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« UN ruling: EU must reassess renewables policy | Main | Climategate and the exclusionary principle »
Monday
Aug272012

Sea level rise - not so much

Thanks to Richard Tol for alerting me to a new paper by Torben Schmith and Peter Thejll of the Danish Meteorological Institute and Søren Johansen of the University of Copenhagen. Johansen is an econometrician and an expert in co-integration, a technique that the new paper applies to the question of sea level rise.

Global sea level rise is widely understood as a consequence of thermal expansion and melting of glaciers and land-based ice caps. Due to the lack of representation of ice-sheet dynamics in present-day physically-based climate models, semi-empirical models have been applied as an alternative for projecting of future sea levels. There are in this, however, potential pitfalls due to the trending nature of the time series. We apply a statistical method called cointegration analysis to observed global sea level and land-ocean surface temperature, capable of handling such peculiarities. We find a relationship between sea level and temperature and find that temperature causally depends on the sea level, which can be understood as a consequence of the large heat capacity of the ocean. We further find that the warming episode in the 1940s is exceptional in the sense that sea level and warming deviates from the expected relationship. This suggests that this warming episode is mainly due to internal dynamics of the ocean rather than external radiative forcing. On the other hand, the present warming follows the expected relationship, suggesting that it is mainly due to radiative forcing. In a second step, we use the total radiative forcing as an explanatory variable, but unexpectedly find that the sea level does not depend on the forcing. We hypothesize that this is due to a long adjustment time scale of the ocean and show that the number of years of data needed to build statistical models that have the relationship expected from physics exceeds what is currently available by a factor of almost ten.

I haven't had time to read the paper (which is not online to the best of my knowledge), but Richard tells me that the authors come up with figure for sea-level rise of 30 cm of sea level rise per degree C of warming -- which is rather lower than Rahmstorf and Vermeer.

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Reader Comments (31)

"Richard tells me that the authors come up with figure for sea-level rise of 30 cm of sea level rise per degree C of warming -- which is rather lower than Rahmstorf and Vermeer."

No surprise there then.

Aug 27, 2012 at 4:15 PM | Unregistered CommenterDon Keiller

There also appears to be yet another "divergence". This time in attributing the causes of sea level rise. According to which studies you believe, up to a third of last century's sea level rise was attributable to aquifer depletion.

A good illustration of just how sensitive sea level is to land storage is the sharp decrease in sea level last year due to heavy rains over Australia and South America. If we can observe that kind of sensitivity from a rainfall, what can we expect from depleting the Oglalla Aquifer in the American Midwest or the Aral Sea?

The counter argument to aquifer depletion is that new reservoirs have balanced the outflows. While that may have some truth to it, it certainly leaves the door wide open to uncertainty.

Aug 27, 2012 at 4:22 PM | Unregistered CommenterGregS

This appears to be an online copy of the paper at the U of Copenhagen:
Statistical analysis of global surface air temperature and sea level
using cointegration methods

http://www.econ.ku.dk/english/research/publications/wp/dp_2011/1126.pdf/

Aug 27, 2012 at 4:32 PM | Unregistered CommenterCharlie A

Just so you know - when a paper is not available online, you can generally email the authors and they will send you a pdf of it. I've tried it in another field and had good success.

Aug 27, 2012 at 5:06 PM | Unregistered CommenterMarkB

For anyone wondering what cointegration is about, perhaps see

Murray M.P. (1994),
A drunk and her dog”,
American Statistician, 48: 37–39.

It is only three pages long, and the first half is enough.

Aug 27, 2012 at 5:50 PM | Unregistered CommenterDouglas J. Keenan

Roger Harrabin on BBC News 24 reporting satellitte showing 30 percent less sea ice in the Arctic
Since records began and he says back to 1979 only 30 years .
He says 30 percent is naturally recurring weather cycle.
He blames green house gases obviously
But he dosent mention the Antarctic.

Aug 27, 2012 at 6:55 PM | Unregistered CommenterJamspid

The final paper is online but paywalled:
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-11-00598.1

Aug 27, 2012 at 6:58 PM | Unregistered CommenterRichard Tol

Aug 27, 2012 at 5:06 PM MarkB

Just so you know - when a paper is not available online, you can generally email the authors and they will send you a pdf of it. I've tried it in another field and had good success.

What happens in other fields is not a good guide to what happens in climate science.

And if it's available online but is behind a paywall? My general experience with climate scientists, when I have requested a copy and explained that I have no access to library facilities and no budget for paywalled papers has been less than positive - to the extent that I have given up bothering.

Aug 27, 2012 at 7:11 PM | Registered CommenterMartin A

Jamspid:

A few nights ago on the BBC 1 weather forecast at the end of the 10 o'clock News, a panic-stricken weatherman showed a graphic of the current Arctic sea-ice extent juxtaposed against another graphic showing where, he said, it should be. It beats me how these Met Office boys can have any idea what the correct extent of Arctic sea ice should be. Can any one, the esteemed Richard Betts for example, explain.

Aug 27, 2012 at 7:19 PM | Unregistered CommenterMike Post

Not checked, but I don't think the 30cm/C is drastically different from Rahmstorf. From memory, this Century Rahmstord had it at 70->150cm from temp IPCC temp forecasts of 2->6C.

Aug 27, 2012 at 7:39 PM | Unregistered CommenterGSW

[Snip - O/T]

Aug 27, 2012 at 8:12 PM | Unregistered CommenterAlecM

Apologies all, correct Rahmstorf range is 75->190cm this century. A little higher, but still ball park.

Aug 27, 2012 at 8:22 PM | Unregistered CommenterGSW

Apologies all, correct Rahmstorf range is 75->190cm this century. A little higher, but still ball park.

Aug 27, 2012 at 8:22 PM | GSW>>>>>

Can you clarify that please. Ball park for what?

Is there an accurate record of sea level rise since 1850?

Aug 27, 2012 at 8:41 PM | Registered CommenterRKS

RKS,

Assumed the arithemtic was fairly straight forward. 75cm SLR for lower IPCC forecast of 2C this century ~ 37cm/degree C. Upper 190cm for 6C gives 33cm/C. Quoted article above says 30cm/C, so lower yes, but not something you would argue over given they are estimates..

Aug 27, 2012 at 8:49 PM | Unregistered CommenterGSW

GSW: You're mixing up the equilibrium response with the transient one. By 2100, sea level rise will be only a fraction of its eventual level.

Aug 27, 2012 at 8:52 PM | Unregistered CommenterRichard Tol

"A recent compilation of tide-gauge data has shown that
during the period 1870–2004 sea level rose by ≈19.5 cm
(Church and White, 2006)."

http://www.the-cryosphere.net/1/59/2007/tc-1-59-2007.pdf

That's for an agreed 0.75C rise in temperature since the end of the Little Ice Age around 1850 [Wikipedia].

So what about this century, global warming stopped 15 years ago [agreed by Richard Betts]

As the model forecasts all proved wrong who is going to predict sea level rises for this century with any degree of accuracy?

Aug 27, 2012 at 8:57 PM | Registered CommenterRKS

Ah! thanks Richard. Haven't read the paper will try and find a copy. Just looked at the headline numbers and thought they were "ball park". Currently at 3mm/yr I believe so on target for 30cm this century without any additional help ~1ft.

Aug 27, 2012 at 9:00 PM | Unregistered CommenterGSW

I worry that in much of this modelling work the geosphere is regarded as an immutable constant.

Although geological processes are slow in human terms, the Earth's crust is as alive as it ever has been, always striving for, but never reaching equilibrium. Thr resultant cumulative effects on the geological time scale sends sealevel up and down locally and/or globally by hundreds of feet like the proverbial fiddlers elbow.

It should not be assumed that in the current stage of knowledge that we have more than a rudimentary grasp of the scale of movement of the seabed (other that a few locally studied areas) in terms of accurate mm/yr changes, nor of the global sediment fill rate (the submarine sediment cone beyond the Amazon mouth for instance is huge and accreting), sedimentary basin compaction and connate water expulsion rate, tectonic and isostatic movements, submarine volcanicity, geothermal gradient variations, and so on.

I think this paper is useful in itself, but needs to be taken in a 'buyer's beware context' in the real world it seeks to evaluate.

Aug 27, 2012 at 9:07 PM | Registered CommenterPharos

First this conclusion "...and find that temperature causally depends on sea level". How interesting. Then this: "In a second step, we use the total radiative forcing as an explanatory variable, but unexpectedly find that the sea level does not depend on the forcing". And conclude that this is caused by a factor 10 shortfall in data. Not by their first conclusion?

Richard Tol, what to make of this?

Aug 27, 2012 at 10:03 PM | Unregistered Commentertetris

@tetris
On apparently reversed causality: the authors note that sea level rise due to thermal expansion is a proxy for the extra heat stored in the ocean -- which of course affects the temperature of the atmosphere.

On radiative forcing and sea level rise: the abstract is cryptic. The sentence is about the disequilibrium dynamics.

Aug 27, 2012 at 10:41 PM | Unregistered CommenterRichard Tol

The paper must be the same linked before by Charlie A (same title and authors).

From the remarks:

---
In the second part of our analysis we introduced the external radiative forcing as an
external, explanatory variable. Contrary to our expectations, this did not extensively change our
overall conclusions. We expected the forcing to determine the development of sea level, but could
not find any sign of this in our data material. A Monte Carlo experiment revealed that we need in
the order of 1000 year of data in order to detect this effect. This is in contrast with results from
global climate model experiments, where a clear signal from expansion of the sea water is seen in
20th century integrations (e.g. Gregory et al., 2001) as a result of the increased forcing. At present,
we can only suggest explanations for this discrepancy. As seen on Fig1b, the sea level has been
rising also well before the forcing (Fig. 1c) increases in the mid-20th century. This secular sea level
rise seems to have persisted for at least some centuries (Kearney, 2001) and may dominate even
today, which may be the reason why we can not detect any influence from the external radiative
forcing on sea level.
---

I don't see anything about 30 cm per degree C.

Aug 27, 2012 at 11:10 PM | Unregistered Commenterplazaeme

plazaeme (Aug 27, 2012 at 11:10 PM):
"I don't see anything about 30 cm per degree C."

From the non-paywalled version linked above, equation (10) contains a factor 3.3 K m-1 for equilibrium between sea level rise and temperature, which amounts to the same thing as 30 cm per degree C. The standard error for the value 3.3 is given as 0.4; hence the one-standard-error range is 27 to 34 cm per K (or degree C if you insist).

Aug 27, 2012 at 11:44 PM | Registered CommenterHaroldW

@ Richard Tol

The puzzling part is, that this would presuppose a preceding forcing that at some point caused the uptake of those calories in the oceans in the first place. Since, given the timescales involved - acknowledged by the authors - it must be viewed as singularly unlikely that this forcing was anthropogenic in nature. So what accounts for it and doesn't it appear to falsify the AGW notion that the oceans are warming -which based on best empirical data is not all all clear, said in passing- due to anthropogenic forcing?

Aug 28, 2012 at 2:25 AM | Unregistered Commentertetris

Ref RKS: You can download sea level data from http://www.psmsl.org/data/

The rate of sea level rise is not a smooth monotonic sequence. Since 1880 its 5-year rate has been as high as 5 mm/year and as low as -3 mm/year. The rate of rise appears to vary in phase with the AMO but with a lag of a decade or so.
http://www.climatedata.info/Discussions/Discussions/opinions.php

Aug 28, 2012 at 3:20 AM | Unregistered CommenterRon

Meanwhile, back in the real world, a sea front property I have been involved with since 1946 has lower king tide levels now than it had then.

In those days the king tides used to cover the property and a levy had to be built around the well to stop the salt water from mixing with the fresh. King tides don't get that high now.

There has actually been a fall in Moreton Bay, Queensland, Australia, SLs since then.

Hard to imagine that world SLs have risen in the last 66 years but Moreton Bay SLs have gone down.

Having spent most of my life by the sea I just keep looking for this illusive SLR and I have other benchmarks that tell me the same thing. No SLR.

I have many old acquaintainces who are water rats with 50 year old jetties etc and none of them has ever said they have seen any evidence of SLR.

Aug 28, 2012 at 5:00 AM | Unregistered Commenterspangled drongo

@Pharos

+1

The tectonic plates at the Tonga trench move 9 inches per year. Many areas of the ocean floor are descending through such actions (some are rising). The overall effect on the ocean basin volume due to such factors has not been studied thoroughly enough to know one way or another what the final result would be.

Aug 28, 2012 at 5:04 AM | Unregistered CommenterBruce Cunningham

I'm not even sure what constitutes '1 degree rise', as surface temperature changes more readily than deeper levels. Rather like 'global temperature', overall sea temperature is a pretty meaningless concept.

Aug 28, 2012 at 9:19 AM | Registered Commenterjamesp

Bruce Cunningham -
The University of Colorado's estimate of sea level includes an adjustment due to ocean basin size of 0.3 mm/yr, discussed here. The page refers to "Sea Level Variations over Geologic Time", which may be found here.

Aug 28, 2012 at 12:04 PM | Registered CommenterHaroldW

The Earth is now cooling. The North Atlantic is cooling. The jet streams are moving nearer the Equator, the classic sign of cooling. total precipitable Water has been falling for 14 years, as has temperature before GISS and NOAA data fiddles.

And especially for Richard Tol, fundamental IR physics proved experimentally shows there can be no CO2-AGW and that the GHE is fixed by the first ~ 900 ppmV water vapour. basically, the IPCC has got every part of the energy transfer wrong, 6 physics' mistakes, a rare example of an historically awesome scientific cock-up.

If you don't believe me, ask Lovelock and wonder why Obama spent $64.8 billion to get the answer he wanted and failed, also why ZDB wants to shut me down without daring to argue the science except to say I'm confronting 100 years of failure!.........

Aug 28, 2012 at 7:24 PM | Unregistered CommenterAlecM

Re: "Global sea level rise is widely understood as a consequence of thermal expansion and [ice] melting..." (from the abstract)

Thermal expansion of the upper layer of the ocean affects (satellite altimeter-measured) sea level of the open ocean, only. It does not affect coastal sea level (measured by tide gauges), because density changes of surface water do not cause lateral water flow. Gravity balances mass, not volume (ref: Archimedes).

Since most ocean warming is of the upper layer, sea level rise due to thermal expansion is of purely academic interest. It does not cause significant real-world consequences, such as coastal inundation.


Re: "In a second step, we use the total radiative forcing as an explanatory variable, but unexpectedly find that the sea level does not depend on the forcing. We hypothesize that this is due to a long adjustment time scale of the ocean and show that the number of years of data needed to build statistical models that have the relationship expected from physics exceeds what is currently available by a factor of almost ten." (from the abstract) and "We expected the forcing to determine the development of sea level, but could not find any sign of this in our data material. A Monte Carlo experiment revealed that we need in the order of 1000 year of data in order to detect this effect." (from the draft)

We have only 19 years of low-quality satellite altimeter-measured sea level data (compared to >100 years of high-quality tide gauge-measured coastal seal level data). Since most ocean warming is of surface water, one should not expect to find that global warming causes measurable sea level changes through the mechanism of thermal expansion.

Moreover, it is well-established in the literature that at least 50-60 years of data is required to reliably detect a trend in sea level change.


Re: "we note that the increase in sea level begins before the warming (and the increase in forcing)." and "sea level has been rising also well before the forcing (Fig. 1c) increases in the mid-20th century. This secular sea level rise seems to have persisted for at least some centuries (Kearney, 2001) and may dominate even today." (from the draft)

That's important!


Re: "We apply the method described in the previous section to the global temperature series and the sea level series by Church and White (2006)."

Why C&W 2006? It exhibited a pre-1930 acceleration in sea level rise which caused a slight average acceleration for the 20th century as a whole, but that acceleration was entirely gone in their 2009 data set.


Re: "The resasons for the temperatures‟ complicated behavior is still unclear: It could be due to variations in the external forcing, mainly anthropogenic and/or volcanic aerosols, and/or it could be due to internal variability in the climate system." (from the draft)

And/or it could be because the temperature data is of poor quality.

Aug 29, 2012 at 2:07 PM | Unregistered CommenterDave Burton

As I have commented on other sites, Florida is rife with fixed-height seawalls, docks, piers, etc. Over the 40 years of my observation, there is not even a whiff of SLR.

Aug 29, 2012 at 5:46 PM | Unregistered CommenterDavid Lemoine

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