When past temperatures were similar to or slightly higher than the present global average, sea levels rose at least 20 feet, suggesting a similar outcome could be in store if current climate trends continue.
Findings published in the journal Science showed that the seas rose in response to melting ice sheets in Greenland and Antarctica, said lead author Andrea Dutton, a University of Florida geochemist.
“This evidence leads us to conclude that the polar ice sheets are out of equilibrium with the present climate,” she said.
Dutton and an international team of scientists assessed evidence of higher sea levels during several periods to understand how polar ice sheets respond to warming. Combining computer models and observations from the geologic record, they found that during past periods with average temperatures 1 to 3 °C (1.8 to 5.4 °F) warmer than preindustrial levels, sea level peaked at least 20 feet higher than today.
“As the planet warms, the poles warm even faster, raising important questions about how ice sheets in Greenland and Antarctica will respond,” she said. “While this amount of sea-level rise will not happen overnight, it is sobering to realize how sensitive the polar ice sheets are to temperatures that we are on path to reach within decades.”
The researchers concluded that sea levels rose 20 to 30 feet higher than present about 125,000 years ago, when global average temperature was 1 °C higher than preindustrial levels (similar to today’s average). Sea level peaked somewhere between 20 and 40 feet above present during an earlier warm period about 400,000 years ago, when global average temperatures are less certain, but estimated to be about 1 to 2 °C warmer than the preindustrial average.
During those times, atmospheric carbon dioxide levels peaked around 280 parts per million, but today’s levels are around 400 ppm and rising. The team of researchers looked at the last time period when carbon dioxide was this high – about 3 million years ago – but couldn’t get a confident estimate on sea-level rise, in part due to land motion that has distorted the position of past shorelines.
The researchers also sought to understand how quickly sea level rose and which ice sheets may be most susceptible. They acknowledged that the rate of sea-level rise associated with polar ice sheet retreat is not well known, and that this is an important target for future research. Developing a better sense of which ice sheet sectors were most susceptible in the past, as well as how quickly this process occurs, could inform how policymakers plan for and mitigate sea-level change.
###
From the AAAS website:
Sea-level rise due to polar ice-sheet mass loss during past warm periods
A. Dutton1,*,A. E. Carlson2, A. J. Long3, G. A. Milne4, P. U. Clark2, R. DeConto5, B. P. Horton6,7, S. Rahmstorf8, M. E. Raymo9
BACKGROUND
Although thermal expansion of seawater and melting of mountain glaciers have dominated global mean sea level (GMSL) rise over the last century, mass loss from the Greenland and Antarctic ice sheets is expected to exceed other contributions to GMSL rise under future warming. To better constrain polar ice-sheet response to warmer temperatures, we draw on evidence from interglacial periods in the geologic record that experienced warmer polar temperatures and higher GMSLs than present. Coastal records of sea level from these previous warm periods demonstrate geographic variability because of the influence of several geophysical processes that operate across a range of magnitudes and time scales. Inferring GMSL and ice-volume changes from these reconstructions is nontrivial and generally requires the use of geophysical models.
ADVANCES
Interdisciplinary studies of geologic archives have ushered in a new era of deciphering magnitudes, rates, and sources of sea-level rise. Advances in our understanding of polar ice-sheet response to warmer climates have been made through an increase in the number and geographic distribution of sea-level reconstructions, better ice-sheet constraints, and the recognition that several geophysical processes cause spatially complex patterns in sea level. In particular, accounting for glacial isostatic processes helps to decipher spatial variability in coastal sea-level records and has reconciled a number of site-specific sea-level reconstructions for warm periods that have occurred within the past several hundred thousand years. This enables us to infer that during recent interglacial periods, small increases in global mean temperature and just a few degrees of polar warming relative to the preindustrial period resulted in ≥6 m of GMSL rise. Mantle-driven dynamic topography introduces large uncertainties on longer time scales, affecting reconstructions for time periods such as the Pliocene (~3 million years ago), when atmospheric CO2 was ~400 parts per million (ppm), similar to that of the present. Both modeling and field evidence suggest that polar ice sheets were smaller during this time period, but because dynamic topography can cause tens of meters of vertical displacement at Earth’s surface on million-year time scales and uncertainty in model predictions of this signal are large, it is currently not possible to make a precise estimate of peak GMSL during the Pliocene.
OUTLOOK
Our present climate is warming to a level associated with significant polar ice-sheet loss in the past, but a number of challenges remain to further constrain ice-sheet sensitivity to climate change using paleo–sea level records. Improving our understanding of rates of GMSL rise due to polar ice-mass loss is perhaps the most societally relevant information the paleorecord can provide, yet robust estimates of rates of GMSL rise associated with polar ice-sheet retreat and/or collapse remain a weakness in existing sea-level reconstructions. Improving existing magnitudes, rates, and sources of GMSL rise will require a better (global) distribution of sea-level reconstructions with high temporal resolution and precise elevations and should include sites close to present and former ice sheets. Translating such sea-level data into a robust GMSL signal demands integration with geophysical models, which in turn can be tested through improved spatial and temporal sampling of coastal records.
Further development is needed to refine estimates of past sea level from geochemical proxies. In particular, paired oxygen isotope and Mg/Ca data are currently unable to provide confident, quantitative estimates of peak sea level during these past warm periods. In some GMSL reconstructions, polar ice-sheet retreat is inferred from the total GMSL budget, but identifying the specific ice-sheet sources is currently hindered by limited field evidence at high latitudes. Given the paucity of such data, emerging geochemical and geophysical techniques show promise for identifying the sectors of the ice sheets that were most vulnerable to collapse in the past and perhaps will be again in the future.
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There is plenty of evidence a!round the UK that sea levels were higher in the MWP, a fact confirmed by H Lamb
(Where incidentally the land is sinking)
the UK land mass is tilting, Scotland is bouncing upward, while SE is sinking; most likely post-glacial rebound. All those SNP MPs will go back north when Houses of Parliament sink into the rising Thames.
People say that but the shoreline tells a different story. Many towns in the SE which were coastal ports 1,000 years ago are now miles inland.
High JohnB
and yet England was connected to continent by Doggerland. Isostatic rebound is not a linear affair, land crust goes up, overshoots, re-balances by going down, and up again, a bit like a weight suspended on a spring. Oscillations of various lengths, from ~ 40 to 60 years to centuries and millennia ((as found at the epicentre -Hudson Bay, R.W. Fairbridge ) are found. I suspect that the N. Atlantic quasi-periodic oscillations are directly linked to the isostatic rebound stretching from the North Canada to Scandinavia.
4-6000 years ago the oceans were a couple of meters deeper, the Gulf of Mexico shore was some 50 miles inland of today’s shoreline. The descending oceans as the Holocene cools could also explain JohnB’s query at 3:48 pm.
Huh?
Only ICPP AR5’s RCP 8.5 W/m^2 predicts multi-meter sea level rise – by the year 2500!!
By re-publishing this rubbish, we are feeding their trolls.
Is “ICPP” the name of the latest racy romantic novel written by the IPCC’s former head, Pachauri?
That or the latest must-have toilet training book for toddlers.
I’d better wear my lifejacket to bed tonight then.
I would. You never know, it might turn her on.
This sounds like Chaucer’s “The Miller’s Tale”. Going to sleep in a lifeboat didn’t work out well for the miller.
“Mae West”?
“Further development is needed to refine estimates of …..” etc – It’s worse than we thought they’re running out of grant money!!
I seem to observe the use of verbal hedges in this paper a little more frequently than one might normally find in association with the term “reasonable estimate.”
Sea level where I used to live in Southampton was rising by a foot per century or so – the title of the land we owned included part of the riverbed. 20ft is not a big deal – if it takes 20 centuries to rise.
http://wattsupwiththat.com/2015/04/25/raising-chicago-how-the-city-of-chicago-defeated-flooding-in-the-1850s/
Al Gore already has an exclusive license to run the Central Park (New York City) gondola concession, when Manhattan is underwater, and executives can only get to work in gondolas, like in Venice.
The poor folks will have to take rowboats and canoes to work.
The 400+ feet rise of sea level since the peak of the last ice age was caused entirely by coal-burning power plants and gasoline-burning SUVs spewing “carbon pollution” on those glaciers (Al Gore told me warming is ONLY caused by CO2. He also blamed the fact that the Arctic ice was not completely melted in 2014, as he had predicted ion 2007, was due to a “risky scheme” implemented by the Chinese in 2007 to spew soot into the air and block the sunlight, and they had been instigated by George W. Bush, who wanted to humiliate Gore a second time after stealing the election from him in 2000).
If you don’t believe me, you can look this up on the internet like I did.
+1
And we can verify every word as completely accurate . Google.
Good place to set up “Water bike” rental stands?
Our children won’t know what dry land is.
Hey Mike,
This is so serious that we need to do something really important like make a documentary about it.
Maybe we could get Kevin Costner to host it and to add some real drama we could get him to find a fast rising ocean and host from a boat as the waters rise in front of our eyes,
And Dennis Hopper and Jeanne Tripplehorn could co host and we gotta give the Doco a really good and scary name like ‘WaterWorld THE DELUGE AND THE DOOM’
And on the boat named Naomi Oreskes Kevin will have a computer and he will show by a comuter model irrefutable and rock solid evidence that all the puppies and ktities will die gruesome and horrible daths and we will then pan to a faster rising ocean littered with millions of their lifeless bodies but even worse the destroyed remains of all those beautiful and earth saving ocean based windmills.
Our three hero hosts will then do another computer model and it will provide, like all Klimate Studies, irrefutable and rock solid evidence that the Fossil fFel Industry, The Koch Boys and Cruella De Ville have joined their Evil Forces to further their evil upon the innocent and fragile WORLD.
Keep an eye out for a Crowd funded source I will soon set up to fund this crucial world saving and absolutely truthful documentary based on the best ever computer models.
Naturally if you decide NOT TO FUND this galaxy saving Doco i shall ,after winning Oscars and Cannes and Nobels and raking in squillions and becoming a good buddy of lennie and george and Michael Moore, I shall make another doco and I will call it… ‘ Dear Children of the World. Mike Smith and ALL WUWT bloggers hate the World and wanna see all The Puppies and Kitties Cark it in Horrible and Gruesome ways’
YOU WILL CONFORM AND BELIEVE!
Sorry, but you’re gonna have to CGI Dennis Hopper. And don’t forget allowing enuf time for Costner to regrow his gills.
Fast rising oceans? Don’t we usually call those tides?
Due to “Climate Activisim” our great-grandchildren won’t know what science is.
Looks like they are taking the long view. They cite two previous interglacials at 125,000 and 400,000 years ago. Then they look back 3 million years, which is 1 million years before the start of the current ice age. The climate back then was a whole different thing. Then they lament the difficulty of generating GMSL trends over the long term due to “dynamic topography”, read as “Continental Drift”.
It looks like what they are really after is a better sea level record going back to a point where continental drift makes things too hard to manage. All in all, it is probably worth a try.
According to the Vostock ice core measurements it was 4 C higher temperature 125 000 years ago than now. Not 0 C as this paper suggests.
Correct, but we should not let data confuse us.
Data doesn’t confuse us… it confused them !!
“According to the Vostock ice core measurements it was 4 C higher temperature 125 000 years ago than now. Not 0 C as this paper suggests”
===================================================
Yet CO2 was the same as now, therefore the ice core is wrong, and the IPCC computer model (“Combining computer models and observations from the geologic record”) tells us what the real T was 125000 years ago.
When observations conflict with computer models of CO2, then the CO2 model wins, just because CO2 always dominates.
What we know for a fact is that sea level is not static. And, over the last 12,000 years (since the last glaciation when global sea levels were 120 meters lower than today) the have risen an AVERAGE of 1 meter per century or so, and life survived and indeed thrived. So we should get used to the idea that sea level can change pretty dramatically over relatively short time frames.
WRT CO2 concentrations, global temps, and sea level I still question the cause/effect premise that CO2 is the driver. It seems far more plausible to me that temp is the driver (triggered by MANY factors of which CO2 is just a fraction I suspect), and that as the temp goes up some ice melts (duh), but more central to the CO2 debate so does some permafrost (which is a high carbon sink) and warming oceans outgas some of the CO2 in solution and collectively these drive up atmospheric concentrations to recorded levels. The oceans are BIG and the delta CO2 not so much in the grand scheme of things.
MHO anyway.
Fastest rate of change seems to be meltwater pulse 1A, during which seas rose 20 meters in a thousand years. This is six feet per hundred years. But it was caused by the (geologically speaking) most rapid phase of continental glacier disintegration.
At current trends, Greenland is not melting, it is growing…as is Antarctic ice. So fro whence will come this rapid rise in the seas?
Anyway, if it really started happening, this would be very easy to engineer a solution. Nuke plants at the Antarctic coast running pumps to the interior, where the temp is double digits below zero C even in summer.
Yesss! Beachfront property at last!
Wait till you see what the property taxes are going to be on your beachfront — then we will see if you celebrate. 🙂
Dude, don’t be such a buzzkill!
Quote: “The researchers concluded that sea levels rose 20 to 30 feet higher than present about 125,000 years ago, when global average temperature was 1 °C higher than preindustrial levels (similar to today’s average).”
Apart from the fact that the Eemian interglacial was very likely even some degrees warmer than today’s climate (and not only “similar to today’s average”), it’s truly hilarious to see how unapologetic they overlook their most beloved “Elephant in the room”: How on Earth could the Eemian interglacial be so warm with only 280 ppm CO2 in the atmosphere? If this trace gas is really the most powerful climate-driver as the warmists constantly preach ???
Shhhhh!
ah beat me to it, yes co2 was sooo low but the seas were so high. hmm?
I live near O’Hare airport, which NOAA lists as being 666 feet above sea level.
Why would I care if someone needed to spin the jacks twice a year, to lift their house the current (estimated) amount of millimeters needed to avoid inundation due to the rising sea levels ?
I live near O’Hare airport,
You’re right. You’ve got lots more to worry about.
NOAA is adjusting that 666 — maybe 555
According to IPPCC AR5 (the mainstream science) the West Antarctic Ice Sheet is expected to collapse sometime between 600 to over a 1000 years In the future.
If you go with the mainstream alarmists you don’t need to worry about sea level rise in this half of the millennium. It’s like ignoring the Black Death happening around you to focus on the Great War in your prophecies.
And that’s assuming the guesswork is right.
This is a somewhat interesting line of thought as a geologist. It prompted me to do a quick overlay of the Cenozoic temperature record from Hansen et al (2008) ; see link: http://wattsupwiththat.com/2011/12/29/unified-theory-of-climate/ ) with the Cenozoic sea level curve of Haq et al (1987) see link ; http://palaeo-electronica.org/1999_2/neptune/fig4_20.htm
There is a reasonable correlation, especially in the longer wavelengths but there is also substantial deviations, such as the Eocene thermal maximum which saw no response in sea level change (maybe all the ice was already gone ?) but also during late Eocene & Antarctic glaciation (jnc in sea level with drop in temps), late Miocene & Pliocene (major sea level changes with out major temp changes) and pretty much during all of Pliocene & Quaternary , the correlation seems to weak on the shorter transitions between glacial periods. This may be a function of scale of these plots though.
If someone has time, it would be really interesting to see zoom in on just the Quaternary & Pliocene temp & sea level curves & what the correlation looks like + what lag their may or may be in the system (sounds like a job for Willis :)) … and what that implies for current equilibrium or lack there of.
My general conclusion from this is there is a lot more going on with sea level than just ice melting, which as a geologist I already knew, but this exercise just confirmed it.
Jeff L
Radical as it may sound, I’d recommend reading the IPCC assessment reports, which address that very question. Caveat: I’ve only looked at the first three and only at the sea level chapter, not at the executive summary which I’ve been told is a political rather than scientific document. Anyway what I’ve read seems entirely reasonable. Let me take a shot at reproducing Table 11.10 from the third report.
I’ll blockquote it in the forlorn home that will discourage the internet from trashing it too badly:
I would say, overall that the ipcc tar authors agree with you — primary cause of current sea level rise is probably thermal expansion, not ice melt
How about Aral Sea being drained, and aquifers the world over being drawn down?
Menicholas July 9, 2015 at 10:25 pm
The IPCC reports mention both aquifer pumping and reservoir storage affects on sea level. I assume they are lumped under *Terrestrial Storage* in the IPCC tar
“… researchers concluded that sea levels rose 20 to 30 feet higher than present about 125,000 years ago, when global average temperature was 1 °C higher than preindustrial levels (similar to today’s average) …”.
======================================
“… we can already tell that Eemian climate was significantly warmer than the climate of the current Holocene interglacial – probably about 5°C warmer. As ice from the Eemian period (albeit disturbed) has been found at all drill sites, we also know that the Greenland ice sheet did not melt away entirely during the warmth of the Eemian. Close analysis of δ18O values in the Eemian ice does indeed suggest that the Eemian Greenland ice sheet was not dramatically smaller than today …”:
http://www.iceandclimate.nbi.ku.dk/research/climatechange/glacial_interglacial/eemian/
Where are the construction plans for Noah’s Ark when you need them?
Genesis 6:14-17 New International Version (NIV)
14 So make yourself an ark of cypress[a] wood; make rooms in it and coat it with pitch inside and out. 15 This is how you are to build it: The ark is to be three hundred cubits long, fifty cubits wide . . .
I have a hammer.
The plans for the ark were simple – when you need more wood, just gopher more.
when you need more wood, just gopher more.
Groan…! I hope you don’t do those ark puns in pairs.
;o)
Mate, down here, Sydney Harbour is rising at a break-neck 0.65mm per year.
Even with my gammy knee, I think I can out-pace that.
Lets see.. allow another 40 years, x 0.65mm = 2.6cm.
Yep, think I can mange it !
Strewth mate, not even the ferries at Circular Quay would notice that increase in sea level. As for the Circular Quay underground railway station, I feel that would be safe for many millennia.
This is just gibberish. Will they present the records to the ice sheets and command them to “not be so sensitive”? Besides every alarmist already knows it’s never been this warm “globally” yet!
Ha! Just when I think they can’t come forth with anymore horse pucky on this day, we get this! Our tax dollars being used to do a bang up job of Gubement work.
“Evidence from past suggests climate trends could yield 20-foot sea-level rise”
Similar evidence from the past, every bit as reliable, suggests that Unicorns will grow to be twice as large as today and that leprechauns will also double in size.
Besides, they may mate like polar bear and grizzly, creating leprechaunicorns, and disappear themselves. Horrible.
They just showed there’s no correlation between CO2 levels and temperature……
“They just showed there’s no correlation between CO2 levels and temperature……”
…as anybody with half a brain can see by looking at any time period longer than, say, 25 years or so…
Hmmm, just “Water is wet” science.
Anybody who has looked at sea levels knows that what they say is quite true, sea levels were also higher a few thousand years ago too during the optimum.
There is no doubt that sea levels are higher during warmer times, the only real question is “How fast will they rise?” 50 years and we have a problem, 1,000 years and don’t worry, predictions that far out will be wrong anyway.
Sorry, but the next 100 years will see a 20 cm rise like the last 100 years and the 100 years before that. Check back with me in a hundred years – oh wait…well maybe you could listen to Nobel Prize Winning Physicist Dr. Ivar Giaever on the subject: –
“For the last hundred years, the ocean has risen 20 cm — but for the previous hundred years the ocean also has risen 20 cm and for the last 300 years, the ocean has also risen 20 cm per 100 years. So there is no unusual rise in sea level….”
You’ve got your centimeters mixed up with your feet – oh just a minor mistake…
Well of course. When reality and the model differ, it’s always reality that’s wrong. It couldn’t be the model.
I have a question. Has the number of orchestrated, lying studies before Paris spiked this year, or has this been building over years?
Kinda a loaded question, almost like asking “Have you stopped beating your wife?”
No ?
No.
I like that answer, short and sweet.
Probably what I deserved.
““Have you stopped beating your wife?””
Hey, I can’t help it if she can’t play Scrabble !