could get sufficient overlap and sufficient points, perhaps they could measure the actual ‘shape’ of the landmass parts of the earth reasonably well and as I say, produce a 3D image – (but I somehow doubt it!). The generic term Geoid is supposed to be applicable to an equipotential earths surface and I seem to remember Grace was supposed to help in this regard, but how it relates to possible satellite height measurements, again, I don’t know!

    Movement between these ‘fixed’ reference points would clearly indicate isostatic or crustal movements – but the crux of the issue is the 3D aspect, which would give an indication of the volumetric change. The more points, the more accurate the indication.

    Hence, if we were to take the view that say increased solar gravity (when we are nearer the sun!) pulls the earth ‘out’ a bit – this could be reflected in the apparent (3D) measured volume? Theoretically, we may even see the ‘tug’ of the moon as it passes around too, along with any other gravitational planetary conjunctions?

    Then, the actual volume of the earth (a rough sphere, or the geoid) is critical in defining the surface area, and thereby, the area upon which a given volume of water can reside.

    Thus, if we imagine a balloon expanding or contracting, with a thin surface thickness of some viscous fluid (treacle?) upon its surface, as the balloon expands, the fluid thickness decreases, or as it contracts, the fluid thickness increases. As a very rough analogy, this is what I imagine an expanding or contracting earth will do to the sea level.

    So, as a reference datum – I feel the earths ‘volume’ measurement (and any variation therein) is critical as a starting point. Thereafter, the next data is likely to be the actual sea level surface at many points around the globe, corrected for lunar/tidal influences. Again, the change in sea level measured around the globe may be seen to be related to the earth reference volume (or not?). As we have seen, SL measurements are seemingly difficult on their own!

    But, also of course – the land mass ‘image’ is only 30% of the earth surface! – so we also need to have an accurate idea of the depth of the seafloor(s) and hence the ‘volume’ of the ocean basins available to ‘hold’ the seawater! We have the mid atlantic ridge, forming crust and widening the ocean floor by cms per year – but is it rising a bit too?, or falling? is this resulting in a net atlantic ocean volume ‘space’ reduction (i.e. sea level rise) or increase (i.e. SL drop!). Then if we consider subduction zones, and uplift of crustal edges, colliding continents, etc – we really are in the realms of the unknown.

    Then there is the real hydrological aspect – i.e. where is all the earthbound water? how much of it has been evaporated into the atmosphere and is water to come back down as rain? has some rainfall been ‘held up’ in the crustal rocks? How much has been laid down as snow/ice? The simple timelags between winter and summer in the higher latitudes will no doubt cause a pulse reaction in available ‘water’, and of course will be subject to local climate variation…LOL.

    I won’t even mention the thermal expansion properties of water, density issues, etc, etc – but I would anticipate that 97% of geologists (and others!) will realise (after about 1 minutes thought) that a simple ‘metric’ comprising a global mean sea level is even more ridiculous than a global mean temperature value – it may be a nice theoretical metric – but it certainly is not something that is a realistic concept – the required amount of measurement(s), gridding, analysis and computation is simply mind boggling….

    I am sure there is much I have missed – but I was just trying to give a flavour of the problems a simple ‘global mean sea level’ value causes.

    regards
    Kev

  86. Thanks Andi. Well thought out.

    Isostacy is the usual English usage (despite the Greek stasis element), or at least it was when I went to school many, many decades ago.

    “Missing information can be measured to improve the accuracy.”, courtesy of Lazy Teenager somewhere above. My son, we already have too many people measuring stuff that is missing without actually determining what the missing stuff is nor where it can be found.

  87. To Andi: Two points I would like to make:
    (1) Air pressure drops on a historical scale is due to AIR MASS LOSSES into Space…
    see a recent Post: Giant veil of plasma detected….” showing that the Sun bites
    at the top atmosphere and chews up air molecules into protons…..
    (This effect is belittled by Warmists because they do not like to deduct air mass from their
    Warming forecasts….)

    (2) I read somewhere that the Earth expands in volume, that the oceans rip open
    [Atlantic 10 cm, Pacific 20 cm/year] and the voids above these crevasses are filled
    with water flowing away from + lifting land shore lines out of the water….
    …. Most plate tectonic explanations nowadays reckon that the same 20 cm lost are
    gained on other shores such as California, whereby plate tectonic occurs by one plate
    disappearing under the second….. But I doubt this because I never heard about a
    distance shrinking of 20 cm between, lets say Hawaii and San Francisco…. where plates are
    reckoned to go under each other….
    For this Earth volume expansion, all known historical harbour sites (Greek, Middle East,
    Pakistan, Japan…etc) are today several meters above the present day sea level….
    Find out more about historical harbours…..
    JS

  88. You are out to lunch..The edge of the continents are subsiding not rebounding..due to slow collapse of the mantle forebulge…This mantle material is slowly sneaking back to the former ice centers (Northern Quebec) and causing rise in those areas …At least half of present day sea level rise in many continental margin areas adjacent to these ice sheets is a result of the this forebulge collapse.

  89. Less moisture in the atmosphere less air pressure?

    But the major problem is that I really cant see anny decreace in local sealevel preassure regional, so whay should it then be global?

  90. The most reliable geographic areas to measure eustatic sea level change would be on the lee side of techtonic plate motion, on stable platforms away from large sediment influxes from major river systems. This would be the east coast of North and South America some distance from the Amazon Delta, and the west coasts of Europe and Africa away from the Congo Delta. All four continents are riding quietly away from the Mid-Atlantic Ridge with negligible vertical movement at their boundaries.

    • Good point, Paul Marko: I mentioned in an earlier comment that I live less than 2 meters above sea level and less than 2 meters from the sea’s edge. If the sea level rises or the sea level falls, either way it is going to greatly damage the property value of my residence. I live on an estuary off of the Chesapeake Bay, in Seaford, Virginia, which is on the east coast of North America. Though we live on the edge of a continent, there is no subduction within a few thousand miles. The last big thing here was an asteroid impact some 35 million years ago. I cannot attest to that as I wasn’t here then. But there are some indications of modern uplift. Notably, if you visit the Cornwallis Cave (of Revlolutionary war fame) in Yorktown, Virginia, the coquiana in which the cave (a very shallow cave) is set shows a peculiar south-south-west strike which has always set me to wondering how and why. The sea rises and falls in my backyard about one meter twice a day. When the wind shifts and blows strong from the east, the sea can flood my entire backyard. That is not unusual in this neck of the woods. Also, as a clarification, when I say that the sea is in my backyard, that is not entirely accurate. The water is brackish, a mixture of fresh and sea water. Sea water salinity usually is 35 to 40 ppt with the Mediterranean and Red Seas being at the high end. When I have measured the salinity in our backyard, it has always been close to 17 ppt.

  91. Fifty years ago I worked in an observatoey unit which measured the irregular rotation of the Earth. This measurement has become much easier since the introduction of GPS satellites, but the causes of the irregularities are still not perfectly known. The astronomers and mathematicians I worked with had never heard of isostasy (I had studied geology). I had to explain that isostatic movements and lack of isostatic equilibrium caused small changes in the planet’s moment of inertia, and hence in the LOD (length of day).

  92. In regard to the chart on the global mean atmospheric pressure (Fig. 5.8) in the root post:

    davidmhoffer talks of precision of measurement. A correction of .16 millibars is needed for every 1 degree C when reading a mercury barometer with a brass scale.

    When we consider the geologic record for warming vs CO2 signals, I frequently see the ppm value of CO2, but seldom do I see estimates of total atmospheric pressure or CO2 partail pressure. Off hand, I think it matters a great deal to the study of climate history whether a given CO2 concentration occurs in a 1013 milibar atmosphere or one of 5000 milibar. I think the question of atmospheric pressure in the geologic record is addressed too little. Who among you when visiting the local Museum of Natural History can remember seeing a discussion of the Cretaceous atmosphere nearby or below the 20+ foot wing span of a giant flying quetzalcoatlus that hangs above your head? http://levenspiel.com/octave/dinosaur4.htm

    “‘The Present is Key to the Past.’ Don’t you believe it!'” said my geology professor. “Two billion years ago, the world was without free oxygen.” What oxygen was being created was quickly consumed to precipitate iron in solution into beds of iron ore.

  93. Brian H says:
    March 4, 2012 at 2:41 am
    Dave Wendt;
    the 1mbar : 1 cm ratio requires some justification. If that’s global, where is the water being moved to/from? Or is that a compressibility factor? I know water, especially saline, is slightly compressible, but that much?

    That argument would come into play if we were talking about global atmospheric pressures which were completely uniform. The Cole graph is of annual global mean pressures which suggests a slight shift of the balance between highs and lows, so a shift in GMSL as a result is clearly possible.

    Personally I consider the notion that we can “know” GMSL to millimeter level accuracy a statistical fantasy. Go to your pocket, or wherever you keep your small change, and grab a couple dimes. Stack those two dimes on a flat surface and look at them. Now consider any experiences you may have had of the oceans of the world, even if the closest you’ve ever come to them is watching reality shows about crab fishermen. Now actually try to think about resolving the mean height of all the surfaces of all the world’s oceans to the height of those two dimes. Some additional points to ponder are that because of the altitude the satellites orbit at (1336 km) each individual ranging ping has a footprint when it hits the surface of between 2 and 10 square miles, depending on atmospheric conditions and whose estimates you choose to believe. The sats are pinging multiple times per second, but the surface is changing chaotically even faster. I used to work in the surveying biz years ago and a common technique we used to try to achieve slightly better accuracy than the limits of our instruments was to repeat each measurement a number of times and take an average. The satellite altimeters take a huge number of measurements, but none of them is ever an exact repeat of any other, so that technique is not applicable. The basis for the calculated GMSL anomalies is not the planet itself, but to a reference ellipsoid and the undulations of the Geoid, both of which are imaginary abstractions which have only a fairly vague relationship to any reaiity of the actual planet,

    Don’t get me wrong. I think these sats, particularly the latest JASON2 units, are some of the finest achievements of human technology ever created. The problem, as I see it, is a basic weakness in human mentality. When you spend years working all day every day with massive quantities of numbers it becomes very difficult for any human, and I include myself, to avoid falling into the trap of believing those numbers are a more “real” reality than the actual reality. It is an absolute necessity to be aware of our mind’s tendency to conflate precision and accuracy.

    The various satellite systems that are providing data for us about what is happening on the planet are some of the most valuable tools we have available but, when attempting to use or argue about all that data they provide, it isalways incumbent on all of us to constantly remind ourselves that that data is almost never anywhere near as accurate as those providing it would suggest. I always suggest for anyone really interested in the area of sea level measurement that they devote some time with this document

    http://www.nodc.noaa.gov/sog/Jason2/userhandbook_4.pdf

    It’s the JASON2 data products handbook and it provides loads of very useful information about the actual process used to produce this data. It is fairly lengthy and in parts quite technical, but if you’re willing to invest some time and have a reasonably critical eye, it will give you a pretty strong basis for discussing this topic.

    • Dave Wendt: Very nice comment. Wow. You said a lot of good things, things which may be new to a majority of readers, but things which all readers need to remind themselves of. Those of us who engage in the art of measuring, we need to be have a conciousness of the sources of error, both random and systematic. I guess that the word error is too strong and implies deceitfulness or a lack of care. That is not true or generally correct. Consider one of my favorite scientists of all times: Hipparchus. I know very little about the man and apparently no copies of his works have survived to this day. Nevertheless, from references to his work, it seems that he managed to make some very remarkable and astute observations as to the motion of the sun, the moon and the stars. The most impressive observation was that the moon did not follow an orbit centered on him, but centered on some point beneath his feet. I cannot find a reference for this at the moment. It is a statement I heard ascribed to him. As astute as Hipparchus was, there are errors in his observations attributable to atmoshperic refratction. We cannot find fault with Hipparchus for this. Atmospheric refraction of light was not known, and not knowable, at the time. We all need to accept that inexplicable, unknowable factors in our measurements may be in play. For instance, consider zero-point depression in glass thermometers.

  94. And one final question. As Cole (2010) discovered, atmospheric pressure has been falling over time.

    ;————————————————————————————————————————

    There was no reference in the thesis to the study which produced the graph other than a comment in the body indicating the data (or the image?) came from the CRU.

    A total of 1.4 mb difference over 100 years and no error bars – I’d classify it as an urban legend.

  95. Much of the above commentary – stemming from, effectively, a simple query, “What is mean sea level?”, of five words, none over five letters, and huge credit to Andi – is right.
    We don’t know.
    There are – as noted – many variables. We probably do not yet know all of them.
    We have, at best, an imprecise idea of a few of their interactions.
    In England, where I live, we get weather – which is hard to forecast; and climate, which seems to be drying out, at least in the south-east, round London. but it’s probably not systemically different from the time Stonehenge was built.
    And, crucially, today is not VERY different from 1000 or 1000 000 years ago.
    And we don’t eally know why.

  96. A significant issue with tide gauges is that they have a location bias. Ports of any size are generally located adjacent to populated areas, which is normally flatter land and as a general rule flat land is flat because it is subsiding, due to isostacy or tectonic uplift elsewhere, eg SE England and Bangladesh.

    Add in that many ports are built on landfill which settles over time, and sea level will rise at a substantial number of, and probably most, tide gauges due to land subsidence.

  97. Suppose the entire atmosphere on the planet were to quickly jump up 10 degrees celsius.
    The atmosphere should expand further out into space and become less dense due to the heat.
    Since it is less dense and there would be fewer molecules in the column of air above me, all the way to the top of the atmosphere, allowing the air pressure to read less.

    The mass would be the same, it would “weigh” the same, only the pressure would be less.

    To argue that there would be no change in air pressure seems to counter logic.
    Air pressure is variable. The weight of the air, and the mass of the air are not variable.

    Is there another explanation?

  98. Dave Wendt says:
    March 4, 2012 at 1:38 pm

    I personally don’t think there is a cat in hells chance of obtaining a realistic GMSL, let alone define some error bars or precision to that figure and then continue over a period of time to accurately measure it! I have the same issue with mean temp anomaly and we KNOW how much that is fecked around with by Messrs GISS et al!
    Sure, it would be nice to know if GMSL is rising or falling, but only if it is extremely fast! – like a few metres in a century or so – oh, wait a minute, isn’t that a Gore/IPCC type prediction? Haha!

    I am not a conspiracy theorist by any means – but when someone (or some ‘body’) starts to use a highly variable, suspect and largely imaginary ‘metric’ – it starts to look as if there must be some form of agenda in the background.

    I simply cannot think of a suitable ‘metric’ analogy to impart the daftness of a global mean sea level. Just thinking of the gazillions of cubic metres of water in the world, and then saying that you ‘know’ where it is because you have measured it, and can then define a GMSL figure to high levels of accuracy seems simply absurd IMO!
    cheers
    Kev

  99. kbray in california says:
    March 3, 2012 at 8:55 pm

    Why don’t we fill all tires with CO2 instead ? A good sequester for CO2 and perfect as a fire extinguisher if you ever have an engine fire… a rubber hose with a nozzle… that would be handy and dandy. And imagine the recycling fees on a tire full of toxic CO2 poison. The taxman and the UN warmers will love it.

    ;————————————————————————————————————

    I carry CO2 cartridge and bicycle tube as a quick fix if I get a flat on my bicycle.

    The problem with CO2 is it has a high thermal expansion coefficient (compared to nitrogen) which means when the tire cools it nearly goes flat. I end up draining the CO2 and replacing it with air.

  100. I ike this one: a 75 million year old mosasaur was found in Lethbridge this winter (the second one actually). Mosasaurs were ocean-going reptiles that could be 6 to 7 metres long.

    http://www.winnipegfreepress.com/breakingnews/alberta-dinosaur-museum-finds-rare-fossil-of-prehistoric-marine-reptile-141134343.html

    Lethbridge is currently 3,000 feet above sea level.

    Okay, over 75 million years, the near-by Rockies were uplifting, but even 75 million years ago, the City was much higher than today’s sea level.

    The centre of North America was flooded by the Ocean from Texas to Inuvik as was Europe and North Africa and the entire Middle East. Sea level was 250 metres higher than today.

    The Atlantic was just a young ocean basin at the time and was not as deep as it is now. The average depth of all the Ocean basins was just less than today and the Ocean had nowhere to go but up onto the Land. The Atlantic is still sinking into the mantle today, at least at the mid-oceanic ridge, and sea level should continue falling until a new ocean basin develops (the Red Sea and the Great Rift Valley).

    Lots to take into account.

  101. crosspatch says:
    March 3, 2012 at 5:50 pm

    Obviously wrong. Since 1976, Japanese cars have made up more of the fleet of cars in the world. Now, motor vehicles burn O2 and produce CO2 plus H2O (octane is typically burned also, as C8H18.

    So, a chemical reaction would be:
    2 C8H18 + 25 O2 =>
    16 CO2 + 18 H2O.

    Now, the 18 H2O will fall as rain, and the 25 O2 = 25 * 32 = 800 mass units, while the 16 CO2 = 16 * 44 = 704 mass units, so the greater fuel efficiency clearly leads to an extra 800 – 704 = 96 mass units remaining in the atmosphere, or 48 mass units for each molecule of octane C8H18 that is not burned. So the net effect of more Japanese autos burning less fuel should be an increase in air pressure, not a decrease. WUWT?

    I was going to add that higher temperatures should lead to higher pressures also, until I calculated the thermodynamics of each of the molecules in the atmosphere in my general circulation model (GCM) of Earth, including radiation, conduction, and convection, and realized that in the absence of any new net molecules in the atmosphere, that the fast molecules would rise a little bit, thus raising the entire atmosphere by an average of a few dozen meters, decreasing the sea level density by an amount exactly equal to the square of the increase in average speed, thus rendering the pressure the same, or something like that.

    • The only good answer to the decreasing air pressure whilst fossil fuel burning amounts to
      injection of heavy molecules is that there is a heavy atmospheric mass loss on the top
      of the atmosphere…see post: “A giant veil of cold plasma… detected….”
      The Sun burns heavily and smashes molecules into plasma and electrones…..and cannot
      grow in vertical extent……
      These heavy losses are set to nil in IPCC GCMs, because a mass loss would show
      a lowering of global warming, which they do not want, only radiation losses are talked about…..

  102. PS – I’m not sure my general circulation model remains valid in the presence of butterflies in Earth’s atmosphere, as the model produces widely divergent results when let run over a 14 day period depending on the direction each butterfly is flying in my initial conditions, so I’ll need a grant to obtain more supercomputing power (I figure a factor of 10^60 for each butterfly-second) in order to correctly model the atmosphere over periods of time greater than the Planck distance divided by c.

    PPS – I’ll also need to model the Feynman sum over histories of each neutrino passing through the Earth, correcting for each observed neutrino.

  103. Pluck says:
    March 4, 2012 at 2:46 pm

    To my mind the primary indication that rising sea level is not a real problem is the herculean effort made to claim that we can measure it to the millimeter. That ubiquitous graphic of rising sea level with its dramatic slope is only possible if people can be convinced of that faulty premise. In the JASON2 data handbook that I referenced above they claim that they hope to achieve a RMS of +/- 3.4 CENTIMETERS for the data they provide. If you slap that error bar on that sea level rise graph it nicely covers the whole range of the history of the measure. If they are actually able to achieve that level of accuracy, it would likely make the present data at least 2 orders of magnitude better than that provided by the TOPEX/ POSIEDON generation of satellites because of the dramatic improvements in orbital accuracy and atmospheric corrections of the latest effort. Trying to weave such disparate data into a continuous record is a fool’s errand

    In reality the only places where sea level measurements are even relevant is at any piece of occupied coast, The satellites are completely incompetent at making measurements there, mostly because of the signal footprint problem I mentioned above. Unless you are on one of the world’s numerous small islands and atolls, what the level of the seas is doing far out from where you live is completely meaningless. If you live somewhere where the the level of the sea is becoming a problem, which areas are fairly rare, odds are it is because of what the land you occupy is doing and has little to do with what the oceans are doing.

  104. a thought provoking article.
    I wonder about the antarctic peninsula.
    it has lost ice, therefore is rising.
    the circular air and water currents in the region are eroding land and seabed mass, therefore increasing said currents.
    there is active volcanism, (climate triggers).
    will the movement of tectonic plates (sth america) increase size and strength of currents ?
    my understanding is that ice did not accumulate on antarctica until the separation of plates allowed clear passage of air and sea currents.
    I reduced the text in this link because there was too much of it. at present I can’t rename it to ‘here’, but of course you can paste the text into a ‘google box’ to access the map. http://www.google.com.au/imgres?imgurl=http://geology.com/world/antarctica-map.jpg&imgrefurl=http://geology.com/world/antarctica-satellite-image.
    ridiculous though it may be, what are the numbers and effects around the conversion of antarctic ice to 1) water, 2) gas ?
    I had a brief ‘aha’ moment, thinking about the reducing atmospheric pressure. during the dinosaur era, atmospheric pressure was much higher. does our current reduction extend that far back ?
    what are the likely mechanisms for increasing atmospheric pressure, and is there an optimum pressure, were we to have geo-engineering ability ?

  105. Many thanks for the thoughtful article. Well written. Having a MS & BSEE in process measurement & feedback & control systems (40yrs), the measurement of variables & inherent feedback systems have always been of great interest to me. As applied to earth & physical sciences, it is readily observable that there are an incredible number of dynamic non-linear forces (equations) and systems that are interacting with each other in ways (multi-dimensional matrix) that we are only now beginning to grasp. Fortunately we now have the basic instrumentation and communications to measure, record and analyze the data…. but we are just starting the data collection process. If we had a couple hundred years of data under our belts, we might be able to start to evaluate system dynamics. I guess that’s the fun & challenge of studying physical science…we are in a very steep learning curve, trying to make sense of the system interactions.

    As a side-light… my wife and I visited the ancient Med. seaport of Ephesus in Turkey a few years back. While this was a seaport 2000 yrs ago, it is now a long distance inland. The classical explanation is sedimentation and river siltation, but since Turkey is also an area of active tectonic plate uplift activity, I have often wondered how much of the elevation displacement was due to plate uplift.

  106. I hope this is relevent to your discussion . i have for many years now studied sites like this one concerning global change . one thing i have noticed is the time scales concerning things such as global warming /atmospheric pressure /earths magnetic field/ . all seemed to change significantly in the mid 80 s . global warming [government told us in the 80 s] was our fault for mainly emmisions . this is not true . If it was then it must be true that dinosaurs were wiped out by there own emissions and not a earth impact . it seems that cattle alone emits more gases into the atmosphere than vehicles do . now look how many and how big dinosaurs were on the earth . BUT what we need to ask ourselves is why have we studied what we learn . what is the outcome and what can we do about it . It seems that at present our environment is definately going to sh*t and we are doing and saying nothing about it . one thing is for sure its affecting our atitudes . more aggresion…

  107. michael says: “i have for many years now studied sites like this one concerning global change . […] It seems that at present our environment is definately going to sh*t and we are doing and saying nothing about it”

    I do not believe you have been studying sites like WUWT? for many years, Michael.
    You would not be able to type that last sentence I have quoted from you above if you had.

  108. kbray in california says:
    March 4, 2012 at 2:19 pm

    To argue that there would be no change in air pressure seems to counter logic.
    Air pressure is variable. The weight of the air, and the mass of the air are not variable.

    Is there another explanation?

    Global air pressure and mass, ignoring loss to space etc., are not variable. Local air pressure is variable because warm light air pushes cold heavy air aside.
    If you heat the whole atmosphere uniformly, the effect on air pressure would be minimal, mainly due to the lesser “weight” of molecules at higher altitude (1/r^2g effect). Negligible.

    According to N&Z, btw, the atmosphere would contrive to dump that extra heat quite quickly.

  109. This is a very interesting topic. I remember a couple of years ago I was reading the annual Pacific Island sea level reports put out by the Australian Bureau of Meteorology and I was surprised to see that the 1997/1998 El Nino had caused a sea level fall of 35 centimetres (yes 13.7 inches) that kept the sea level anomaly in the Pacific Island region negative for about three years; That’s a pretty dynamic system were looking at.
    I also find the whole concept of plate tectonics and deep time really fascinating
    That is why I chose the blog name that I did. I love the fact that the summit of Mount Everest is made of marine shale and there are shells there.

    Marine_Shale

    • To Marine_shale:
      This sediments in the Himalayans clearly prover that in plate tectonics the plates do not
      slide one below the other but rather pound each other until the softest goes up…..
      Only where plates drift away from each other there is an annual growing opening crevasse
      where the expanding Earth volume/size occurs……
      This is a process of lowering the sea level, whereas others as thermal expansion
      leads to increase [maybe] or land ground water usage discharged into the oceans….

  110. I live in Chester, England and formerly lived near to Parkgate mentioned above, and as a regurlar visitor to this blog I was surprised and delighted to see a photograph of Parkgate on here today. I can confirm it is an amazing and bizarre exprerience to visit the former seaside promenade, where it apprears someone has photoshpped out the sea and replaced this with grassland amost as far as the eye can see – and old photographs of fishing activity as recently as the 1930’s. I would reccommend a visit – still great fish and chips and ice cream served as if it were a seaside town!
    One explanation for this is that the dee estuary was once the site of a massive glacier during the ice age, which could have pressed down on the (now) riverbed. However raise in river bed level is just one factor. The now lack of glacier also means the dee estuary is too big to be maintained by the scour of the relatively small dee river and tidal scour – so silting became intevitable over time. The remarkable regression of the sea near parkgate in recent years is mostly attributed therefore to silting and and added mass due to vegetation taking hold. This is most pronouced at parkgate due to the course of the river being rerouted and dredged toward the welsh side of the estuary in the 17th century as an attempt to allow shipping access to Chester to be maintained. You can see the rerouting clearly on google earth and appreciate how it would have had this effect on the northern shore of the dee.

  111. EternalOptimist says:
    March 4, 2012 at 1:02 am
    @Lazy teenager
    when water warms, it expands. are you sure about that ?
    when ice melts it flows into the sea. are you sure about that ?

    Both statements are false. 0-4C. evaporation.

    Actually, for saline (sea-) water, the “expands” is true. It’s only false for fresh water.
    And evaporation/sublimation are indeed potent. Just observe Kilimanjaro! No snow, dry winds, and the ice cap is/was shrivelling away. Regrowing now, though, IIRC.

  112. Marine_Shale says:
    March 4, 2012 at 9:42 pm

    I’d be interested to know how many mainstream media outlets reported that negative sea level anomaly?? How many headlines were there about the receding sea front and loss of fishing grounds due to shallowing seas, etc, etc, etc? LOL

    BTW – An interesting blog name – but a bit of a misnomer, surely? After all, all shales are of water origin, so I think the ‘marine’ part is a bit unnecessary? Just saying…..(I suppose you could be explicitly excluding freshwater derived shales though!).

  113. Brian H says:
    March 4, 2012 at 7:58 pm

    “Global air pressure and mass, ignoring loss to space etc., are not variable. Local air pressure is variable because warm light air pushes cold heavy air aside.”
    ——————————————————————————————-
    Brian H,
    I have some questions for you…

    Do jets flying through the air add to the weight or mass of the atmosphere?
    Does the 390,000 pounds of jet fuel burned on one long flight add to the weight or mass of the atmosphere?
    Do volcanic ash and gasses from an eruption add to the weight or mass of the atmosphere?
    Does a helium balloon released from the hand of a child add to the weight or mass of the atmosphere ?
    Does helium gas released into the air add to the weight or mass of the atmosphere?
    Do all the particulates, soot, and gasses released from smokestacks add to the weight or mass of the atmosphere?
    Does smoke from a forest fire add to the weight or mass of the atmosphere?
    Does dust from space or a dust storm add to the weight or mass of the atmosphere?

    Can you answer any of those for me?

  114. It just occurred to me that every super tanker floating in the ocean adds to sea level rise.
    Every boat or bit of debris or submarine or even whales or fish or even plankton for that matter…
    Man, we are really in trouble.

    To control this deluge we need to pull every ship onto dry land. A lottery could be imposed to allow only so many ships to be at sea at one time. A “sea level damage tax” could be levied on every ocean going vessel. This idea is my contribution to saving the planet. I feel better now. sarc. in case you missed it.

    Ps: Maybe dredging the ocean would help too… shovel ready jobs digging sand in the sea…

  115. Dr Burns says:
    March 3, 2012 at 11:06 pm

    Mean sea level atmospheric pressure is 1013mb. Cole’s graph suggests around 1008mb. Seems strange.

    Thanks. I thought I was going mad and had misremembered that.

    DaveE.

  116. I seem to recollect that the 1013.25 Mb pressure is used internationally to define air-corridors or Flight Levels. Setting FL210 (notional 21000 feet) relative to 1013.25 means that as local pressure changes, the Flight Level will actually move up and down. But since all planes are using the same barometric setting of 1013.25, all aircraft will move up and down in unison.

    Choosing 1013.25 was an arbitrary decision that would allow a super-low pressure (say 990) to lower the Flight Level, but not to any dangerous extent where it would either hit the ground, or interfere with aircraft operating below.

    I also seem to recollect that 1000 Mb was originally chosen by the Met Office as the average barometric setting at sea-level

    To those refering to the “Geoid” – who’s Geoid would you use? Look in your GPS and see how many Datums are available – although WGS84 seems pretty standard, there are lots of others, each based on a local Geoid !!! Just to complicate things further

    Andi

  117. As I remember Andi, the pressure entered by our pilots never deviated far from 1013mb. Where we were in East Anglia the deviation would not be far from sea level pressure.

    BTW. Too high a pressure could lead to flying into the ground on low level sorties!

    DaveE.

  118. Ground open up & eat me now! Too low a pressure could lead to flying into the ground!

  119. Dave Wendt says:
    March 4, 2012 at 5:24 pm

    Quite! (but don’t mention that to Nick Stokes or he will be around again telling us how an anomaly ‘measure’ disregards all that inaccuracy stuff!)

  120. Andi Cockroft says:
    March 5, 2012 at 12:40 pm

    To those refering to the “Geoid” – who’s Geoid would you use? Look in your GPS and see how many Datums are available – although WGS84 seems pretty standard, there are lots of others, each based on a local Geoid !!! Just to complicate things further

    The Geoid model used in sea level altimetry is EGM96

    3.2.4. Geoid
    OSTM/Jason-2 (O)(I)GDRs use the EGM96 geopotential to compute the geoid [Lemoine et al., 1998]. The EGM96 geopotential model has been used to calculate point values of geoid undulation on a 0.25 x 0.25 degree grid that spans the latitude range +85.0 deg. to -85.0 deg. The EGM96 model is complete to spherical harmonic degree and order 360, and has been corrected appropriately so as to refer to the mean tide system as far as the permanent tide is concerned [Rapp et al., 1991]. The k2 Love number used in this conversion was 0.3. The geoid undulations are given with respect to an ideal geocentric mean Earth ellipsoid, whose semi-major axis remains undefined (i.e., there is no zero-degree term in the spherical harmonic series of these geoid undulations). The flattening of this reference ellipsoid is f=1/298.257 so that values are consistent with constants adopted for T/P.
    Since the geoid undulations have been computed from an expansion to degree 360, the resolution of the undulations will be on the order of 50km. Data used to derived the EGM96 model include surface gravity data from different regions of the globe, altimeter derived gravity anomalies from the GEOSAT Geodetic Mission, altimeter derived anomalies from ERS-1, direct satellite altimetry from T/P, ERS-1 and GEOSAT, and satellite tracking to over 20 satellites using satellite laser ranging, GPS, DORIS, the Tracking and Data Relay Satellite System (TDRSS), and TRANET.

  121. Andi Cockroft says:
    March 5, 2012 at 12:40 pm

    The Geoid concept is quite important, and as you say, there are many variants. However, as per my earlier post, my feeling is that there must be a suitable Base geoid reference (if you like).

    I was mindlessly pondering the measurement aspect and wondering if it would be possible to use the moon as a measurement device/reflector. I am not aux fais with surveying techniques but I understand they measure earth-moon distance with lasers? Would it not be possible to use the moon as a distant reference point for fixed earth points? (yes, I am aware the lunar distance varies, of course). If we had say a dozen fixed earth points all firing a laser at the moon and getting a direct relative distance, and this was then repeated over days, in theory the relative distances would always be the same unless the earths shape had changed? The extra distance from moon to earth instead of GPS satellite to earth would increase accuracy too, I presume?
    I’m probably way off base here – but it just seems that to get a 3d measurement of a big object, one needs to view it from afar, and I was thinking of how they scan an object with a laser to digitize it. Is the technology available to place a laser on the moon to digitise the earth, constantly, and then note any changes in shape?

  122. Dave Wendt says:
    March 4, 2012 at 1:38 am

    In regard to the difference between satellite observations and tidal gauges see this map

    ;——————————————————————————————————————

    Hey, that image reminds me of El Nino.

  123. The equatorial bulge is often not considered as a prime factor in the potential for global rearrangement, both historically and in the future. How much bulge of water can be formed before a “bulge” collapse. Are accounts of GREAT floods a result of past cyclic collapse of the equatorial bulge? Are melting ice caps feeding the bulge? Is there a “tipping” point where equatorial bulge collapses. Does a weakening barometric pressure contribute to such a phenomena?

    Apparently the bulge is growing….

    Always more questions than answers unfortunately.

    http://beyondprophecy.blogspot.com/2010/05/equatorial-bulge-growing.html

  124. Interesting posts at Ecotreras on the sea level:

    http://ecotretas.blogspot.com/2008/12/descida-dos-nveis-do-mar.html

    2008: trend 3.3 mm/year. total 1993-2008 15 years = 49.5 mm

    http://ecotretas.blogspot.com/2009/04/subida-descer.html

    2009: trend 3.2 mm/year. see the very flat 2006-2009. total 16 years = 51.2 mm

    http://ecotretas.blogspot.com/2010/10/going-down.html

    2010: trend 3.1 mm/year, total 17 years = 52.7
    And the last one from CU home page:

    http://sealevel.colorado.edu/

    2011/2: trend 3.1 mm/year (-0.3) = 2.8 mm/year , total 18 years =50.4
    I saw a mention at Ecotreras that trend was down from 3.5 in 2006 does anybody know, was it for the whole period 1993-2006?

  125. hello again everyone . could i please have your attention . i am no scientist but i am sure there are a few leaving comments on this site . allthough i dont understand a lot about physics and quantom mechanics and such . if their is one thing i know . We need to bring our environment back into a healthy balance right . well i have a few suggestions 1 we need to put less heated buildings on our land they are acting like blankets on the ground that must have something to do with global warming . 2 we definately have to stop destroying forests not only do they give us life giving oxygen as you know /and take carbon dioxide out of the atmos . surely with more plants and trees shade is being produced which in turn cools down the ground . 3 now ask yourselfs where are the hottest parts of the earth ? deserts surely well one thing we do know is that deserts are slowly spreading again making the globe warm up further ? we need to stop this happening one way to do this is to start getting along with our freinds all over the world and then we all build our homes there ime sure theres enough machinery manpower and resources to flatten it out [ leaves more fertile land to grow FOOD allso bird population might start to rise again nature would have their home back .eco allmost sorted right .4 leaves you scientists to keep it in balance instead of having to try and fix it gives you more time to go fossil hunting . so their you have it north and south pole would refreeze more polar bears and penguins no more rising tides oxygen levels improve earth should chill out not as many earth quakes eruptions sunamis and such like MAKES SENSE TO ME . and the added bonus everyone would have a job . thankyou i rest my case …..oh ps did you know Mary Schweitzer PHD found intact blood cells and soft material in a T REX thigh bone . thats impossible unless t rex lived less than 100 000 years ago .

  126. michael says:
    March 6, 2012 at 6:57 pm

    You have an interesting response.
    How many months of school have you had? What was your highest level of school? What year?
    What subjects did you take?
    If not English, what is your native language?

    Your answers will help us determine how to talk to you.

    (Note to all: Remember, he votes. He may not pay taxes, or earn income, but he votes.)

  127. hello Mr Cook . to your responce never went to school self taught and yes i dont pay tax anymore since i lost my job as an electrical and mechanical engineer last year .spent all my school days staying away from bullies hiding in the woods . being stoned and beaten with sticks thrown in boating lakes hounded everytime i left school . AND THAT WAS JUST PRIMARY SCHOOL . too much violence in this world .

  128. I can sympathize with the loss of your job – Did you know your job loss was due to the current liberal politicians’ obsession with “green energy” and their socialistic CAGW theories about fossil fuels in the US, UK, Australia, Spain, the EU, and much else of the UN?

    My own “self-taught” classes were possibly as equally difficult as yours: I earned 39 credit hours towards my first degree by advance placement studies, national and local tests, and self-study. But those, to be true, were only in freshman and sophomore classes: first and second years of chemistry, a few semesters of calculus, analytical math, a bunch of years of mechanical and electrical physics, the basics (history, English literature, writing, etc.) But nothing really past sophomore level courses. Its funny, but somebody did require that I finish about 120 more hours of other higher-levels courses before Texas let me declare myself an engineer of anything. (See, it’s actually illegal to declare yourself an engineer, or be employed as an engineer, without such documented classes and a complete degree. Academics are funny that way. Seems they use their political influence to get their legislatures to write laws so ensure their own academic careers always justify continued employment by the schools that are funded by the legislatures.

    But I do applaud your ‘electrical and mechanical” engineering job earned that way.

  129. Mr Cook . I do praise you for your achievments . But your speculation skills need some work . I lost my job due to ill health . i blame the liberals AND conservatives for that . And no ime not an eco tree hugger . i just beleive we should take more care of the way we go about things . one example the deep sea drilling disaster . was,nt the people in charge of that job supposed to be highly educated . I have spent over 30 years working in some very dangerous environments and i have never made a mistake . oh sorry yes i did make one mistake not shouting loud enough at a highly educated health and safety executive for not taking more care about my work environment . That caused my health problem . Mr Cook in my world i got my hands dirty and PAID MY TAXES .work experiance and hard labour gained me my education .

  130. Orogenesis: The Cause of Global Mountain Uplifts
    Donald Patten, a geographer, proposed that the global mountain uplifts came from a close encounter with an astral body. He uses physical mechanisms and mountain arc data from J. Tuzo Wilson to show how the major mountain chains were pulled up. I am an astrogeophysicist by training and I never could accept the fact that horizontal forces on a sphere could push up 28,000 foot mountains. I suggest the following chapter from
    Patten, Donald W. (1966) “The Biblical Flood and the Ice Epoch: A Study in Scientific History,” (Seattle: Pacific Meridian Publishing Co.) [Online: http://www.creationism.org/patten/
    Chapter V – Orogenesis: The Cause of Global Mountain Uplifts [http://www.creationism.org/patten/PattenBiblFlood/PattenBiblFlood05.htm]

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