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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 201 to 250 out of 316:

  1. When will data about the first 4 months of 2014 be available? Particularly on volume of ice. I see comparisons of 2007 to 1979 used often. What about 1984 to today?

    I just read the data on the rise of all the Great lakes back to about the 100 year normal. That had to take a lot of water out of the oceans. For example, the avg glacial loss of the entire Himalayas mountain range was 2 gigatonnes per yer in the early 2000's. Some would tout this as adding to the seal level rise. However, this year, 50 gigatonnes of ice was added just to lake Superior, Which rose 14 inches year over year, and is 32,700 square miles in area. It seems like climate reporters use the term gigatonne to describe loss of ice and the avg low info person thinks that it represents a very very large amount. So they report the Him. Mts. lost 2 gigatonnes of glacial ice in 2003 and that the rate of loss is increasing 10% over the rate from just 10 years earlier. When in fact, Lake Superior just gained 25 times as much ice as that this past winter. So I wonder since it is all quiet about this year's ice volumes that possibly the avg arctic ice volume has recovered most of the 5500 gigatonnes of avg loss since 1979. Even choosing 1979 as the baseline is rediculous. 1979 was the year that the great lakes ice coverage record was set that still stands and was not broken this year, but it came within 1-2 percent of being broken (~94%). Seems like 1979 was cherry picked. Just Lake Superior alone gained 50 gigatonnes of ice this past winter. The lake is still 67% ice covered on May 1. I calculated the 48 cu miles of that really bad year of ice loss from Greenland and spread it into the Earth's ocean surface area and multiplied it by 87 years and got 1.87 inches of sea level rise. What a sigh of relief it was.

  2. It is curious this controversy on a scientific level. "They have a millimeter measurement" for 68 years ... every day ... well documented ... Panama Canal.
    Repeat ... for 68 years
    Without any pressure from powerful groups and only practical for the normal functioning of locks filing purposes.
    The levels of the Pacific and the Atlantic, have been unchanged in the last 68 years.

    Give a bit of a laugh to see how each to defend a theory and make specific studies in specific geographic areas and draw overall conclusions.
    Governments need to collect more taxes, and for that... we have to blame something.


    [TD]  Please provide a citation for your claim.  NOAA's Sea Level Trends page shows trend of increase since 1908/1909 on both ends of the canal.  (Click the arrows on that page to see more info, and in the resulting dialog window click the "Linear Trend" link.)

  3. TD inline @202

    Cristobal JASL trend, 1907-2010: 1.5861 mm/yr.  Note that there is a large dip in sea level around 2000, with a rapid recovery (nearby stations show trends of 13.788 and 13.707 mm per year in the period of recovery) such that by carefull enough chery picking you might find a period with near zero trend depite the rapid overall rise.

    Balboa JASL 1907-2010: 1.5494 mm/year (previous link).  In both cases extending the data beyond that held for the PSMSL stations increases the rate of sea level rise.  That strongly suggests that any lack of sea level rise Maui claims is, at best, the result of cherry picking.

  4. I think that a lot of you are missing the point, including the contributing author. Are sea levels rising? It would seem so. Is mankind in some way causing this phenomenon? Doubtful. The current period of climate change with accompanying measuements of atmospheric temperature and CO2 levels started approximately 18,000 years ago. There have been four periods where atmospheric temperatures and CO2 levels have been as high or higher than presently in the last 400,000 years (Source: Mankind was obviously not the cause of any of these occurrences. The graph showing the rise in sea levels in the article posted here shows steadily rising sea levels since the 1870s. That should be expected when you consider that the "mini ice age" lasted from the 1300s to about 1850 and that is when the glaciers and sea ice reached their peaks. As that water becomes available again, sea levels rise. A way to look at it would be to look at Pevensey Castle, which was on England's South coast in 1066. Pevensey Castle is now a mile inland! (Source:


    [Rob P] - Please note that WUWT is a spoof climate science site. For an understanding of the historical context of sea level rise since the last glacial maximum see these SkS posts:

    1Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years.

    2Sea Level Isn't Level: This Elastic Earth.

    3. Sea Level Isn't Level: Ocean Siphoning, Levered Continents and the Holocene Sea Level Highstand.

    Note that these SkS posts are based upon actual research by experts in the relevant scientific disciplines. I think that the main point is that non-expert expectations of sea level response are incredibly naive - you need to understand all the factors that affect relative sea level at any particular site. Why else do you think that specific site was chosen, and the 'big picture' blithely ignored? 

  5. Holdean...  SLR is merely one piece of the larger picture related to man-made climate change and is fully consistent with all the other science on the issue. So, no, it's not "doubtful" in the least.

    I don't know where you get the idea that "the current period of climate change [...] started approx 18k years ago." That's just not the case. The planet came out of a glacial into a new interglacial starting about 18k years ago. Since ~6000 years ago the planet had started into a neoglaciation that was abruptly ended with the start of the industrial revolution (See Miller 2010, Section 12.2). 

    No one rejects that there have been periods of higher temp and higher CO2 levels. That's not the problem. The issue is with the rate of change that natural systems, as well as human civilization, will be unlikely be able to adapt quickly enough to. Past rapid rapid climate change events are marked by mass extinctions such as the End Permian.

  6. Holdean, Pevensey is an area that used to be a marsh, and the reason that the castle is now a mile inland is because the marsh silted up (c.f. the medieval shipyard at smallhythe that is also used to make similar arguments).  There are numerous medieval (or older) villages and towns along the Sussex coast, which would have been underwater had sea levels been significantly higher prior to the little ice age.  It doesn't take much basic fact checking to find that out.  The plural of anecdote is not data.

  7. Holdean wrote "There have been four periods where atmospheric temperatures and CO2 levels have been as high or higher than presently in the last 400,000 years (Source: Mankind was obviously not the cause of any of these occurrences."

    Yes, obviously, but that would be relevant to the current temperature increase only if we had no idea what controls temperature.  In fact, we do know.  See:

    Holdean wrote "The 'mini ice age' lasted from the 1300s to about 1850 and that is when the glaciers and sea ice reached their peaks. As that water becomes available again, sea levels rise."

    But the "mini ice age" (a.k.a. the Little Ice Age) was not in any way an "ice age" (we currently are in an ice age and have been for a long time), nor a glacial period within an ice age (currently we are in an interglacial period).  Nor was the "mini ice age" global, and "it" was not even a single event.  Instead, there were some isolated periods of strictly regional cooling separated by as much as hundreds of years.  So the very existence of a global Little Ice Age is a myth.  Those cooler periods loomed large in the minds of people who were living in those regions, and the cultural prominence of the opinions and writings of those people made those cooler periods seem singular, severe, and global.

    See also "We're Coming Out of the Little Ice Age."

    In all Skeptical Science posts, be sure to read not just the Basic tabbed pane, but the Intermediate and Advanced ones if they exist.

  8. Holdean wrote "There have been four periods where atmospheric temperatures and CO2 levels have been as high or higher than presently in the last 400,000 years (Source: Mankind was obviously not the cause of any of these occurrences."

    This is incorrect.  Present is 2014 with an atmospheric concentration of ~400ppm.  In the ice core record, "present" is 1950.  We are currently 100ppm higher than any point in that record.

  9. Is there still "close agreement" that SLR is "steadily accelerating" as per the 2009 claim, or have some sensible adjustments been made since then?


    [DB] Please provide your definition of "sensible adjustments".

  10. Earthling - Yes, there is indeed continuing agreement that sea level rise continues, and over the longer term is accelerating, as per basic physics and observational data. Note that a five year period ("since 2009") is a _very_ short time given year to year variations.

    What kind of "sensible adjustments" do you have in mind? And are they backed by any kind of data?

  11. (DB) & KR - The meaning of sensible adjustments should be obvious, especially as SLR has slowed to around 2.54 mm/yr, as opposed to "accelerating."

    ARGO + GRACE finds sea levels rising at 2.31 mm/yr.

    Even the up adjusted from 1.59 mm/yr ENVISO rate is 2.96 mm/yr.

  12. Earthling - Long term observations show continuing acceleration of SLR, with shorter term (including multidecadal) variation superimposed. For example, IPCC AR5 Chapter 13, which states from observations:

    When a 60-year oscillation is modelled along with an acceleration term, the estimated acceleration in GMSL (twice the quadratic term) computed over 1900–2010 ranges from 0.000 [–0.002 to 0.002] mm yr–2 in the Ray and Douglas (2011) record, to 0.013 [0.007 to 0.019] mm yr–2 in the Jevrejeva et al. (2008) record, and 0.012 [0.009 to 0.015] mm yr–2 in the Church and White (2011) record. For comparison, Church and White (2011) estimated the acceleration term to be 0.009 [0.004 to 0.014] mm yr–2 over the 1880–2009 time span when the 60-year cycle is not considered.

    Even with variations the current rise rate is considerably higher than the numbers you posted:

    CU Sea Level Research Group


    You seem to be emphasizing (or selecting) short term variations over longer term trends. That's of little use over longer periods, as variations will regress to the mean trend. And I'm still seeing no support for your "sensible adjustments".

  13. If you would like a pictorial measure of sea level change, there are some great interactive photos taken in England and of the Normandy landings 70 years ago, and again last summer. Little has changed.

    There are other phots, not interactive, which show the same thing.

    Of course, these photos were simply before and after photos, with NO agenda.


    [Rob P] - You can't expect to be taken seriously unless you provide some background context for the photos. All readers here will be familiar with high and low tide. 

  14. whsmith @213, the IPCC stated:

    "It is likely that the rate of global mean sea level rise has continued to increase since the early 20th century, with estimates that range from 0.000 [–0.002 to 0.002] mm yr–2 to 0.013 [0.007 to 0.019] mm yr–2. It is very likely that the global mean rate was 1.7 [1.5 to 1.9] mm yr–1 between 1901 and 2010 for a total sea level rise of 0.19 [0.17 to 0.21] m."

    I'll take the high end of that likely range, so 1.9 mm per year, or 95 mm over the 50 years from 1944 to 2014.  So, you are claiming, by showing those photos that you can detect a difference of just under 4 inches in sea level between the Normandy landing photos, and the present day photos and conclude that it is not their.  You can do this, moreover, without knowing the relative state of the tide, and despite obvious changes in the water front structures (in the first photo).

    It is amazing the perceptive powers ideology grants ... (ROFLAO)

  15. Whsmith,

    Perhaps looking at pictures of beaches at low tide do not show the sea level rise much.  As Tom states, it has only been 4 inches and they are used to meters of tidal range there.  I note many pictures show beach erosion and cliff retreat, but I do not know if the cliffs were eroding before the war.

    If you looked a little harder you might find a reference like this which documents the increase in sediment accretion of salt marshes in Normandy, France over the past 120 years.  The marshes must accumulate sediment to keep ahead of sea level rise.  These marshes are expanding since more area is salty now due to sea level rise.

  16. Norrism:

    The data that you have presented from the IPCC show a  clear acceleration of sea level rise over the past 100 years.  The data show that the rate of increase in increasing over the time period analyzed.  The IPCC then did a linear fit to the data to get the rates you quote.

    When you fit a line to an accelerating function you obtain approximatley the average of the rate of increase over the time period, not the instantaneous rate.  Your claim of 3.2 mm/yr (increased from your previous rate of 3.0 mm/yr) is probably close to the rate during 2001.  According to my calender, it is now 2017.

    Deniers often use the IPCC rate from 1901-2010 of 1.7 mm/yr.  Your choice is not as bad a cherry pick as that, but it still minimizes the current increase in sea level by averaging in old data.  The 4.0 mm/yr rate I have cited is the current (2017) rate and is a conservative estimate since the data shows the rate is accelerating.  This conservative rate with the current acceleration of the rate gives 95 cm as a conservative increase in sea level by 2100. You usually choose the minimum rates of whatever you are discussing.

    Scientists are not generally allowed to cherry pick data in the fashion you do.  We use the most up to date data possible, not data from years ago.  Claiming that the sea level rise is only 3.2 mm/yr when up to date data show the rate is 4 mm/yr and accelerating is considered a cherry pick and is not a convincing argument.

    It seems to me that lawers are trying to demponstrate that their argument is correct.  They cherry pick information to make it appear their argument is correct even when it is incorrect.  Scientists want to deduce the actual behaviour of nature.  The most up to date data is used.  At SkS we want to reveal what is actually happening in nature.  

    Here is a link to an analysis by Tamino.  He discusses some of the techniques of analyzing data like this. His estimate of current sea level rise (data goes to 2013) is about 3.9 mm/yr.  Dr. Nerem  has data up to 2017.  There are small differences between satalite data (Dr. Nerem) and tide guage data (Tamino).  Tamino is a statistician who has published on climate change.

    If you want you can use 3.2 mm/yr as the sea level rise but it is not an accurate number and it minimizses the problem of sea level rise.  Note that the data in the OP here ends about 2010, it is not current.

  17. michael sweet at 216

    Thanks for the reply.  When it comes to "what is happening" versus "what should be do about it", I think my attitude has settled on focussing on two observations and trying to understand them.  They are temperature rise and sea level rise.  This way I do not have to engage in areas of technical expertise such as the predictability of climate models where it would be hopeless for me to fully understand the complexities.

    Obviously temperature increases and sea levels are intimately intertwined in that a large part of sea level rise is expansion.

    I will look more carefully at your references and look at the most recent papers. 

    Can you explain from what date you are measuring the sea level rise?

    I asked this question of someone else on the 1C temperature rise and found that there was not a clear agreement but I think we are dealing with  ballpark 1850 to 1880.  Is that the same for sea level rise?

    On the "what should we do about it" question, is there a better place to discuss the 2010 Abbott paper which suggests we move to thermal solar for base load rather than wind or PV solar?

  18. NorrisM:

    I used 25 cm from somewhere up thread for the sea level rise from before 2017.  If you go to Tamino's thread (previously linked)  the next to last graph (easiest to read) shows sea level as -160  mm in 1880 and +70 mm in 2013.  That is a total of 230 mm which is 23 cm.  At 4 mm/yr for the past 4 years add 16 mm = 1.6 cm.  Total = 25 cm. before 2017.  I used d= vt + 1/2at2 to calculate 95 cm sea level rise using v= 4 mm/yr and 0.1 mm/yr2 = acceleration (83 years from 2017 to 2100).

    This post from Zillow estimates damages from 6 feet of sea level rise in the USA as $882 billioon today. That is only the houses, not businesses, government, farms and infrastructure.  It is a place to start.  There are several problems I see with their analysis:

    1: The sea level map they used shows inundation from sea level rise with 6 feet of sea level rise from mean higher high water (MHHW).  Houses are never built at MHHW because then any storm surge would flood the house.  (Storm surges of 1-2 feet are common).  However, they used 6 feet which is closer to the upper end of sea level rise currently expected.  I think the damage they estimate is about what 4 feet of sea level rise would cause because of the effect of storm surge.

    2: They only count as damaged houses that are inundated.  All of Miami that remained would be an island with 6 ft sea level rise.  In addition, many houses are on small islands with several miles of the road leading to them inundated.  How much is a house worth when the neighbors house is inundated and you have to drive through several miles of water to reach it?

    3: Miami's water supply is located at 3 feet above sea level and is already having salt water intrusion problems.  With only 3 feet of sea level rise they will be out of water.  How much will Miami houses be worth when they have no water?

    Read very carefully anything about damages caused by sea level rise.  There are many ways to make a mistake.  In general, scientific reports are written to be conservative.  I recommend reading a lot of material before you make up your mind what you think.  Tamino's work is always first class.  This post from Real Climate (from 2013) is written by a sea level expert, take it very seriously.  New data since then has raised expectations of sea level rise.

  19. NorrisM:

    RealClimate also has a search box. Put in "Sea level rise" and you will find several posts (including the one that michael sweet has pointed you to). Another good one is What Makes Sea Level Rise?.

    In comment #217 you say '..."what is happening" versus "what should be do about it"...'. You have left out "what will happen". The whole aspect of acceleration in the next 80 years is not found by studying what has happened in the past 100 purely from the sea level data.

    You need to understand why sea level has changed (both in the past century and the past 20,000 years). and apply that knowledge to what will happen by the year 2100. The physics of warming water already in the oceas, land ice melt, and transfers between ocean and land will play different roles - they are not expected to contribute in the same proportions as the planet warms. That's why simple extrapolation of past patterns is not enough. You need to know how oceans warm, and why ice sheets melt and decay (and that ice sheet melt will not be linear...)

    As another analogy, consider paying off a home mortgage, amortized over 25 years with a monthly payment of $2000. In the first year, nearly all the payment goes to interest, and little of the principle is paid off. After one year, you still owe almost the full amount - much more than 24/25ths. Extrapolating that at a constant rate over 25 years would lead you to conclude that there is no way to pay off the mortgage. On the oher hand, understanding how interest and principle are calculated and paid off makes you realize you will eventually own your house free and clear.

  20. Norrism:

    I found this description on Climate Central of the map that was used by Zillow for their analysis:

    "This analysis uses elevation data on a roughly 90-meter horizontal resolution grid derived from  NASA’s Shuttle Radar Topography Mission (SRTM). SRTM provides surface elevations, not bare earth
    elevations, causing it to commonly overestimate elevations, especially in areas with dense and tall buildings (Gamba et. al, 2002) or vegetation (Shortridge et. al, 2011) . Therefore, this analysis very likely underestimates, and Mapping Choices under-portrays, areas that could be submerged at each lockedin sea level, and so the following analysis and visualization should be seen as likely lower bounds" (my emphasis).

    Source.  (Zillo cites NASA but it  is the same map that Climate Central uses). This is a serious problem with most sea level damage analysis.  Many informed people are not aware of this problem.  Obviously, people cannot live on top of trees and buildings when the land is covered with water.  I had thought that Climate Central used actual land heights.  Actual damages are certain to be much higher than estimated by Zillow.  Scientists make conservative estimates.

  21. michael sweet and Bob Loblaw

    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."

    And Bob Loblaw @ 219 states:

    "You need to understand why sea level has changed (both in the past century and the past 20,000 years) and apply that knowledge to what will happen by the year 2100."

    It seems now that Steve Koonin has posed the very same question in a critique issued by him on October 10, 2017 prior to the release of the CSSR report which I understand just happened.  You can read his criticique at

    I am not saying that the recent sea level rise since 1993 is not more relevant than the average over the 20th century but does it not behoove scientists to either explain the 1920 to 1950 rise or admit that they do not know?

    And I agree with Koonin that the CSSR, by not including this information in the Executive Summary (which is intended for the layman), shows that it is not just a scientific report but rather one which is intended to "move the agenda".   It is this attitude of the "consensus side" which drives conservatives crazy.  If the facts were honestly stated on both sides then you would not get this kind of dismissive reaction from Republicans who you have to convince ( a common theme in my posts).

    Is there a scientific explanation for why sea level rises during the period 1920-1950 were close to the same as the present rates?  

  22. NorrisM:

    I have no interest in what Steve Koonin has asked - he has no credibility as a scientific source on climate change, due to reasons already explained. Judith Curry is also of no interest to me. Most of what gets posted on her site is a waste of time.

    In comment 219, I posted a link to RealClimate. It includes the following graph:

    Sea Level rise


    I assume that you have followed the links given to you, or have a reason not to. What is it about this figure that you question? What about it fails to answer the question you are posing about cause of changes in sea level rise in the past century?


    [DB] Fixed image width.

  23. Crap. That figure ended up being a lot wider than I expected. Moderators, can you please fix?


    [JH] Fixed.

  24. NorrisM @221

    As evidenced in the new research summarized in the following article, sea level rise is a very complex subject matter. You would do well to focus your time and energy on peer-reviewed papers published in reputable scientific journals rather than on the pseudo-science poppycock posted on Judith Curry's website.

    New science suggests the ocean could rise more — and faster — than we thought by Chris Mooney, Energy & Envronment, Oct 26, 2017 

  25. Thanks, gentlemen. I should know better.

  26. It is sad to see Koonin's ideas spiralling down into crankdom.

    Koonin is only 65, and yet for some years now there has been increasing evidence of that widely-known but poorly-understood phenomenon: "Going Emeritus".   Considering his previous prominent administrative/advisory governmental jobs, it is possible that there may also be a touch of LDS motivating him [ LDS = Limelight Deprivation Syndrome ].

    While LDS is probably a minor part of the affliction suffered by the average professor who retires, it is neverthless clearly not at the heart of the "Emeritus" condition.  But I fear it will be a very long time until the physiologists & neuro-psychologists come to a good understanding of the mechanisms producing the science-denier mind-set of such "Gone Emeritus" cases.

    In the meantime, we (including NorrisM) will just have to ponder the mystery of how an intelligent science-literate guy like Koonin is able to get it so terribly wrong about such basic scientific thinking.  And while he is lecturing climate scientists about them "not looking at the bigger context" . . . he himself is blithely turning a blind eye to the necessity of seeking causations for physical events (and he is losing himself in a mess of cherrypicking & statistical abstractions, rather than looking at the real world).

    More than sad, it is tragic.  

  27. Norrism:

    I recommended to you that you should read Tamino's posts on sea level rise.  You wasted your time at Curry's blog.

    If you had gone to Tamino you would have seen this graph of the speed of sea level rise calculated from Church and White:

    sea level rise

    This graph indicates that currently sea level is rising at approximately double the maximum rate during the 20th century.  Please present data to support your wild claim that the current rate is similar to the rate in 1950. The acceleration was similar in 1930 but it did not last as long and started from a much lower base.  Koonin does not discuss acceleration.

    From a brief examination of this graph and the post of Koonin at Curry's blog it appears that most of the similarity in speed of sea level rise Koonin claims is due to Koonin cherry picking the time period that was analized. 

    Koonin's graph under "what the literature says" ends in 1995. I note that in 1995 Tamino's graph indicates the sea level rise was approximately the same as the peak in 1950.  Unfortunately, my calendar says it is 2017.  Koonin's graph is an 18 year running average.  Becasue sea level rose so fast after 2000, the running average is much lower than the yearly (smoothed) average.

    Keep in mind that the IPCC data is all at least 6 years old and Tamino's graph shows rapid acceleration over the last six years.  I reviewed the sea level section of the CSSR and they do not have a comparable graph.

    I do not know why you point out that Koonin posted his remark just before the report was released.  The release date was set several years ago and it was the Fifth draft of the report.  Koonin knew what was going to be in the report before it was released.  

    Denier's who rely on obviously cherry picked  data to  make their points are dishonest.  It is this attitude of the "denier side" which drives scientists crazy.  If the facts were honestly stated on both sides then you would not get this kind of dismissive reaction from scientists.

    This information was not included in the Executive Summary because it is false.

    You consistently pick minimums and claim deniers arguments that are cherry picked are equal to data anlysis by scientists.  This is a false argument.  You need to raise your game.  By continously bringing up false claims you make people think you are just a troll and are not interested in learning about the causes and problems of AGW.

    You asked: "Is there a scientific explanation for why sea level rises during the period 1920-1950 were close to the same as the present rates?"  

    The answer is: current rates are double the rates from 1920-1950.  You fell for a cherry picked argument by deniers.

    If you refer to Koonin as a reliable authority on AGW again I will refer to this post and point out that Koonin is a cherry picker whose primary purpose is to mislead.  It makes you look bad to refer to him so much.

  28. Norrism:

    Your post is a perfect example of why scientists do not want to engage in a "Red-Blue" team discussion with Koonin as moderator, as you have suggested.  

    When one team deliberately falsifies the data the public thinks that scientists have not reached consensus.  In this example of sea level rise, everyone who has looked at the data agrees that sea level rise is twice as much now as it was in 1950.

    Koonan is not an acceptable person to moderate such a debate since he has demonstated that he in completely uninformed of the data and deliberatly misinforms his audience.  There is no excuse for Noonan's use of data that is 12 years out of date to make claims of current sea level rise.  If Noonan wants to make public criticism of scienitsts he is required to use the current data that was in the report he criticized.

    The analysis from Dr. Nerem, linked at 216, gives enough data to realize Koonin's claim is false on its face.  I linked the article containing Tamino's graph there also.  You have been given the actual data.  Every time you use Curries' blog as a reference everyone here knows that you are misleading them.  Why have you not learned Curry is not a credible source from your previous postings of false information using her as the source?  Do lawyers always continue to use references after they have been shown to be incorrect several times? 

    Koonin cites the IPCC to support his lie that sea level rise is approximately the same now as in 1950.  The intent of the CSSR is to update data in the IPCC report.  The scientists who wrote the CSSR are required to use the most up to date data.  In addition, the data in the IPCC report was 7 years old when that report was written 6 years ago.  Do we really need to reargue data that is 13 years old when current data is available?

    Do you lawyers sit around and endlessly argue if it is fair to count blacks as only 3/5 of a vote and whether separate but equal facilities are acceptable???  Why do you ask scientists to reargue current sea level rise based on 13 year old data?

    As I paraphrased from your post:  " It is this attitude of the "denier side" which drives scientists crazy. If the facts were honestly stated on both sides then you would not get this kind of dismissive reaction from scientists."  

    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.  

  29. This Koonin blather raised by NorrisM includes a WSJ opinion piece by Koonin (paywalled) entitled "A Deceptive New Report on Climate", this concerning the draft of a Climate Science Special Report (CSSR). Blog Mom Judy Curry has a post suppling some excerpts from the WSJ item and from the Koonin memo to the authors of the CSSR,  the memo itself being also posted at Judy's site (where NorrisM linked to it @221).

    The Koonin criticism sets out to fudge the inevitability of serious SLR by branding SLR rates since 1993 as "not statistically different from those during the first half of the 20th Century," this description being required so as to "not misleadingly alarm the non‐expert reader into believing that recent rates of rise are unprecedented." And he also wants mention of 2m SLR by 2100 setting out that this would require a rate of 24mm/yr so as to "help illustrate for the non‐expert reader just how dramatic the projected changes are." Or should that be 'how unbelievable'?

    So here we have somebody in denial over AGW-induced SLR.

    And he is not the only one. In the same post, Judy links to a slide show of her own titled "Sea Level Rise: Past, Present & Future"  which also shows signs of denial. And Judy's prediction of global SLR 2017-50 is presented on Slide 35 as 3" to 8" which works out as an average SLR over the period of 4.2mm/yr(+/-2mm).

  30. michael sweet @ 218, Bob Loblaw @ 219 and MA Rodger and John Hartz

    I have read the references in the above citations and I am still confused as to the statement by the IPCC in the 2013 Assessment which, again, has the following summary:

    "It is very likely that the global mean rate was 1.7 [1.5 to 1.9] mm yr–1 between 1901 and 2010 for a total sea level rise of 0.19 [0.17 to 0.21] m. Between 1993 and 2010, the rate was very likely higher at 3.2 [2.8 to 3.6] mm yr–1; similarly high rates likely occurred between 1920 and 1950. {3.7.2, 3.7.4, 5.6.3, 13.2.1, 13.2.2, Figure 13.3}"

    The graph of Church & White presented in Tamino and reproduced in michael sweet's post at 227 seem to be inconsistent with a statement of fact in the 2013 IPPC statement.  The rate shown in the Church & White graph (is this fully Church & White or an extension added to a Church & White graph that ended earlier?) does not show a similar rate in 1920 to 1950 at approximately 3.2 mm/yr.  Surely this is what "similar high rates" has to mean.

    Responding to Bob Loblaw, of course new information on sea level rises since 2013 are relevant but it does not explain this statement by the IPCC made in 2013.  At that time it was either right or wrong.  From what I can gather, the new CCSR report effectively repeats this analysis in the main report but does not reference this in the Executive Summary which is Koonin's complaint.

    Moderator @ 224

    I have not fully read the Mooney discussion nor have I got through this entire thread which I intend to do as part of my understanding on this issue. 

    But I thought I should respond to what seems to be an inconsistency between the Church & White graph and what the IPCC (and I believe the CCSR) have said about this period 1920- 1950.

    I thought I was going to get an explanation of why the rate during 1920-1950 was close to the same but the answer comes back that the rate was no where near 3.2 mm/yr at all during this latter period.   If all the IPCC was referencing was a short term acceleration during this period at the same rate for a much shorter time than the 30 years, then that could have been made a lot clearer because that is not what was stated.   But that is not even supported by the Church & White graph.

    I certainly agree that Koonin's most recent statements would suggest that he is not looking to becoming the Chair of any Red Team Blue Team panel unless Pruitt intends to have Co-Chairs, one from each side of this issue.

  31. NorrisM:

    In the Tamino link provided above, he states:

    "If we smooth the data, a lot depends on the time scale for smoothing. Too short a time scale will tell us about the ubiquitous wiggles, which is not what we’re interested in."

    In the figure just after that statement, he shows the smooth fit he produced:

    Tamino sea level (Church and White)

    Note that Tamino's curve does not follow every "ubiquitous wiggle". Less smoothing will give greater variation in rate over shorter time intervals. The IPCC report does not state (that I can see from a quick glance) how short a time interval they used to get "similar" rates. Section does, however, state:

    "Interannual and decadal-scale variability is superimposed on the long-term MSL trend, and Chapter 3 noted that discrepancies between the various published MSL records are present at these shorter time scales.


    "Because of the presence of low-frequency variations (e.g., multi-decadal variations seen in some tidal gauge records; Chambers et al. (2012)), sea level acceleration results are sensitive to the choice of the analysis time span.

    If you make the time span short enough, you'll get twice-daily tides with very high rates of change. Not "sea level rise", though. The IPCC is probably looking at shorter time scales than Tamino.

  32. With respect to acceleration, and whether it will continue, the figure I included in comment 222 shows that Greenland and Antarctica are having an increasingly large contribution. Ice sheets like these are slow to react, and they are just getting going in response to recent warming. The major question on what will happen by 2100 is "what will happen with Greenland and Antarctica?"

  33. NorrisM @230.

    Yous seem to be asking two things. Firstly, why do we not see "similarly high rates" to 3,2mm/yr(+/-0.4mm/yr) in the Tamino graph? Secondly, what caused the rate of SLR 1920-50 to be higher than periods before and after?

    The methods used to create the Tamino graph have been explained @231/232 but this is probably not enough for you.

    To address your first question concerning the IPCC quote, be aware that the quote originates in the Executive Summary of AR5 Chapter 13 so is not what I would call definitive, and indeed the quote you give cites references elsewhere within AR5. (You call this quote "fact" which is seriously wrong.)

    If you refer to Section 3.7.4 you will see that it is not just Church & White that are being cited and that  in Fig 3.14 Church & White data yields the lowest SLR through this 1920-50 period, hitting a momentary peak of just 2.3mm/yr from 18-year lnear trend calculations. (It is not clear from AR5 but this is certainly Church & White (2011) not C&W(2006) which would yield significantly higher levels of SLR through these years. Note C&W(2011) plot 16-year linear trends which also peak at 2.3mm/yr.) The Tamino graph uses differing methods and yields a peak of 2.1mm/yr through these year.

    Your second question has no definite answer. Note that C&W(2011) speculate that the ice-melt contribution in 1920-50 could have been greater than is usually estimated. And if you look at zonal temperature records (ie GISTemp below), the place with the big temperature during the early 20th century was the high northern latutudes that do conveniently have ample ice to melt.

    GISTEMP zonal graphic

  34. Norrism:

    Bob Loblaw and M.A. Rodger have address some of the data analysis.  If you read Tamino's post you will get a more detailed account.  The IPCC does not state how their data was calculated.  The method is undoubtedly somewhere in the references.  It looks to me like they used a short analysis period, but it may be due to the data sources they used.

    It appears that the IPCC graph that Koonan used was graphed with the 18 year data point at the start of the 18 year period (Noonan did not copy the caption so I could not tell from his graph).  That means the data reached to 2011 and was up to date when it was written.  My last post incorrectly dated the graph.  

    We know that sea level rise has increased rapidly for the last 6 years.  That means the sea level now is about 20% greater than it was in 2011 when the IPCC data was written.   Comparing to 1950 it is less likely that 1950 was as fast as today than in 2011 since sea lefel rise is greater.

    In addition, papers have evaluated all the data sets graphed in the IPCC reports and some of those data sets have been updated.  That would change the data (I am not sure what those changes are).  In order to make a valid comparison today you need to use the updated data sets.

    The writers of the CSSR reports used the updated data sets to reach their  conclusions.  They reached a valid scientific conclusion.  Koonan cherry picked old data because he thought it supported his preconceived notions.   His claims are not scientificly valid.  The CSSR report supersedes the IPCC report because it is a more recent in depth review.

  35. Ancillary to Bob Loblaw's fine comment at 232, previous research has shown that ice sheet mass contributions from land-based ice sheets have exceeded thermal expansion as the biggest contributor to global sea level rise.  Recent research just submitted now has isolated the individual ice sheet contributions to global sea level rise.

    Per Hsu and Velicogna 2017, between April 2002 and October 2014 global mean sea level grew by about 1.8 millimeters per year, with 43 percent of the increased water mass coming from Greenland, 16 percent from Antarctica, and 30 percent from mountain glaciers.

    Hsu and Velicogna 2017 - Detection of Sea Level Fingerprints derived from GRACE gravity data

    SLR Fingerprints

  36. Just published in December 2017 issue of “Earth Systems and Environment” the most authoritative and objective analysis yet of sea-level rise globally.
    Should finally put this issue to bed. The next time you hear about sea-levels rising several feet this century remember there’s no evidence of this rate to date despite the explosion of CO2 since early in the 20th century.

  37. As this is your first post, Skeptical Science respectfully reminds you to please follow our comments policy. Thank You!

  38. yppo: "the most authoritative and objective analysis yet of sea-level rise globally."

    Sorry, I'm skeptical.  Your citation is to the second of two issues of a brand new journal.  From the 'Preface' to the first issue, published three months ago:

    It is our great pleasure to present the inaugural issue of our newly launched scientific journal “Earth Systems and Environment,” the official journal of King Abdulaziz University, which has now become a reality with Springer Nature in Germany. Our main objective is to establish very high standards for the journal so as to support research and innovation in the greater Middle East region and to promote the exchange of scientific knowledge between local scientists in the region and the international community.

    With all due respect to King Abdulaziz and his namesake University, its new house organ has yet to establish how 'authoritative' it is. As for whether Short-Term Tide Gauge Records from One Location are Inadequate to Infer Global Sea-Level Acceleration will "finally put this issue to bed", that's up to post-publication peer review to decide. 

    As an armachair climate scientist, I'm hardly a 'peer' of any working SLR specialist, but I'll offer my two cents.  I noted this in the article's Introduction:

    The loud divergence between sea-level reality and climate change theory—the climate models predict an accelerated sea-level rise driven by the anthropogenic CO2 emission—has been also evidenced in other works such as Boretti (2012a, b), Boretti and Watson (2012), Douglas (1992), Douglas and Peltier (2002), Fasullo et al. (2016), Jevrejeva et al. (2006), Holgate (2007), Houston and Dean (2011), Mörner 2010a, b, 2016), Mörner and Parker (2013), Scafetta (2014), Wenzel and Schröter (2010) and Wunsch et al. (2007) reporting on the recent lack of any detectable acceleration in the rate of sea-level rise.

    Candidly, citing the likes of Mörner and Scafetta to support a claim of "loud divergence between sea-level reality and climate change theory" won't help to "establish very high standards for the journal."

  39. yppo: "Albert Parker" or "Alberto Boretti", the nome de plume that he sometimes writes under, is well known to make up his data on sea level rise.  Please suggest a reason we should listen to his prattle now? (for those new to science, writing under two names in considered dishonest in science.  "Alberto Borelli" has written positive comments about "Albert Parker's" work.)

  40. michael sweet @239,

    I think it is more correct to state that "Albert Parker" was known as "Alberto Boretti" and that at some point prior to September 2012, as confirmed by the University of Ballarat on October 1st 2012, "Alberto Boretti ... changed his name to Albert Parker." Of course, this allows Parker to say nice things about Boretti. But is there actually evidence of Boretti returning to say nice things about Parker?

    And let us not forget Parker's co-author in this allegedly "most authoritative and objective analysis yet of sea-level rise globally" who is an octogenarian with a bit of a problem accepting there is significant ice loss from the Greenland & Antarctic ice caps.

  41. MA Rodger:

    In addition to the link michael sweet gave to a Tamino article, there are several other blog posts that Tamino has done on Parker/Boretti's work. A search at Tamino's provides a list.

    One of those posts (also linked to in the Tamino post michael points us to) has more details on the paper that Boretti/Parker sent in two comments on (both published). Although I haven't read the comments to see if Boretti said anything about Parker, it is clear that Parker did not stop using the Boretti name just because it wasn't his legal name any more.

    Perhaps he just forgot some of the tnings he wanted to comment on when he sent in the first comment, and then forgot he'd already sent in a comment using his other name when he sent in the second comment.

  42. As Mal Adapted points out, the journal this recent paper came out in is quite new.

    I noticed that issue #2 has a correction in it, for a paper from issue #1. Although it is to the credit of the authors and journal to correct errors, I hope that this is not the start of a pattern of error-riddled papers.

  43. Bob Loblaw @241,

    Further to this Boretti/Parker issue, my understanding as per @240 was that there was one odd date (likely explainable), and all else pointed to a simple name-change. In the Tamino discussion you refer to dated 26Sept2012, there is mention of 3 published comments, one of these from Boretti and one from Parker. The Parker comment is published 6Sept2012 and cites the Boretti comment as being "In Press". The authorship of the Parker comment must then post-date the Boretti comment. And they both must have been published prior to the Tamino post of 26Sept2012.

    So here is the one odd date, the Boretti comment publication is dated 11Oct2012. I can but assume this for some reason was written, and published in some form prior to both the Parker comment and the Tamino post but has for some reason acquired a later date of publication in the form linked above. Beyond this, I initially saw no Boretti literature on this subject that post-dates the arrival of Parker.

    That did suggest a name change (as per the commenting here on a different paper) and that Parker was not acting as a sock-puppet for Boretti. However....

    ...Boretti has acted as a sock-puppet for Parker (hat-tip DeSmogBlog who got no sense from Parker when they asked him abot the two names). And Parker also continues to use the name Alberto Boretti when publishing in his day job so Parker continues to be a nom de plume, perhaps used to build a firewall between the responses he gets to his purile writings on climatology (which "would be unacceptable in an undergraduate lab report") from his more serious Mechanical Engineering work (eg here).

    Which ever way you see it, Parker/Boretti's use of different names within scientific publications is unacceptable.

  44. The following comment was deleted by mistake. My bad.


    @236 @yypo

    "Short-Term Tide Gauge Records from One Location ..."

    I am no expert on sea level rise but the title says it all and says nothing. I hardly need a scientific paper to tell me that short time scales and one location are not enough. Indeed, the first point made in this Skeptical Science article is "A variety of different measurements find steadily rising sea levels over the past century.".

    What is the reputation of “Earth Systems and Environment"? And what is your justification for saying "the most authoritative and objective analysis yet of sea-level rise globally"? Just asserting it does not make it so.

  45. MA Rodger, Bob Loblaw and Michael Sweet,

    After more carefully looking at Figure 3.14 in the IPCC Fifth Assessment, I think the real answer to my question is that the IPCC is not relying on Church & White but rather on Jevrejeva el al and Ray and Douglas estimates to come to the conclusion that "similar rates" (ie 3.2 mm/yr) were found in the period of 1920-1950.

    So then, just when some papers are coming out with projected 4 mm/yr rates, here we have Daniel Bailey at 235, in the course of discussing that there is a larger contribution to SLR from ice sheets rather than thermal expansion he states as follows:

    "Per Hsu and Velicogna 2017, between April 2002 and October 2014 global mean sea level grew by about 1.8 millimeters per year"

    What gives?

    It would seem that there is a lot of disagreement on one of these basic issues, namely, how much SLR are we experiencing?


    [DB] No disagreement.  As this, per NASA, makes clear:

    3.4 millimeters per year, margin: ±0.4


    Just not this:

    Skeptic SLR

  46. Daniel Bailey @ 235 is clearly talking about ice sheet contribution to SLR, NOT total SLR.

    "Ancillary to Bob Loblaw's fine comment at 232, previous research has shown that ice sheet mass contributions from land-based ice sheets have exceeded thermal expansion as the biggest contributor to global sea level rise. Recent research just submitted now has isolated the individual ice sheet contributions to global sea level rise.

    Per Hsu and Velicogna 2017, between April 2002 and October 2014 global mean sea level grew by about 1.8 millimeters per year, with 43 percent of the increased water mass coming from Greenland, 16 percent from Antarctica, and 30 percent from mountain glaciers.

    Hsu and Velicogna 2017 - Detection of Sea Level Fingerprints derived from GRACE gravity data"

  47. "235 is clearly talking about ice sheet contribution to SLR, NOT total SLR"

    Yes, indeed.  And that the ongoing mass losses from our dwindling, land-based ice sheets are now the dominant contributor to SLR...and will continue to be so, for longer than any now alive shall live.

  48. Norris M: As I stated updthread, sea level rise is a very complex subject matter

    One of the major complexities of sea level rise is that it is not uniform throughout the global ocean system. The following article dramtically illustrates this key fact:

    Scientists may have solved mystery of rapidly rising Indian Ocean sea level by Olivia Trani, GeoSpace, AGU Blogosphere, Nov 7, 2017

  49. John Hartz @ 248 and squishy

    I think I will get back to reading the balance of this thread. Indian Ocean discussion interesting but seems to suggest that talking about an average SLR over all oceans is challenging. 

    DB could have been clearer but I see that he was clearly referring only to the contribution from ice sheets.

    Do you agree that the IPCC reference to the 1920-1950 period had to be referencing the two studies other than Church & White shown in the 3.14 graph?

  50. NorrisM @249.

    As you become interested in IPCC AR5 Fig 3.14, do note that the three data sets presented are derived from tidal gauges using two significantly different approaches. The first used by Jevrejeva et al (2008) attempts to reconstruct a global coastal SLR and the second used by Church & White (2011) and Ray & Douglas (2011) attempts to reconstruct a global ocean SLR. The full set of approaches employed across all the various studies is listed out in AR5 Section 3.7.2.

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