Is Sea Level Rise Accelerating?

Guest post by Paul Homewood

 

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It is generally accepted that sea levels increased during the 20thC at a rate of about 185mm or about 7”. Furthermore studies suggest that there was no acceleration in this rate during that time. One of the best known studies was by Bruce Douglas, who produced the above graph from Tide Gauge records for 23 geologically stable sites.

Satellite monitoring of sea level, which began in 1993, however, shows that the current rate of increase is about 2.8mm/year.

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So, question – has the rate of sea level rise really accelerated in the last two decades. In this study, I will be extending Douglas’s work up to 2011 to find out.

 

 

 

Methodology

Douglas based his work on tide gauge records from PSMSL, (The Permanent Service for Mean Sea Level), and used the following criteria :

  • Each record should be at least 60 years in length
  • Not be located at collisional plate boundaries
  • At least 80% complete
  • Show reasonable agreement at low frequencies with nearby gauges sampling the same water mass
  • Not be located in regions subject to large post glacial rebound. 

    He subsequently identified 23 sites that met these criteria. (These are listed in Appendix A). The tide records at each site were adjusted for any post glacial (isostatic) rebound, i.e any rise or sinking of the land, so as to isolate the eustatic sea level, i.e. the quantity of water in the ocean.

    Of Douglas’s 23 sites, only 12 have full or nearly full records since. (Newlyn’s records go up to 2009, but are included). From these 12 stations, I have reconstructed the Douglas graph.

    A point I will keep emphasising is that I am not trying to establish “the actual amount of sea level rise”, but am looking to quantify “the relative rate of change”. In other words, is the current rate of rise greater (or smaller) than the rise during the last century.

    Bearing this in mind, my reconstruction is not adjusted for isostatic rebound. There are two reasons for this :-

    1) Any such adjustment is adding a certain amount of subjectivity, which is absolutely not necessary.

    2) As the objective is to compare the rate of sea level change between 1900-2000 and 2001-2011, the isostatic factor is irrelevant, as it is, to all intents and purposes, a fixed amount.

     

    Reconstruction

    Figure 1 shows the spaghetti graph for each station, which naturally does not tell us a huge deal. However Figure 2 averages all twelve stations together, with a cumulative three year running average plot, exactly as Douglas did.

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    Figure 1

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    Figure 2

    Two things stand out :-

    1) The new reconstruction indicates a sea level rise from 1900-2000 of 168mm, actually a pretty good fit with the original Douglas calculation of 185mm. The difference between the two datasets can be ascribed to two factors :-

    a) No adjustment for isostatic rebound in the new reconstruction.

    b) The elimination of the 11 stations, which do not have recent records.

    We have already discussed isostatic rebound and this does not affect the trend line of the graph one way or the other.

    As for the reduction in the number of stations, Appendix A shows that there are now no Southern Hemisphere sites in the new dataset. Could this be skewing the average? More on this later, though.

    2) The sea level rise has stuck pretty close to the long term trend (red line), both throughout the record, but more significantly in the last decade. This is our first indication that there has been no acceleration in the trend, at least in these 12 stations. Contrast the last decade, for instance, with the period 1940-60 when levels were consistently rising faster than trend.

    Before we look more closely at the figures, it is worth remembering that the three year average used above combines both the 2011 La Nina and the 2010 El Nino in the 2011 average, thus smoothing out any ENSO variability. (With no such smoothing, the 2011 figure would show a sharp drop.)

     

    A closer look

    We don’t have to rely on eyeballing the graph in Figure 2. Figure 3 shows the year on year changes in sea level (rather than the cumulative change).

     

    DOUGLAS UPDATE_htm_m55835242

    Figure 3

    While there is considerable inter annual variability, the 10 year running average indicates no upward trend. But we can actually go one step further, by focusing in on the 10 year average and therefore a much smaller range, as shown in Figure 4.

    DOUGLAS UPDATE_htm_ef9a71a

    Figure 4

    The red line is the trend and actually shows a small decline since 1900, although the last 10 years are slightly higher than trend at 2.15mm/year. However, the 10 year figures are comparing 2011 with 2001, when sea levels were lower than usual, having declined for two years, as Figure 2 illustrates.

    Figure 5 gives a broader perspective by listing the average annual increase to 2011, depending on which start year is selected.

    Start Year mm/yr increase to 2011
    1990 2.20
    1991 1.41
    1992 0.23
    1993 1.00
    1994 1.44
    1995 0.35
    1996 1.09
    1997 -1.08
    1998 0.65
    1999 0.78
    2000 1.89
    2001 2.15

    Figure 5

     

    Bearing in mind the increase in the 20thC was 1.68mm/yr, there has been nothing unusual in trends since the 1990’s, regardless of which year you compare with. Indeed, the evidence would suggest a declining trend.

     

    Southern Hemisphere

    As previously mentioned, the reconstruction now includes no Southern Hemisphere sites, with three New Zealand sites (Auckland, Dunedin and Lyttleton) and two Argentine sites (Buenos Aires and Quequen) disappearing because of the lack of recent records. Could the recent trend be biased because of this?

    Although there are now no sites with records back to 1900 in the Southern Hemisphere, there are a few with continuous records since the 1960’s. In New Zealand and Argentina, Wellington and Palermo respectively fit the bill. To these I have added two Australian stations, Port Adelaide and Port Lincoln. There are no such records available in other Southern Hemisphere countries. The sea level changes are plotted in Figure 6 and make interesting reading.

     

    SOUTH HEMISPHEE_htm_m557ab7ee

    Figure 6

    There is a clear decline in the trend, which the actual figures emphasise. Between 1966 and 2000, sea levels rose by 2.99mm/year, at the four stations averaged together. (1966 is the earliest year that we have records for all four sites). By comparison, between 2000 and 2010, they actually fell by 1.73mm/year. Furthermore, because there are no records for any of these sites in 2011, the plot finishes in 2010, when global sea levels appeared to be higher than normal.

    In other words, the exclusion of Southern Hemisphere stations, far from causing the reconstructed sea level trends to be understated, seems to have had the opposite effect. (For the record the New Zealand and Australian stations show falls since 2000, whilst Palermo shows an increasing trend).

    Let me make this clear. I am not claiming this small sample is representative of the Southern Hemisphere as a whole. But I would claim that it is a reasonable substitution for the stations excluded from the original Douglas study.

    Church & White

    In 2011, John Church and Neil White published their paper, “Sea Level Rise from the Late 19th to the Early 21st Century”. This attempted to reconcile sea level measurements from tide gauges and satellites. They concluded that between 1993 and 2009, sea levels rose by 3.2mm and 2.8mm per annum as measured by satellites and tide gauges respectively, as shown below in Figure 7.

     

    MediaObjects/10712_2011_9119_Fig4_HTML.gif

     

    Figure 7

    Global average sea level from 1990 to 2009 as estimated from the coastal and island sea-level data (blue with one standard deviation uncertainty estimates) and as estimated from the satellite altimeter data from 1993 (red). The satellite and the in situ yearly averaged estimates have the same value in 1993 and the in situ data are zeroed in 1990. The dashed vertical lines indicate the transition from TOPEX Side A to TOPEX Side B, and the commencement of the Jason-1 and OSTM/Jason-2 records

    Two things stand out though.

    1) 1993 is used as the starting point (being the start of the satellite record). However, as Church and White themselves point out :

    “However, the reconstruction indicates there was little net change in sea level from 1990 to 1993, most likely as a result of the volcanic eruption of Mount Pinatubo in 1991. “

    In other words, the trends have been calculated from an abnormally low point in the long term record. (Shades of 1979 and satellite temperatures!). This dip can be seen very well on the original Douglas graph, shown again below.

     

    image

     

    2) The exercise stops in 2009, when sea levels were at a cyclical peak, as confirmed by both satellite records and tidal gauges.

    So Church and White are comparing an unusually low point in the cycle with an unusually high one. Of course, their choice of dates was purely circumstantial, but, particularly over such a short period of time, such a choice of dates renders their results pretty meaningless. (Figure 5 shows just how much difference the choice of start dates can make). Satellites suggest a drop of 5mm from 2010 to 2011. Based on this, Church and White’s tidal gauge estimate of 2.8mm/year becomes 2.2mm/year, from 1993 to 2011.

     

    Is 2011 unrepresentative?

    Both satellites and tide gauges confirm that sea levels fell in 2011 with La Nina. So, is using 2011 as the end year disguising an accelerating trend?

    I would answer this in two ways :-

    1) As previously mentioned, I have opted for a 3 year average, in order to replicate the Douglas exercise. This has conveniently averaged together the 2009/10 El Nino and the 2010/11 La Nina within the 2011 “3 year average”, and consequently giving a robust underlying number. (Over the next two years this number should decline as the 2009 and 2010 figures are removed from the average, assuming, of course, no new El Ninos).

    2) I have also shown 10 year averages, which to some extent dilute and smooth out  changes in a single year. (For interest, if sea levels in 2010 and 2011 are averaged together in the reconstruction, the 2011 figure is increased by about 10mm. If the average annual increases in Figure 5 were calculated against the 2010/11 average, the increase since, for example, 1993 would be 1.56mm/year , instead of 1.00mm).

     

    Conclusions

    In the reconstructed analysis, there is no evidence of an acceleration in the long term rate of sea level rise, which remains at below 2mm/year. Furthermore an analysis of Southern Hemisphere sites suggests a slowing down in the rate. The sample sizes in both cases are small and give limited geographical coverage. Nevertheless, they give a similar coverage to the original Douglas study, which has generally been accepted as giving an accurate assessment of 20th Century rise. (For instance, the IPCC quote a figure of 1.7mm/year).

    The divergence with satellite data can, logically, only be due to one or more of the following factors :-

    1) The original Douglas study is based on an unrepresentative sample or inaccurate records. If this is so, it would suggest that the rise of 1.85mm/year, that Douglas calculated for the 20th Century, is significantly understated.

    2) Satellite measurements are wrong.

    3) The relatively short satellite record is too short to give a accurate long term trend, particularly as it starts at a low point in the cycle.

    4) The exclusion of 11 stations from the reconstruction has reduced the true rate of sea level rise. It would appear, however, hugely unlikely and coincidental that these 11 stations had a rapidly increasing trend, while the other 12 showed no trend change at all. In any event, we have seen that this is not the case in the Southern Hemisphere analysis.

    One final comment. From this study, it appears that the number of reliable tidal gauge sites, with reasonably long and complete records, is on the decline. Is too much reliance being put on satellites? Maybe. But when sea level rise is such an important and controversial topic, I find it both astonishing and rather sad that this is being allowed to happen.

     

    References

    1) PSMSL data is available here.

    2) Further information is available from the University of Colorado Sea Level Research Group.

    3) Details of the Bruce Douglas study are here.

     

    APPENDIX A

    LIST OF SITES

    Location Country/State Sea Level

    mm

    2000

    Sea Level

    mm

    2011

    Increase

    mm/yr

    1900-2000

    Increase

    mm/yr

    2000-2011

    Trieste Italy 7060 7070 1.44 0.91
    Santa Monica CA 6996 7011 2.19 1.36
    San Francisco CA 7050 7086 1.53 3.27
    San Diego CA 7059 7115 1.49 5.09
    Marseilles France 6990 7035 0.82 4.09
    Fernandina FL 7262 7225 2.22 -3.36
    Brest France 7133 7115 1.97 -1.64
    Honolulu HI 7044 7068 1.36 2.18
    Key West FL 7211 7215 2.16 0.36
    Newlyn UK 7097 7157 1.46 6.66
    Pensacola FL 7064 7095 2.51 2.82
    La Jolla CA 7060 7104 1.63 4.00
    AVERAGE 1.68 2.14

    LIST OF SITES ORIGINALLY IN DOUGLAS, BUT EXCLUDED DUE TO LACK OF RECENT RECORDS

    Location Country/State
    Auckland NZ
    Balboa Panama
    Buenos Aires Argentina
    Cascais Portugal
    Cristobal Panama
    Dunedin NZ
    Genoa Italy
    Lagos Nigeria
    Lyttleton NZ
    Quequen Argentina
    Santa Cruz Tenerife
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It should be obvious that if the southern hemisphere has zero sea level change, and all the sea level change is in the northern hemisphere, that that change is all due to post-ice-age rebound issues, period.

Leg

Paul: Thanks for the article. For some reason I was not fully aware of the variability of the sea level from year to year and your graphs show that clearly. Would you or someone kindly illuminate me as to the theorized reasons for the variability? I suspect the heating and cooling cycles of the oceans plays a large role, but what else influences the variability?

gerrydorrian66

Again thanks for the debunking of more lies by the Establishment. The thing is, if they’ve read their Republic, they’ll know that truth (says “Socrates”) is subservient to political purposes; by which definition the real inconvenient truths are the ones we tell, the ones that schoolchildren and students are not to be allowed to hear.

crosspatch

What I can’t understand about tide gauges is why it is so difficult to make them. For example, it should a fairly simple matter to do something like place a device on the Golden Gate bridge that has a GPS device that knows its current altitude and can determine the distance to the surface of the water below. There are many other such bridges, the Chesapeake Bay Bridge Tunnel would be a perfect example. You can account for any changes due to changes in altitude of the measuring device and get an accurate measurement to the surface of the water below. Having a network of tide gauges on bridges over salt water shouldn’t be a huge problem, I wouldn’t think.

Brian H

H/T to me (I think). 😉
The manufacture and marketing of trends is particularly prominent in CS-oceanography. The underwater cabinet meeting will be an embarrassment for the ages!

Personally, I have yet to see a photo before-after of some harbor or cliff, which shows higher sea level today than in 1900 or so. So far, I have seen none but saw a lot of pictures, which looks about the same.

phlogiston

No. Its decelerating.

Kelvin Vaughan

Start the graph in 2011. Wow it’s going up a lot faster now! Looks about 10mm a year.

shortie of Greenbank

I would say, just from looking at the list, that it is too small a list due to it being concentrated in only a few geographical areas, France, CA or I gather California and FL or Florida.
Then you look at the numbers and few of these geographically close locations are the slightest bit similar to each other in results.
Newlyn in the UK, must be hell since 2000…….

Harriet Harridan

Poorly written introduction: “It is generally accepted that sea levels increased during the 20thC at a rate of about 185mm (1.85mm/yr)….. Satellite monitoring of sea level, which began in 1993, however, shows that the current rate of increase is about 2.8mm/year.”
So sea level is accelerating – and then you claim it’s not. Lose the “However” to make the intro make sense.

Jens Bagh

Were sea levels to be rising this would slow down the rotation of the earth. Has any change been noted in the rate of change of rotation and if so how does this compare to the present study?

Philip Bradley

To quantify the impact of volcanic eruptions we average monthly GSL data from 830 tide gauge records around five major volcanic eruptions. Surprisingly, we find that the initial response to a volcanic eruption is a significant rise in sea level of 9 ± 3 mm in the first year after the eruption. This rise is followed by a drop of 7 ± 3 mm in the period 2–3 years after the eruption relative to preeruption sea level. These results are statistically robust and no particular volcanic eruption or ocean region dominates the signature we find. Neither the drop nor especially the rise in GSL can be explained by models of lower oceanic heat content. We suggest that the mechanism is a transient disturbance of the water cycle with a delayed response of land river runoff relative to ocean evaporation and global precipitation that affects global sea level. The volcanic impact on the water cycle and sea levels is comparable in magnitude to that of a large El Niño–La Niña cycle, amounting to ≈5% of global land precipitation.
http://www.pnas.org/content/104/50/19730.full
Volcanic eruptions increase precipitation, then decrease it. Presumably because the aerosols seed precipitating clouds, and reduce solar insolation and hence ocean evaporation.
The mainstream argument that volcanic eruptions reduce solar insolation and reduce thermal expansion of the oceans was never plausible.

Good work!
I had noticed the same 3 years ago, when I did a little study on the same issue. It is a pity that Cascais, in Portugal, one of the oldest in the World, isn’t being recorded… I used 53 stations then, with the same criteria as Douglas. Please see at:
http://ecotretas.blogspot.pt/2009/07/sea-level-decline.html
The complete report is at:
http://www.slideshare.net/Ecotretas/sealevel-1792065
Ecotretas

Spector

I wonder if the satellite measurements are referenced to the center of the Earth or some average ‘Land Level’ that could reflect gradual minor changes in the effective radius of the surface of the Earth due to minor changes in the average interior temperature of the Earth.

Agnostic

I found this to be an extremely interesting and balanced post. Clear about what is being claimed and what is not being claimed., with justifications and pointing out possible problems. Also, very clearly written and easy to digest. Thank you.

Point of information.
How does the eruption of a volcano affect measured rise in sea level?

polistra

I don’t know why anyone would even think that a mathematically-adjusted “measurement” from thousands of miles out in space should compete with a painstakingly careful direct measurement of the real thing! The direct measurement should instantly replace all simulations.

Bloke down the pub

Comparing the figures for Newlyn with those of Brest, it seems odd that while their older rates of change were similar, the recent rates have diverged with Brest going negative and Newlyn strongly positive. As comparatively close sites which might be expected to keep in step, I wonder if the reason that Newlyn stopped reporting was that it had started to subside?

richard verney

It does not appear, from observational evidence, that sea level rise is accelerating, or at any rate, not to any alarming extent. From observational evidence, there is little reason to be concerned as to sea level changes in the next 100 or so years.
It would be interesting to see the following plots:
1. estimated annual sea level change due to estimated glacier melt, plotted against observed sea level change.
2.estimated annual sea level change due to observed sea temperature, plotted against observed sea level change.
3.estimated annual sea level change due to estimated glacier melt and observed sea temperature change, plotted against observed sea level change.
4. estimated sea level change due to estimated isostatic rebound, plotted against observed sea level change.
5, plots 1 to 3 above but ‘adjusted’ for estimated annual isostatic rebound.
It is important to get a grasp on why sea levels are changing (if they are indeed changing) and to what extent this truly correlates with conjecture, ie glacier melt and thermal expansion.

AllanJ

Nice report.
CAGW theory says there is a link from carbon dioxide to global warming to ice melting to sea level rise. Implicit in this report is the question of whether sea level rise has accelerated in response to the late twentieth century rise in atmospheric CO2. Mr. Homewood has confined himself to the data. I will speculate beyond the data to say that this report would seem to be another pretty solid “fail” for CAGW theory.

AJ

It looks like, as in politics, all sea level rises are local.

Otter

Bloke down the pub~ please keep us aBrest of the situation!

Just how alarming are these sea level rises of less than 2mm pa?
Global sea level rose by about 120 m during the several millennia that followed the end of the last ice age (approximately 21,000 years ago)…” IPCC report AR4 FAQ 5.1
That’s 5.7mm pa. More if you take out the last 2,000 years when they say it stabilised. They also say the 20thC rise was about 1.7mm pa.
Global average sea level was likely between 4 and 6 m higher during the last interglacial period, about 125,000 years ago, than during the 20th century…” IPCC report AR4 TS.3.5
At 1.7mm pa – OK say 2mm pa – it would take 2,000 years to rise 4m, ie. to the height of 125,000 years ago. We will be running out of fossil fuels in just a fifth of that time, maybe even less.

M Courtney

Bloke down the pub says:
May 16, 2012 at 2:32 am
You ask about Newlyn’s accelerating sea level rise.
Just a thought but the National Trust has started (about 2008) to concrete in the causeway to St Michael’s Mount (just around the bay). I’ve thought that fixing the rocks down, instead of letting the sand flow beneath as the Victorians did, was likely to cause a change in the flows. Although the need to do that may be indicative of a change anyway.
Perhaps the tides in the bay have been changed.

spangled drongo

I live in the southern hemisphere and a waterfront house property of an uncle and aunt where I stayed as a boy in 1946 used to have the king tides come up on the lawn [it was flat, low lying land]. I was talking to my cousin a couple of days ago and he still lives in the same area but a different house. He has been a keen boating man all his life and he said that the king tides do exactly the same thing at the old house sealevel-wise that they did 66 years ago. He cannot detect any change in SLR.

Geoff Smith

What is the point of posting this when you have posted several other articles discussing how there has been NO rise in sea level.
I am finding this site is going around in circles and getting to bogged down in political crap

@Bloke Down The Pub
Comparing the figures for Newlyn with those of Brest, it seems odd that while their older rates of change were similar, the recent rates have diverged with Brest going negative and Newlyn strongly positive.
I guess this shows just how variable sea level can be in the short term. In the 1990’s, sea level was falling at Newlyn, so in comparing 2009 with 2000, we are comparing to an unusually low year.
The rate of increase over, say, 20 years shows nothing unusual happening.
BTW – Newlyn is sinking at about 1.1mm/yr.
http://notalotofpeopleknowthat.wordpress.com/2012/04/16/sea-level-changes-at-newlyn/

3mm a year ? an Australian expert disagrees
– You can listen to a podcats from the Alternate Reality,
Climate Commissioner : Tim “Wrong-Again” Flannery told us “in the next DECADE ‘or so’ we will see significant sea level rise of UPTO a metre”

10’30” in to the podcast

…… (note “the get out of FAIL phrases” : ‘or so’ & UPTO)
– he said that just after being asked about his OWN waterfront house
(I paraphrase) “my property is 6m above the water” … “it won’t be effected for thousands of years”

Ian W

The La Nina of the El Nino Southern Oscillation is caused – so Bob Tisdale tells us – by upwelling of cold water due to winds pushing the hotter surface water of the equatorial Pacific to the West. The El Nino is the warm surface water returning in a Kelvin wave to the East. If this is the case ENSO does not alter the actual volume of the oceans merely the distribution of warm and cold waters in the equatorial Pacific. Why is it that the different mixing of warm and cold water in the equatorial pacific should show up as a rise or drop in ‘global’ seal level?
It appears illogical.

Baa Humbug

Pretending to measure sea (ocean) levels to millimetres and fractions of millimetres on a monthly and yearly basis is at best a statistical hobby.
Sea levels take millenia to change enough for anyone to worry about. No decision maker is going to make decisions about what may or may not happen in hundreds of years time.
The sea level rise meme is just plain stupid waste of time.

Paul S

When putting together a tide gauge ensemble in order to err.. gauge recent sea level trends it’s a good idea to check against the satellite data to see if your station choices are representative of recent regional patterns of sea level change:
http://www.aviso.oceanobs.com/fileadmin/images/news/indic/msl/MSL_Map_MERGED_Global_IB_RWT_NoGIA_Adjust.png
One third of your stations are situated in California, which has seen a small negative sea level trend since 1993. You have zero stations around Australia, East Africa or South East Asia: a larger portion of the world which has seen sea level rising much faster than the global average. The fact that this ensemble doesn’t contain recent acceleration is, unfortunately, meaningless if you want to talk about global sea level trends: the sample is simply not representative.

Jimbo

But…….but……the glaciers are melting (worse than we thought), thermal expansion has kicked in, snowpack / ice cover is in rapid decline so you must be wrong. There has to be an acceleration – all that melting ice has to go somewhere.
/END SARC.
Message for Warmists: The IPCC finds no evidence of acceleration. All the scare stories are based on IF and climate models. Observations win every time.

Ian_UK

In a debate in the UK parliament last night, the leader of the Green Party stated that the British government is planning to upgrade the Thames Barrier to cope with a projected (IPCC, of course) sea level rise of 1.9m. The above report (and similar studies) suggest this would be a waste of money. I’ve written to my MP asking if the story’s true, if so, how much it will cost and what due diligence the government has carried out to justify the expense. I don’t expect to get a sensible answer, though.

Dave

I have a hard time believing that sea level rise can even be measured using tide gauges. The surface area of the world’s oceans and the topography of its bottoms are in a state of constant change due to plate tectonics. Undersea volcanic activity also displaces water. To assume that these processes have no effect on sea level as measured by a mechanical gauges fixed at (slowly) moving locations seems a bit naive to me. How does one separate the signal from unquantifiable changes to the volume of the oceans from the increase in sea height due to melting glaciers? I would put more stock in satellite measurements.

Latitude

Like UHI, satellite measurements are added to…..
satellites fall out of orbit…..you would subtract not add
Then an additional addition for the ocean floor sinking……………../snark

knots340

Why is no one doing the obvious? The data is in the form of sea level vs time, so take the derivative which gives the velocity in mm/year; which is the slope of the trend line. Next take the second derivative which will give the acceleration. What is that value? I would guess, given an almost perfect straight line fit to the data, that the acceleration is very close to zero.
This is just elementary calculus. Reminds me of what Prof. Brown said in a previous thread of people doing analysis that would not even yield a passing grade in intro. calculus.

@ Richard Verney
It would be interesting to see the following plots:
1. estimated annual sea level change due to estimated glacier melt, plotted against observed sea level change.
2.estimated annual sea level change due to observed sea temperature, plotted against observed sea level change.

Back in 2006 Bruce Douglas put out a paper which suggested the “theoretical” sea level increase (as caused by melting glaciers, thermal expansion etc) was actually less than the tidal gauges suggested.
http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/RateAndCauses.pdf

@ Paul S
The fact that this ensemble doesn’t contain recent acceleration is, unfortunately, meaningless if you want to talk about global sea level trends: the sample is simply not representative.
The aim was to replicate Bruce Douglas’s study, not to create a new global assessment.
Incidentally sea levels at Port Adelaide and Port Lincoln in Australia show sea levels falling in the last decade.

phlogiston

knots340 says:
May 16, 2012 at 6:02 am
Why is no one doing the obvious? The data is in the form of sea level vs time, so take the derivative which gives the velocity in mm/year; which is the slope of the trend line. Next take the second derivative which will give the acceleration. What is that value? I would guess, given an almost perfect straight line fit to the data, that the acceleration is very close to zero.
The derivative i.e. change of seal level in mm/year is given at Climate4you.
Go to the ocean page and scroll to near the bottom. The rate of change mm/yr has been falling for 15 years and for most of the last year was below zero.

Brad

They can more easily cook the books using satellites, thus LET THE REAL DATA DIE and let the models and the manipulation live!

Ian-Uk said
‘In a debate in the UK parliament last night, the leader of the Green Party stated that the British government is planning to upgrade the Thames Barrier to cope with a projected (IPCC, of course) sea level rise of 1.9m.’
It is complete nonsense of course. Here is a BBC report that almost gets to the heart of the matter
http://news.bbc.co.uk/1/hi/5092218.stm
John Prescott deemed that London would get tens of thousands of houses in the Thames Gateway. The EA refuse to allow developers to breach national flooding guidelines by building on sites without protection and developers dont want to build without some guarantee that the houses they build won’t flood and purchasers will be able to get insurance. There is no such IPCC projection as 1.9m in any accepted timescale such as 2100 and around 30cm seems more likely which includes land sinking and a continuation of the very modest sea level rise over the last century.
The green party have scare mongering form on this, but are right inside the govt environment committees and make outlandish claims that few dare to question.
I asked Caroline Lucas what temperature reduction would be achieved if their harsh policy of co2 reduction was implemented-after much deliberation they refused to tell me. (the answer is so embarassingly small they wouldn’t want to let their troops know).
tonyb

M Courtney says:
May 16, 2012 at 3:47 am
“Bloke down the pub says:
May 16, 2012 at 2:32 am
You ask about Newlyn’s accelerating sea level rise. Just a thought but the National Trust has started (about 2008) to concrete in the causeway to St Michael’s Mount (just around the bay)’
—– ——-
In my article here I wrote about changes in sea level in a historic context from the Holocene to the Romans..
http://judithcurry.com/2011/07/12/historic-variations-in-sea-levels-part-1-from-the-holocene-to-romans/
A couple of paragraphs in you will see a reference to a ‘longer document.’ This will take you to the full article which carries out an extensive study on the sea levels around St Michaels Mount. Current Levels appear to be slightly lower than those experienced by the Romans when they used the harbour for collecting tin.
tonyb

Watchman

This is not a hemispheric distribution of sites, but rather almost entirely four distinct clusters – Calfornia coast (one small area of eastern edge of the Pacific), Florida (which at least covers two seas), two very close readings in Brest and Newlyn (Britanny and Cornwall are parallel peninsulas – so the divergence in results needs explanation there) and a cluster in the mediterranean. Nothing in the Indian or Artic oceans, or on the western edge of the Pacific. Only one observation not on a continental shelf as well – which might be significant. If this is the information we have to go on, I would be reluctant to base anything on it.

The sites lost from Douglas include 3 in New Zealand (quite a cluster!) and 2 in Panama and 1 on a volcanic island (Tenerife). These I would deem unacceptable from a tectonic point of view. Are you measuring sea level change or change in the rise of the ground (distance to the center of the earth) from tectonic forces and magma displacement? So, no loss there.
Let’s look at the stations that are used:
Hawaii – Volcanic Island
San Diego, Santa Monica, San Francisco, La Jolla – a stones throw from a major tectonic plate boundary with movement of 50 mm per year!
3 in Florida – a suspicious cluster that I would rather treat as one location with three redundant readings. If Florida moves, they all move.
Trieste Italy – another plate boundary, micro plate to be sure, but Italy sticks above the water for a reason.
I think a separate study needs to be done using tide gauges anchored into granitic plutons and measure sea level, glacial rebound and all. Favor the passive margins of continents.

Hector M.

About the dropped Argentine sites: Quequen is indeed a seaside location, but Buenos Aires is at the upper part of the River Plate freshwater estuary, and could not possibly be used to gauge sea level, I guess.

Excellent article. TIde gauges are the way to go for monitoring sea levels. After all, what is really important is the relative change of sea level with respect to land. Forget the rebound correction used by the warmists, that is stuipid for determining if a city or shoreline is going to be submerged under water. Satellite data may be interesting but not is better than monitoring sea level were it actually counts – on the ground right at the waters edge.
Satellite data is too easily corrupted by personal biases since numerous “corrections’ have to be made to the data. Following tide gauges also lets you monitor individual locations, some could be going up and some down, allowing you to determine if a particular location has a potential problem that has nothing to do with the overall sea level change.

Seems like you missed out finding recent data. For a start have a look that the paper by P J Watson “Is There Evidence Yet of Acceleration in Mean Sea Level Rise around Mainland Australia?” Journal of Coastal Research Mar 2011. For Fremantle in WA records go back to 1897. Sydney Habour (Fort Denison) goes back to 1914. There is a paper “The Sea Level at Port Arthur, Tasmania, from 1841 to the Present” by Hunter et al in Geophysical Research Letters

Richard "BAJA" Bell

Like many thousands of the worlds population who go down to enjoy the sea, I have been walking on the same beach on the south coast of the UK for over 50 years. NOTHING HAS CHANGED and I do not expect it too. Could any sane person really notice any kind of rise measured in a fraction of an inch ( or euro mm ! ) .
Just like a tiny temperature rise over a time period IT IS IRRELEVANT ………most people go on holiday to a hot country for the specific purpose of being in a warmer climate than they usually live ……… in a lot of cases this will be on a beach somewhere in the world, which most likely has not changed either !!!
Paraphrasing my favorite weather guru ENJOYS THE SEA IT THE ONLY SEA YOU’VE GOT

Sorry the above was posted before I finished. The latter paper is GPRL no7 2003. but you should able to find more recent information on the BOM web site. The sea level rise at Port Arthur from 1841 averages 0.8mm/yr. A similar rise is presently occuring on the East Coast of the Australian mainland Port Kembla, Sydney, Newcastle, Brisbane and Bundaberg which all have records of over 60 years.

We are all aware of the diurnal Oceanic Tides. And we should be always keep in mind that when we speak of a 1.8 mm/yr or better 180 mm/century trend, it needs to be compared with a 1000 mm (Tuvalu) -10000 mm (Anchorage, AK) daily tidal amplitude.
But there is also the lesser know, Earth Tide where the Moon deformes the Earth’s Mantle and crust by as much as 384 mm — twice a day. So, there is no tidal gauge that is at a constant elevation. Just another complication. 😉
“Eppur si muove”