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How much is sea level rising?

What the science says...

Select a level... Basic Intermediate

A variety of different measurements find steadily rising sea levels over the past century.

Climate Myth...

Sea level rise is exaggerated

"We are told sea level is rising and will soon swamp all of our cities. Everybody knows that the Pacific island of Tuvalu is sinking. ...

Around 1990 it became obvious the local tide-gauge did not agree - there was no evidence of 'sinking.' So scientists at Flinders University, Adelaide, set up new, modern, tide-gauges in 12 Pacific islands.

Recently, the whole project was abandoned as there was no sign of a change in sea level at any of the 12 islands for the past 16 years." Vincent Gray).

Gavin Schmidt investigated the claim that tide gauges on islands in the Pacific Ocean show no sea level rise and found that the data show a rising sea level trend at every single station.  But what about global sea level rise?

Sea level rises as ice on land melts and as warming ocean waters expand. As well as being a threat to coastal habitation and environments, sea level rise corroborates other evidence of global warming 

The blue line in the graph below clearly shows sea level as rising, while the upward curve suggests sea level is rising faster as time goes on. The upward curve agrees with global temperature trends and with the accelerating melting of ice in Greenland and other places.

Because sea level behavior is such an important signal for tracking climate change, skeptics seize on the sea level record in an effort to cast doubt on this evidence. Sea level bounces up and down slightly from year to year so it's possible to cherry-pick data falsely suggesting the overall trend is flat, falling or linear. You can try this yourself. Starting with two closely spaced data points on the graph below, lay a straight-edge between them and notice how for a short period of time you can create almost any slope you prefer, simply by being selective about what data points you use. Now choose data points farther apart. Notice that as your selected data points cover more time, the more your mini-graph reflects the big picture. The lesson? Always look at all the data, don't be fooled by selective presentations.

graph from Church (2008)

Other skeptic arguments about sea level concern the validity of observations, obtained via tide gauges and more recently satellite altimeter observations.

Tide gauges must take into account changes in the height of land itself caused by local geologic processes, a favorite distraction for skeptics to highlight. Not surprisingly, scientists measuring sea level with tide gauges are aware of and compensate for these factors. Confounding influences are accounted for in measurements and while they leave some noise in the record they cannot account for the observed upward trend.

Various technical criticisms are mounted against satellite altimeter measurements by skeptics. Indeed, deriving millimeter-level accuracy from orbit is a stunning technical feat so it's not hard to understand why some people find such an accomplishment unbelievable. In reality, researchers demonstrate this height measurement technique's accuracy to be within 1mm/year. Most importantly there is no form of residual error that could falsely produce the upward trend in observations. 

As can be seen in an inset of the graph above, tide gauge and satellite altimeter measurements track each other with remarkable similarity. These two independent systems mutually support the observed trend in sea level. If an argument depends on skipping certain observations or emphasizes uncertainty while ignoring an obvious trend, that's a clue you're being steered as opposed to informed. Don't be mislead by only a carefully-selected portion of the available evidence being disclosed.

Current sea level rise is after all not exaggerated, in fact the opposite case is more plausible. Observational data and changing conditions in such places as Greenland suggest if there's a real problem here it's underestimation of future sea level rise. IPCC synthesis reports offer conservative projections of sea level increase based on assumptions about future behavior of ice sheets and glaciers, leading to estimates of sea level roughly following a linear upward trend mimicking that of recent decades. In point of fact, observed sea level rise is already above IPCC projections and strongly hints at acceleration while at the same time it appears the mass balance of continental ice envisioned by the IPCC is overly optimistic (Rahmstorf 2010).

Basic rebuttal written by doug_bostrom

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

This rebuttal was updated by Judith Matz on September 13, 2021 to replace broken links. The updates are a result of our call for help published in May 2021.

Last updated on 5 July 2015 by pattimer. View Archives

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Comments 251 to 300 out of 316:

  1. MA Rodger @ 250

    Thanks for the explanation.  I suspect that when I get through this thread I will tackle Chapters 3 and 13 in IPCC AR5.  Probably should read those first but this is easier reading (I do not want to say more entertaining).

  2. michael sweet @ 228

    I have now read this full thread and am on to reading Chapter 3 of the IPCC AR5 relating to sea level changes (with Chapter 13 to follow). 

    After re-reading your post at 228 above I think I have to reply to you because in a number of places in that post you suggest that Koonin and the writer are "lying" when referring to the fact that the IPCC had suggested that there was a period of "similar rates" during he period 1920-1950.  

    Here are two of the quotes:  

    "Koonin cites the IPCC to support his lie that sea level rise is approximately the same now as in 1950." 

    "Raise your game. You have been posting here at SkS for a long time and you still post these obviously false claims from sources you have been repeatedly shown are spouting lies. It is time consuming to find the actual data to respond to these lies."

    I am somewhat disappointed that the Moderator of this website did not "snip" parts of your post @ 228 because if these are not "ad hominen" comments (or what I might also describe as "bullying") then I do not know what is.  These are comments directed not to the issues but to the person either making the comments or being quoted as a source.  Is there a different standard for those posters on this website who seem to be "regulars" supporting the positions of SKS?

    What concerns me is that based upon your knowledge level of sea level issues (evidenced both from this thread and others) that in all likelihood you knew at the time I made my post @ 221 that you fully knew where my confusion arose in that at the time of that post I had not realized that the IPCC statement of "similar rates" was based upon the IPCC referencing the Jevrejeva and Ray & Douglas estimates of sea level rise (not the Church & White lower estimates) which studies did in fact show "similar rates" during the 1920-1950 period.

    I am also sure that you were fully aware at the time of your post of the discussions of the IPCC in Sections 3.7.4 to 3.7.6 inclusive of Chapter 3 where this "similar rate" and explanation of same are discussed. 

    Therefore your use of the word "lies" was completely inappropriate.

    Moderator:  I had hoped to post a copy of the Figure 3.14 graph with this post but could not figure out how to do it.  Copy and paste from a pdf does not work.  If you could post a copy it would be appreciated to clarify to others where this confusion arose.  Any help on how to do so myself would also be appreciated.  I was not able to "lift" the graph from the pdf itself. 

  3. MA Rodger @ 250

    Thanks for the additional information.  As noted above, I am working through all of Chapter 3.

  4. Norrism @251,

    The US CSSR report contains data up to 2016.  The IPCC report only contains data up to 2012.  SInce the CSSR contains more up to data, Noonan cannot use an outdated graph from the IPCC report to claim that the CSSR is incorrect. The knowledge of scientists has increased since the SR5 was written.

    The data on sea level rise and acceleration has been updated since the AR5 was written.  The CSSR report is now the gold standard.  Noonan knew that the data he used was out of date when he wrote his article.  If he wants to complain he needs to use the most recent data available.  The fact that he did not use current data indicates that either he is ignorant of the data (and cannot complain about what he does not know) or he is trying to obscure the conclusion. 

    IPCC graph

    The data from Jevrejeva et al graphed in figure 3.14 above (sorry it is blurry) was published in 2008.  It has been updated since then.  Sea level rise has dramatically increased since then.  If the graph was drawn with current data the result would be different.

    I have provided data that show that sea level rise has accelerated over the past decade.  Noonan relies on data almost 10 years old for his claim.  That is not an honest claim when we know the rate is accelerating.

    You came here and were angry that the claim that current sea level rise was comparable from 1920-1950 was not included in the CSSR.  Your claim was based on Noonan's article.  You have previously been provided with data that shows Noonan is not a reliable source of information.  You need to be much more skeptical when you read information on Currie's blog, it has a reputation for misleading information.  

    If you came here and asked why this claim was left out and linked Noonan's article it would have been explained to you.  When you are upset the claim was left out (because it is incorrect) you are not  treated the same.  

  5. NorrisM, you indeed seem to not know what constitutes an ad hominem argument. It is the logical fallacy that consists of attacking a person on some irrelevant element in an attempt to invalidate the argument made by that person. Michael Sweet's comment is relevant, on point, and does not say anything about your person, only about your failure to scrutinize information; you did fail to exercise proper diligence and apply due skepticism to the weak attempt by Koonin at misleading. This should be brought to your attention. It was. No logical fallacy there.

  6. Phillipe Chantreau @ 255

    This all began on this thread @ 221 with my comment as follows:

    "In an earlier post on another thread (which discussion has properly moved to this location) I posed the following question:

    'It is interesting that in the above IPCC quote we had similar "high rates" during the period 1920-1950. Curious as to whether there is any explanation of that anomaly.'

    I then referenced the fact that Steve Koonin had, since I had made my comment, picked up on this very same question about "similar rates" during the period 1920-1950 and was critical of the CSSR because in the CSSR Executive Summary there should have been a reference to this period of similar high rates to provide a proper scientific balance.

    This however gets turned to Koonin being a "liar" and me being one spreading lies.

    The definition of "ad hominen", straight out of wikipedia is a little more direct that your soft-pedalled definition.  It states as follows:

    "an argumentative strategy whereby an argument is rebutted by attacking the character, motive or other attribute of the person rather than attacking the substance of the argument itself".

    If calling someone a liar is not an an hominem attack on a person then I do not know what is.  The statement of Koonin gets turned around to the following:

    "Koonin cites the IPCC to support his lie that sea level rise is approximately the same now as in 1950."

    He did NOT say that.  He said that there were rates of increase in the 1920-1950 period comparable to the present and he felt that a more even handed CSSR report would have made reference to this fact in the same way the IPCC did in its Executive Summary to Chapter 3 of the AR5 report.

    We are not talking about "more up to date evidence".   We are talking about the present compared to a period in the past.  If someone here is going to say, well, Koonin totally misrepresented things because we are now around 4 mm/yr rather than 3.2 mm/yr, I will pull up some quotes from this very same thread from a number of years ago about how inappropriate it is to use a couple of years results for any analysis.  In any event, that is no basis to label someone a liar. 

    To be very honest, I cannot see why that is not just an ad hominen comment but moves into a libellous statement against Koonin.

  7. With all due respect to you, NorrisM :- my OED defines ad hominem as "Directed to the preferences or principles of the individual, not to abstract truth".    Can there be a better English authority than the OED?

    Michael Sweet has directed his criticism to the abstract truth which is the evidence of SLR caused by AGW.   He has exposed Koonin [or "Noonan", as Sweet's Irish blood seems to mislabel it, often] as presenting flawed, incomplete, false, deceptive & misleading information about SLR (and by extension, about AGW).

    Koonin presents information without its proper context, and in a deliberately misleading way.   We can be reasonably sure Koonin is being deliberately misleading in this case, because his action here is part of a larger pattern of deceptive & misleading activities in connection with the subject of AGW.   And we can be doubly sure of that, because Koonin is an intelligent, science-literate man, in whom such errors are inexcusable & could not occur without deliberate choice by him.

    All this reflects very badly on Koonin — reflects very badly on his "preferences and principles".  But that is consequential on Koonin's own activities.  Sweet points out that Koonin is reprehensibly wrong (but that is not in itself an ad hominem attack).

    NorrisM, the question you should ask yourself is: Why should you (or anyone) defend Koonin's untruthful behavior?   Koonin for some years now has been bending over backwards to give false & misleading presentation of the science of climate/AGW.  There must be some strange subconscious emotional force which compels Koonin to plunge into the fiery heart of madness which is science-denial (and you too, NorrisM, seem a Moth which is attracted into the same flame).

    NorrisM, you cannot describe yourself as "luke-warm" when your wings are already badly singed.   ;-)

  8. NorrisM @256.

    Pointing to a quote up-thread which cautions against using "a couple of years results for an analysis" will not assist you in explaining the high rate of SLR over the period since the IPCC AR5. The following SLR graphic is from Tamino and certainly indicates a strong level of SLR acceleration since the IPCC AR5 analysis. And if you are considering saying that the data supporting that Tamino finding is inadequate, I would suggest you examine the data supporting those accelerations back in the 1940s and see if that is similarly inadequate.

    Tamino SLR to 2017

  9. MA Rodger @ 258

    I am not saying that we ignore the most recent measurements since IPCC AR5 but that they have to be taken in context.  Here is what Dan Bailey said at post 184 above when responding to a period 2004 to 2008 when things seem to have flattened out or, looking at the above graph, had even declined:

    "[DB] In addition, per Willis and Leuiette (2011):

    "Because of both uncertainties in the observational systems and interannual variations, it has been estimated that a minimum of 10 years is necessary to meaningfully interpret global trends in sea level rise and its components (Nerem et al., 1999)."

    In other words, use the period 1993 onwards just averaging in each subsequent year.  My understanding is that we are using 1993 because satellite measurements began around this time.  Someone (somewhere) has posted a comment that if the period 1992-1994 had been averaged (as the starting point), the rate of increase would not have been as high as 3.2 mm/yr because 1993 was significantly lower than 1992 and 1994.  I have to admit that I do not have a source for this but I suspect this can be easily proven or disproven.

  10. eclectic @ 257

    I have made my point and I do not think we need to pursue this any further. 

    I trust you will agree that no one should be called a liar on this website unless they can prove a statement to be untruthful unless he or she is prepared to back it up in court defending a libel suit.  A statement can be wrong but "liar" connotes an intention on the part of the person making it and that is not appropriate on this website.   Again, if that is not "ad hominen" I do not know what is.

    It remains the case that none of the comments on this thread have "dealt with the substance of the argument itself" which is the following:

    "He said that there were rates of increase in the 1920-1950 period comparable to the present and he felt that a more even handed CSSR report would have made reference to this fact in the same way the IPCC did in its Executive Summary to Chapter 3 of the AR5 report."

    Koonin is making the point that the failure by the CSSR not to include this statement in the Executive Summary (which the IPCC properly disclosed in AR5 Chp 3 and 13) indicates that the CSSR has an "agenda" it is promoting and is not just reporting, as scientists should do, the scientific information available both for and against the propostion of AGW.   It is this very attitude that creates distrust in those (ie  X% of the US public) not fully convinced that AGW is as serious as it has been made out to be.

    Has anyone commented on this argument of Koonin's? Do you not agree that the CSSR should have followed the same disclosure as the IPCC? And if so, why not?


    [JH] Further regurtitation by you of Koonin's claim about sea level rise will constitute "excessive repetition" and "slogaqneering." As you well know, both are prohibited by the SkS Comments Policy.

  11. Norrism:

    You and Koonan argue that the CSSR should include the claim that rates of sea level rise in the time era 1920-1950 were compaarable to current rates.  Jeverejeva et al 2014 specifically address this claim.

    From the introduction to Jevrejeva et al 2014:

    "However, there have been suggestions that the rate is not historically exceptional. For example, similar rates were observed in tide gauge records during the period 1920–1950 (Jevrejeva et al., 2006) and in decadal mean rates in the 1950s and 1970s (Church and White, 2006), and even a rate of 5.3 mm·yr−1 centred on the 1980s by Holgate (2007). 

    To identify the long-term changes and variability of sea level over the past 200 years ..."

    From the conclusion:

    "However, Fig. 15 and the associated uncertainties discussed in Section 3.4 show that long term estimates of time variable sea level acceleration in 203 year global reconstruction are significantly positive, which supports our previous finding (Jevrejeva et al., 2008a), that despite strong low frequency variability (larger than 60 years) the rate of sea level rise is increasing with time." (my emphasis)

    Koonan's claim that the current rate of sea level rise is not exceptional is in contradiction to the conclusions of scientists working in the field.  It is not included in the CSSR because scientists have concluded that the rate of sea level rise is accelerating.  The current rate of sea level rise is historically exceptional. 

    In addition, the rate of sea level rise is expected to strongly accelerate in the future.


    This is the same conclusion that I posted at the start of this discussion where I provided data showing that the rate of sea level rise has accelerated strongly over the period of satelite analysis.  The data show that the rate of acceleration of sea level rise is accelerating.

    Koonan and you are attempting to cherry pick sentences that suggest sea level rise is not accelerating and is not a problem.  That is in contradiction to the scientific conclusion.  The CSSR is required to discuss the scientific conclusion, not some potitically correct BS.

  12. NorrisM @259.

    You are verging into the incomprehensible so you will understand if I am at cross purposes.

    You seem to object to the use of recent data but at the same time happy to consider 10+ year assessments of SLR. So let us look at the satellite data (which is available 1993-2017) calculating 11yr OLS trends. Note that IPCC AR5 data collection stopped in 2011 so we have six more years of data. The final 11 years of data used by AR5 showed a trend of 2.8mm/yr and such trends would continue to drop to 2.55mm/yr by the following year. Since that time, SLR has risen sharpely and the last 11 year of data shows a trend of 4.2mm/yr. There is yet no sign of any let-up in that acceleration. (It is running along the same track as shown in the Tamino graphic @258, just past the vertical blue line.)

    And using Church & White tidal gauge data (which today only runs to 2013 but AR5 had data to 2009), the final years are running above 4mm/yr while such 11-yr trends calculated through the full record never top 3mm/yr.

  13. NorrisM likes this definition : "an argumentative strategy whereby an argument is rebutted by attacking the character, motive or other attribute of the person rather than attacking the substance of the argument itself."

    I said: "the logical fallacy that consists of attacking a person on some irrelevant element in an attempt to invalidate the argument made by that person."

    Any attempt at convincing me that there is a significant difference between these two descriptions is an argument in bad faith that has no merit. I know without a doubt that one who would try to do that is trying to take me for a ride. It is total nonsense. I certainly have better things to do with the time given to me in this life than going back over NorrisM overall contribution on this site, but my recollection of said contribution is telling me that there is a pattern here. The abundant verbiage to say what amounts to nothing and the rather laughable litigation threats are also familiar signs. The obligation to remain polite and tolerant toward this kind of sophisticated abuse of the forum was one of the reason why I gave up moderating years ago. It is quite an ungreateful task that the moderatros tackle...


    [JH] Please note my Moderator's comment on NorrisM's most recent post. As far as I am concerned, he is skating on the thin ice of relinquishing his privilege of posting comments on this site.

  14. As far as I can see no-one has used the word "liar" other than NorrisM. 

    I don't think I have any more to say on that. 

  15. MA Rodger @ 262

    If I understand you correctly, the satellite data averaged over the last 11 years shows an average increase of 4.2 mm/yr?  And in the case of tide gauge data, although the most recent years show an annual increase over 4 mm/yr the average over the last 11 years is something below 3 mm/yr? Your use of the term "trend" suggests that I might not have this right. 

    From what I have read there seems to be an unresolved discrepancy between satellite readings and tide gauge readings which seems to be borne out by the difference in these rates.  They can still show the same acceleration but the measurements do not coincide.

  16. Phillipe Chantreau @ 263

    I have never said that there was a significant difference between your definition and mine.  I just felt yours was somewhat softer.  The term "ad hominen" in Latin means "at or to the man".  The principal point I was trying to make is that this website should not allow posters to allege that particular people are telling or spreading lies.  That is a very serious allegation.  I agree that no one other than the writer has actually used the noun "liar" but is that not what you call someone who lies?   I think I have made my point and I suspect most agree that it is not appropriate to make such allegations when the term "misrepresentation" can be used which probably more accurately describes what the poster intended to say.  


    [JH] You wrote:

    ...this (SkS) website should not allow posters to allege that particular people are telling or spreading lies.

    Have you posted a similar statement on Curry's website? On WUWT? 

  17. There are: misrepresentations, damned misrepresentations, and statistics !

    Oh, where is our Disraeli or our Churchill when we need him, eh NorrisM.   Churchill, I am sure, would make short work of Koonin and Koonin's misrepresentations — and Churchill would use a three-letter word, not a polysyllabic. 

    In particular for Koonin's statement on SLR's . . . "The rates since 1993 are at the high end of this range, but are not statistically different from those during the first half of the 20th Century."    ~ That being the sort of weasel statistics up with which Churchill would not put.

    "Not statistically different" is a term we have heard before — during the transient "Hiatus" in surface temperatures during the Noughties of this Century.   ~ A pseudo-analysis by science-denialists, which deliberately and clearly ignored the vast weight of evidence [ocean warming] and ignored the most basic physical processes [CO2/GHG effect] still going on unabated.   It was a phrase which sailed very close to, but not quite over the edge of . . . damned misrepresentation.  It was designed to pull the wool over the eyes of the casual reader who did not bother to think it through, and who had little climate knowledge.

    And now [stated October 2017] Koonin is saying sea-level rise for the 21st Century is as yet not statistically different from earlier times.   He ignores the fact that the 1940-ish SLR "bump" was a small and minor variation from the background rising trend, and was quite a different kettle of fish from the high/accelerating rise of recent decades (which has very clear causation by ongoing thermal expansion of the ocean and by large-scale ongoing melting of land-based ice sheets.   And Koonin makes his statements despite having the hindsight from (late) 2017.

    Such misrepresentation by Koonin (for a man of considerable scientific ability) could not be accidental or unintentional.   Indeed, it is all one, with the typical science-denier strategy of continual misrepresentation of what is really happening in our physical world, in regard to AGW.   Rather obviously, Koonin is wishing to imply to the casual reader, that Global Warming is non-existent or of minimal importance.

    # NorrisM, there is no need for you to reply to my post here.   Koonin seems to be on a long campaign of various misrepresentations . . . and I am reasonably sure there is nothing you could say to redeem his current reputation.

    We should move on, to the pure science of sea-level rise where of course [re your post #265] there's a small difference of figures from satellite and tide-gauge measurements — since they are measuring two slightly different things [not different by much: but coastal measurements can never be exactly the same as "coastal + mid ocean" ].

  18. NorrisM @265.

    Indeed, you do not have it right.

    I have taken the data from C&W and from NASA. For each of the two records, I have calculated linear trends through 11-years, from beginning to end of each record.

    Thus the latest such trend for C&W is centred on 2008 covering the years 2003-2013. It has a trend of 4.2mm/yr. The data centred 2005-08 all yields trends above 4mm/yr and the data centred 1998-2004 yields trends 3mm/yr ot 4mm/yr. Levels of SLR above 3mm/yr are not evident on the C&W record even in a single year. Prior to this latest acceleration, only 10 years on the 134 year record managed to top 2.5mm/yr.

    Your second paragraph begins "From what I have read..." and then delves again into nonsensicalnessism. What do you mean by "They can still show the same acceleration but the measurements do not coincide."?

    I should perhaps add that the dip in satelite-derived SLR shown by these 11-yr OLS calculations, illustrated @258 and described @262: that dip would disappear if the suggested-but-unpublished adjustments to TOPEX are borne out. (Note the researchers were not at all happy with Nature's use of the word "SNAFU".) The adjustment removes the dip and reveals a strong acceleration as per the C&W data.

    Nerem SLR with TOPEX adjusted

  19. MA Rodger @ 268

    By the use of the term "trend", I am assuming that you do not mean that you add the yearly increases over the period and divide by the number of years which would be the average.  Is this a term in statistics?  If so, could you point me to a "beginner" summary of statistics terms.  I have to admit that I took one course in statistics at university but it was my least favourite subject and that was a long time ago.  I get standard deviation and bell curves but suspect that "trend" is a statistical analysis and does not refer to the simple average.

    As for my comment on the different rates for satellites and tide gauge, I do not think it was "nonsensical", in that Eclectic understood what I was getting at.  What I was saying is that you could have two different measurments of sea level rise but the curves are parallel.  Just one above the other in measurements of y axis.


    [DB] Sloganeering snipped.

  20. Eclectic @ 267

    In Canadian law, we use  various levels of the term "misrepresentation", moving from innocent misrepresentation to intentional misrepresentation to fraudulent misrepresentation.  This last term, if proven, can put you in jail.  It is the one which is equivalent to saying someone has lied.

    Moderator.  As I have noted before on this website, I never look at WUWT but I promise to do so on Curry's website if I ever see such a statement.  If you want to point me to a recent instance on the Curry site, I am happy to go online and make the very same comment and then reference you to my comment

    I just hope everyone appreciates that someone can have questions they would like answered in the area of climate change and also think that what is happening in the US with the Republicans taking health care from millions of people to pay for their tax cuts to the rich is disgusting and raises real questions about the political process in the US.   I suspect that Koonin (a Democat, I assume) is also disgusted with the Republicans on that issue.  I just do not think people who have different views should be demonized.  I think he has the best interests of the US public (you see I do not use the term "the American people") at heart but just has differing views of what that best interest is.  I think it is perfectly acceptable for criticisms to be levelled at him as long as they do not go past what I have referred to as "intentional misrepresentation".


    [DB] Off-topic snipped.

  21. It's becoming ever more dfficult to take NorrisM seriously. Euphemisms, half-assed language and all around BS have dug their way so deep in the culture that even their chief users get tangled in the rotten semantics with which they have flooded the world.

    Here is the interesting argument that a misrepresentation is better than a lie. NorrisM, in a tremendous rethorical effort, throws a little analysis of why the word lie is mean because it implies intent to deceive, then goes on to misrepresetation as if it did not imply an intent to deceive. That is really funny. NorrisM is explaining to us that it is bad to tell lies because that's the crude way to do things; misrepresentations are much better because they don't readily open one up for being exposed as a fraud. A misrepresentation is a higher skilled sort of lie, it uses better language, it's what smart liers do. Yeah, misrepresentations are much better. So are deceptions, dissimulations and all manners of devious behaviors that can't be immediately pinned down for what they are. Way to go.

    To summarize recent contributions, we've heard it's bad to try to intimidate others in the same post as we received litigation threats, and that misrepresentations are much better than lies. Impressive.

    And that's not even counting all the objective stuff about hard data that has been covered by other contributors, who showed that there is no doubt about what is going with Koonin. We're flogging a dead horse here. I'm done.

  22. Lastly, this demonstrates generously why having lawyers run any kind of debate about physical reality is the worst idea. I have read enough of NorrisM contributions to see that calling it "one can have questions" is the best possible example of a misrepresentation. 

  23. NorrisM @269.

    If you examine my comments above about trends, I have been using the term OLS quite frequently. The term OLS is googleable and the acronym finders that act helpfully (ie not slang, street-speek, etc) all get it at the first, the first and first attempt. Even google's top suggestion is this wikithing page. However, as you are statistic-averse, this little video will tell you all you need to know.

    And parallel cirves is not an issue. Likely it would simply suggest use of differing base periods.

  24. This just in....

    New York City has plenty to worry about from sea level rise. But according to a new study by NASA researchers, it should worry specifically about two major glacier systems in Greenland’s northeast and northwest — but not so much about other parts of the vast northern ice sheet.

    The research draws on a curious and counterintuitive insight that sea level researchers have emphasized in recent years: As ocean levels rise around the globe, they will not do so evenly. Rather, because of the enormous scale of the ice masses that are melting and feeding the oceans, there will be gravitational effects and even subtle effects on the crust and rotation of the Earth. This, in turn, will leave behind a particular “fingerprint” of sea level rise, depending on when and precisely which parts of Greenland or Antarctica collapse.

    Now, Eric Larour, Erik Ivins and Surendra Adhikari of NASA’s Jet Propulsion Laboratory have teased out one fascinating implication of this finding: Different cities should fear the collapse of different large glaciers.

    These are the melting glaciers that might someday drown your city, according to NASA by Chris Mooney, Energy & Environment, Washington Post, Nov 15, 2017

  25. MA Rodger @ 223

    Thanks.  The video helped.  I guess I have to spend some time understanding regression analysis (it is not the first time this has come up).  Generally, it seems that what you are really trying to do is determine the slope based upon the data.  It was actually another YouTube video of McLoughlin (sp) that was more helpful. 

  26. [JH] Recommended supplemental reading:

    Does NASA Data Show That Global Warming Isn’t Causing a Sea Level Rise? by Alex Kasprak, Snopes, Aug 1, 2017

  27. I guess Manhattan must be elevating to actually show a decrease in sea level since 2010.  And certainly no acceleration in sea level rise for more than 150 years.


    [PS] Precisely what point are you trying to make here from the basis of a single tide station? The relevance to the article is not clear.

  28. George @277 , the tide gauge records collated by NOAA, for The Battery, on Manhattan, show a 400 mm rise in sea level during the past 160 years.   (Strangely, the record shows a gap from about 1879 - 1893.)   As you say, the reference no. is 8518750.

    Mean sea level rise approx 2.8 mm per year, over that 160 years. 

    Possibly Manhattan Island is developing a strong tilt in recent times, with the northern end of the island lifiting high?   I must look more closely at the Empire State Building, to see if it appears out of plumb.  My previous impressions were that it was nowhere like as bad as that skyscraper in Pisa (fortunately).

  29. George,

    While there is no rise since 2010, there is a large rise since 2008.  The long term rise is clear.  Do you have a reason for selecting 2010 or was it just to cherry pick your claim?

    Have you ever seen the escalator?


    Do you think you could make a similar graph from the tide guage in New York?  

  30. Here are a couple more around the U.S.

    There is certainly no acceleration in sea level rise and in fact a drop in sea level since 2010.
    My belief is that there has been additional snow and ice buildup causing the drop in sea level.  

    "Cherry Pick since 2010"?  Eight years of opposing data is not enough to make you question your hypothesis?


    [DB] Multiple comments using the same failed rhetoric are unhelpful.  The facts are, global sea levels have risen since 2010.  Attempting to find a few areas where sea levels show different results is like using the existence of smaller waves at the oceanside following larger ones in an attempt to show that the tide has somehow stopped coming in.  It's a fallacy.

    Altimetric SLR

    We also know which of the components of SLR contribute to it most (mass increases vs thermal expansion):

    Mass increases

    And, from Hsu and Velicogna 2017, which areas will see more resultant SLR than others:

    SLR Fingerprints

    No amount of effusive prestidigitation (handwaving) can make that go away:

    Fake-skeptic SLR

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  31. George,

    Your first link (I cannot get the graph to copy here) is from Monterey Bay.  While it has a lower long range trend, the trend from 2010-present is very high, the opposite of your claim.  Your second graph, from Nantucket, shows a high long range trend but lower from 2010-present.  You must konw that individual locations have high noise and also land height change issues.  If that is the best you can find in the entire USA that indicates that sea level is rising rapidly.

    If you get some guages from Alaska they will actually show a long term decrease in sea level since there is strong isostatic lift (increase in land height) due to the melting of the glaciers from the ice age.  That does not mean the sea level is not rising, just that the land is rising faster.


    7:00 no sea level rise in La Jolla, CA
    12:00 Topex/Poseidon Satellite measurements are crude
    12:43 ENVISAT, European satellite with higher resolution, much lower sea level rise, decrease since 2010

    How do you explain Manhattan?  Has the land elevated there?


    [Rob P] - Not surprisingly, sea level at New York has risen over the long-term. In the short-term, fluctuations in the ocean circulation are having an effect. Now that ice mass loss from the Greenland ice sheet is fully underway it will be interesting to see how that alters sea level rise along the North American east coast. There's a recent paper on the subject here: Causes of accelerating sea level on the East Coast of North America (Davis & Vinogradova [2017])

  33. George,

    Manhattan is a very noisy record.  There are many short periods where it appears to not rise while the long term (actual) trend is increasing.  Since land elevation is a long term issue that would primarily afect the long term trend and not the noise.  Tamino has a lot of sea level analysis where he explains the statistics.

    The noise is affected by the weather and by issues like El Nino/La Nina.  Longer term processes like the Arctic ocellation would also affect the noise.

  34. George,

    I noticed that you did not link the graph for La Jolla.  Here it is.  Long term trend 2.17 mm/yr, not no sea level rise.  Read some of Tamino's stuf and you will be better able to determine if there is a trend from a graph.

  35. FFGeorge,

    The ENVISAT satalite has been shut down since April 2012.  How can you possibly suggest that it has more accurate data for the period 2010-2017 when it has not collected data for most of that time?  The video you linked is unreliable.

    You are choosing a time period that is too short to measure the sea level rise.  You are focusing on the noise and not the signal.

    Find a reliable source of information.  Read Tamino.

  36. I started at about post #7 with sea level rising at 2.46 mm per year. Eight years later, that may be 3 mm per year (3.46 +/- 0.4) or so ... so about 0.1 in per year ... less than a foot by 2100.

    California has accepted a new building code, expecting 10 feet by 2100.

    Does this make any sense? Should we all be investing in Dutch dike companies?


    [DB] And yet, per Nerem et al 2018:

    "Global sea level rise is not cruising along at a steady 3 mm per year, it's accelerating a little every year, like a driver merging onto a highway, according to a powerful new assessment led by CIRES Fellow Steve Nerem. He and his colleagues harnessed 25 years of satellite data to calculate that the rate is increasing by about 0.08 mm/year every year—which could mean an annual rate of sea level rise of 10 mm/year, or even more, by 2100."

    "This acceleration, driven mainly by accelerated melting in Greenland and Antarctica, has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate—to more than 60 cm instead of about 30." said Nerem, who is also a professor of Aerospace Engineering Sciences at the University of Colorado Boulder. "And this is almost certainly a conservative estimate," he added. "Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."


    "the observed acceleration will more than double the amount of sea-level rise by 2100 compared with the current rate of sea-level rise continuing unchanged. This projection of future sea-level rise is based only on the satellite-observed changes over the last 25 y, assuming that sea level changes similarly in the future. If sea level begins changing more rapidly, for example due to rapid changes in ice sheet dynamics, then this simple extrapolation will likely represent a conservative lower bound on future sea-level change."

    SLR acceleration

  37. Chez Provence: You wrote:

    California has accepted a new building code, expecting 10 feet by 2100.

    Please document and link to the source of this claim.

  38. w6g-9-2018-exhibits.pdf


  39. Thanks for the Nerem reference. This may be a local politics thing ... In the draft report of the California Coastal Commission, they acknowledged the 800mm rise shown by, Nerem ... added their own sense, suggesting that the most likely will be 1.2 m, worst case 2 m ... and proposed regulation for 3 m. Starting point is fig 4 on page 46 of the w6g reference above.

  40. ChezProvence: Thank you for providing the documentation per my request.

    The headline of the Scientiic American article:

    Prepare for 10 Feet of Sea Level Rise, California Commission Tells Coastal Cities 

    The sub-headline of the article qualifies the headline: 

    Though an extreme scenario, it should be factored in to coastal infrastructure planning, new guidance suggests

    That is quite different than your statement:

    California has accepted a new building code, expecting 10 feet by 2100.

  41. ChezProvence: Furthermore, the head-line and sub-headline of the SA article do not comport with the facts set forth in the first three paragraphs of the article:

    California coastal cities should be prepared for the possibility that oceans will rise more than 10 feet by 2100 and submerge parts of beach towns, the state Coastal Commission warns in new draft guidance.

    The powerful agency, which oversees most development along 1,100 miles of coast, will consider approving the guidance this fall. A staff report recommending the changes was released last week.

    Earlier commission guidance put top sea-level rise at 6 feet by 2100. But according to the new report, there’s the “potential for rapid ice loss to result in an extreme scenario of 10.2 feet of sea level rise” by the end of the century.

    As Yogi Berra was wont to say, "It ain't over until the fat lady sings!"

  42. I encounter some extreme fringe RWNJ deniers on various investor sites. They literally don't care if the West Coast or Northeast have issues with SLR "because Democrats live there" (no, I'm not kidding). So I would like to put it in terms that they might care about. At approximately what year does SLR become "a problem" for Florida (that big swing state needed to win elections)? The Houston Ship Channel (which would be supremely ironic)? Has there been any science done at that kind of level?

  43. I think Miami is already struggling with sealevel rise. Cant help with Houston Ship Channel sorry.

  44. AFT: Try 

  45. The deniers are saying the satellite equipment that can only measure distances in centimeters cannot produce sea level measurements in millimeters. Can someone address this or provide a link where this is addressed. I can’t find anything on this. Thanks.

  46. Hank: Sea level is a population parameter that is estimated by combining multiple sample measurements of it. The Law of Large Numbers explains that the precision of the combined estimate increases with the number of sample measurements. Look up Law of Large Numbers in a textbook or in Wikipedia, then prove it yourself using a spreadsheet. There is a tutorial on satellite measurement of sea level linked right above the image at the bottom of This NOAA page, though currently it does not work, probably due to the government shutdown.

  47. Thanks Tom. As an engineer I’m familiar with the Law of Large Numbers and thought that might be at least part of the explanation. I look forward to reading the tutorial if the government ever opens.


    [DB] The Internet Archive has a backup of the tutorial page, here.

  48. Just what I was looking for. Thank you.

  49. Do an Earth mean sea level has any real meaning ?

    Relative Sea Level Trends


    [DB] As a professional nautical cartographer, I can assure you that mean sea level has a concrete meaning.  If you have an actual question, please be more specific.

    Reduced image width (keep image widths below 500 to avoid breaking page formatting).

  50. Sealevel rise is not even across the globe.


    Note that sealevel measured from satellite altimetry is based on height change with respect to the reference ellipsoid, avoiding the issue of subsidence or tectonics which plague tide guages (though both measurements systems yield comparable results).

    Sealevels are falling close to melting ice thanks to reduced gravitional attraction and isostatic rebound. See here for more detailed explanation.

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