However, other analyses show the opposite…
Correcting estimates of sea level rise
Acceleration in sea level rise far larger than initially thought
The acceleration in global sea level from the 20th century to the last two decades has been significantly larger than scientists previously thought, according to a new Harvard study.
The study, co-authored by Carling Hay, a post-doctoral fellow in the Department of Earth and Planetary Sciences (EPS), and Eric Morrow, a recent PhD graduate of EPS, shows that previous estimates of global sea-level rise from 1900-1990 had been over-estimated by as much as 30 percent. The report, however, confirms previous estimates of sea-level change since 1990, suggesting that the rate of sea-level change is increasing more quickly than previously believed. The new work is described in a January 14 paper published in Nature.
“What this paper shows is that sea-level acceleration over the past century has been greater than had been estimated by others,” Morrow said. “It’s a larger problem than we initially thought.”
“Scientists now believe that most of the world’s ice sheets and mountain glaciers are melting in response to rising temperatures.” Hay added. “Melting ice sheets cause global mean sea level to rise. Understanding this contribution is critical in a warming world.”
Previous estimates had placed sea-level rise at between 1.5 and 1.8 millimeters annually over the 20th century. Hay and Morrow, however, suggest that from 1901 until 1990, the figure was closer to 1.2 millimeters per year. But everyone agrees that global sea level has risen by about 3 millimeters annually since that time, and so the new study points to a larger acceleration in global sea level.
“Another concern with this is that many efforts to project sea-level change into the future use estimates of sea level over the time period from 1900 to 1990,” Morrow said. “If we’ve been over-estimating the sea-level change during that period, it means that these models are not calibrated appropriately, and that calls into question the accuracy of projections out to the end of the 21st century.”
To obtain their improved estimate of 20th century global sea level, Hay and Morrow approached the challenge of estimating sea-level rise from a completely new perspective.
Typically, Hay said, estimates of sea-level rise are created by dividing the world’s oceans into sub-regions, and gathering records from tide gauges – essentially yard-sticks used to measure ocean tides – from each area. Using records that contain the most complete data, researchers average them together to create estimates of sea level for each region, then average those rates together to create a global estimate.
“But these simple averages aren’t representative of a true global mean value” Hay explained. “Tide gauges are located along coasts, therefore large areas of the ocean aren’t being included in these estimates. And the records that do exist commonly have large gaps.”
“Part of the problem is related to the sparsity of these records, even along the coastlines,” Morrow said. “It wasn’t until the 1950s that there began to be more global coverage of these observations, and earlier estimates of global mean sea-level change across the 20th century were biased by that sparsity.”
“We know the sea level is changing for a variety of reasons,” Hay said. “There are ongoing effects due to the last ice age, heating and expansion of the ocean due to global warming, changes in ocean circulation, and present-day melting of land-ice, all of which result in unique patterns of sea-level change. These processes combine to produce the observed global mean sea-level rise.”
The new estimates developed by Hay and Morrow grew out of a separate project aimed at modeling the physics that underpin sea-level “fingerprints” – explainer from previous story.
“What we were interested in – and remain interested in – was whether we can detect the sea-level fingerprints we predicted in our computer simulations in sea-level records,” Morrow said. “Using a global set of observations, our goal has been to infer how individual ice sheets are contributing to global sea-level rise.”
The challenge, Hay said, is that doing so requires working with a “very noisy, sparse records.”
“We have to account for ice age signals, and we have to understand how ocean circulation patterns are changing and how thermal expansion is contributing to both regional patterns and the global mean,” she explained. “We try to correct for all those signals using our simulations and statistical methods, then look at what’s left and see if it fits with the patterns we expect to see from different ice sheets.”
“We are looking at all the available sea-level records and trying to say that Greenland has been melting at this rate, the Arctic at this rate, the Antarctic at this rate, etc.” she continued. “We then sum these contributions and add in the rate that the oceans are changing due to thermal expansion to estimate a rate of global mean sea-level change.”
To their surprise, Hay said, it quickly became clear that previous estimates of sea-level rise over most of the 20th century were too high.
“We expected that we would estimate the individual contributions, and that their sum would get us back to the 1.5 to 1.8 mm per year that other people had predicted,” Hay said. “But the math doesn’t work out that way. Unfortunately, our new lower rate of sea-level rise prior to 1990 means that the sea-level acceleration that resulted in higher rates over the last 20 years is really much larger than anyone thought.”
###
[UPDATE] My sub-oceanic source has sent me a copy of the actual study. Here is the abstract:
Estimating and accounting for twentieth-century global mean sealevel (GMSL) rise is critical to characterizing current and future human-induced sea-level change. Several previous analyses of tide gauge records1–6—employing different methods to accommodate the spatial sparsity and temporal incompleteness of the data and to constrain the geometry of long-term sea-level change—have concluded that GMSL rose over the twentieth century at a mean rate of 1.6 to 1.9 millimetres per year. Efforts to account for this rate by summing estimates of individual contributions from glacier and ice-sheet mass loss, ocean thermal expansion, and changes in land water storage fall significantly short in the period before 19907. The failure to close the budget of GMSL during this period has led to suggestions that several contributions may have been systematically underestimated8. However, the extent to which the limitations of tide gauge analyses have affected estimates of the GMSL rate of change is unclear. Here we revisit estimates of twentieth-centuryGMSL rise using probabilistic techniques9,10 and find a rate of GMSL rise from1901 to 1990 of 1.260.2 millimetres per year (90% confidence interval). Based on individual contributions tabulated in the Fifth Assessment Report7 of the Intergovernmental Panel on Climate Change, this estimate closes the twentieth-century sea-level budget. Our analysis, which combines tide gauge records with physics-based and model-derived geometries of the various contributing signals, also indicates that GMSL rose at a rate of 3.060.7 millimetres per year between 1993 and 2010, consistent with prior estimates from tide gauge records4. The increase in rate relative to the 1901–90 trend is accordingly larger than previously thought; this revision may affect some projections11 of future sea-level rise.
Regards to all,
w.
Maybe. Maybe not. This minority opinion isn’t necessarily right or wrong. All it means is that the science is not settled.
Ah, now that’s certainly wrong.
If it was a problem we would have noticed. As we didn’t notice any particular problem with sea-level rise (our infrastructure adapted without any extra expense save routine renewal)…
Well, it still isn’t a problem, is it?
So let me get this straight. The hard data, the observational data was not sufficient enough to create an accurate historical record of sea level rise. So instead, they created “fingerprints” in models built for other purposes, then used those model created “fingerprints” to infer how ice sheets are affecting sea level rise. These values are added together with thermal expansion numbers gleaned from other models, and then an estimate is made. I love new science! No more tedious observations having to be made. Just ask a computer to create the values for you.
” I love new science! …Just ask a computer to create the values for you.”
Hey, it gets the grants and that’s the name of the game.
And when the “data” is proven wrong, get another grant to study it further.
BTW, everybody knows that from 1992 thru 2003 the current data says the rate of rise was 3.5 mm/yr and from 2004 up to today that rate is only 2.9 mm/yr. Everybody knows that right?
Foots loosely with the pause. There are several papers even worse than this new Harvard one (simply laughable) that tried to explain the recent SLR ‘slowdown’ as not pause related. Those were the main objects of derision in essay Pseudo Precision, since they posited things that are utterly impossible after a few moments thought. Fine examples of the corruption of climate science and the failure of ‘pal’ review.
Uh current data from CU’s Sea Level Research Group
“But everyone agrees that global sea level has risen by about 3 millimeters annually since that time, and so the new study points to a larger acceleration in global sea level.”
No, everyone doesn’t agree! The tide gauges that showed less than 2 mm/year prior to the satellites still showed less than 2 mm/year during the satellite era. The apples-to-oranges comparisons of the two different methods while hiding this fact was one key thing that convinced me that the “climate establishment” could not be trusted.
Anyone who thinks we know the altitude of these satellites to within a mm/year so that we can rely on them over the best tide gauges has to be smoking something…
The satellite altimetry problem is worse than you portray. The newest, Jason 2, has a design spec local geographic precision of 3.5 cm, and a design instrument drift of 1mm/year. Details and references in essay Pseudo Precision.
And furthermore… #(:))
“The difference between tide gauge data and space based data is over 100% in the left graph, 1.5 mm/yr versus 3.2mm/yr. Of course those who claim that sea level rise is accelerating accept this data without question, but obviously one of the two data sets (or possibly both) is not representative of reality, and {NASA} JPL’s GRASP team aims to fix this problem they have identified:
…”
AND
“The uncertainty is quite clear in Table 1, which has error ranges larger than the data in some cases: {Table 1}”
http://wattsupwiththat.com/2012/12/03/why-ice-loss-and-sea-level-measurements-via-satellite-and-the-new-shepard-et-al-paper-are-highly-uncertain-at-the-moment/
Janice, +10 at least.
Tide gauges have been (in some, not all) cases corrected for rebound/subsidence (land moves also) by differential GPS, supposedly good to within a mm. (Supposedly.) The land elevation change corrected tide gauges do reconcile to satellite altimetry to within the error of estimate. Which is large in context of this discussion. To the extent that NOAA can be trusted ( which is not very much on temperature records) they have all this out there in the public domain. Just takes effort to find, which I expended writing Pseudo Precision.
Curt: And this article shows how well instrumentation currently works.
http://notrickszone.com/#sthash.Oz2WUoBn.dpbs
Even JPL, who built the satellites, knows they are showing spurious SLR acceleration. Reported right here Oct. 2012. http://wattsupwiththat.com/2012/10/30/finally-jpl-intends-to-get-a-grasp-on-accurate-sea-level-and-ice-measurements/
“but obviously one of the two data sets (or possibly both) is not representative of reality,” –JPL
Is it obvious? The tide gauges and the satellites are not measuring the same thing. As I’ve said elsewhere, the missing factor is vertical crustal displacement. Be very careful before trying to “correct” data that is “obviously” wrong. It may be that one of your underlying presumptions is what is actually in error. The discrepancy between the tide and satellite data is very intriguing and may ultimately turn out to be highly consequential for geology as well as climatology — unfortunately, for the time being I think the significance has been missed due to the uncritical acceptance of the satellite data as superseding, rather than contrasting with, the tide gauge readings.
Scientific Speculation
Note that the revised long-term estimate of sea level rise estimated from a selected set of tide gauge stations, while lower than the IPCC approved estimates, is within the range of previously published estimates. It also happens to be approximately half of the “official: rate when I first had to give expert evidence on sea level rise in 1984.
The recent “acceleration” is a consequence of a step change that occurs with the introduction of satellite altimetry data into the analysis be the use of reconstructed GMSL data. Without a reconciliation of the results produced by the different techniques the highlight interpretation is not reliable. The few published and unpublished attempts to better match satellite and tide gauge data produce a lower rate post 1993 than used by this paper.
It is also well known that there are decadal scale fluctuations in the rate of sea level rise (which vary between the different ocean basins), and that comparison of a short term trend (60 years) is misleading. Particularly at present with good evidence that both satellite and tide gauge rates of sea level rise are decreasing.
My personal view is that a heavily smoothed global sea level record doesn’t tell us much of practical value for coastal management issues
Well how could those young scientists have ever hope to get a tenure track appointment if they tried to publish a study that concluded SLR was effectively near zero and lost in the tidal data with their statistical methods? Seriously.
They could have published in the Journal of Null Results. And then gone looking for new employment at McDonald’s. Until the incentive system changes, we will continue to get these kinds of “new age science.”
sad but true
But, given their lack of ethics, could you trust them to serve food without doctoring it? Seeking tenure is no justification for being dishonest.
Harvard is the ne plus ultra training ground of upper level managers in the US Gov’t bureaucracy. Their efforts are directed at maintaining and increasing the power of the Federal Gov’t,, while buttressing their own personal wealth and power- nothing more and nothing less.
Just like any experiment that adds heat in we should add all the heat derived by burning fossil fuel to the supposed base temp and look at the result. We also might try to calculate cubic meters of water extracted from the ground and add it to a base sea level, ya probably not much but it could explain some of the possible rise.
TC in the OC
January 14, 2015 at 1:04 pm
The weld boathouse has been used by the Harvard crew since 1906. A question for all the Harvard and MIT grads…have the docks been raised to account for all the sea level rise in the last 118 years?
This is the test that even a simpleton like Frank can do. Allez-y Frank. We expect the answer tomorrow.
There is a damn and lock between the MIT boathouse on the Charles and the harbor – SLR wouldn’t effect the boathouse unless it got REALLY large.
The Charles has locks between itself and Boston Harbor to prevent flooding on spring tides. The 1912 lock was replaced in 1978, but not because of SLR. Rowed out of Weld, know these things.
Nice ‘own goal’, by a ‘simpleton’ who couldn’t be bothered to adequately research the subject!
How much ocean rise is due to silting and volcanos , man mad objects and structures and garbage in or floating on the oceans?
The big things are plate techtonics and isostatic rebound. U. Colorado models the so called GIA adjustment as +0.3mm/yr. So the oft talked about sayellite era 3.1mm/yr is really only 2.8+/- 0.4 from the perspecive of actual coastlines and tide guages. Details and references in essay Pseudo Precision.
Do the satellite altimeters also measure land level rise/fall? If not why not? I have seen measurements of change in glacial height, but rarely of land height itself. The global isostatic adjustment stuff seems to be more theoretical than empirical.
[The only claimed (widely publicized) isostatic adjustments to date have been under-ice land height adjustments needed to justify the final assumed glacier melt rates. .mod]
not much
When made aware of these latest revelations from “science”, Ms H Penny was observed to suddenly run down the street, crossing repeatedly back and forth across a busy road shouting ” THE SEA IS RISING, THE SEA IS RISING!”
To repeat someone (I forget who, but Josh drew a wonderful cartoon), from a couple of years or so ago – the water’s still only halfway up the duck!
I would think rising temps would increase rainfall from increased evaporation of the oceans and much of that would become groundwater never to be seen again. This would far outweigh the water from a few glaciers especially when they are good and gone. I for one am sick and tired of hearing about glaciers.
Bad news, we’re in an interglacial of our current ice age.
If glaciers go it’s likely no more ice age.
Last time that happened it got real hot.
Nice point, Jim (and I agree)!
Jim and Janice, you would enjoy essay Pseudo Precision. The groundwater thingy was used in three papers to explain the ‘SLR slowdown’ as not pause related. Doesn’t wash (pun intended). But reveals much about the increasingly desparate state of ‘climate science’ and pal review.
Jim’s groundwater hypothesis over the long haul, don’t know. This was very short haul stuff trying to explain a SLR slowdown that quite likely was just instrument error needing no ridiculous explanations in the first place. Hence the essay title.
Thank you, Rud Istvan — I think you are right — in this book, correct?http://www.amazon.com/Thermodynamics-Kinetics-Microphysics-Clouds-Khvorostyanov/dp/1107016037/ref=sr_1_2?s=books&ie=UTF8&qid=1421276034&sr=1-2&keywords=Judith+Curry
No, in my own newest book Blowing Smoke: essays on energy and climate. Foreward only is by Judith. You reference her new $90 textbook on the microphysics of clouds. WAY beyond my pay grade. My much simpler and illustrated for non-academic laypersons (like me) book is available iBooks, Amazon Kindle, BN Nook, KoBo… And is cheap -$9.99.
Regards.
I finally figured it out… http://wattsupwiththat.com/2015/01/14/claim-acceleration-in-sea-level-rise-worse-than-we-thought/#comment-1835805
(eye roll) — thanks for persevering.
If the sea level rise is approx. 3 mm a year, that means a little over an inch every nine years, or less than a foot in a century. What exactly is the big deal? Even if no more sediment comes down from Pennsylvania, I still won’t be able to take my boat across the Susquehanna Flats at low tide.
its not too well known but Colorado University states that their global mean sea level numbers (GMSL) are for purposes of measuring ocean volume and not relative sea levels at the coast…
“The global mean sea level (GMSL) we estimate is an average over the oceans (limited by the satellite inclination to ± 66 degrees latitude), and it cannot be used to predict relative sea level changes along the coasts”
“We apply a correction for GIA because we want our sea level time series to reflect purely oceanographic phenomena. In essence, we would like our GMSL time series to be a proxy for ocean water volume changes. This is what is needed for comparisons to global climate models, for example, and other oceanographic datasets.”
http://sealevel.colorado.edu/content/what-glacial-isostatic-adjustment-gia-and-why-do-you-correct-it
That lets them claim a bigger number due to basin expansion (ocean volume is increasing faster than sea level rise because of the basin increase).
Why anyone would care about ocean volume increase more than sea level rise is one of those questions that is discouraged.
The basin expansion is very questionable in any case. The GIA correction is based on the ICE-5G model which is known to be grossly inaccurate for the most important area, Antarctica.
Good point.
Shockingly, they didn’t actually measure the basin expansion. But they have a model! So never mind your tide gauge measurements.
Funny how she hastily mumbles something about tide gauges being along coastlines, then runs away….from the obvious fact that if sea level rise were to become a problem, it would be along those same coastlines…and that the tide gauges show no alarming rate. Funny, huh?
Hilarious — not!
(but, your witty writing about your good point made me chuckle)
So! Had any good arguments with AGWers down at the gym lately?
Go, (genuine) Meteorologist MacGuire!
I mean (oh BROTHER!)!! Mike BROMLEY (not Mike M.)! Stay safe, over there.
Yes, I will try to be more careful from now on.
I have searched specifically and methodically for an increase in the sea level rise rate in the last 20 years. I can’t find good evidence for it. Got kind of bored looking for it.
See “The Search For Acceleration”
https://climatesanity.wordpress.com/the-search-for-acceleration/
A piece in Nature concluded there was no detectable acceleration trend since 1930.
http://www.nature.com/ncomms/2014/140414/ncomms4635/full/ncomms4635.html
For the period 1930–2009, none of the 12 records has an acceleration significantly different from zero (except Brest), in general agreement with results from the controversial study of Houston and Dean21. The acceleration at Brest is different from Newlyn, despite their close proximity, and may appear significantly different from zero because of a data gap in the 1940s
There was nothing “controversial” about Houston and Dean, except that it offended the biases of a few alarmists. Objectively it was a rock solid study.
Nice. You quote one line from the Nature piece you link to, relevant to a specific technique only and against which they offer a strict caveat in the next paragrapah. In fact, their conclusion is precisely the opposite of what you claim:
“there is substantial evidence, in both GMSL data sets2, 24 and coastal averaged sea level time series (corrected for internal variability27), for the existence and significance of a sustained increase in the rate of sea level rise over the 20th century and early part of the 21st century. In addition, the magnitude of the acceleration currently being observed is consistent with the latest understanding of sea level budgets45 and since about 1990 cannot be explained solely as part of internal variability44.”
Harry — Of course they say that, they don’t want to be blacklisted. But no acceleration since 1930 is problematic for alarmists irrespective of any caveats.
The caveats are sort of pointless anyway, since even their analysis says statistically significant accelerations irrespective of chosen start dates won’t even be detectable until the 2020s.
Note the part of the summary you left off:
“The public and policy makers might prefer to see evidence of a significant acceleration in their local tide gauge records. However, our results clearly show that it could be several decades before the acceleration detection methods considered here reveal (in a statistically significant sense to 95% confidence) such a discernable acceleration in individual tide gauge records. This is due mainly to the considerable interannual to multidecadal variability evident in sea level at a local scale, and our inability to account fully for all of it at present. Our results imply that if/when the currently understood components of the variability in the records are removed, then accelerations significantly different from zero are likely to become detectable in individual tide gauge records later this decade or early next decade, using the methods considered here.”
So, in other words, we really have no idea whether GMSL is accelerating, and won’t for some time. But the current IPCC models can’t be ruled out (shockingly).
I wonder how this discussion would look if the whole “CO2 is pollution vs CO2 is not a big problem” unspoken agenda was gone.
Me too, but global warming has left the building and CO2 is up 10% over The Pause with no discernible radiative forcing, and we have daily infusions of crap science making it into the popular press so, I’m hypothesizing it is not about science, good or bad, at all. It is fodder and I’m pretty sure I don’t even have to bother testing that hypothesis – hey they don’t.
With much less grant money.
Yes, because without the implied link to “it is our fault because we emit so much CO2” it is doubtful things like this would garner much attention at all.
If you are not completely sick of this bogus SLR and feel the need to torture yourself further, you may read about it all over again here: (not recommending that, but rather a frosty beside the fire)
http://www.latimes.com/science/sciencenow/la-sci-sn-climate-sea-level-20150113-story.html
How much would the level increase be from JUST the depletion/use of the water stored in the various continental aquifers, e.g., the Ogallala Aquifer in the Western US and the Florida peninsula which have dropped hundreds of feet and tens of feet respectively?
Globally negligible. World is a big place. Land Aquifers hundreds of feet deep have little impact on oceans miles deep covering 79% of the planet.
97% of the world’s water is the oceans. 2% is icecaps and glaciers. Everything else, rivers, lakes, aquifers is 1% (well actually according to USGS just 0.9%). See my ebook Gaia’s Limits for explanations of the profound consequences, including specific discussion of the Ogallala and South Florida aquifers.
See essay Pseudo Precision in ebook Blowing Smoke for a debunking of the groundwater storage idea used by ‘climate scientists’ to explain the recent possible ‘SLR slowdown’.
Regards to someone who is thinking.
But surely the ground water goes right on top. Where it would be most obvious!!!***!!!
“”“We are looking at all the available sea-level records and trying to say that Greenland has been melting at this rate, the Arctic at this rate, the Antarctic at this rate, etc.” she continued. “We then sum these contributions and add in the rate that the oceans are changing due to thermal expansion to estimate a rate of global mean sea-level change.””
So we have no data on the thickness of any of the ice sheets before 1990 that is of much use. We have no empirical measurements of any rates of melt before 1990 so we take this almost complete lack of data and put it into a model and it does not come out to the same as the tide gauge data. We therefore throw up our arms in amazement and declare that the work of all previous scientists is completely wrong and we have to rush out and buy waders before 2150 or we will all get cold knees. Where do they get these twits from. Is there some kind of Harvard selection process that only scouts the local pig farms?
Nah, the pigs are smarter than that. Harvard must really have to work hard to find this “depth of dumbness”
Ouch. Oink.
Some of us survived the brainwashing. So are doubly dangerous.
Excess phlogiston spells global doom.
hehe
boston sea level has dropped in last 5 years