Guest essay by: Jan Kjetil Andersen
There is a well-established consensus concluding that the global sea level has risen over the last century, and that the level continues to rise. However, the question about whether the rate is accelerating or not, is more inconclusive.
To cast some light on this, I have analyzed the latest scientific papers on this topic. Thereafter I made my own time series analyzes based on tide gauges in the GLOSS network.
All data and software used in the analysis are available for download. See links in the end of the article.
I invite the readers to a discussion about the conclusions.
Firstly the findings from the academic papers:
I start by the IPPC AR5.
Chapter 3 is about Ocean observations, and here is exactly what I am looking for:
Figure 1 (IPCC AR 5 page 287 their figure 3.13)
(a) Shows the global mean sea level anomalies (in mm) from the different measuring systems as they have evolved in time, plotted relative to 5-year mean values that start at 1900. We see that the sea level has risen with 20-25 cm in the last 130 years, which gives an average rate of 1.5 to 1.9 mm/year.
(b) Shows the gauges observations from Church & White compared with satellite altimeter. In this close-up, we see a rise of 5 cm in 19 years, which gives an annual rate of 2.6 mm/year.
This shows that the rate has been higher in the last two decades than in the last century, but the next figure in AR 5 shows that this rate is not unprecedented in the record.
Figure 2: (IPCC AR5 page 289 their Figure 3.14)
Quote from IPCC text: “18-year trends of GMSL rise estimated at 1-year intervals. The time is the start date of the 18-year period, and the shading represents the 90% confidence.
The estimate from satellite altimetry is also given, with the 90% confidence given as
an error bar.”
The figure need some extra explanation to be understood outside the context of the AR5 report. According to the figure, there has been no accelerating since 1920. We see that both Church & White and Ray & Douglas observe approximately the same annual rise of around 2.5 mm/year between 1920 and 1940, and then there is a fall 1 mm/year before the rate rebounds to 2.5 mm in the late 1980-ies.
The Jevrejeva et. Al observes a maximum rate of 4 mm/year in the 1940-es but the series stop before the increase in recent decades. Satellite altimeters shows a steady rise with a relative small variation between 2.9 and 3.9 mm/year.
The satellite measurements has a very short series in the figure because the series only goes from 1992 to 2012. That means that only two years can be calculated with an 18-years trend.
I think a very important piece of information comes out of this figure. We see here that in reality IPCC find no evidence for accelerating sea level rise after 1920. The rise before 1920 was real, but can hardly have been caused by the small amounts of greenhouse gases emitted at that time. The CO2 level in 1920 was according to Nasa 303 ppm, or just 10% above the pre-industrial level and the warming that could have caused the sea level rise has to come before that. (http://data.giss.nasa.gov/modelforce/ghgases/Fig1A.ext.txt)
So why are we then hearing about the accelerating sea level rise in the media? Well, I think there are at least two reasons for that; firstly even though the figure does not show any acceleration, they does not draw that conclusion from it. What they say is this (AR5 Page 290): ”while there is more disagreement on the value of a 20th century acceleration in GMSL when accounting for multi-decadal fluctuations, two out of three records still indicate a significant positive value. The trend in GMSL observed since 1993, however, is not significantly larger than the estimate of 18-year trends in previous decades”.
This is rather inconclusive.
Secondly, other academic papers show an acceleration, I examine one of those below.
First, I want to update the IPCC analysis with the latest data.
The results presented in this section of AR5 are quite old. The newest of the three papers presented in the figure is Church & White, which was published in 2011, and this paper use data up to December 2009 only.
However, the authors keep extending the raw data used in their paper and the data series now includes December 2013. The reason for not having newer data is that quite many stations around the globe report late and a large bias would be introduced if the last years were based on the early reporters only.
I have run the extended series through my own statistical analysis created in php, Javascript and Google Graph, which gives the results below.
Figure 3: Blue line show Church & White 2011, with data up to Decemebr 2009. Yellow line is the authors later added data. Red line is satellite altimeter data used in AR5. Green line is altimeter until February 2016.
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Figure 4: My Results from running an18-year trends of GMSL rise estimated at 1-year intervals. The time is the start date of the 18-year period. This should be similar to IPCC figure for Church & White and Altimeter, except that I have not included any confidence interval, but I think the uncertainty is equally well visualized by plotting each monthly data point. I think the match is close, although not perfect, but it should be close enough to confirm that the same data sources are used.
Then I have extended with latest Church & White data, and latest altimeter data.
Figure 5. The data in this plot goes to December 2014 for Church & White and, February 2016 for Satellite altimeter.
We see that the last added gauge data (in orange color) lift the last part of the plot to unprecedented high rate, but the period is far too short to make any conclusions from that.
This is what we get out of the AR5 with updated data.
I then go to another recently published paper on the topic.
A resent paper is the Temperature driven global sea level variability in the Common Era by Kopp et al. of Rutgers University, published in PNAS January 4th 2016. This paper provides an estimate of the global sea level changes over the last 3000 years.
They claim:
Historic GSL rise began in the 19th century, and it is very likely (P≥0.93 P≥0.93) that GSL has risen over every 40-y interval since 1860 CE. The average rate of GSL rise was 0.4±0.5 0.4±0.5 mm/y from 1860 CE to 1900 CE and 1.4±0.2 1.4±0.2 mm/y over the 20th century. It is extremely likely (P≥0.95 P≥0.95) that 20th century GSL rise was faster than during any preceding century since at least −800 CE. “
That may be right, but it does not answer whether we experience an accelerating rate or not. The figure below is from this paper.
H
Figure 6 (From Kopp et al; PNAS2016 their figure 1d)
What I read from figure 6 is that the sea level started to rise in the 19th century, well before climate change could have any effect and has continued on a quite stable rate since then, but the authors project that an acceleration may occur soon.
Rather than to continue searching more academic papers, I decided it was time to make my own research, so I went to the sources.
Analysis of gauge data from the GLOSS network
Global Sea Level Observing System (Gloss) is a network of 281 globally distributed coastal tide gauge stations. The Core Network is designed to provide an approximately evenly-distributed sampling of global coastal sea level variations.
http://www.gloss-sealevel.org/
One of the challenges in making use of statistics from gauge stations is the importance of using a so-called common vertical datum i.e. a reference point. The stations in the GLOSS network has such reference called Revised Local Reference (RLR). Each station use a calibrated local datum for all the data series, but there are no common global vertical datum for all stations. This means that we get an error if we try to mend together different short series to make one large average.
However, if we limit the series and analysis to a timespan where all the selected series goes continuously from start to end, we do not need any common datum to make a correct average.
I have selected three set of series, which I call very long series, long series and medium long series.
Very long series are 1900 through 2013; long series 1925 through 2014 and medium long are 1950 through 2014.
In addition, all selected series have at least 80% complete monthly readings.
Of the 281 stations in the Gloss network only 6 fulfils the criteria for very long series, 9 for long series and 22 for medium long series. The list of these stations is given in the end of the article.
Two averages are made for each set of series; one simple average, and one global gridded average. The latter one was computed by dividing the globe in a 6×12 grid consisting of 72 cells measuring 30 degrees latitude times 30 degrees longitude. First, an average of all stations within each grid cell are computed. The global average is then an average of the all grid cells with a weighting of each grid cells according to its area. Because degrees longitude are shorter closer to the poles, the grid cells are also smaller. The relative length of one degree longitude, is cosinus of the degree latitude at the same spot. The weight of each grid cell is therefore the absolute value of cosinus of the degree latitude in the middle of the cell.
The benefit with this method is that we get less bias toward the areas with most stations. The gridded average is therefore the most important of the two.
The plots of absolute rise and 18-year trend are shown below.
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| a)Very long series(1900 through 2013):Simple average in blue, gridded in red. The plot shows 36 months floating average and linear trendline of mean sea level above local reference point. | b)18-year trend for very long series. Both start and end years for the 18-year period are shown. No discernible acceleration is evident from the moving average plot, but the linear trend line reveals a very small acceleration. However, all of this small acceleration is due to the small spikes in each end of the series. |
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| c)Long series (1924 through 2014): The gridded average show smaller growths | d)18-year trend for long series. We see that the largest rise occurred in the period starting around 1965. No discernible acceleration can be seen after the 1965 – 1973 period |
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| e)Medium long series(1950 through 2014), simple average in blue, gridded in red | f)18-year trend for medium long series. We see an acceleration for the simple average, but any acceleration for the gridded set is more dubious. Except for a very short spike in the end, the rise in recent decades are no higher than 1960-ies. All the trend in the gridded series is due to the spike since 2011. To visualize this I have included a trend line of a series that stops in 2011 (green color). |
Figure 7 a)-f). Absolute rise and 18-year trend for three different time intervals.
The plots in figure 7 suggest that there has been a small spike in the rise the last few years. This spike is also consistent with altimeter readings http://sealevel.colorado.edu/.
However, this spike may be contributed to natural variability. All the studies presented in AR5 above indicate 18-year trends that were significantly higher than the 20th century average at certain times and lower at other periods. This is likely related to multi-decadal variability like the Atlantic Multi-decadal Oscillation and/or Pacific Decadal Oscillation. The last spike may also have been caused by such a natural occurring variation.
So what to make of all this?
I have not made any regression analysis to show whether the small increase is statistically significant or not. I welcome anyone to do that. However, I think the graphs gives a quite clear message even without further analysis; if there is any acceleration, it is infinitesimal.
Regards
/Jan
References:
1. IPCC AR5 Chapter 3:
https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter03_FINAL.pdf
2. The Global Sea Level Observing System (GLOSS): http://www.gloss-sealevel.org/
3. Church, J. A., and N. J. White, 2011: Sea-level rise from the late 19th to the early 21st century. Surv. Geophys., 32, 585–602.
Both the paper and sources are freely accessible http://link.springer.com/article/10.1007%2Fs10712-011-9119-1
4. Kopp & al. Temperature-driven global sea-level variability in the Common Era. PNAS 2016
Full text: http://www.pnas.org/content/113/11/E1434.full
5. Nasa GHG gases: (http://data.giss.nasa.gov/modelforce/ghgases/Fig1A.ext.txt)
6. Satellite altimeter at Boulder university: http://sealevel.colorado.edu/
7. Data and software used to make this analysis: http://csens.org/mysource-txt/
List of GLOSS stations used:
Very long series (6 stations):
| Station | Country code | Station ID |
| Fremantle | AUS | 111 |
| Stockholm | SWE | 78 |
| Trieste | ITA | 154 |
| Brest | FRA | 1 |
| Marseille | FRA | 61 |
| San Francisco | USA | 10 |
Long series (9 stations):
| Tuapse | RUS | 215 |
| Pensacol | USA | 246 |
| Newlyn | GBR | 202 |
| Atlantic City | USA | 180 |
| Galveston II | USA | 161 |
| Key West | USA | 188 |
| Balboa | PAN | 163 |
| La Jolla | USA | 256 |
| Honolulu | USA | 155 |
Medium long series (22 stations):
| Kushiro | JPN | 518 |
| Mera | JPN | 359 |
| Manila | PHL | 145 |
| Legaspi Albay | PHL | 522 |
| Ko Lak | THA | 174 |
| Tregde | NOR | 302 |
| Adak Sweeper Cove | USA | 487 |
| Newport | 351 | USA |
| Fort Pulaski USA 395 | ||
| Hilo Hawaii | USA | 300 |
| Ceuta | ESP | 498 |
| La Couna | ESP | 484 |
| Barentsburg | SJM | 541 |
| Antofagasta 2 | CHL | 510 |
| Tofino | CAN | 165 |
| Prince Rupert | CAN | 167 |
| Sitka | USA | 426 |
| Apra Harbur Guam | GUM | 540 |
| Pago Pago | ASM | 539 |
| Kwajalein | MHL | 513 |
| Midway Island | UMI | 523 |
| Wellington Harbour | NZL | 221 |
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To get to a two meter rise by 2100 would require an acceleration of 3.7%. Which means it would have to rise some 8cm IN THE LAST YEAR! This is physically impossible. Having any acceleration is meaningless, it mathematically it has to be 3.7% to make the 2 meters.
There’s other ways to get 2m sea level rise than by constant acceleration.
Also 3.7% isn’t an acceleration. Accelerations are in distance/(time)^2 like x mm per year per year.
Acceleration and compound growth are mathematically the same thing. Any distance/time^2 increases at a specific percent rate.
“There’s other ways to get 2m sea level rise than by constant acceleration.”
Nope. Mathematically it is the only way. Try it on a spread sheet. Unless you mean at a constant rate, which means sea level would instantaneously have to jump to 20mm per year from the current 1.74mm per year. Nature doesnt work that way, there is always an acceleration to change rates.
Yes, but a constant acceleration requires the smallest constant
rises. Any other model requires that if it doesn’t go up much now
it has to accelerate even more in the future.
You need a time in there to make it an acceleration. 3.7% for how long? For example, per year^2.
Also, a percentage increase per year^2 isn’t a constant acceleration. A constant acceleration would be the same amount increase per year^2. A constant percentage per year^2 means a larger acceleration when the value is larger.
“However, I think the graphs gives a quite clear message even without further analysis; if there is any acceleration, it is infinitesimal.”
Great article, and great conclusion. I, obviously, concur 100 percent. Sometimes just looking at a graph tells us all we need to know.
Yep! If I’ve learned anything from W Briggs it’s that when investigating a time series, all you have to do sometimes is to look at it!
Yes! That’s why we make graphs. So we can see, with our eyes, the trend of the data.
Good post, and I think graphs are a reasonable way to deal with noisy data. A shift from 2.5 to 4mm a year to 40+mm a year looks patently unreasonable.
Grinsted et al. 2009, defend that sea level started to increase around 1700. Every century afterwards appears to have seen an increase in sea level rise. IPCC projection appears reasonable if global warming continues. If there is an acceleration in sea level rise it is likely to be small, as the IPCC projects.
http://i1039.photobucket.com/albums/a475/Knownuthing/Grinsted2009sealevel2_zpsvjnorrmn.png
Javier says:
….sea level started to increase around 1700. Every century afterwards appears to have seen an increase in sea level rise…
Yes.
…IPCC projection appears reasonable if global warming continues.
No.
UN/IPCC is politics. Period, full stop. Disregard them
If sea level rise began to increase in the 1700’a, there is no way that human emissions were the cause.
Clearly not the cause of the rise since 1700. According to that last graph is steeper recently, so that does not preclude a human contribution. Since that data is showing increasing variability over the whole period that recent increase is not necessarily AGW either.
dbstealy says:
If sea level rise began to increase in the 1700’a, there is no way that human emissions were the cause.
Which begs the question: what is the cause? The CAGW hypothesis is inadequate as the rise predates any application of the hypothesis. Nothing in the prevailing scientific earth science paradigm provides an explanation for an increasing rate of rise over three centuries.
Time to review the paradigm by questioning all assumed knowledge and where possible adopting alternative explanations from the perspective of alternate paradigms.
Oh, look. There’s the Medieval Warm Period and the Little Ice Age. Gee, maybe it is all/mostly Natural Variation!
There was supposed to be a “/sarc” tag, but it didn’t display.
Bob,
I didn’t see anything that needed a sarc tag…only the null hypothesis expressed with maybe a little dig at the warmists.
Bob Shapiro says:
‘Oh, look. There’s the Medieval Warm Period and the Little Ice Age. Gee, maybe it is all/mostly Natural Variation!’
The MWP & LIA represent Natural Variation to the extent that the hypothesis is accepted that thermal expansion is the primary driver of sea level rise, ie that the heat is hiding in the oceans. However on longer time scales indications are that sea level rise has been near relentless.
The Cobb et al 2016 paper referenced in this text above figure 6 found only one period of sea level decline over 27 centuries of sea level rise.
If this is correct then there are other factors driving sea level rise. I think that restricting the cause of sea level rise to thermal expansion is reducing a complex problem to a neat solution, but it does not really provide a persuasive argument for me.
Dave Burton came to a similar conclusion after extensive study of the data.
https://rclutz.wordpress.com/2016/02/22/sea-level-rise-just-the-facts/
Uh oh – “… scientists now believe the Arctic is locked onto a course of continually shrinking sea ice”.
We’re all going to die.
http://www.theguardian.com/environment/2016/mar/28/arctic-sea-ice-record-low-winter?CMP=Share_AndroidApp_Tweet
..Slight correction …” they does not draw that conclusion from it. ”
……….. Does should be do ?
Thank you Marcus,
Can the moderator please correct this?
/Jan
Sorry, could I ask for help? I need a link to any good critique of Parrenin, et al’s paper in which he insists that the rise of CO2 and temperature are historically synchronous. I keep searching for “wuwt Parrenin” or any other likely terms, but no matter what search engine I use I get that malfunction that I don’t have a name for: The search results all show Parrenin & a complimentary phrase, but when you click on it, the site has nil about Parrenin or his paper. I’m sure I explained that badly. If you try it yourself you’ll see what I mean.
Hello Penelope,
I see what you mean. I tried:
parrenin global warming
and got a huge number of hits on a music group.
parrenin+global warming+wuwt
got all global warming (and a huge chunk of the entire internet)
parrenin + global warming + wuwt
got good results. I used Duck Duck Go, not G**gle. No idea why it is so fussy about spaces surrounding the ‘+’.
Here is a paper at NoTricksZone:
http://notrickszone.com/2013/03/10/clear-solar-impact-on-climate-shown-by-new-study-german-meteorologist-calls-parrenin-et-al-paper-the-latest-gag/
They do not think too much of the paper.
Thanks, Tony, that was the only one I had already found. I was hoping for something more substantial than just calling it a gag. I, of course, know of a couple studies that contradict Parrenin’s conclusions. But I had it thrown up to me & would like to be able to actually comment on it.
Maybe someone else has actually seen something on it I can’t imagine how they get the search engines to malfunction like this. Really annoying.
Even if it WAS accelerating, what the hell does anybody think they could do about it? Invest in mountainside chalets?
I find it paradoxical that they scare us with 2 meter rise on coastal cities, but they dont say a peep about major earthquakes on those same cities.
Nice point. In a 1905 paper, Akitsune Imamura predicted the big one would hit Tokyo and cause 100,000 deaths due to the subsequent fires. He recommended beefing up fire fighting capability. He was ridiculed for spreading ‘groundless rumor that deludes the society.’ Of course the big one did hit in 1923, killing 100,000 in a fire storm.
Wonder how much California is investing in earthquake response compared to ‘green’ energy. Instead of shutting down functioning energy producers, how about demolishing a few thousand unsound (death trap) apartment buildings?
cm, mm, inches, feet, furlongs, km, miles — make up your mind! Pick one unit and use it on all the graphs. That way moving from one to another won’t give the false impression of some great slope or change.
Regarding figure 6 – RCP 8.5 W/m^2 is the worst*4 scenario requiring almost 1,000 ppm CO2, melting of the ice sheets and multi-m rises & taking until year 2500.
So…with supposedly massive amounts of CO2 being spewed into the air by humanity, even since 1950, there has been absolutely NO CHANGE at all, that could be considered an “acceleration” in the NATURAL sea level rise trend, on this planet, at all.
Well THAT has to suck for a theory that depends on stuff like that happening…
Succinct, accurate and smile inducing. Good comment.
My search for acceleration…
https://climatesanity.wordpress.com/the-search-for-acceleration/
A video showing NOAA sea level data for all locations where the data spans at least 75 years. In each case the trend is extrapolated to 2100 and compared to what would be required to get to 1 meter ot 1.8 meters additional by 2100…
https://climatesanity.wordpress.com/2016/02/28/sea-level-projections-vs-tide-gauge-data/
In my opinion the measurements of sea level are nearly worthless.
Statistical analysis can not make the data accurate.
Statistics applied to inaccurate data is just mathematical m asturbation.
I doubt if sea level can be determined to the nearest +/- two inches
What kind of accuracy can you get with only 281 stations in the Gloss network?
A quick analysis in my head says each station must cover 500,000 square miles of ocean !!!
281 measurements for 70% of our planet’s surface are a wild guess, not accurate data.
When the data are no good, alternate indicators are needed:
(1) Are rich people around the world still building huge homes on the ocean?
Answer” Yes.
Do they know something about sea level we don’t know?
(2) Are the Republic of Maldives atolls getting huge new resorts, and they already have a big airport?
Answer: Yes.
Do they know something about sea level we don’t know?
http://www.amatraveller.com/2015/06/27/the-st-regis-vommuli-resort-maldives-opening-2016/
http://www.panoramio.com/photo/12055649
Do all these rich people and corporations want to throw their money away building something that will be threatened by accelerating sea level rise?
Of course not.
My conclusion is sea level rise is not accelerating, unless there good data to prove it is.
Good data do not exist.
Alternate data suggest some very smart and rich people do not see any sea level risk.
Bingo!
Bongo.
Tide gauges cover the local where they are sited. The fact that water is a liquid means that you do not need to measure every square mile of open ocean.
Richard Greene,
There is some good data. Not much, but what there is indicates thar sea level rise is pretty close to zero.
There are photographs taken a century ago that show no sea level rise. And the late, great John Daly wrote about a high tide MSL mark cut into stone that shows current sea levels are not much more than when the mark was cut in the early 1800’s.
Don’t forget that local tectonics are similar to or even exceed sea level rise. Globally, the sea level is rising, but numerous areas are stagnant or rising out of the ocean due to various reasons.
“(1) Are rich people around the world still building huge homes on the ocean?
Answer” Yes.
Do they know something about sea level we don’t know?”
They probably know that they can buy a huge home on the ocean today and move to another huge home on the ocean in 10 years. (for some rich people, it’s way less than 10 years) When you have huge amount of money, and still earn more than what you can use in the same time, you need to spend it, otherwise it’s worthless.
For the hotels in the Maldives, you have to ask them in how many years they expect to break even. If their business plan tell them that it’s 10 years, they don’t really care about sea level in 20 years.
Thank you Richard, but I if we could use rich people’s behavior as a proxy to understand sea level change that would mean that the rich people knew something we other do not know.
And I don’t think they do, at least not about the rate of sea level change.
/Jan
What is the latest numbers by year from the tide gauges.
When I worked with Church and White’s database, I always wondered why they selected a certain subset of the all the tide gauges available. The number was very high, but they left out a large number that just looked like data selection to me.
Of course, the PMSL database is so, so hard to work with and I wonder how you did it. I think nobody has been able to say that the average tide gauge rose by 1.5 mms/year in 2013 for example versus 1.4 mms/year in 2012.
The issue is, we have to be able to say that there is no acceleration starting in 1992 and ending in 2014 from the tide gauges because this is when the satellite algorithms say there has been an acceleration. But no one can really work out by year what the tide gauges are really saying.
Here you find a list of all the gauges: http://www.psmsl.org/data/obtaining/
This is the latest numbers
I did it the hard way.
I right clicked and downloaded the monthly records of all the GLOSS stations.
Then I wrote php code for analyzing it.
The software is available for anyone here: http://csens.org/
(Select Sea Level / Gloss Gauges avg)
/Jan
Ah yes, SLA, that other dubious ENSO proxy …
http://s27.postimg.org/5eh3rl669/SLS_NS.png
Figure 1(b) shows a distinct spike of about 5 mm above the long-term trend at 1997-98 in both tide gauge and satellite data followed by a lapse back to their long-term trends. I am trying to get my head around how an El Niño event could cause a short-term sea level rise. Any ideas on this would be welcome, from those who know about oceans and weather and such.
Other than that, I would say that the satellite altimeter measurements in figure 1(b) show – if they show anything – a slight deceleration starting about 2007. Certainly no acceleration.
Glad to see I’m not the only one who thinks eyes are a very good tool for picking trends out of graphically presented data series.
A good read: “El Nino – Unlocking the Secrets of the Master Weather-Maker” J. Madeline Nash. Mentions how El Nino affects levels.
groundwater abstraction for irrigation is apparently resposible for something like 0.8mm/ year, and only started after WWII. Tends to squash any arguments over unprecedented rise as without it the rise would have been lower in recent decades than previous
I live in the later stages of an interglacial, during yet another warmish phase, one which is not likely to last. Like the viagra-popping grandpa, I’m grateful for whatever slight rise I can still get.
A little old but worth the read.
http://joannenova.com.au/2012/12/are-sea-levels-rising-nils-axel-morner-documents-a-decided-lack-of-rising-seas/
If the solid surface of the earth was smooth, it would be entirely covered in water with a bit of ice, some floating, some not. The solid surface is not smooth but is seen as a bucket. We can’t measure the water level very well. We can measure the changes in the volume of the bucket even less well. The margins of error seem a bit pointless.
Jan, you have done a lot of work to get your conclusions. I think you are working too hard. Let me show you a shortcut you would benefit from. First, I ignore all the accelerator guys and go back to basics. I like what Chao, Yu and Li did (Science April 11th 2008). They corrected all available sea level data since 1900 for any water held back in artificial reservoirs. This gave them a straight line water level curve for the last 80 years. Anything that has been linear that long is not about to change anytime soon. The slope of their straight line section was 2.46 millimeters per year. That works out to just under 10 inches per century. Al Gore at the same time was touting 20 foot dea risf per century. According to him that was enough to inundate Florida so he shows a map of Florida under water in his book. And gets a Nobel Prize for that trash. I don’t doubt that there can be some deviations from the prediction based on Chao Yu & Li paper but I expect it to hold in the long run and will not be surprised if a hundred years of melting will give us a sea level rise of just10 inches. As to all these half meter or two meter sea level changes, these are just fantasies of novices you can safely ignore.
Thank you for the link Arno, I will study it tonight, after work
/Jan
Arno, I see they estimate that about 30 mm of sea-level equivalent is now stored in man-made dams and the surrounding soils, and I see that they then get a straight line in their estimates.
However, there are several studies of sea level rise with diverging results and this 30 mm is not enough to explain the difference.
Church and White use the results from Chao Lu and Li, and argues that about a third of this effect are offset by groundwater depletion which contribute to ocean rising.
One very interesting information concerning reservoirs is that globally, the rate of dam entrapment has slowed significantly in the last decade or two. This should contribute to some acceleration in the sea level rise.
/Jan
A better question and which cannot be answered because we don’t know enough about sea level change is “is sea level change unexpected?” At this question, which btw ignores the direction of change, we can examine our expectations and try to understand why our expectations lead us where uncertainty suggests we have no business going. Based on what we know we lack the moral authority to conclude anything about sea level change.
From 1960-2016 there has been no measurable increase in sea level, at Hobart Tasmania and at Albany Western Australia. From 1915-2016 at Fort Denison, Sydney New South Wales, there has been a 5 cm rise in sea level. At Port Pirie in South Australia, there has been a 10cm fall from 1945 to 2016. I cannot see any acceleration or even net rise coming out of these figures. The variation in level between consecutive years is often far greater than the variation over the century.
I think that this question remains in play because the Warmistas and CAGW fanatics want it so desperately to be true, even if the figures do not support them.
There is very substantial lag built into the system by the specific “heat” of water. This lag is currently unknown due to unknown relationships between generally (but not exclusively) stratified layers.
Tell me how Ninos (at least by the multivariate index) seemingly affect GMSL:
And we may well get down the road a bit explaining sea level variability.
Interesting plot. However, you need to consider that MEI ( is that what you are plotting ) is partially a temperature index. You have detrended SSL It is to be expected that temperature changes will be visible in SSL due to thermal expansion, so noting that temperature causes thermal expansion is not a shock result.
To be clear was neither my plot nor my idea to compare the two.
http://sealevel.colorado.edu/
As we currently understand it, the atmospheric and oceanic components of ENSO do not create cold or warm water. They just spread the water across the ocean surface in different ways. This is what makes the relationship surprising.