Modeling sea level rise is an 'uneven' proposition

Nigel Harris says:
February 21, 2013 at 4:10 am
Gosh I really wish I was as bright as some of the other commenters here. Able, without even reading the paper, to dismiss this work as rubbish because of their superior intelligence and knowledge. Able, in a few seconds of thought, to cut through to the heart of the matter, spotting glaring errors that teams of so-called scientists, who have no doubt spent entire careers studying the subject-matter, have stupidly missed.
How such intellects are wasted carping on about AGW! Anthony, you need to organize some sort of program to harness these wonderful minds that you have gathered around you, and set them to work on some of the world’s real problems. We’d have fusion power cracked in a few weeks, I’m sure. Mars terraformed and colonized by 2015.

How is the IPCC’s temperature projections turning out? They spent their careers making their projections and they were WRONG.
Perhaps you can:

“organize some sort of program to harness these wonderful minds that you have gathered around you, and set them to work on some of the world’s real problems..”

like fuel poverty, homelessness, hunger, over-fishing, malaria, pollution, maternal health………………………. instead of focusing on gas phantoms of your own making.

A competition!
Opening sentences that make you stop reading.
“Sophisticated computer modelling…” is my early favourite.

That last line should read:
“Lana’i isn’t sinking fast enough to drown the beach rock yet”.

I like these scientist who use modells. Theiy always get the answers they want.

Co-author Jonathan Bamber, of Bristol University, says, “This is the first study to examine the regional pattern of sea level changes using sophisticated model predictions of the wastage of glaciers and ice sheets over the next century.”
Gotcha!!! Pocket OED, 1925: Sophisticated, to spoil the simplicity or purity or naturalness of, corrupt or adulterate or tamper with.
Seems familiar, when will they ever learn? 😉

If I’m not doing this simple math wrong, the gravitational force exerted by the Greenland ice on objects within a few thousand kilometres is basically the same order as that exerted by the moon. Somebody feel free to point out my error – not like I compute gravitational forces regularly or anything…
If this is correct:
Mass of greenland ice: 2.67 x 10^18 kg
Mass of moon: 7.35 x 10^22 kg
Distance earth to moon: 3.84 x 10^8 m.
given F = g x m1 x m2 / (r^2),
then for any unit mass m2, the force between the moon and m2 is:
(6.67 * 10 ^ – 11) * (7.35 * 10 ^ 22) * m2 / (3.84 * 10 ^ 8)^2 = 12.77m2 * 10 ^ -5 N.
where for Greenland ice, lets take an r of 5 x 10^3 km for the sake of argument:
(6.67 * 10 ^ – 11) * (2.67 * 10 ^ 18) * m2 / (5 * 10^6) = 3.56m2 * 10 ^ -5 N.
I wouldn’t-a-thunk-it, but that’s what the math looks like. Note that I’ve made no argument regarding what this does to sea level, was just trying to get a feel for the plausibility of scale of forces here.

What’s with the anthropomorphising of sea level? Fingerprint?
… sea-level variations (fingerprints) …
if ‘fingerprints’ means ‘variations’ what’s wrong with using ‘variations’ throughout the paper?
I suspect a pathetic attempt at ‘climate communication’.

You are aware that the sea isn’t really level? The deviations are small. but measurable and are, I’m assured, used in roughly mapping sea floor geography. Presumably, they have been confirmed by sonar. I read recently that seamounts only a km or so high can be identified and mapped using sea level variations. Static Variations in sea level due to sea bottom topography, wind patterns , rotation are NOT the same thing as sea level changes due to ice melt, runoff, glacial isostacy, tectonics. Sometimes folks have trouble keeping that straight.
Agreed. The deviations are small but measurable and nearly static as sea floor topography is a very, very slowly varying function. Nevertheless, the areas of the tectonic plates underlying the oceans and continents is very large, so even small changes as the plates move around can have significant effects on overall ocean level or its apparent depth relative to the local land surface.
I like the way you separate the “local” changes from global ones — overall SLR is driven by average temperature (thermal expansion), the melting of land based ice, and tectonics, where the latter is, I would guess, spectacularly difficult to accurately measure or estimate as it would require a detailed measurement of the precise location of the Earth’s crust in some absolute coordinate frame. We can probably manage that for the land surface at this point, but I’m infinitely dubious about our ability to do so for the ocean floor. Locally, water may pile up a bit more or less here or there as the decadal oscillations vary and oceanic currents wander around or local changes occur in topography that are somehow distinct from the more global tectonic changes, but they have very little global effect in SLR and are at most small perturbations of the globally varying level.
There is a large energy cost to making the ocean surface deviate too much from a coriolis-corrected gravitational equipotential. It’s an open system with heat inputs and outputs, so it can self-organize to sustain small deviations as water warms and expands in one place SO that it provides pressure gradients driving currents to someplace else, but most of that stuff is well-established and stationary too. Predicting changes from this stationary behavior is second or even third order stuff, and my gut says that the changes will be very, very small compared to those associated with direct thermal, melt, or tectonic/volumetric effects.
And I have a very hard time believing that we need to be terribly concerned about the gravitational field of the Greenland or Antarctica ice packs, given that it would take millennia to significantly alter the ice mass in either case even if it warmed significantly. We’re talking a lot of mass, all of it insulated by the mass on top of it. Also, there is that pernicious 1/r^2 in the law of gravitation.
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We know that the first order answer — the water spreads evenly– is wrong, but its better than #1 which is just ignorant. So the best we can do is REDUCE the wrongness of #2 by using the best science we have. Not perfect science. Not settled science. Just the best we have
Which is perfectly reasonable. Of course a true cynic would note that it really is equivalent to making a hypothesis like “A gamma ray burst hits the Earth” or “Supposed the supervolcano under Yellowstone suddenly became active” or “the Earth gets hit by a 10 km asteroid” — things that are pretty unlikely but possible, in any short term time frame. Fun to think about, in a slightly twisted sort of way, but completely irrelevant to the climate debate even though in all three cases they would have enormous climate consequences.
Except that the results aren’t going to be presented as being completely irrelevant, are they? Nobody will bother to tell people that it would take a few thousand — or even tens of thousands — of years to melt the ice in Greenland or Antarctica, and that over the same time frame other changes would occur that would very likely make the “predicted” changes disappear into the noise associated with more important local changes (that themselves have to be predicated into the model or the icecaps won’t melt in the first place). Chances are good that people will take these predictions seriously as the basis of claims that the ocean is going to rise a lot here instead of there, and money will be spent to ameliorate a prediction of damage made on the basis of a model that even the modellers knew wouldn’t actually occur in a time frame relevant to contemporary human endeavor.
Many places are starting to spend money — in many cases a rather lot of money — to proactively prevent damage from a hypothetical rise of sea level that models predict will be as large as a meter or more by 2100. In the meantime the actual data for SLR shows that SLR rates have held approximately steady at less than 10 inches per century over the entire interval over which they have been measured, some 140 years. In order to reach the goal of a meter plus by 2100, the rate of SLR would have to more than triple, sustained, for the next 87 years, to order of a centimeter a year (which still wouldn’t do it, but would get close). At a whole centimeter a year, one would have decades to deal with the consequences before it became a serious issue anywhere in the world, and we haven’t the slightest actual evidence that it will reach a centimeter a year ever.
So the reason WUWT readers are less inclined to play the “nifty what-if science” game is because they see past the nominal result to the political subtext and the way the science will be distorted by those seeking to profit from exaggerated or misused claims. This happens all the time, right? Superstorm Sandy is evidence of climate change! So is Katrina! So is the latest major weather event, no matter what it is!
SLR is the single most important aspect of catastrophic climate change predictions. There is likely to be almost no net damage at all from global warming, anthropogenic or otherwise, especially if it takes place at a decadal crawl as it has for most of the last several hundred decades. Yes, patterns of rainfall and drought might change, but they change all the time anyway (see “Great Dust Bowl” or look at the paleoclimate evidence of drought distributions over the Holocene) and it isn’t likely that the changes we see will be qualitatitively or quantitatively particularly different than what we get naturally all the time. An argument can be made than on average the world would benefit from being warmer — it certainly has in all of the warm periods in the historical record.
No, the real argument for catastrophe is all SLR. If the ocean rises a meter or more in a century, it will flood a fairly predictable amount of shoreline and displace coastal or island residents. This has a computable, predictable cost, and that cost is very high because people like to live along ocean shores because of the climate and economic advantages to be found there. Take away SLR, and the “catastrophic” prediction devolves to egregious assertions of massive droughts or catastrophic superstorms, both of which are easily refuted by the actual data if one can just shut up the people that are openly lying about it in the political media.
Which is fine, but it makes SLR a politically crucial issue, because there is no cause for alarm in any possible mix of the gauge level or satellite derived SLR measurements! It isn’t that the ocean is doing alarming things, it is that we predict that eventually it will do alarming things. Maybe. If all the hypotheses and what-ifs that go into the models are right. If the water that melts in greenland or antarctica actually makes it to the ocean instead of just re-freezing (an instructive exercise is to compute the heat needed to melt all that water) and guestimate the time frame required for it to melt given surface to volume, albedo, and variation of surface forcing).
So when an article appears predicting the outcome of something that will almost certainly never happen, something that if it started to happen today might actually complete by the year 7500 CE, one does indeed have to be a bit cynical about whether or not it won’t appear in a lead article in some newspaper that is interpreted in just the right way to panic the residents of Patagonia or some island in the South Pacific into thinking that they mean that all of this is going to happen in the next thirty or forty years as that meter and a half SLR finally starts to happen.
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