From the University of Southampton
What the past tells us about modern sea-level rise
Researchers from the University of Southampton and the Australian National University report that sea-level rise since the industrial revolution has been fast by natural standards and – at current rates – may reach 80cm above the modern level by 2100 and 2.5 metres by 2200.
The team used geological evidence of the past few million years to derive a background pattern of natural sea-level rise. This was compared with historical tide-gauge and satellite observations of sea-level change for the ‘global warming’ period, since the industrial revolution. The study, which was funded by the Natural Environment Research Council (iGlass consortium) and Australian Research Council (Laureate Fellowship), is published in the journal Scientific Reports.
Lead author Professor Eelco Rohling, from the Australian National University and formerly of the University of Southampton, says: “Our natural background pattern from geological evidence should not be confused with a model-based prediction. It instead uses data to illustrate how fast sea level might change if only normal, natural processes were at work. There is no speculation about any new mechanisms that might develop due to man-made global warming. Put simply, we consider purely what nature has done before, and therefore could do again.”
Co-author Dr Gavin Foster, a Reader in Ocean and Earth Science at the University of Southampton, who is based at the National Oceanography Centre, Southampton (NOCS), explains: “Geological data showed that sea level would likely rise by nine metres or more as the climate system adjusts to today’s greenhouse effect. But the timescale for this was unclear. So we studied past rates and timescales of sea-level rise, and used these to determine the natural background pattern.”
Co-author Dr Ivan Haigh, lecturer in coastal oceanography at the University of Southampton and also based at NOCS, adds: “Historical observations show a rising sea level from about 1800 as sea water warmed up and melt water from glaciers and ice fields flowed into the oceans. Around 2000, sea level was rising by about three mm per year. That may sound slow, but it produces a significant change over time.”
The natural background pattern allowed the team to see whether recent sea-level changes are exceptional or within the normal range, and whether they are faster, equal, or slower than natural changes.
Professor Rohling concludes: “For the first time, we can see that the modern sea-level rise is quite fast by natural standards. Based on our natural background pattern, only about half the observed sea-level rise would be expected.
“Although fast, the observed rise still is (just) within the ‘natural range’. While we are within this range, our current understanding of ice-mass loss is adequate. Continued monitoring of future sea-level rise will show if and when it goes outside the natural range. If that happens, then this means that our current understanding falls short, potentially with severe consequences.”
BS, it makes the GRASS GROW GREEN, BS (basic science), it makes the grass grow tall.
3mm per year… And the satellite accuracy is????
The above introduction is sung to Srgt. Musgrave’s dance (the Bridge on the River Kwai theme.)
After my Father taught me that, in certain “social circumstances” we could walk away from someone who had told us something, and he’d just whistle the tune.
are they removing the GIA ‘adjustment’ from the modern sea level rise?
Hmm, let’s take a look at state of the art equipment put on pacific islands around 18 years ago to measure sea level rise,
South Pacific sea levels Best records show little or no rise?! « JoNova
joannenova.com.au/2010/08/south-pacific-sea-levels-no-rise-since-1993/
18 Aug 2010 – The Seaframe stations are state of the art, and regularly checked to compensate for all these changes. The Seaframe equipment used to measure sea levels is carefully … yet at least in the South Pacific, it’s not clear that sea levels have risen. …. as an exceptionally low year for seal level on all these islands.
Around 2000, sea level was rising by about three mm per year. That may sound slow, but it produces a significant change over time.
Of course it does, but who says that this pace will stay that way over the next 300 years? Perhaps sea level rise also goes in 60 year cycles so a linear extrapolation may not be warranted.
Around the UK there are many settlements that in medieval times were on the coast, but are now many miles inland due to sea level reduction. This is not due to isostacy as in the South the land is sinking. Everything that goes around, comes around, and one day the sea will come to collect the debt owed.
And sea level in the Pacific apparently fell during the Little Ice Age. As we swing from a high level of solar magnetic activity to a low level of solar magnetic activity, extrapolating broken AGW models for 200 years leaves me unimpressed.
This is a curious conclusion, considering that Conrad (2013, Solid Earth Influences on Tides, GSA Bulletin) found that:
“On the shortest time scales (1–10 yr), elastic deformation [of the crust] causes the ground surface to uplift instantaneously near deglaciating areas while the sea surface depresses due to diminished gravitational attraction. This produces spatial variations in rates of relative sea-level change (measured relative to the ground surface), with amplitudes of several millimeters per year. These sea-level “fingerprints” are characteristic of (and may help identify) the deglaciation source, and they can have significant societal importance because they will control rates of coastal inundation in the coming century.”
In other words, crustal deformation exerts sea level controls on multiple, overlapping time scales ranging from years to billions of years. But, if you put on blinders, the ONLY causes of mm/yr variations in sea level just HAVE to be glacial meltwater and sea water expansion both caused solely by AGW.
Of course it does, but who says that this pace will stay that way over the next 300 years? Perhaps sea level rise also goes in 60 year cycles so a linear extrapolation may not be warranted.
Yes indeed. In fact one could look at the historical tide gauge data to see that this is precisely the case, and that SLR was as even more rapid than it is today during the first half of the 20th century in good alignment with the thermometric record of post-LIA warming. Gravitation-corrected SLR is currently lower than what the satellites appear to be reporting IIRC, at around 2mm/year, which is almost exactly the long term post-LIA average rate. There is no sign of “acceleration” due to supposed anthropogenic CO_2 effects.
What amuses me about all of these predictions is that they are all — without exception — predicated on some sort of ill-defined mean increase in GASTA predicted by the various GCMs and on a whole raft of assumptions about things like how rapidly Antarctica and the Greenland ice pack are supposed to melt. It’s sort of like “If GASTA increases by 5 C by 2100, and if that increase suffices to cause the melting of a kilometer or so of Antarctic ice pack, and if the ocean expands by thus and such amount due to the warming, then we’ll see X meters of SLR by 2100”. Frequently the claims are literally absurd — melting Antarctica on a timescale of decades shows some sort of serious problem understanding latent heat of fusion (which is huge), high albedo, six months of night and low high-tilt summertime insolation, and surface to volume ratios.
They also seem absolutely impervious to empirical data. “Boiling seas” Hansen was publicly making his wildly speculative 5 meter SLR by 2100 guess well over a decade ago (which is as irresponsible for a scientist to do as showing “fire” in a crowded theater because you have linearly extrapolated the temperature increase inside due to being recently filled with warm bodies to the ignition point of paper in 100 years). Here it is, 2013, one eight of the way through the interval from 2000 to 2100 and the total SLR of the last decade is (drum roll please) at MOST an inch. More likely 3/4 of an inch — a couple of lousy centimeters.
So we have Yet Another Paper — one that lacks even an effort to pretend to analyze the physics of icepack melting on high-latitude plateaus but instead equates things like melt rates in mid-interglacial transition to melting rates today — calling for as much as 80 cm by 2100 and lord knows what by 2200. Hey, I should be glad — at least it’s down from the meter previously being called for in papers of this type as people are beginning to twig to the fact that if we’re going to see SLR of this magnitude it has to start sometime and gee, it hasn’t started yet. Nor is it likely to be starting, as the planet has experienced no significant warming since the burst associated with the 1997/1998 Super ENSO even, and may even be quietly cooling a bit in spite of recent attempts to rewrite the temperature record yet again, this time at the very tail end of inconvenient stasis, so that one can compare infilled kumquats to multiply-adjusted modern era oranges to sparsely sampled, non-infilled thermometric apples in the more distant past (all to get an ANOMALY as we can’t for the life of us actually compute the global average surface temperature TODAY to within a degree K).
Some arithmetic: 80 cm by 2100 is roughly 0.9 cm a year or an inch every 2-3 years. It is over three times the greatest rate observed (on several occasions, not just in the recent past) in the entire reliable historic record (tide gauge data). Every year with only 2-3 mm of rise tacks on an extra 6-7 mm that have to be made up in the following years. Measuring SLR is actually enormously complex — simply determining the current “sea level” is highly nontrivial because it has to be extracted from sparse measurements on a fluid surface with both systematic (but imprecisely predictable) time variation and with an enormous amount of multiple-timescale fractal noise and then corrected for the motion of the Earth’s crust and slow variability in the near-surface gravitational field (both magnitude and direction). The sea level could be rising even if there is no contribution from melting icepack, or it could be rising far more slowly than one would expect from melting icepack because land uplift or subsidence could be cancelling the effect. We barely have the tools to start seriously examining the issue of SLR, and have a pitifully short data secant based on those tools, which are still in the process of showing mutual (e.g. gravitometric) inconsistencies in the whole system.
Why do referees permit the publication of doubly conditional speculation like this? At the moment, the GCMs are busy failing, although there is a widespread effort to pretend that this isn’t the case. Basing physics-free multiply-conditional papers asserting that we are going to have all sorts of SLR that is going to start any decade now because the GCMs say so is a waste of time unless and until the GCMs start exhibiting any predictive skill at all!
So far, they have no predictive skill at all. That doesn’t mean that they won’t in the future, but in the meantime, the paper above is like publishing a paper that says “If superluminal neutrinos are observed, maybe we can build time machines” without even including a single actual equation to explain why, but relying on the fact that in medieval times clocks often ran fast or slow by as much as an hour a day.
Sure, and if pigs had wings, then they could fly, and I’ve got a predictive model for evolution that states that if we continue to throw pigs out of helicopters and breed only the survivors, pigs will have wings in less than 100 years. Maybe I should go ahead and found a pig-hunting club that only shoots pigs on the wing. Yeah. Why not?
rgb
Sigh.
@Bloke: An excellent point, Sir! The land around the Solent has dropped about 20 feet since the pre-Roman settlement was occupied, but in the days of King John, the Wash was a tidal zone.
A link to the paper itself is needed.
The paper appears to be Rohling, E.J, Haigh, I.D., Foster, G.L., Roberts, A.P., and Grant, K.M., A geological perspective on potential future sea-level rise. Scientific Reports (12 December 2013 in press), see http://www.highstand.org/erohling/ejrhome.htm
Scientific Reports appears to be part of Nature Publishing Group.
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From the same author, E J Rohling:
Gavin Foster & Eelco Rohling
Proceedings of the National Academy of Sciences, 22 January 2013, Pages 1209-1214
Abstract:
On 103- to 106-year timescales, global sea level is determined largely by the volume of ice stored on land, which in turn largely reflects the thermal state of the Earth system. Here we use observations from five well-studied time slices covering the last 40 My to identify a well-defined and clearly sigmoidal relationship between atmospheric CO2 and sea level on geological (near-equilibrium) timescales. This strongly supports the dominant role of CO2 in determining Earth’s climate on these timescales and suggests that other variables that influence long-term global climate (e.g., topography, ocean circulation) play a secondary role. The relationship between CO2 and sea level we describe portrays the “likely” (68% probability) long-term sea-level response after Earth system adjustment over many centuries. Because it appears largely independent of other boundary condition changes, it also may provide useful long-range predictions of future sea level. For instance, with CO2 stabilized at 400-450 ppm (as required for the frequently quoted “acceptable warming” of 2 °C), or even at AD 2011 levels of 392 ppm, we infer a likely (68% confidence) long-term sea-level rise of more than 9 m above the present. Therefore, our results imply that to avoid significantly elevated sea level in the long term, atmospheric CO2 should be reduced to levels similar to those of preindustrial times. []
My comment : It looks like Eelco Rohling makes the simple error of coming into this subject with an unverified assumption, namely that the observed sea level rises were caused by CO2. We know that in fact a warming ocean releases CO2, so Rohling’s observed relationship between CO2 and sea level is likely to be caused by temperature. For Rohling’s observations to support the “ dominant role of CO2, the alternative explanation – that temperature is the driver – needs to be eliminated.
This latest paper places sea level rise “(just) within the ‘natural range’“. I wonder whether another simple error has been made, namely comparing high-resolution modern data with low-resolution geological data. Without a link to the paper I can’t tell.
rgbatduke says:
December 12, 2013 at 12:08 pm
“flying pigs….”
can I help out there during the flying pig season?? I don’t seem to be having too much luck with the pheasants here in Scotland at the moment, flying pigs sound more in my league.
Just more of the “sea level rise is accelerating” nonsense. If you look at the the record, sea level rise has a long term average of 3-4mm per year. So for the level to increase another 80cm by 2100 the average rate of increase would have to double or triple over the next 84 years. Then it would have to triple again to hit their 2.5 meter increase by 2200.
Complete and utter nonsense!
There is no such thing as “normal times.”
“The team used geological evidence of the past few million years to derive a background pattern of natural sea-level rise. This was compared with historical tide-gauge and satellite observations of sea-level change for the ‘global warming’ period, since the industrial revolution.”
Yet another example of someone tacking a modern instrumental record onto the end of a proxy dataset and pretending the result is meaningful.
Wow…you can smell the bias in his words. Sea level rise is within the natural range…but he had to insert a “just” in there to make it sound less “natural”. This directly contradicts his “quite fast by natural standards” statement too. Which is it? If the rise is within the natural range, it cannot also be “quite fast by natural standards”. He really really wants to say sea level is rising “too fast”, doesn’t he?
How the heck do you define normal and natural? Is it before, during or after the various ice ages we have had over the last million years ? How has the rate varied during those various periods ? Based on this summary, this does not make any sense at all.
rgbatduke;
so that one can compare infilled kumquats to multiply-adjusted modern era oranges to sparsely sampled, non-infilled thermometric apples in the more distant past (all to get an ANOMALY as we can’t for the life of us actually compute the global average surface temperature TODAY to within a degree K).
>>>>>>>>>>>>>>>>>>>>>
I have to learn to keep my coffee cup out of reach when reading your comments. The cost in coffee and ruined key boards is starting to mount. In this case, I had just done cleaning up from that quip when I encountered the flying pigs quip and had to start all over again.
Hat tip to RGB!
Magisterial.
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“Continued monitoring of future sea-level rise will show if and when it goes outside the natural range. If that happens, then this means that our current understanding falls short, potentially with severe consequences.”
The last two sentences from the abstract appear to translate as ‘Send more money’.
If you want flying pigs, head to Cincinnati, Oh. They’re all over the place in good’ol porkopolis.
rgbatduke says:
December 12, 2013 at 12:08 pm
I so look forward to reading your posts….
That’s one take on things. Here are some other take on things.
So what are we to conclude?
Yep. Another example of magnified significance. Take a small but fine tuned segment of data and scale it so all the wriggles show up than wave hands wildly at the obvious significance of the dangerous rise (or fall, or whatever you imagine the dangerous wriggles are telling you). I echo others here. Stop comparing find grained data with historical WAG data.
oops…fine grain. Not find grain.
They keep trying on willing the rate of sea level rise to accelerate. They keep trying on willing Antarctica to go into thermal, spiral meltdown. Here is their latest effort in Antarctica.
Yet Antarctica denies them to the East while extent stays stubbornly near record highs. Now here is a finding that has bearing on East Antarctica and sea levels for 2100.
OK…Who else has had it with being told that you can look at a bunch of rocks and measure isotopes and calculate that sea level or temperature or whatever changed 0.000003 between the years of 1,004, 209 BCE and 1,004, 003 BCE? It’s bad enough that people sell these rotten apples, let alone proceeding to authoritatively compare them to the oranges of actual measurements taken over the last 30 years.