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.
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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.
How does this qualify as science? They looked at past history and saw when co2 levels were higher and note that sea levels were higher? Isn’t that something I could do on Google with a search in 1 minute? This is good enough to get in the prestigious science mag? I think the standards for science publication have dropped so low it’s ridiculous. An article was recently published on phys.org that showed biology students were as likely as non-biology majors in choosing false biology statements. The biology students had more reasons why the false statement was true!!
The article points out as I’ve seen that many students of science cannot distinguish what is known and what they think is true. The fact has been shown throughout history that what seems logical and conforms to internally generated common sense doesn’t mean it is factual. This is a crucial skill for a scientist. It is sorely lacking from practically every climate science article I read. There are exceptions but so much is just worthless. Are our science institutions turning into stupid farms?
Certain areas of seem ripe with hopeless poverty of understanding what science really is. Nutrition, biology, environmentalism, climate. In these areas the merest association implies causality. Leveraging unproven assumptions to deduce further unproven conclusions. Science being turned into a popularity contest. It sounds like the Middle Ages returning.
“There is something fascinating about science. One gets such wholesale returns of conjecture out of such trifling investment of facts.”
Mark Twain
So, where are the facts?
Reply to
Just an engineer
July 10, 2015 at 7:31 am
So, where are the facts?
—————————————————-
CO2 is a gas
Climate changes
The poles are colder than the tropics
Ice melts
Water freezes
How many relevant facts do you want? I’m certain I could find some more.
Especially if the data is outrageously so cherry picked.
Anyone familiar with the geologic record knows that the granularity is about. 10K years at the best, so it’s hard to take claims about. 2 degree increases and a 20 ft sea level rise within this century very seriously.
Perhaps a bit oversimplified. Temporal resolution depends on what you are looking at. For ice cores, tree rings and varved clays it can be one year. For really old stuff it can be millions of years. But in general your point is correct. With rare exceptions paleo data on most everything is pretty awful.
Al Gore: 20 ft, 20 centimeters, at this point, what difference does it make?
Al Gore: Look, I have a minimal carbon footprint. My jet travel uses Xena gas (the female version is more powerful than the male xenon version).
Leonardo DiCaprio: Those press stories about me staying in Brazil for the 2014 World Cup aboard a mega motor yacht were false. The alleged photos were photoshop frauds. I actually sailed from Malibu to Brazil, in a 90-foot 19th-century frigate, burning no fuel whatsoever.
Naome Oreskes: I didn’t lie in my Facebook posts I wasn’t lying about skiing in Utah. But,from San Diego, I bummed rides on hang gliders launching from Torrey Pines. In Boston, I x-country skied up to Cansda, and caught dogsled rides to the rockies, then x-country skied down to Deer Valley. I don’t use fossil fuel. It is evil.
Christiana Figueres: Fossil fuel burning must be shut down. I windsurf across the Atlantic and and Pacific.
Barry O: You think AF1 is burning fossil fuel? Think again. DARPA has given me technology that flies me, and my family on solar winds. The White House? We use no heating or A/C. My carbon footprint is smaller than Al Gore’s.
Upcoming Paris COP21 attendees: Some of us are swimming across the Atlantic, Med and Pacific. Others are using sailboards. We learned a lesson from John Kerry, a master windsurfer who sailboarded from D. C. to Geneva to convince the Iranians to not develop nukes. But nobody is flying on a fossil-fuel/ CO2-spewing jet. And we are not riding in cars–especially limos–to the convention from our tent city. We are all riding bikes.
97% of climate scientists who constituted John Cook’s papers-review who were contacted subsequently stated, in response to his personal inquiry: i used to fly indiscriminately, but I never fly anywhere, anymore. I don’t drive a fossil-fuel-burning car. I only walk, bike and drive a solar-cell-covered car. That’s how much I believe that anthropogenic global warming will destroy the world. ( I just don’t get it why Cook didn’t publish this poll. He has the data.)
These and other anti-fossil-fuel voices all have decided not to burn fossil fuels to travel, or heat or cool their abodes. This is a FACT. The Science is In, the Debate is Over.
There’s time for another hundred or so alarming papers before the Paris do. Remember Cook sorted through 12,000 peer reviewed climate papers published in one decade for his study!!! This is 5.5 papers per work day!! Amazing output in a science in which no one knows much for sure. How many papers on general relativity and quantum mechanics were written in any decade you would like to choose? Where are all these 2-300,000 climate scientists going to find work when the market closes. With only one simple equation that no one is permitted to change or replace, what in the dickens can you say in 12,000 papers. That is a bigger mystery to me than the details of climate.
“What the “other” orientation was I can’t recall.”. Transgender?
Re Dickens
They were the best of times, they were the worst of times.
It is far far better thing I do than I have ever done.
I think Paris (the city not the man) comes in there somewhere.
The sea level about 40-60k years ago was about 100 metres lower than today – how does that information squeeze in between the blue bars of the graph in the summary above? What was the CO2 level then?
A number of commenters noticed the level from 25,000 yrs ago was missing. Here’s the revised version.
“to temperatures that we are on path to reach within decades”
The current trend will take us, within decades, exactly nowhere different than where we are now. Temperature-wise, that is.
As for sea level, even during the fastest pulse of the Holocene ice melting, sea levels rose about 2 meters per hundred years.
If we somehow matched the rate of rise of meltwater pulse 1A, it would take three hundred years for seas to rise twenty feet.
But getting back to this “path” we are on, how is it that people can write articles that seem to assume that the CGMs are somehow reality, but the actual temperature trends are not?
How did this paper get past peer review? Every good warmist knows that the temperatures of today are unprecedented. So how could they possibly show us what sea levels were when temperatures were as warm or warmer than today? /sarc
Easy. It`s Science and the editor is…..?
Could not be bothered to read that verbiage to the end.
On a more serious note I remember being told by an old teacher (R.I.P.) that our moon moves away from us by about 1.5 inches per year.
That means she has departed by 9.125 feet since I was born.
Now given the lunar effect on tides/sea levels, to whome should I apply to for a space at the Global Warming grant trough to carry out a “pier” reviewed study into the consequences of same.
No doubt there is at least one gifted commentator among Anthony’s Army on here who can give me guidance.
waterside4 July 10, 2015 at 1:42 am
May I please be the first pier reviewer? I just bought a nice mid-weight rig (9′ medium action paired with a Garcia Ambassadeur 5000 Special Edition. Holds a ton of 20# test and casts a mile) and I’m willing to personally go to all the piers where you collected data and conduct a thorough pier review. Of course you’ll have to throw in a little request for funds in that grant to cover my portion of the research expenses; travel, food, lodging, and bait.
Thanks in advance.
HR
“Of course you’ll have to throw in a little request for funds in that grant to cover my portion of the research expenses; travel, food, lodging, beer and bait.”
Better?
Auto
It is interesting to note those little maps in the figures. It seems that they count on about 1/3 of the Greenland Ice-Sheet melting in the Eemian. That is equivalent to about 2 meters sea-level rise. And even that is stretching things. Every deep ice-drilling project on the Greenland ice-cap, including Dye 3 in the south, has found Eemian ice, so the ice cap obviously didn’t shrink drastically. Even the small isolated Renland Icecap on the East Coast has Eemian ice in it.
A complete collapse of the West Antarctic icesheet (WAIS) would only add about 3 meters more to sea-level. This is a much smaller figure than those usually bandied about (like 7 meters), but since most of the WAIS is below sea-level much of the meltwater is “used up” filling out the new ocean, particularly since sea-water is about 10% denser than glacier ice. Also much of the WAIS is on land, or is otherwise dynamically unable to collapse. And indeed ice older than the Eemian is known to be present in highland areas in West Antarctica.
Even factoring in thermosteric expansion 6 meters sea-level rise in the Eemian is barely feasible, and indeed a simple world-wide averaging of Eemian sea-level markers gives something like 4-5 meters. However all estimates based on preserved Eemian sea level markers will be biased upwards, since coastlines below present sea level are very difficult to find, and evidence for coast-lines close to present sea-level have usually been removed or overprinted by Holocene seas.
Incidentally world-wide Eemian seal levels vary from 990 meters above present sea-level (New Zealand) to 360 meter below (Northern Italy).
Personally I put most trust in evidence from Southern Australia (Gawler Craton) which is tectonically very stable and has a unique horizontal Eemian coastline stretching for 500 km. No such large area has ever been known to have moved as a rigid block anywhere in the World, so it has probably not moved vertically since the Eemian. The Eemian sea-level there was about 2 meters higher than at present.
However it is meaningless to put a single figure to “sea level rise” in the Eemian. The geoid has changed. The Ice-age before the Eemian was very different from the last, The ice-sheets were much larger for one thing, and there was no “Younger Dryas” pause in deglaciation, so isostasy was very different, with effects up to several thousand kilometers from former ice-sheets. The remaining ice-sheets were different with consequently differing self-gravity effects. The coasts have either sunk or risen tectonically practically everywhere. Weather patterns (average winds, barometric pressure and ocean currents) were different in a warmer, wetter world with significantly different geography. This means that if we could reconstruct “true” Eemian sea-levels exactly (which we can’t, and never will, short of a time machine) they would still differ by several meters in different parts of the World
South Australia data shows stage 11 sea level is about 0! This is based on geological evidence, of which the writers seem to know very little.
last time i checked, Greenland was roughly 7 times smaller than Antarctica, and had at least 10 times less ice. Why they are represented at same size, you can imagine.
And even the warmistas’ colonized wikipedia states that “during the last interglacial period, 130,000–116,000 years ago, when local temperatures were on average 5 °C (9 °F) higher than now, the glaciers on Greenland did not completely melt away.[66]”
I wonder how half as much is a rise in T is supposed to accomplish more a melting …
The Pliocene sea level estimate is strictly a cherry-pick.
Between 3.25 Mya and 2.7 Mya (when the ice ages started), sea level was as high as 20 metres above today as a low as -50 metres below today, the average was -12 metres below today’s sea level.
Furthermore, the CO2 levels are a cherry-pick. Between 3.25 Mya and 2.7 Mya, CO2 was as low as 208 ppm and as high as 452 ppm, the average was 317 ppm.
The root of their problem is their adherence to the enviro-religious belief in a “pre-industrial equilibrium” of climate. The climate always changing so any one point in time is just an isolated sample of the state of a complex system. It says nothing about other samples in and of itself. Only a true understanding of the whole system could help but we all know that is neither available today nor desired by the CAGW crowd. A real climate scientist would have to admit that ther is no such thing as equilibrium.
So my layman’s take-away from this article: it was warmer in the past (before fossil fuel use), there was as much or more CO2 in the atmosphere as there is now, and those two situations did not necessarily occur at the same time. Oh, and ice melted and we don’t know why.
Did I get this right?
cartoon like graphic seems , easy on the eye for those that suffer eye strain when they have to think about what they are seeing.
The quality of the science appears inversely proportional to the number of co-authors.
Spot on. All are warmists anyway.
I totally have the easiest, low cost solution for rising sea levels. Death Valley in eastern California is as much as 282 feet below sea level and has an area of about 3,000 square miles. All that is required is a suitable sized pipeline from the nearby Pacific ocean, running over the mountains and terminating so it drains into the deepest point in Death Valley. Once a pumping system is put in place and the sea water begins to flow downhill, gravity will take over and a constant flow of water will be established, lowerin he ocean level slowly, and gradually filling the Death Valley basin. The new inland lake would be non-tidal, so the salt would settle out, providing a potential huge fresh water supply for California, and the cooler lake surface would have an effect on the regional temperature, reversing global warming. For the first time, humans could test the effect by adjusting and regulating the flow into the new lake, increasing its size to cool things, decreasing it if things get too cool. Once the lake reaches an adequate volume, fresh water could be pumped into the California aquifer, possibly via the Colorado river, to support irrigation and consumer needs for millenia.
A quick back of the envelope calculation with the following assumptions: average depth of 140 feet, 3000 square miles would yeild roughly 79.5 cubic miles of water capacity. One could further assume that some amount would soak into the ground (and into the aquifer) thus allowing extra/future means of reducing GMSL. I don’t have the figures at hand but that still probably won’t have much impact on sea level. Maybe someone can run the numbers if they have the info needed.
Ken L, SHHHHH, not so loud! If California politicians get wind of this idea they will push for a federal tax to support subsidies to their friends to construct the pipeline. Then, when they discover syphoning can only be done over a hump of about 3 meters, there will be a tax to build wind mills and solar arrays (also via subsidies to their friends) to power pumps to move the sea water. Then, when they discover “green” power is too unreliable, there will be a plan to use hydro turbines in the downhill leg to power the uphill pumps. Then when that is discovered to be unfeasible, there will be a surcharge on electricity consumers to pay for the pumping.
Once seawater starts to flow into Death Valley, the anticipation of a new source of fresh water will be used as reason to dump all the water impounded in Northern California into the Sacramento river to save introduced fish. When it is discovered that salt will not settle out of seawater when there is no tide (Note Mediterranean Sea has no tide), what will come next? Will desalination plants be built just to make a fresh water lake out of the new salt lake?
SR
Time to get my micrometer out and head down to the beach.
Always knew that those old feeler gauges that we used to used to adjust valve clearances and spark plugs would come in useful some day.
Fascinating how whatever is stuidied, even over millions of years, it always comes down to CO2 and the necessity for wrecking the developed world’s economies lest we have disaster a decade or two out. It’s almost like you have to say stuff like that to get published nowadays.
Absolutely sight. Same too with any chance of getting a research grant – however daft the proposal, and there have a few!
“When past temperatures were similar to or slightly higher than the present global average…”
So they’re admitting today’s meaningless global average isn’t unprecedented after all, when compared to past, estimated meaningless global averages.
I think the whole charade is meaningless.