Discussion > A Debating Motion- Sea level rise is a threat.
What is the annual sea level rise due to land erosion?
Radical Rodent posed this question and SandyS found the relevant data.
I would say that we have not found a reliable figure for how much mineral matter moves from land to sea each year. The 75 billion tons figure apparently comes from a single review article. In the absence of more definite information, I would characterise this figure as "somebody's guess". (My intuition suggests that the estimate will be biased in the direction of being greater than the reality.)
It is not stated what proportion of the supposed 75 G tons finishes in the sea and how much finishes elsewhere on the land
"Each year, about 75 billion tons of soil is eroded from the land—a rate that is about 13-40 times as fast as the natural rate of erosion."[62][62] Zuazo, Victor H.D. & Pleguezuelo, Carmen R.R. (2009). "Soil-erosion and runoff prevention by plant covers: a review". In Lichtfouse, Eric et al. Sustainable agriculture. Springer. p. 785. ISBN 978-90-481-2665-1.
http://en.wikipedia.org/wiki/Erosion
I have sent a question to the National Oceanography Centre via their website: Hello, I want to find an authoritative estimate of the mass of mineral matter that moves from land into the ocean annually. Please tell me who I should contact for this information. Thank you. Martin A
Taking the 75 billion tons (=76.20 billion tonnes) and SandyS's 90% guess gives 68.6 billion tonnes. Using the guess of 2 g/cm³ density gives 3.43 × 10^10 m³ volume.
The surface area of the oceans has been given as 361,900,000 km sq = 3.6×10^14 m²
http://www.ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html
Dividing the volume increment by the area to get the depth increment gives nearly 0.1mm as the annual rise in sea level resulting from land erosion.
What is the accuracy of this figure? I would say "the true figure is probably less than 1mm and is probably greater than 0.001 mm" in view of the following three things being guesses:
- The annual tonnage of land erosion (I assume it is a guess, lacking information otherwise)
- The average density of the lost material
- The proportion of this that ends up in the sea (my intuition says that this is the guess with the greatest uncertainty)
Martin A
Martin A
I agree with your assessment of that data. I'm not sure how they came to the conclusion as I didn't read the paper. When people ask questions like the one Radical Rodent did and you repeated I've often seen something relevant when checking other stuff out perhaps months before. I like to know what's been checked and how it works, when I read claims in the press.
The immediate follow up questions were triggered is the amount of land area growing or shrinking (volcanic creation of islands I can recall 3 in my lifetime, and probably a few which haven't been detected as they seem to surprise everyone when popping out of the sea.)? Does coastal erosion increase apparent sea-level on the remaining land, in the same way we're discussing? Have growing river deltas been taken into account? Has anyone taken volcanic dust into account? What about isostatic rebound? Finally converting hydro-carbons into energy not only creates CO2 but H2O as well, that will have had a miniscule but increasing effect on the whole thing.
All of these can be discounted in isolation as being only 0.1mm, but what is the total and how is it changing.
I do not know the answer to any of these questions, I'd be willing to bet none of the sea-level catastrophists do either, far less rates of acceleration, as we know everything is getting worse thanks to man.
SandyS
A lot of things in climate/earth science are hard to track down to their original source. Sometimes it seems that things are regarded as established facts which are little more than somebody's guess, passed via a chain which is hard to retrace.
The "75 billion tons" is attributed in the Wikipedia article to the reference I quoted above. It is available
here.
It attributes the 75 billion to Pimentel D., Kounang N. (1998) Ecology and soil erosion in
ecosystems. Ecosystems 1.416-426
A later paper by one of these authors (Pimentel) attributes the 75 billion to:
Myers, N.: 1993, Gaia: An Atlas of Planet Management, Garden City, NY, Anchor/Doubleday.
I'd surmise that that was the origin of the 75 billion estimate and that, for the last twenty-one years, it has been treated pretty much as an established fact. Maybe it's just me, but the last reference does not really have the air of being a report on an authoritative study.
The references focus on the loss of agricultural land due to erosion, rather than the mass arriving in the sea.
Martin A
Just an aside but its interesting to note that James Hutton, regarded as the father of geology, began his career by considering the same question about erosion.
But he was (among other things) a farmer and his interest was more than purely academic...he could see literally his lands and livelihood disappearing down the river!
Latimer Alder
What nobody has noticed is the fault in my post containing the question of silt on sea-levels. I noticed it soon after posting, and am surprised no-one else has… call yourself observant scientists (or, at least, scientifically-thinking)?!
The majority of the coral islands, such as Tuvalu, are actually growing (as I stated); however, they are not growing as Bangladesh is, by deposited silt washed down from higher ground, but by the entrapment of sand – water-ground coral. In other words, these islands (and other examples, no doubt) are actually removing mineral solids from the sea. This, obviously, could be considered some sort of balance for the land erosion (both wind and water).
Another point that SandyS has hit upon is submerged volcanic activity. SandyS mentioned volcanic islands rising out of the sea, but there is an awful lot of volcanic emission occurring deep, deep underwater that has no obvious visible sign – the famous “smoke-stacks” being excellent examples (as well as showing that marine life can quite happily live and thrive in extraordinarily acidic – truly, truly acidic, not just the Believers’ “terrifying acidification” of a pH fall from 8.5 to 8.1 – waters). The mid-Atlantic ridge is basically a several thousand-mile split in the Earth’s crust, constantly oozing magma into the ocean; surely, something like that, as well as the new, huge volcano that has been discovered in the Pacific, plus many, many others, will also be having some effect upon sea-levels; the sea-bed is yet another of the many non-constants Mother Earth keeps us entertained with. To just blame sea-level changes, whether positive or negative, on just ONE cause – CO2, of course – has to be either the height of naivety, or the depths of disingenuousness.
Radical Rodent
RR - where does the coral itself come from?
If you remove *dissolved* minerals from water, you generally make very little change to its volume.
Martin A
There are few coral atolls, and not much area overall. Their accumulation of sand doesn't amount to a drop in the ocean.
HaroldW
HaroldW - I think it *would* be 'just a drop in the ocean'.
But the point I was trying to make is that if the 'sand' is 'water-ground coral' then it will have originated primarily from dissolved carbonate. If this guess is correct, then the growth of coral islands will not result in the migration of sediment from below sea level to above sea level nor in a change in the volume of sea water.
Martin A
Dec 21, 2014 at 7:38 PM | Registered CommenterRadical Rodent
RR, Any sediment that is added to a basin will tend to flex the crust it is sitting upon. According to this page, you can form 2.5 times the water depth in a sedimentary basin, ie 6km of water could accumulate 15km of sediment.
http://www.earth.ox.ac.uk/~tony/watts/basins.htm
In fact, my final year geophysics undergraduate project was a very simple model to show the peripheral bulge that forms when loading a basin up with sediment. Think, of a ruler overhanging the edge of the desk and pushing the end down, the rise you see here is mirrored in the Geology we see.
Rob Burton
Did EM bail out? Does this mean that SkS don't have the means to rebut this display of out and out denialology?
diogenes
Even Lex Luther informed General Zod he had an affinity for beach front property and he wanted Australia.
So how much are premium luxury coastal / beach front properties these days.
The Property Sharks are circling looking to make a killing from scary Climate Change driving off the locals in land.
The government in the Maldives kicked out Mark Lynas before he had a chance to sell out the Maldives tourist industry to foreign corporations.
Now with two extra airports and their tourist economy is booming for somewhere that should have been under three foot water by now.Million US Dollars for a Timeshare Condo sounds more like a treat not a threat.
jamspid
Dec 23, 2014 at 10:24 AM | Unregistered CommenterRob Burton
Rob - if you dump solid material into a 'basin' and it flexes the crust (so that the basin becomes deeper) does the surrounding area get pushed up to compensate? Is the compensation 100%? (ie giving the same effect as if the sediment were spread uniformly over the sea bottom)
Martin A
Is the compensation 100%? (ie giving the same effect as if the sediment were spread uniformly over the sea bottom)
If you have ever walked on a bog covered with thick vegetation that's exactly what happens.
Breath of Fresh Air
Dec 27, 2014 at 3:15 PM | Martin A
Not sure what the overall effect is. The crust itself is being pushed down but it could easily pop up elsewhere. What effect does plates going into subduction zones have and new crust appearing at a ridge?
Rob Burton
Are we wandering a bit off-topic, here? That said, I think we are all agreed that the original motion is… well, just that – a motion. A motion left by the proposer, who seems to have abandoned the argument. Perhaps he has realised that it was a bit too vague a notion for a motion in debate, but can’t be bothered clearing up the mess he’s made. Am I mixing my metaphors a little too much?
As a summation of the debate, so far: the general agreement is that what sea-level rise there has been, and that is threatened to be, is not sufficient to cause any alarm to anyone; and, the factors involved in sea-level changes are many and varied, not just temperatures, but erosion and fluctuations in the sea-bed itself, by either plate tectonics, silting pressures or volcanic activity. To date, the only conclusion that could be reached is that sea-level rise is NOT a threat, and this idea is just another of the many red herrings being fired from a very fishy think-tank (wow! My metaphors are on fire – metaphorically-speaking, of course). Indeed, with the data we have, to announce it as a threat, where, at most, it could only ever be considered a mild concern in isolated areas, could be a good reason to be labelled an alarmist scare-monger, and to be suitably ostracised.
Radical Rodent
RR - a drop more vin rouge?
"Are we wandering a bit off-topic, here?" You yourself asked
Has anyone considered the possibility that erosion might also play some part in sea level rise? I have no idea how many millions (billions?) of tonnes of rock are being washed into the sea each year, but surely that has to have some displacement? (...)
Dec 17, 2014 at 9:46 PM Radical Rodent
It was a good question and several contributors together attempted to answer it. It seems that the contribution of erosion to sea level rise is minor but possibly not altogether negligible. The discussion is still chewing over the last bits of that question.
But the overall conclusion of the "debate" is that sea level rise does not merit a place even in EM's nightmares about what the future has in store.
Martin A
Hmmm. Good point. It was more of an aside, really; I hadn't expected the question to be followed quite so vigorously.
Radical Rodent
Martin A
"This is how the world ends, not with a bang but with a whimper."
Miami has started down the path I expect many other coastal cities to follow.
Entropic man
Latimer Alder
I wanted to see if there was a linear correalation between forcing due to CO2 and rate of sea level rise.
I got the sea level rise rate here .
I got CO2 concentration here .
Forcings in Watts/square metre were calculated as usual using 5.35ln(C/Co) . Since for the last few millennia the sea level has been roughly constant and the CO2 concentration 280ppm, for simplicity I took that as my zero forcing, zero sea level rise origin.
This is the data. Each row is listed in order; year, rate of sea level rise, forcing, CO2
1880, 0.5, 0 280
1890, 1.0, 0.18, 290
1900, 0.6, 0.37, 300
1910, 0.4, 0.4, 302
1920, 0.1, 0.44, 304
1930, 1.0, 0.48, 306
1940, 2.1, 0.54, 310
1950, 2.0, 0.60, 313
1960, 1.7, 0.68, 318
1970, 1.6, 0.80, 325
1980, 1.6, 0.91, 332
1990, 2.2, 1.19, 350
2000, 2.7, 1.49, 370
,2010, 3.2, 1.77, 390
I plotted forcing against rate of rise and got quite a good fit between expectation and observations, specially at the high end. For the expected values I drew a line from the highest forcing point back through the origin. Try your own plot.
I am not sure how to go from expected sea level rise rates to an expected graph of 20th century sea level. Perhaps you could have a go. If you have the software, it would also be interesting to get an R^2 between the observed rates and my calculated forcings.
Entropic man
EM - well I have always loved Miami South Beach and the Florida Keys, so I would be sad to see them disappear. But those lovely Art Deco hotels were built in the 30's and, eighty odd years later, are still well above sea level, so it looks as if they'll be around longer than you seem to think.
What Florida suffers from is not sea level rise but the occasional hurricane the worst of which was the 1935 hurricane that destroyed the railroad to Key West (and washed a passenger train off the line in the process). http://fox41blogs.typepad.com/.a/6a0148c78b79ee970c01a73e0ec591970d-pi
But if you believe this stuff you linked to:
(...)
The ocean around South Florida, which sits on porous limestone, is expected to rise nearly three feet in the next 86 years*, according to Florida State University research.
(...)To compound the problem: Hurricanes may gain strength, researchers predict, and strike more often as average annual temperatures in the southeast heat as much as nine degrees.
(...)
then, you'll (like the Pope) believe anything.
*3 feet in 86 years = one foot per thirty years = between ¼ inch and ½ inch per year.
Martin A
Yes, Martin A, I have seen many new buildings in Charleston SC where they are built on stilts in locations that are particularly vulnerable to hurricanes. (Houses containing wood are also already commonly built above ground on concrete pillars to minimise termite damage, so no sudden global-warming catastrophe to be found there either.) It's really not that difficult.
After the great fire of Seattle, originally built on tidal zones that flooded, the city was rebuilt about two stories higher. You can go on guided tours of the underground.
michael hart
EM,
there is no provenance for your rate of sea level rise data other than a plot at realclimate. One has to ask questions such as how is the tide gauge data differentiated to get the rise rate, how is the data smoothed (it's undoubtedly smoothed).
Not with standing these fundamental questions surely you can determine the R^2 value for your plot (0.74). More importantly it is only a trivial exercise to take your model and integrate it between now and 2100 to find the total sea level rise you would predict.
Paul Dennis
Entropic man -
Given the source of your data -- a graph of sea level rise rates & temperatures -- and the fact that temperatures can directly induce sea level rise whereas CO2 is only indirectly linked, it would have been more advisable to suggest a linear relationship between temperature (rather than pCO2) and sea level rise rates.
Secondly, you should revisit your digitization of the graph. Given that the lowest plottable value of sea level rise [on that graph] is 0.5 mm/yr, I question the lower values in your table. I've obtained good, if laborious, results by using Excel, creating a blank grid, making it transparent, and overlaying it on the pasted original graph, resizing it as necessary. A modern version of tracing paper, if you will.
But most importantly, what is the true source data for sea level rise? A graph from RealClimate is not raw data.* Moreover, it appears to conflicts with other sources such as Jevrejeva et al. and Church & White.
* It is obviously not *raw* data because both curves have been strongly smoothed (or low-pass-filtered). [And in fact, the high r^2 which is obtained owes a lot to using a smoothed series, which inherently increases the r^2, compared to raw data.]
HaroldW
Thought we had just covered the fact that there are many factors other than temperatures and CO2 that could be involved with sea-level rise change? Remember, correlation does not mean causation: apparently, the number of homosexuals in Birmingham directly correlates to the number of lamp-posts; now, does that mean that lamp-posts in Birmingham cause homosexuality, does it mean that homosexuals are drawn to the lamp-posts in Birmingham, or does it mean that the rising number of homosexuals in Birmingham are insisting on more lamp-posts?
Quite why you are fixated on the dangers of rising sea-levels is a puzzle to me, Entropic Mann. Surely, the snapping up of beach-front properties by the likes of Al Gore and other profiteers prophets of doom has to make you wonder at their motives for their pronouncements?
Radical Rodent
@entropic
Surely a hindcast is straightforward if a bit tedious. Your method indicates that sea level rise is a function in CO2 alone
Take the known values of CO2 (for example every 5 years). Use your method for each. Plot the graph of sealevel vs CO2 and show that it's quantitative predictions agree pretty well with known values from, eg Jevrejeva