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Sealevelgate

Filed under: — stefan @ 11 March 2010 - (Italian)

Imagine this. In its latest report, the IPCC has predicted up to 3 meters of sea level rise by the end of this century. But “climate sceptics” websites were quick to reveal a few problems (or “tricks”, as they called it).

First, although the temperature scenarios of IPCC project a maximum warming of 6.4 ºC (Table SPM3), the upper limit of sea level rise has been computed assuming a warming of 7.6 ºC. Second, the IPCC chose to compute sea level rise up to the year 2105 rather than 2100 – just to add that extra bit of alarmism. Worse, the IPCC report shows that over the past 40 years, sea level has in fact risen 50% less than predicted by its models – yet these same models are used uncorrected to predict the future! And finally, the future projections assume a massive ice sheet decay which is rather at odds with past ice sheet behaviour.

Some scientists within IPCC warned early that all this could lead to a credibility problem, but the IPCC decided to go ahead anyway.

Now, the blogosphere and their great media amplifiers are up in arms. Heads must roll!

Unthinkable? Indeed. I am convinced that IPCC would never have done this.


The North Sea (see Stefan’s photostream on Flickr)

But here is what actually did happen.

In its latest report, the IPCC has predicted up to 59 cm of sea level rise by the end of this century. But realclimate soon revealed a few problems.

First, although the temperature scenarios of IPCC project a maximum warming of 6.4 ºC (Table SPM3), the upper limit of sea level rise has been computed for a warming of only 5.2 ºC – which reduced the estimate by about 15 cm. Second, the IPCC chose to compute sea level rise up to the year 2095 rather than 2100 – just to cut off another 5 cm. Worse, the IPCC report shows that over the past 40 years, sea level has in fact risen 50% more than predicted by its models – yet these same models are used uncorrected to predict the future! And finally, the future projections assume that the Antarctic ice sheet gains mass, thus lowering sea level, rather at odds with past ice sheet behaviour.**

Some scientists within IPCC warned early that all this could lead to a credibility problem, but the IPCC decided to go ahead anyway.

Nobody cared about this.

I mention this because there is a lesson in it. IPCC would never have published an implausibly high 3 meter upper limit like this, but it did not hesitate with the implausibly low 59 cm. That is because within the IPCC culture, being “alarmist” is bad and being “conservative” (i.e. underestimating the potential severity of things) is good.

Note that this culture is the opposite of “erring on the safe side” (assuming it is better to have overestimated the problem and made the transition to a low-carbon society a little earlier than needed, rather than to have underestimated it and sunk coastal cities and entire island nations). Just to avoid any misunderstandings here: I am squarely against exaggerating climate change to “err on the safe side”. I am deeply convinced that scientists must avoid erring on any side, they must always give the most balanced assessment they are capable of (and that is why I have often spoken up against “alarmist” exaggeration of climate science, see e.g. here and here).

Why do I find this IPCC problem far worse than the Himalaya error? Because it is not a slip-up by a Working Group 2 author who failed to properly follow procedures and cited an unreliable source. Rather, this is the result of intensive deliberations by Working Group 1 climate experts. Unlike the Himalaya mistake, this is one of the central predictions of IPCC, prominently discussed in the Summary for Policy Makers. What went wrong in this case needs to be carefully looked at when considering future improvements to the IPCC process.

And let’s see whether we learn another lesson here, this time about society and the media. Will this evidence for an underestimation of the climate problem by IPCC, presented by an IPCC lead author who studies sea level, be just as widely reported and discussed as, say, faulty claims by a blogger about “Amazongate”?

p.s. Recent sea level results. A number of broadly based assessments have appeared since the last IPCC report, which all conclude that global sea level rise by the year 2100 could exceed one meter: The assessment of the Dutch Delta Commission, the Synthesis Report of the Copenhagen Climate Congress, the Copenhagen Diagnosis report as well as the SCAR report on Antarctic Climate Change. This is also the conclusion of a number of recent peer-reviewed papers: Rahmstorf 2007, Horton et al. 2008, Pfeffer et al. 2008, Grinsted et al. 2009, Vermeer and Rahmstorf 2009, Jevrejeva et al. 2010 (in press with GRL). The notable exception – Siddall et al. 2009 – was withdrawn by its authors after we revealed numerical errors on Realclimate. This is a good example of self-correction in science (in stark contrast with the climate sceptics’ practice of endlessly perpetuating false information). Rather bizarrely, Fox News managed to turn this into the headline “More Questions About Validity of Global Warming Theory“.

** About the numbers stated above. Regarding the actual IPCC AR4 numbers, adjust the IPCC upper estimate of 59 cm by adding 15 cm to make it apply to 6.4 ºC warming (not just 5.2 ºC) and 5 cm to make it go up to 2100 (not just 2095). That gives you 79 cm. Add 50% to adjust for the underestimation of past sea level rise and you get 119 cm.
For the hypothetical case at the start of this post, just introduce similar errors in the other direction. Let’s add 31 cm by going up to 7.6 ºC and the year 2105 (in fact that is “conservative” but it gives a nice round number, 150 cm). Now assume you have a model compared to which actual sea level is rising 50% slower (rather 50% faster): now you’re at the 3 meters mentioned above. For details, see The IPCC sea level numbers.


305 Responses to “Sealevelgate”

  1. 151
    Ray Ladbury says:

    GlenFergus,
    There is a “right way” to err on the side of caution (or “bound”) and estimate–and that is to specify a confidence interval. Most engineers do not do this. The bad ones take their estimates as gospel and the good ones add a fudge factor based on years of experience.

    Bounding is crucial to risk management in part because it allows risk avoidance. However, because mitigation is costly, bounding allows us to ensure that the cost of mitigation does not exceed the risk posed by the threat and to balance risk and mitigation between competing threats.

  2. 152
    Jean B says:

    @144
    “. Yet, US oil production is projected to INCREASE by 25% by 2027 and continue at a rate 20% higher than current production. ”
    Assuming this goes as predicted (which is very unlikely, the data already being vastly revised to lower values every year, as you can see from AEO09 to AEO10), going from 5 to 6 million barrels (i.e +1 million barrel) over 20years is PEANUTS ! It’s decreased 4 million barrels/day over the past 40years !
    How is demand going to increase ?
    Why has Saudi Arabia & Iran production DECREASED over 2005-2008 while price was going UP ?

    Unconventional resources are taken into account in IFP documents.

  3. 153
    Ray Ladbury says:

    GlenFergus,
    There is a right way to “err on the side of caution” (or “bound”) an estimate, and that is to specify a confidence interval. In my experience, most engineers don’t do this. The bad ones take their estimates as “gospel,” and the good ones add a fudge factor based on long experience (that often began with taking their estimates as gospel). The problem with this approach is that the fudge factor is subjective–depending on the tolerance of risk for the individual engineer–and we have no way of estimating how conservative it is.

    A confidence interval–even if it is Bayesian–at least gives some estimate of conservatism, especially if it is clear how it was determined. It also allows mitigation resources to be balanced among different risks in a way that minimizes overall risk.

  4. 154
    Andrew Hobbs says:

    #145 Dave Burton.

    Your analysis of sea level rises is full of holes. In your analysis you highlight Vaasa and Galveston. A quick check of just these two stations show that the whole area around Vaasa is rapidly uplifting at the rate of about 8 mm per year (Due to the loss of the ice sheet from the last ice age) and Galveston was sinking rapidly due in part to ground water extraction. I am sure there must be many other stations with problems. Yet clearly you have not adjusted any of the station data to take such effects into account. So all your conclusions are nonsense and bear little relation to reality.

    Didn’t it occur to you that there might have been a bit of a problem with the raw data when you had sea level decreasing by 8 mm per year in one area and increasing by similar amounts in another area, over a period of a century or so?

  5. 155
    wilt says:

    Stefan commented on only one of the two remarks I made in a previous post on sea level rise (# 113).

    In the other remark that remained unanswered, I wrote that we apparently agreed that the rate of sea level rise since 1880 does indeed fluctuate wildly up and down, and that I therefore found it strange that he did not consider the mean yearly (or decadal) sea level rise over the period since 1880, but just took two values (from around 1900 and around 2000) to claim that since those values happened to be 1 and 3 mm/ year respectively, the rate would have ‘roughly tripled’ during the century whereas this clearly is not the case when you look at the whole set of data (http://www.climatedata.info/Impacts/Impacts/sealevels.html)

    Now, I dislike the use of words like cherry picking. Shall we call it ‘selective citation’?

    [Response: I think I made it clear already that one needs to look at longer time scales, not those short-term fluctuations. I was referring to the fact that in the early part of the record - say, 1870-1920 - sea level was rising on average at about 1 mm/year, while in the latter part of the record - say the past 20 years - it's been rising at over 3 mm/year. Before you accuse scientists of 'selective citation', why don't you just look at the scientific papers they actually wrote? The long-term changes in the rate of sea level rise are the very basis of Rahmstorf (2007) and Vermeer and Rahmstorf (2009) and are pictured there, and they have nothing to do with picking particular points in time. They are based on the entire record. Note, by the way, that the Church and White (2006) paper, where the sea level record was originally published, is titled: "A 20th century acceleration in global sea-level rise". -stefan]

  6. 156
    Hunt Janin says:

    I’m new to this game and may be doing this wrong but I’m writing an introductory survey (for a U.S. publisher) on sea level rise and would very much value any comments on the adverse consequences of a sea level rise of 2 m by 2100. Please reply to me directly, if convenient.

    Thanks.

    Hunt Janin (huntjanin – at – aol.com)

  7. 157
    Dave Burton says:

    Mr. Hobbs,

    Obviously you did you even bother to read it. I did not “highlight” Vaasa and Galveston, other than by pointing out that they are the GLOSS-LTT tide gauges with the lowest and highest MSL trend, respectively. I am obviously aware of the fact that local factors such as crustal rebound and local subsidence due to groundwater pumping are predominate in both cases. In fact, if you’d bothered to read any further you’d have read the following:

    “…much (probably at least half) of the MSL trend at most sites is due to local conditions, rather than the global MSL trend.”
    It is right here:
    http://www.burtonsys.com/climategate/global_msl_trend_analysis.html#insight2

    A simple average of the GLOSS-LTT tide stations Local Mean Sea Level trends yields an average annual MSL Trend of 0.6 mm/year. Weighting the stations by length of operation yields 0.5 mm/year. The median LMSL trend is 1.1 mm/year.

    A more sophisticated distance-weighted average, in which stations are weighted according to their proximity other stations (i.e., weighted less if they are near other stations, to prevent distortion of the global average due to disparate weighting the impact of local conditions) also results in a global average MSL trend of 1.1 mm/year.

    If varying numbers of “outliers” (like Vaasa and Houston) are discarded, the resulting averages still never exceed about 1.2 mm/year (see the “example6″ script). Likewise, if the parameters used for distance-weighted averaging are adjusted over a wide range, the resulting averages still never exceed about 1.2 mm/year. There is no way of torturing the data into supporting a global average MSL trend of more than about +1.2 mm/year.

    What’s more, if you look at the MSL graph for the longest and most reliable tide gauge records, you cannot fail to notice that, even as CO2 levels have taken off, there has been no corresponding acceleration in MSL trend since the late 19th century — in direct contradiction of AR4′s false claim that “coastal tide gauge measurements confirm” an accelerating rate MSL rise.

    All the code and data is available for download, along with simple instructions to make it easy for you to duplicate and verify the results:
    http://www.burtonsys.com/climate/whatif.html
    Your criticism is most welcome, Mr. Hobbs, but please do me the courtesy of READING it first:
    http://www.burtonsys.com/global_msl_trend_analysis.html

    Dave Burton

  8. 158
    John E. Pearson says:

    136 Gilles wrote: “That’s a very general statement : if the reaction timescale is much larger than a century , then we can’t do much to avoid it before 2100 since it has already started and will last for a long time, and if not, then the sea level will saturate at rather modest values. Choose your preferred scenario.”

    I don’t buy this. I know that people routinely discuss inertia with regard to climate but there isn’t actual physical inertia. You are arguing as if there is.
    It takes a long time for the oceans to absorb the heat due to a change in forcing because the changes in forcing are small and the oceans are big. If the forcing increases for a while and then drops back to its initial value all in less than an equilibration time the oceans simply won’t equilibrate to the maximal forcing. If the forcing goes up and stays up for millennia then the oceans will equilibrate. What we do matters.

  9. 159
    Hank Roberts says:

    > he’s always wrong…. Because … he’s an engineer. (Flood warnings)

    Sullenberger, who landed that plane safely in the Hudson, was interviewed on NPR a month or two ago. I recall he said much the same thing about the airlines — that they used to be owned and managed by professionals who did their very best on everything, going far beyond the minimum.

    He said now, airlines are managed by beancounters who hire the cheapest maintenance people in the world, and direct them to do the work legally required but take no extra effort or expense whatsoever. And that quality control is one of those excess costs the beancounters have eliminated.

    He said where under the old procedure a pilot in an emergency might have had a 2x or 3x margin of safety doing something beyond the design spec, presently a pilot would be lucky taking the aircraft to the design spec limit.

    He’s retired now.

  10. 160
    Hank Roberts says:

    > the best and longest coastal tide gauge records
    > Dave Burton.

    Opining that one (tide gauge) data set is “the best and longest” isn’t convincing, without reasons, when it’s so easy to look up sources. The uplift and subsidence information is, as Andrew Hobbs points out, used in doing this kind of analysis — except by you. Why?

  11. 161
    Gilles says:

    John :I don’t buy this. I know that people routinely discuss inertia with regard to climate but there isn’t actual physical inertia. You are arguing as if there is.
    It takes a long time for the oceans to absorb the heat due to a change in forcing because the changes in forcing are small and the oceans are big. If the forcing increases for a while and then drops back to its initial value all in less than an equilibration time the oceans simply won’t equilibrate to the maximal forcing. If the forcing goes up and stays up for millennia then the oceans will equilibrate. What we do matters.”

    But the forcing can NOT drop, since even if we stopped just now any emission of fossils fuels, the temperature would remain constant, and it IS the forcing for sea level. According to Stefan, the 0.3 current rise would only be a small part of the asymptotic level which would be only reached in 1000 years, giving 3 meters. That’s the absolute minimum. But it is very unlikely that we could avoid + 2°C, so we’re heading to a + 10 meters rise whatever the reasonable efforts we could do. The difference between being very active just now to limit the amount of fossil fuels, and burning two or 3 times this quantity ; would result in an asymptotic value from 10 to 20 or 30 meters – the coast lines are doomed anyway (reached only after one millenium of course). So I wonder if it is not better to keep fossil fuels to rebuild the countries at higher altitudes than to give them up and fight a 10 meter rise with our hands. That’s an interesting debate – if Stefan is right of course.

    [Response: What is your argument: that 10 meter rise is not worse than 3 meter rise, because in either case we are "doomed"? That may be true if you live on the Maldives, but not in most other parts of the world. It would seem a rather far-fetched justification for a do-nothing attitude. -stefan]

  12. 162

    #155 wilt

    Try relevant citation.


    The Climate Lobby
    Understand the Issue
    http://www.climatelobby.com/fee-and-dividend/
    Sign the Petition!
    http://www.climatelobby.com

  13. 163
    Hank Roberts says:

    For Dave Burton, just an example of how uplift and subsidence are discussed, here is a rather good recent geology blogger’s post on recent science:

    http://dynamic-earth.blogspot.com/2009/11/cyclic-subsidence-and-uplift-in.html

    — excerpt follows —-

    … Interpreting how these forcers interacted with the Mississippi delta system makes up a fair component of the literature, and has provided some interesting insights and entertaining arguments for many years. A recent paper by Blum et al (2008) has revealed a previously unknown driver of change within the deltaic system: cyclic uplift and subsidence driven by changing sediment volumes in the lower Mississippi valley.

    Blum et al (2008) point out that the subsidence recorded along the Gulf Coast is different, depending on where you measure it. The figure below is from Blum et al (20088, their Figure 1 on p. 676). Notice how the Alabama and Texas coasts are pretty different from the Valley edge subsidence patterns. Of course, this has been recognized before. Tornqvist et al (2004) interpreted this signal as a result of ongoing glacio-isostaic adjustments. Using marshland peats as baselines, and correcting for the subsidence pattern, Tornqvist et al (2004) reconstructed a sea-level curve for the Mississippi delta.

    However, an unexpected result of the Tornqvist model was a phase of “unacceptably high” rate of uplift in the peat benchmarks during the mid-holocene, corresponding to a mid-Holocene sea-level high. Tornqvist et al (2004) did not think that a phase of such large-scale uplift was very realistic, and discounted it.

    However, Blum et al (2008) may have identified a viable mechanism for rapid uplift and subsequent subsidence in the Mississippi Delta. Using the same data points and subsidence curves as Tornqvist et al (2004), Blum et al (2008) preformed a series of 1-D and 3-D isostatic modelling exercises that explain the observed uplift pattern (shown below is their Figure 3, on p. 677)….”

  14. 164
    wilt says:

    Hunt Janin (#156), you wrote that you would very much value any comments on the adverse consequences of a sea level rise of 2 m by 2100, because of an introductory survey you want to write. Now anyone is free to write whatever he or she wants, but before you start shouldn’t you put things in perspective? The IPCC report (2007) has several scenarios. B1 based on 1.8 degree Celsius increase yields a projection of 18-38 cm sea level rise for the 21st century, A1F1 (based on 4 degrees) gives 26-59 cm. Many if not most people, even when they believe in AGW, think that 4 degrees temperature increase in 2100 is very unlikely. Very few experts (Rahmsdorf being one of them) predict a sea level rise above 1 m. So a story about 2 m sea level rise by 2100 may sound very scary, but its credibility is so low that few people would even start reading it, and my humble advice would be to think again. If you are really dedicated to the cause of informing the public about AGW and climate change, then more exaggerations are really not helpful.

  15. 165
    Hank Roberts says:

    Speaking of ‘wrong … because he’s an engineer’ and margins of safety, I just happened on this, found at a wonderful blog by a meteorologist:
    http://www.flame.org/~cdoswell/ServiceAss/Challenger&Feynman.pdf

    No, that’s not about the “safety margins” on the O-rings. It’s another problem discovered later, _also_ “managed” by relaxing the safety margin.
    Gad.

  16. 166
    Brian Dodge says:

    “But this should be true for any cause of variation of the forcing, including the Milankovitch cycles, so the main amplifier should be the water vapor, and not the CO2 which is only a (almost passive) tracker when it’s not the primary cause of change?” Comment by Gilles — 13 March 2010 @ 2:46 AM

    No, because water vapor doesn’t work as a linear feedback over ice age cycles because of the energy balance of phase change. More energy going into wet ice melts the ice faster, but the temperature and water vapor stay the same. Much of the additional water vapor that goes into the atmosphere as the SST rises gets quickly sucked out as precipitation; the precipitation falling on ice sheets acts as a rapid sink for atmospheric water vapor. This results in a non-linear global average water vapor gamma, whose value is proportional to the percentage of permanent ice coverage. If the gamma for water vapor were high enough to kick start the end of an ice age with Milankovic forcing, when the ice coverage is largest, then the response to currently observed forcings (Pinatubo, solar cycles) would have to be larger. I expect that the transition of the Arctic Ocean from perennial to annually ice covered will increase the water vapor feedback – we’ve already lost 4 million km^2 of perennial ice covered water vapor sink. Some of the water vapor that used to be deposited on the ice cover as precipitation or direct condensation at temperatures of zero Celsius or lower are now transporting latent heat to the Greenland Ice Sheet, contributing to its rising mass loss and sea level rise. (Ta-da! Brought the discussion back on topic &;;>)

  17. 167
    Mark A. York says:

    This is a nice presentation I went to at JPL last fall. The sea level session is by Lee Fu.

    Present day sea level rise = 1/3 thermal expansion +
    1/3 melting of mountain glaciers +
    1/3 melting of ice on Greenland and Antarctica

    Recent rates of sea level rise are 10 times larger than historic rates. 3.2 mm per year.

    http://climate.nasa.gov/files/Fu_Oct24_09.ppt

    http://climate.nasa.gov/ClimateSymposium/

  18. 168
    CM says:

    Gilles, #161: “even if we stopped just now any emission of fossils fuels, the temperature would remain constant”

    Apparently not. Remember?
    http://www.realclimate.org/index.php/archives/2010/03/climate-change-commitments/

  19. 169
    Septic Matthew says:

    165, Hank Roberts

    What in your opinion is the best reference for sea level change, complete with data, graphs and code?

  20. 170
    Gerry Quinn says:

    Re #119. Stefan claims that the work of Church and White, and Jerevana, show acceleration of sea level rise during the past century. Quite simply, they don’t.

    [Response: Hmmm. The Church and White (2006) paper is titled: "A 20th century acceleration in global sea-level rise". If you think that paper does not show an acceleration, why don't you submit a comment to the peer-reviewed literature? -stefan]

    Jerejeva is essentially about paleo-temperatures, and is complex to understand and seems relatively irrelevant anyway.

    Church and White take data from the last 140 years, and fit various curves to it. But the raw data used by both Church and White, and Jerejeva, and shown in graphs on both, is derived from tide-gauge measurements. So is the Wikipedia graph (this comes from the work of Douglas, which I’m sure Stefan will be familiar with), simply does not show the claimed acceleration over this period.

    From the graphs in all three sources, it is quite obvious that the actual measured sea level rise has been approximately linear for the last century. Prior to 1910 or thereabouts, sea level appears to have been rising more slowly (though on the other hand the tide gauge measurements before that period are less plentiful and soon peter out).

    In short, forget the projections and equations, and look at the data! No significant acceleration over the past century. The apparent acceleration took place a century ago, and since then sea level rise has been approximately constant.

  21. 171
    Hank Roberts says:

    > Gerry Quinn
    > … but the raw data … derived from tide gauge measurements … does not

    Have you met Dave? This has already been discussed once in recent days here.

  22. 172
    Didactylos says:

    Gerry Quinn:

    You are seriously reaching, given that the title of Church and White is “A 20th century acceleration in global sea-level rise”.

    So, if you are contending that you know enough about this subject to be able to challenge these results – where is your own paper on the subject?

    I think you are confusing the term “acceleration” with the idea of “perfectly quadratic”. Obviously we don’t expect a perfect fit from noisy data like this – but the acceleration is undeniable. Look at the residuals! In your denial, you even have to make a little exception “prior to 1910 or thereabouts, sea level appears to have been rising more slowly” in order to pretend that the acceleration isn’t there. Clue: you can’t delete the acceleration then claim it isn’t there.

    Your argument boils down to “it looks linear, except where it isn’t”.

    If you want to challenge the statistics, then you will have to provide a statistical argument, instead of handwaving and appealing to eyeballing graphs.

    Your post is particularly disingenuous given that Church and White directly address the change in rate around 1930:

    Another approach, given the clear change of slope at 1930, is to do linear regressions on the two halves (1870–1935 and 1936–2001) of the record. The slopes are 0.71 ± 0.40 and 1.84 ± 0.19 mm/yr respectively, implying an acceleration of 0.017 ± 0.007 mm/yr/yr (95%).

    They have you coming and going.

  23. 173
    Mark Bahner says:

    “A number of broadly based assessments have appeared since the last IPCC report, which all conclude that global sea level rise by the year 2100 could exceed one meter:”

    Obviously, global sea level rise by the year 2100 “could” exceed one meter. What was the most probable sea level rise in each of the assessments?

  24. 174
    GlenFergus says:

    #140 : On floods, uncertainty, and the engineering response

    “…should be a transparent and previously agreed procedure.”

    Of course Stefan. It’ll all be there in the manual, fully argued and justified. We’re not talking some cavalier or arbitrary fudge. And that “most useful answer” obviously depends on the sophistication of the target audience. (I guess you’d want to know what his best estimate was, and what his error distribution is in that basin, and how he got to that.)

    The AGW discussion desperately needs to move beyond mere understanding and on to more of what to do about it. Science does the understanding; engineering is about doing – efficiently (time and money) and with justifiable confidence (manage the risks, allow a margin). There’s a huge peer reviewed literature on that second bit, little of which seems to be ref’d in AR4 (WG2 bugger all, WG3 some).

    [Response: I completely agree. Risk assessment and risk management are the key words for dealing with climate change, and there is a lot of experience on those topics in other fields like engineering. Now that a review of the approach and procedures of IPCC has been announced, I'd argue that this should be one of the key issues: the IPCC needs to provide a proper risk assessment, based on those established procedures adopted in other areas of public risk. -stefan]

    I don’t know what I’m suggesting, but it’s sure not to keep underestimating impacts because some d’head denier might complain.

  25. 175
    Andrew Hobbs says:

    #157 Dave Burton

    I have reread all the pages you indicate and your current conclusions are still unsupportable.

    I only looked at Vaasa and Galveston because you yourself named them in your analysis. I didn’t looked at any others though I suspect many of the stations would need adjusting. As you said most stations are likely to be affected by local conditions. Yet you still go ahead and use the basic data without corrections.

    It is not sufficient to simply cull stations on the basis of sea level rise you don’t like. You should not just cull the outliers, or even cull all the negative values. In fact it is not appropriate to cull stations in any way, on the basis of values of sea level rise alone. The only acceptable process is to go through each and every station and find out using knowledge and data independent of the sea level data, whether there are any anomolies associated with that station. Glacial Isostatic Adjustment would be the major effect causing uplifting, but there could also be sinking (eg for Galveston) or even whether tidal stations have been moved etc. You then need to apply those corrections to the data.

    Once you have done that, collated the information and its sources, then perhaps you might have a decent basis for an analysis. If your results are still different from the published values then one can start looking at the reasons. It doesn’t mean that you would be correct or incorrect, but it would provide a reasonable basis for comparison and making some decisions about who is correct, and why.

    As for your other conclusions

    Your conclusion #2 “Because of the large variation in rate of sea level change between different seaside locations, changes in the global average rate of sea level increase have much less effect on seaside communities than one might guess.”

    (Not technically correct since the values are tidal gauge readings rather than actual changes in sea levels – which in this context does make a difference)

    This conclusion may be currently correct but it has little to do with global changes in sea level, but rather in many cases, the local effects that were mentioned. However such local effects could well be swamped by global sea level rise in the future.

    Your conclusion #3 “If the global MSL trend had actually accelerated by about +1.3 mm/year since 1993, as the IPCC claims, that fact would be apparent at these tide stations, as a doubling or tripling of the measured rate of MSL rise. But there is no evidence of any such acceleration.”

    All you did was to look at a few of the records; no analysis in any way. Your eyeball just says it doesn’t look like it has increased. Since you haven’t used good data anyway, and with no analysis, such a conclusion is nonsense.

    For those that want a pointer to the results of a reasonable analysis of sea level data try


    Church, J. A., and N. J. White (2006), A 20th century acceleration in
    global sea-level rise”, Geophys. Res. Lett., 33, L01602, doi:10.1029/2005GL024826.

  26. 176
    Edward Greisch says:

    121 Hank Roberts: Don’t believe me. It isn’t my thesis. Just read:
    “Six Degrees” by Mark Lynas
    “Under a Green Sky” by Peter D. Ward
    “The Long Summer” by Brian Fagan
    “Collapse” by Jared Diamond.
    “Climate Code Red” by David Spratt and Philip Sutton
    “The Vanishing Face of Gaia” by James Lovelock

    http://www.sciam.com/article.cfm?articleID=00037A5D-A938-150E-A93883414B7F0000&sc=I100322

    http://www.geosociety.org/meetings/2003/prPennStateKump.htm
    http://www.astrobio.net is a NASA web zine. See:

    http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=672

    http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1535

    http://www.astrobio.net/news/article2509.html

    http://astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2429&mode=thread&order=0&thold=0

    Yes, I know that there are people who will just give up and die. There is no way to get them to do anything else.

    But MOST PEOPLE AND MOST GOVERNMENTS ARE MOTIVATED BY FEAR AND LITTLE ELSE.

    IF we take strong action immediately, WE CAN AVOID THE BAD CONSEQUENCES! If you continue to tell them that GW is nothing to be afraid of, they will do nothing.

    FEAR MOTIVATES GOVERNMENTS. Why else would our defense budget be 1/2 TRILLION dollars/year? Our government should fear GW at least as much, and in dollars. If it did, GW would soon be over.

    I am NOT a doomsayer. I am an advocate of strong GW legislation. The stronger the better. The sooner the better. RC should do likewise.

  27. 177
    Hank Roberts says:

    > Mark Bahner
    http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/428.htm — and look at various answers for specific assumptions and scenarios. There’s no simple answer.

    Edward, your thesis isn’t RC’s thesis.
    Drill down past the news article or press release, find the actual science paper, read it, and quote from the actual science. Provide a cite and link.

    Same advice for anyone making claims about what science says.

  28. 178
    Septic Matthew says:

    175, Andrew Hobbs.

    I have selected the following from the Church and White article that you linked:

    [11] If this acceleration was maintained through the 21st
    century, sea level in 2100 would be 310 ± 30 mm higher
    than in 1990, overlapping with the central range of projections
    in the Intergovernmental Panel on Climate Change
    Third Assessment Report (IPCC TAR) [Church et al.,
    2001]. For 1910 to 1990, the acceleration in ocean thermal
    expansion (only) in these climate models range from 0.005 ±
    0.003 mm yr2 to 0.014 ± 0.004 mm yr2 (Table 11.2 of the
    IPCC TAR), consistent with the present estimates of
    0.013 mm yr2 and 0.017 mm yr2 for the 132 year period
    and the 0.008 mm yr2 for the 20th century.
    [12] Between 1930 and 1960, GMSL rises faster than the
    quadratic curve at a rate of about 2.5 mm yr1 (Figure 2c),
    following (with about a 20 year lag) the 1910 to 1940
    period of more rapid global temperature rise [Folland et al.,
    2001]. Variability in GMSL trends prior to 1930 are not
    significant. After 1960, there are minima in the rates of rise
    in the 1960s and 1980s, each followed by more rapid rates
    of rise (peaking at over 3 mm yr1), consistent with Holgate
    and Woodworth [2004].

    Are these considered to be reliable results by most supporters of AGW? They posit that fluctuations in sea level rate of increase are concordant with earlier changes in temperature (seeming to imply a belief that temperature has not changed at a constant rate); have there been follow-on analyses of this via vector autoregressive or other multivariate time series methods?

  29. 179
    Mark A. York says:

    RE: 178 The Le Fu JPL sea level presentation cites this paper for the graphic. You would have to look at the slide to see it though.

  30. 180
    Andrew Hobbs says:

    #178 Septic Matthew

    I pointed out the paper as an example of the type of data corrections and analysis that has been used. ie a simple averaging of raw culled station data as used by Dave Burton is not appropriate.

    As for their actual results, they are out of date now, with rather larger values calculated from more recent data, including satellite data. In addition, the predictions from this study are purely extrapolation of historical values. They obviously cannot take into account any ‘sudden’ qualitative changes such as ice sheet collapse and increased glacier movement which seems to have become a feature over the last few years. For the latter reason many researchers now appear to consider a rather greater rate of sea level rise more likely.

  31. 181
    Mark Bahner says:

    Hank Roberts(177) “http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/428.htm — and look at various answers for specific assumptions and scenarios. There’s no simple answer.”

    The source you reference (the TAR) contains no “most likely” estimate for sea level rise in the 21st century. It’s also obviously not something published after AR4.

  32. 182
    Hank Roberts says:

    You asked for all of them. The first is on paper; the second and third are in the link I gave. As I said, there’s no single simple answer; there are various scenarios, ‘what if’ situations, not predictions. You mistake — oh, you’re that Bahner. You know all this.

    Sorry I took the bait.

  33. 183
    Edward Greisch says:

    177 Hank Roberts: “find the actual science paper, read it, and quote from the actual science. Provide a cite and link.”:
    I have done that as much as I can. I do not have access to most of those papers. They are in journals that cost $ way too much/year each. I am a federal retiree, not a professor at a major university. No, I can’t just drive 50 miles, then walk a few blocks, then spend all day in the library. I can’t walk that far, among other things. I do what I can at the library that is accessible to me.

    Since you are so young and well endowed, why don’t you do it for me?

    Notice that I am not complaining about the journals not being free on line. They are not free on line, so don’t complain that I am not reading them. The local public library is free, and the book authors have summarized the journals for me.

  34. 184
    Hank Roberts says:

    The bait being that Mark Bahner knows there’s no single “most likely” estimate in the material so far; they’re consistently discussing probabilities in ranges higher than came out of the assessment in the fourth IPCC publication.

    E.g. for California — various scenarios from more recent assessments:

    “Over the past several decades, sea level measured at tide gages along the California coast has risen at a rate of about 17–20 centimeters (cm) per century, a rate that is nearly the same as that from global sea level rise estimates (Church and White 2006). A paper authored by Rahmstorf (2007) demonstrated that over the last century observed global sea level rise can be linked to global mean surface air temperature. This provides a methodology to estimate global sea level using the surface air temperature projected by the global climate model simulations, and it leads to larger rates of sea level rise than those produced by other recent estimates (Cayan et al. 2008). The present estimates include those of Rahmstorf’s method, assuming that sea level rise along the Southern California coast will be the same as the global estimates. Also, the projections here include a second set of estimates that are a modification of Rahmstorf’s method that attempts to account for the global growth of dams and reservoirs, which have artificially changed surface runoff into the oceans (Chao et al. 2008), in addition to the effects of climate change. Using the global surface air temperature from the GCMs included in this assessment, the resulting estimates in Figures 17 and 18 indicate that potential sea level rise over the next century will increase over its historical rate by a considerable amount. Each model has a different rendition of global surface air temperature within the historical period within its “20C3M” historical simulation,1 so that simulated historical sea levels vary between models. But in the experiments run here, the sea level estimates were adjusted so that for year 2000 their value was constrained to the same, zero value—this allows for comparison across the simulations of the amount of projected sea level rise over the twenty-first century. By 2050, sea level rise, relative to the 2000 level, ranges from 30 cm to 45 cm. As sea level rises, there will be an increased rate of extreme high sea level events (Figure 19 and Table 7), which occur during high tides, often when accompanied by winter storms and sometimes exacerbated by El Niño occurrences (Cayan et al. 2008c). Importantly, as decades proceed, these simulations also contain an increasing tendency for heightened sea level events to persist for more hours, which would seem to imply a greater threat of coastal erosion and other damage. Virtually all of the increase in frequency and magnitude of sea level exceedances can be ascribed to the underlying secular increase in mean sea level….”
    http://water.usgs.gov/nrp/proj.bib/Publications/2009/cayan_tyree_etal_2009.pdf
    CLIMATE CHANGE SCENARIOS AND SEA LEVEL RISE ESTIMATES FOR THE CALIFORNIA 2009 CLIMATE CHANGE SCENARIOS ASSESSMENT, section 8, at p.30

  35. 185

    An interesting article which very clearly illustrates how the conclusions depend on your prejudices. Again, I am baffled that no one else seems to see the obvious.

    What you are saying is that current models of sea level change which, when applied to the last 40 years, a period for which we have good climate data, predict a sea level rise which is only 2/3 of the one that actually happened. Correct?

    OK, we have a model and we have data. Fine! The model underestimates the change in the measured variable by 50%. We can then draw the following conclusions:

    1) The model gets the right sign of the effect.
    2) The model gets the incorrect result

    When we have a model that fails to reproduce the observed results but doesn’t give a crazy result we can choose between two conclusions:

    a) Either the model is seriously wrong (which it could be even if it got the right result)

    or

    b) The model is reasonable but some other extra effect(s) is at play which is not accounted for in the model

    Depending on the exact details on the model we can choose to try to “correct” it to make it account for the observed values. This kind of “fine tuning” may sometimes be useful in an engineering context but is shunned in all real science. What you do is simply throw away important scientific information – the discrepancy between the model and the data clearly shows that you have missed some understanding of the physics. If you “correct” that without understanding what you are doing the model will essentially loose all of its predictable power except perhaps in the very nearest future.

    If current models of sea level rise are 50% percent wrong in the estimate of the current sea level change we thus have an unknown factor, certainly not necessarily linear, which is important. If this unknown factor reverses (which it of course may well do – remember it is unknown – it could well be e.g. cyclic) and the rest of the model is right the resulting sea level rise in the next 100 years will probably only be about half of what is predicted or about 30 cm. Given the large uncertainties in the forecasted temperatures [which, apart from physics, also depend on politics – the “scenarios”] for the future I would say that it is safe to say the current sea level models aren’t really useful to predict anything reliable in a 100 years perspective.

    Finally, it might be interesting to discuss the size and relevance of these values. Living in a country (Sweden) where post-glacial rebound makes the sea level fall at up to 1 m per century (and has done so for many centuries) it is quite safe to conclude that sea level changes of this order and probably much larger, isn’t much of problem. We live in a dynamic world where change is the most important factor. The idea of a static world is simply a flawed model.

  36. 186
    Dave Burton says:

    Hank Roberts wrote:
    > Opining that one (tide gauge) data set is “the best and longest” isn’t convincing, without reasons, when it’s so easy to look up sources.

    They are the GLOSS-LTT stations. Google it:
    http://www.google.com/search?q=“GLOSS-LTT”
    The first link result should convince you.

    Hank continued:
    > The uplift and subsidence information is, as Andrew Hobbs points out, used in doing this kind of analysis — except by you. Why?

    Not just “except by me.” E.g., Nakiboglu and Lambeck (1991) used a spatial decomposition approach.

    The problem to be solved is separating the global average isostatic MSL trend from local effects. If we actually had trustworthy uplift and subsidence measurements, we could just add the uplift or subtract the subsidence. But we don’t. What we have is not actual measured data for uplift and subsidence. Rather, it is the result of computer modeling of very poorly understood systems.

    You’ve heard “garbage in, garbage out?” Well, adding garbage to data is like adding root beer to lemon-lime soda. What you get is garbage, not data. Like root beer, garbage has the dominant flavor.

    Fully 2/3 of the GLOSS-LTT tide gauges have recorded local MSL trends of less than the Church/IPCC claimed 1.8 mm/year, most of them MUCH less than that. That should make it obvious that there is something wrong with their method.

    Rather than adding untrustworthy model-based “corrections” (garbage) to actual measured data, it is much better to work with the real, measured data we have, and eliminate the local effects from the global averages by weighting the tide stations according to whether or not they are close enough to other tide stations to be affected by the same local factors.

    We have good tide gauge data going back to the 1800s, some of it from tide stations which are not significantly affected by crustal rebound (the main factor which the models attempt to account for). If you want real, trustworthy answers, you should use real, trustworthy data.

    Mark A. York wrote:
    > This is a nice presentation I went to at JPL last fall. The sea level session is by Lee Fu.
    > …Recent rates of sea level rise are 10 times larger than historic rates. 3.2 mm per year.
    > http://climate.nasa.gov/files/Fu_Oct24_09.ppt
    > http://climate.nasa.gov/ClimateSymposium/

    Thanks for the links, Mark, but fooey on Mr. Fu.

    On the basis of “23 Annual Tide Gauge Records” (which ones are unspecified) he claims that the rate of sea level rise increased around approximately 1910 (or 1925, depending on which of his graphs you look at) to 2.0 mm/year, a rate which his first tide gauge line shows holding steady through the end of the 20th century, but the second one purports to show increasing to 3.2 mm/year around 1985.

    He’s completely wrong.

    Worse, much of his error is INTENTIONAL.

    Take a look at his 2nd graph, labeled “Church and White, 2006″ (open the powerpoint and hit PgDn 11 times). That’s the graph which shows rates of 0.8 mm/yr to 1925, then 2.0 mm/yr to 1985, then 3.2 mm/yr to 2000. Do you see the chicanery? HE RESET THE STARTING POINTS DOWNWARD for the trend lines! For both the 2.0mm/yr and 3.2 mm/yr line segments, he intentionally skewed the slopes higher by starting with a negative noise spike, and for the 3.2 mm/yr segment he also ended it on a positive noise spike (and had to stop the segment prematurely to find the highest one)!

    That is obvious, shameless, intentional biasing of the results. Is it any wonder that Hansen/NASA are in such ill repute?

    In the second place, why do you suppose that Fu/NASA chose to look at just 23 tide gauges? There are 159 in the GLOSS-LTT set, chosen specifically for monitoring long term sea level trends, because of the quality of their records and their good geographical distribution. 70% of them have recorded local MSL trends of less than Fu’s claimed 2.0 mm/yr. 44 of the 159 GLOSS-LTT tide stations have tide records dating from the 1800s, though two ceased operation in the 1930s, leaving 42. 36 of the 42 (86%) show MSL trends of less than 2.0 mm/yr.

    In the third place, look at Fu’s first tide gauge graph, labeled “Historic Sea Level Rise / 120 years” (open the powerpoint & press PgDn 6 times). It shows NO increase in MSL trend at any time since 1910. But anthropogenic CO2 emissions were a tiny trickle in 1910, compared to today. So where’s the effect on sea level from CO2? The answer, from coastal tide gauge measurements, is THERE IS NONE.

    In the fourth place, if you actually look at the graphed local MSLs for the tide station which have been in operation since the late 1800s, you will not find ANY evidence of an uptick in MSL trend around 1910 or 1925 — nor, for most stations, at any other date. But don’t take my word for it, see for yourself. Go to the spreadsheet:
    http://www.burtonsys.com/climate/MSL_global_trendtable1.html
    and look at the 44 GLOSS-LTT tide stations which have been in operation since the 1800s. Click on the tide station names to view the graph (at noaa.gov) of Local Mean Sea Level at that tide station. There are 44 of them (though two of them ceased operation during the Depression.) I defy you to find even one which shows the 1910 or 1925 uptick that Fu claims.

    For a nice example of a good tide gauge record, take a look at Warnemunde, Germany:
    http://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.shtml?stnid=120-012
    It records a continuous MSL record from 1855 to 2005, with an absolutely flat mean sea level trend of 1.20 millimeters/year for the entire 160 year period. (Some others tide stations show a slight increase somewhere between 1860 and 1880.)

    Or, ironically, consider Copenhagen, Denmark. It records a continuous, straight local MSL trend of 0.49 millimeters/year from 1889 to 2006, with no sustained uptick in rate at any date:
    http://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.shtml?stnid=130-021

    Or consider Sydney, Australia. It records a continuous, straight local MSL trend of 0.59 mm/yr from 1886 to 2003, with no sustained uptick in rate at any date:
    http://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.shtml?stnid=680-140

    The fact is that the best available tide gauge data shows that the global average MSL trend has been steady at less than 1.2 mm/year for at least 120 years, with no sign of acceleration in 1910 or 1925 (Fu) or 1993 (IPCC) or any other date.

    See: http://www.burtonsys.com/climate/global_msl_trend_analysis.html

  37. 187
    Gilles says:

    “illes, #161: “even if we stopped just now any emission of fossils fuels, the temperature would remain constant”

    Apparently not. Remember?
    http://www.realclimate.org/index.php/archives/2010/03/climate-change-commitments/“”

    the blue curve corresponding to zero emission IS constant ! not with Bern model, but I understand with the model presented here. Now as I said zero emission is anyway unrealistic, and I think 2 degrees are hardly avoidable (and hence a +10 m sea level rise whatever we’ll do – if Stefan is right, of course).

  38. 188
    Didactylos says:

    Septic Matthew:

    Church and White (2006) don’t attempt any attribution of the acceleration they calculate. They do discuss probable causes and reference the appropriate literature.

    I suggest that if you are genuinely interested, you read the papers that are cited as actually addressing attribution for sea level rise.

    You say “seeming to imply a belief that temperature has not changed at a constant rate” – but I am hopeful that you are aware that global temperature has not changed at a constant rate through the period discussed in the paper. If you are unaware of this, then I can direct you to products such as GISTEMP and HADCRUT….. but you can’t possibly be ignorant of this. You are just kicking up dust.

  39. 189
    Didactylos says:

    Dave Burton:

    You complain an awful lot about corrections, but seriously demanding that uncorrected data be used leads to complete nonsense – such as that produced by Beck for CO2.

    You also complain about cherrypicking end-points! Given that the conclusion is not dependant on endpoints, but is merely an illustration of the acceleration, your complaints are completely spurious.

    You complain a lot, but your substance is curiously lacking.

    When it comes to concrete evidence, you suddenly decide to cherry pick yourself – not an endpoint, but singling out individual tide records, in the vain hope that we would forget about the rest. I like to believe that RC readers are not that stupid.

    If your “source” (which seems to be mainly yourself) had any genuine evidence, they would have published it by now, would they not?

    I see you also stoop to that most contemptible trick of graphing fraudsters: expand the Y axis enough, and magically any trend will disappear. “Look! It’s flat!” you cry. Well, of course it is. You scaled the data inappropriately. When you are interested in mm/year, a Y axis scaled in metres is a pretty big clue that you are Doing It Wrong.

  40. 190
    John E. Pearson says:

    Gilles says:
    14 March 2010 at 7:04 AM
    “illes, #161: “even if we stopped just now any emission of fossils fuels, the temperature would remain constant”

    Apparently not. Remember?

    The blue curve wasn’t the only curve. There was another one with a negative slope. Capitalizing a false assertion doesn’t make it correct. There is no physical reason that the excess forcing can’t drop. There is a range of temperatures associated with any scenario. Perhaps the most likely scenario is the one presented in that letter. More likely, further study is required to nail it down.
    WIth your do-nothing approach you advocate pushing the temperatures as high as possible. In fact there is a range of temperatures not “2 degrees” that “you think” but more like “2-4″ degrees. Focusing on the bottom temperature of the range is disingenuous. It is plausible that we can quit coal by mid century and there is no reason at all to not aim for that.

  41. 191
    Mike Donald says:

    Here’s what I think is a useful lecture on sea levels. It’s the third one down in the video gallery.

    Rising Sea Levels Demystified
    Mr John Englander,
    Chief Executive Officer, The International SeaKeepers Society

    http://www.imarest.org/Events.aspx/EventGallery.aspx

    http://www.imarest.org/Events.aspx/IMarESTEvents/StanleyGray/24thMarch2009Completed.aspx

  42. 192
    Hank Roberts says:

    > Edward G
    > why don’t you do it for me

    Google Scholar finds the science papers behind the links you’re posting. You can use that right from your chair.

    I’m as busy and as retired as you are, and without a pension. We all have all the work we can do about these issues, and I’m sincerely trying to be helpful — by urging you to be careful and cite your sources correctly.

    I’m giving you the same advice I give anyone posting claims, whatever their political goals — you can cite them yourself. Don’t stop at the first Scholar link if it gets only the abstract; check the other versions Scholar suggests.

    And recheck what you couldn’t find.
    More papers are becoming available every day at the authors’ websites.

    Interlibrary L o a n is your friend. If you’re unable to go to the library, your library will bring or send material to you. Ask at your local library.

  43. 193
    wilt says:

    Stefan commented on my contribution #155, and clarified his previous comment (#38). He now states that he meant to refer to the 1870-1920 period instead of ‘at the beginning of the 20th century’ which I thought was implying only a single observation point. I therefore withdraw my suggestion of selective citation.
    In the same comment, he points my attention to the Church & White article (GRL 2006). This is remarkable, because Church & White conclude that during the 20th century there was only a very small acceleration of sea level rise (0.013 mm/year per year). If the accelaration remained constant the 1990 to 2100 sea level rise would be between 280 and 340 mm. Here is the complete abstract of their article:
    “Multi-century sea-level records and climate models indicate an acceleration of sea-level rise, but no 20th century acceleration has previously been detected. A reconstruction of global sea level using tide-gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea-level rise but no significant acceleration over this period. Here, we extend the reconstruction of global mean sea level back to 1870 and find a sea-level rise from January 1870 to December 2004 of 195 mm, a 20th century rate of sea-level rise of 1.7 ± 0.3 mm yr−1 and a significant acceleration of sea-level rise of 0.013 ± 0.006 mm yr−2. This acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed. If this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm, consistent with projections in the IPCC TAR.”. Link:
    Church, J. A., and N. J. White (2006), A 20th century acceleration in
    global sea-level rise”, Geophys. Res. Lett., 33, L01602, doi:10.1029/2005GL024826.

    [Response: That you call the acceleration found by Church and White (0.013 mm/year per year) "very small" is your value judgement. It applies to a 130-year period, so it means that in their quadratic fit, the rate of rise in the year 2001 is 1.7 mm/year larger than in 1870 (namely 0.013 * 130).

    In addition, I cannot quite reproduce their result. Letting matlab do a quadratic fit (with function polyfit) on their data gives me an acceleration of 0.016 mm/year per year. The rate of rise in 1870 in this quadratic is 0.8 mm/year, in 2001 it is 2.9 mm/year, with the difference being 2.1 mm/year and not only 1.7 mm/year. (Note that this is a 3.6-fold increase in the rate of sea level rise since 1870.) Be that as it may, if you attribute those additional 2.1 mm/year to 0.8 ºC warming (as is done in the semi-empirical models) you get a "sea level sensitivity" of 2.1/0.8= 2.6 mm/year/degree, a bit less than the 3.4 mm/year/degree which I found in my 2007 paper. The difference is due to the fact that the actual sea level data deviate from a quadratic curve. However, the bottom line is that there is no fundamental disagreement between the acceleration found by fitting a quadratic and that used in the semi-empirical models, although there is some difference in exact numbers.

    Your second point, that future sea level rise would be quite small if the rate of acceleration remained constant, is correct - but in the semi-empirical approach, a constant acceleration rate would imply that in the next 130 years, global temperature will again rise by only 0.8 ºC as it did in the last 130 years. This is well below any realistic temperature scenario. -stefan]

  44. 194
    Hank Roberts says:

    Insist the old data is the most reliable while ignoring new work?

    The old data is known inadequate to show sea level change, according to the references I find.

    Look, I’m just an ordinary reader with a penchant for looking stuff up, but in a few minutes, I find that GLOSS-LTT is old data known lacking and there has been a worldwide effort to improve on it. You can look this up yourself.

    Scholar finds three hits for “GLOSS-LTT” since 1994.
    http://scholar.google.com/scholar?hl=en&q=GLOSS-LTT&as_sdt=2000&as_ylo=1994&as_vis=0

    Look at all three.

    A review of sea-level research from tide gauges during the World Ocean …
    PL Woodworth, C Le Provost, LJ 2002 – books.google.com
    (you can read and search it)
    This mentions what’s lacking in the GLOSS-LTT system — a way to handle uplift and subsidence — and discusses the additions being made to address that lack of information in the old data. References include the Fu (2001) paper mentioned above.

    The Permanent Service for Mean Sea Level: An Update to the 21stCentury
    P. L. Woodworth and R. Player
    Journal of Coastal Research, Vol. 19, No. 2 (Spring, 2003), pp. 287-295
    (first of 9 pages available as a PDF) also mentions
    http://www.jstor.org/stable/4299170

  45. 195
    Mark Bahner says:

    Hank Roberts (182) writes:

    “You asked for all of them. The first is on paper; the second and third are in the link I gave.”

    No, what I asked for were the “most likely” values from the studies Stefan referenced when he wrote, “A number of broadly based assessments have appeared since the last IPCC report, which all conclude that global sea level rise by the year 2100 could exceed one meter:…”

    You linked to the THIRD assessment report, which can not possibly be relevant to the studies Stefan was referring to, which occurred after the FOURTH assessment report.

    Why not save us all a lot of trouble, and let Stefan answer the question (since he’s the one who made the orginal statement)?

  46. 196
    Mark A. York says:

    RE: Le Fu “He’s completely wrong.”

    No he isn’t. This is how much sea level rise has increased. Your problem seems to be the credibility of NASA. You start with that proposition and then claim to prove it. You’ve been called on it by knowledgeable people here. Certainly you know that sea level rise is not uniform, right?

  47. 197
    Hunt Janin says:

    My thanks to Wilt and to any others who have commented on my first-ever post, asking about the bad effects of a 2 m rise in sea level (for an introductory survey I’m writing now). Wilt, please rest assured that I don’t plan to tell my readers to get ready for a 2 m rise. As a mere generalist, I just want to know what a relatively worst-case scenario might involve.

    [Response: The key issue is: 2 meters by when? Highly unlikely to get there by the year 2100, but getting quite likely by 2200. -stefan]

  48. 198
    Septic Matthew says:

    188, Didactylos: Church and White (2006) don’t attempt any attribution of the acceleration they calculate. They do discuss probable causes and reference the appropriate literature.

    That’s not different from what I wrote.

    but I am hopeful that you are aware that global temperature has not changed at a constant rate through the period discussed in the paper.

    I have written that myself, but there has been some disputation as to the nature of the “nonconstancy”.

    You are just kicking up dust.

    No, I asked whether someone had used a particular method (VAR analysis) to test a particular hypothesis (increases and decreases in rate of sea level rise related to increases and non-increases in global mean temp.)

    I suggest that if you are genuinely interested, you read the papers that are cited as actually addressing attribution for sea level rise.

    Lead me to one (your “favorite”) and I’ll read it, with or without genuine interest.

    180, Andrew Hobbs,
    Thank you. Would you like to provide a link or citation of one of the more recent papers that you mention? One including satellite data through 2009 would be best, but might not yet be peer-reviewed.

  49. 199
    Edward Greisch says:

    RC: Is it the Hatch Act?

  50. 200
    CM says:

    Gilles #187, my bad. Got my graphs mixed up. So I have no issue with your statement about temperatures remaining constant after zero emissions, though as you and John Pearson both noted it’s not the only possibility.


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