Wednesday, April 14, 2010

Can't you see the acceleration ?

The current rate of global sea-level rise is 2-3 mm/year. To hit 1 m of sea-level rise in 2100 this rate should  have to accelerate at least to 10 mm/year or faster at some point in th 21st century. While we await this to happen we may have a look at the un-smoothed monthly global sea-level data from satellite measurements. But before watching the data plot, think for a few seconds what you are expecting to see..

 Global monthly mean sea-level from Topex-Poseidon-Jason, corrected for barometric effect and isostatic adjustment

I must confess that at first sight I was a bit surprised, and maybe you as well. I had seen the multi-yearly smoothed data often, and I did not expect that by eyeballing the acceleration in this period seems to be negative. A linear fit to a parabola yields a negative value of the quadratic term. The bootstrap confidence interval (5%-95%) of the linear fit suggest a possible development for the global sea-level in the next 10 years. Or perhaps the up-tick in the past 4 years will continue. 
Do not take this too seriously. It is just a pastime while we wait.

The lines represent the bootstrap 5%-95% confidence interval of the mean response (no including residuals)  . The calculation of the confidence intervals takes into account the full serial correlation structure of the regression residuals.

For those of you who may be wondering, this fit implies a 95% probability for 35 cm or less of sea-level rise in 2100.


P Gosselin said...

As I've written before, I have yet to find a single scientist who is willing to bet on 6mm/yr for the next 10 years - let alone 10mm or 16mm or 20mm! Not even Stefan Rahmstrof, who has already bet "big money" on temperature rise for the next 10 years.

Many of these projections are made I think because it attracts a lot of publicity and attention.

Donna Laframboise has just announced that she'll be releasing the results of her comprehensive audit of the IPCC 2007 AR4 references today! (I know the results already, but I'll let Donna have the fun of releasing them).

P Gosselin said...

Somewhere I recall reading that Hans von Storch gave a range of 40-80 cm, if I'm not mistaken. That should allow him to bet another bottle of wine.

ghost said...

hm, 2100 is maybe a bit late for deciding the bet...

one remark: there are interesting papers about the recent sea level... at least for me as lay person: eg.

interesting is to know, what slowed the rise. In the linked paper showed the thermal expansion or its reduction could be the main reason. Seeing La Nina/El Nino as well as the temperature development of the last years, this could explain it... not sure.

Another figure in this paper was also nice and some fun: showing the MSL + R07 projection + AR4 projection. MSL is on the lower end of R07 and on the upper end of the AR4 projection.

PS: did you imply, smoothing was "misleading" visually or worse: smoothed data may caused false trends in computations?

Marco said...

Hi P Gosselin: You did some great work. Too bad you labeled all books as "not peer reviewed". Wrong!

Back to the drawing board!

isaacschumann said...

I came across this:

'”Instead of using temperature to calculate the rise in sea levels, we have used the radiation balance on Earth – taking into account both the warming effect of greenhouse gasses and the cooling effect from the sulfur clouds of large volcanic eruptions, which block radiation”, explains Aslak Grinsted, PhD'

I was only able to see the abstract, but I would be interested to hear your commentary on this when you get a chance to read it.

It predicts at least roughly 70cm of sea level rise with aggressive mitigation, 1.2m without. These claims seem too deterministic to me, but then again, I'm no expert. How does this analysis compare to the temperature to sea level model discussed in your last post?

P Gosselin said...

So much for the Bible of AGW:

Marcel Severijnen said...

The rate of change of the sealevel is an interesting phenomenon. Simon Holgate from Proudman Oceanographic Laboratory wrote about it in GEOPHYSICAL RESEARCH LETTERS (doi:10.1029/2006GL028492) in using a selection of stations worldwide to follow the rates of change. I took the opportunity to mirror sealevel rate change at one Dutch station (Den Helder, annual mean sealevel rise 1,46 mm) with one of Holgate's selection, UK station Newly in a historical reconstruction from 1916. Complete with rate changes of Jason satellite measurements, which fit quite well in the picture.
In Dutch, but that is easily understood in Hamburg......

Marco said...

@P Gosselin:

Is there a grade lower than F? It would be the grade you guys and gals would get for that shoddy piece of work. The very first part I checked (1a) not only completely ignored books and agency reports (often these ARE peer reviewed), it even does not label IPCC reports as peer-reviewed. A howler of a mistake!

eduardo said...

@ 3


thank you for the link. Indeed, sea-level is a very complex and interesting topic.
Another paper worth reading is the one by Walter Munk, A sea-level enigma, although some of the discrepancies outlined there have been in the meantime lessened.

What I learn is that when one talks about accelerating sea-level, one compares the present rate with the one at the beginning of the 20th century, for when only a few records are available. From 1950 onwards it is very difficult to detect an increase in the rate of change

'PS: did you imply, smoothing was "misleading" visually or worse: smoothed data may caused false trends in computations?'

Of course not! climate scientist always present the data in the most objective way possible.

P Gosselin said...


The process has to be rigorous and it simply cannot count everything under the sun with a copyright symbol as "peer-reviewed".

Even peer-reviewed is not a guarantee in any way. The process has been corrupted more than once, and "science" like the Hockey Stick have been stamped as settled science. Peer-reviwed, and flawed.

If anything should come out of this debate, it is that the peer review process and criteria have to be more clearly defined and adhered to. The IPCC wnet over the line in selling the report to the public. Look at the quotes:

They exaggerated and were less than truthful. Now the price has to be paid.

Marco said...

In short, P Gosselin, you created a strawman: you made up a new definition of "peer reviewed" without telling anyone, then claimed a lot was not "peer reviewed" (but only based on that new definition that was not described), and when caught start complaining that peer review is not even a guarantee. Oh, and that's actually what scientists are saying anyway. Nonetheless, peer review is peer review, and by definition also includes book chapters and reports and whatmore that have gone through a formal review by an expert and judged on its merits before publication.

Oh, and I guess the price you believe the IPCC should pay is people like you and your fellow 'auditors' making things up. Great. Attacking what you believe to be untrue by being less than truthful.

Rob Maris said...

Marco: I'd suggest you to ignore P. Gosselin's post. This helps lowering stress levels. I already ignore his posts since two weeks, and as long as his posts are not too frequent, this works OK for me.

Note: it is said that austrian people know a level beyond ignoring: "I don't even ignore him!".

P Gosselin said...

Jo Nova:
"Every time the IPCC have spat on a scientist with “that’s not peer reviewed”, they have set themselves up to look like duplicitous fools when caught relying on student theses, magazine articles, and boot cleaning guides."

Boot cleaning guide?

I couldn't have said that better.
The IPCC is a victim of its own arrogance. They've tried ignoring us for years, and now it's catching up to them.

Rob Maris said...

eduardo: In Werners "Chill-out" posting (april 4th) you noted sea-level that "It attained a maximum at the so called Midholocene High Stand, about 5000 years ago 2 meters higher than today, and has been declining, at these long time scales, since then.".

Can you provide some links to up-to-date sea-level information that covers this time span?

ghost said...


thank you very much... a bit sarcastic... hm. ;)

hm, what I always find really frustrating in "your" research area is the combination of missing "perfect" data from the past and the long timescales that are needed for validating results. of course, there are really great, very impressive works that try to improve this situation. But still...

I mean, for the last 17 years one can see a slight decrease in the rise rate (several times are flat periods), but compared to the beginning of 20th there is an acceleration (probably). What is the noise, what is the signal? Is both noise? I assume, that is one problem of semi-empirical models (what about the other, not VR09/R07 approaches, they show similar results?), while the other (physical) projections do not know all processes or processes in detail. Despite the progress, still a bit frustrating for a lay person like me.

Actually, for me, 50cm look bad enough and the rise won't stop in 2100, I think 1m or 2m rise or more will also cause problems in the 22nd or 23rd century, I assume... well, except the Vulcans are coming.

Marco said...

@Rob Maris,

Don't worry, I'm not stressed that much. But I think someone needs to point out, for those less aware of the facts, that there are other 'opinions'.

_Flin_ said...

Please correct me if I am wrong:
Isn't the key issue concerning sea levels the stability of the big ice shelfs (Greenland, WAIS, EAIS)?

And isn't our knowledge concerning these rather limited?

So if the shelfs stay stable, the whole sea level issue will be existent, but non-catastrophic, because we can easily adapt to a meter higher sea (at least those of us not living on the Maledives).
But if the shelfs do not stay stable, our whole projections are going down the drain.

Currently we think that the ice shelfs are not an issue. But recent measurements can be interpreted that we might have underestimated a few things.

Or did I severly misunderstand something here?

eduardo said...

@ 14


Depending on your background these references could be useful

eduardo said...

@ 15


yes, it is sometimes frustrating, because the conclusions are often soft, based on assumptions that are difficult to check. In some sense it is even worse than astrophysics. In astrophysics they cannot do experiments but they can observe many stars or galaxies. We have just one object, long time scales and many confounding factors. This is the main reason for all these endless debates. There are mostly no debates in numerical weather prediction, as they can test their results everyday.
However, when you gloss over the political implications, it is very attractive science because you are forced to think from many different angles. The discussion about sea-level variations and its possible causes is a nice example.

eduardo said...

@ 17

I would say you are mostly right. However 'recent measurements' are exactly that, recent, and lack the long-term perspective. Low and Gregory mention this in their commentary. Measurements of outet glacier velocities in Greenland are very variable showing some years with high velocities followed by stand-still. It is difficult then to estimate a long-term mean because the measurements cover barely 10 years or so and only some locations.

Anonymous said...

This is a nice academic debate but in practice, we need better downscaled models and more local studies. Local sea-level rise can vary a lot from global average and engineers need to have numbers for their area.

I work with a city engineer in a coastal town where the dikes are already close to their limit. It is a highly controversial topic, therefore, I chose the anonymous option. On top of global sea-level rise, the engineer has to take into account:
- geological processes
- tides
- low-frequency climate cycles
- episodic storm events such as storm surges
- surface waves

Even if global sea level rise might be limited to 35cm in 100years (what I strongly doubt), it might still lead to a dike breach in combination with the other factors. For example, it has been suggested that climate change will also lead to a higher frequency of storm events.

Most areas of that town are under sea level already and a dike breach could have severe consequences. Therefore, the engineer argues that we need adaptation measures now. Problem is: Local residents are confused by the climate change debate and don`t believe in sea-level rise anymore - therefore, they object all adaptation measures. In particular, they don`t want higher dikes blocking their views and they don`t want to participate in the costs. Local politicians now stopped work on the dikes because they don`t want to upset the public.

Major concern of the city is responsibility and liability in case of a dike breach. Insurance companies pulled out long ago - they won`t pay anybody... In another municipality that was actually hit by a small flood, residents sued the city. Who is liable? The city? The scientist?

This is the practical dilemma beyond the academic debate. And the stakes are high - a flood or dike breach can ruin a community and even lifes may be at risk.

Rob Maris said...

eduardo: thanks for your pointers. I have read the abstracts, found 1 interesting quote "Early Holocene eustatic rise in sea level and late Holocene hydro-isostatic decline in sea level combined to produce a regionally variable mid-Holocene highstand in tropical Pacific sea level that stood 1.0–2.6 m above modern sea level.",
which coincides with that what you said.

However, when I look at other places (via google search), e.g.
- danish location research yield monotonous rise figure.
- A readable article for an engineer like me makes the impression to present scientific data.

Regarding my "Wattenmeer"-Buch reading: there it is suggested that the Waddensea area has grown to its today's "shape" thanks to relative steady sea level rise.

Footnote: I'd consider eustatic long term sea-level change over the past 2000 years as helpful to better interpret what is going on the past 100 years.

eduardo said...

@ 21

Anonymous , would you like to pen a longer blog post on this particular case? I think the interaction between climate projections and local public policies would be of interest for many here

P Gosselin said...

This is interesting:

Anonymous said...

@ 23 eduardo

I really would like to but this particular case is highly contentious at the moment. Until summer, a new zoning plan is debated with the participation of local citizens and I don`t want to get my engineering colleague into trouble.

I could either write a longer report on this case later, when the plan process is finished. Or I could write about another planning and climate change case where I was involved and which was less contentious. However, that one took place in the interior and sea-level rise didn`t play a role.

P Gosselin said...

Last week some hecklers in the blogospehre saw fit to try to trash the excellent results of Donna Laframboise's Citizen's Audit.
Well, don't take my word, read Richard Tol's comments here.
Perhaps his comments ought to be posted here at Klimazwiebel.