From high and dry University of Arizona, home of the world famous parking lot USHCN weather station, we have word via Eurekalert that a simulation says it will be bad as “sea levels are expected to rise by up to three feet by the end of this century”.
They say we can now ignore thermal expansion of seawater due to rising temperatures because it “contributed only slightly to rising sea levels”. It may be too late already, gosh. At the present 3 mm per year rate measured by satellite, and with 89.5 years left, that works out to 89.5yrs x 3.1mm/yr = 277.5 mm which works out to 0.91 feet or 10.9 inches. UofA, and especially Jonathan Overpeck are going to have to kick it into high gear if they are going to make three feet by 2100.
Rising oceans — too late to turn the tide?
Melting ice sheets contributed much more to rising sea levels than thermal expansion of warming ocean waters during the Last Interglacial Period, a UA-led team of researchers has found.
Simulation of Rising Sea Levels
Thermal expansion of seawater contributed only slightly to rising sea levels compared to melting ice sheets during the Last Interglacial Period, a University of Arizona-led team of researchers has found.
The study combined paleoclimate records with computer simulations of atmosphere-ocean interactions and the team’s co-authored paper is accepted for publication in Geophysical Research Letters.
As the world’s climate becomes warmer due to increased greenhouse gases in the atmosphere, sea levels are expected to rise by up to three feet by the end of this century.
But the question remains: How much of that will be due to ice sheets melting as opposed to the oceans’ 332 million cubic miles of water increasing in volume as they warm up?
For the study, UA team members analyzed paleoceanic records of global distribution of sea surface temperatures of the warmest 5,000-year period during the Last Interglacial, a warm period that lasted from 130,000 to 120,000 years ago.
The researchers then compared the data to results of computer-based climate models simulating ocean temperatures during a 200-year snapshot as if taken 125,000 years ago and calculating the contributions from thermal expansion of sea water.
The team found that thermal expansion could have contributed no more than 40 centimeters – less than 1.5 feet – to the rising sea levels during that time, which exceeded today’s level up to eight meters or 26 feet.
At the same time, the paleoclimate data revealed average ocean temperatures that were only about 0.7 degrees Celsius, or 1.3 degrees Fahrenheit, above those of today.
“This means that even small amounts of warming may have committed us to more ice sheet melting than we previously thought. The temperature during that time of high sea levels wasn’t that much warmer than it is today,” said Nicholas McKay, a doctoral student at the UA’s department of geosciences and the paper’s lead author.
McKay pointed out that even if ocean levels rose to similar heights as during the Last Interglacial, they would do so at a rate of up to three feet per century.
“Even though the oceans are absorbing a good deal of the total global warming, the atmosphere is warming faster than the oceans,” McKay added. “Moreover, ocean warming is lagging behind the warming of the atmosphere. The melting of large polar ice sheets lags even farther behind.”
“As a result, even if we stopped greenhouse gas emissions right now, the Earth would keep warming, the oceans would keep warming, the ice sheets would keep shrinking, and sea levels would keep rising for a long time,” he explained.
They are absorbing most of that heat, but they lag behind. Especially the large ice sheets are not in equilibrium with global climate,” McKay added. ”
Jonathan Overpeck, co-director of the UA’s Institute of the Environment and a professor with joint appointments in the department of geosciences and atmospheric sciences, said: “This study marks the strongest case yet made that humans – by warming the atmosphere and oceans – are pushing the Earth’s climate toward the threshold where we will likely be committed to four to six or even more meters of sea level rise in coming centuries.”
Overpeck, who is McKay’s doctoral advisor and a co-author of the study, added: “Unless we dramatically curb global warming, we are in for centuries of sea level rise at a rate of up to three feet per century, with the bulk of the water coming from the melting of the great polar ice sheets – both the Greenland and Antarctic Ice Sheets.”
According to the authors, the new results imply that 4.1 to 5.8 meters, or 13.5 to 19 feet, of sea level rise during the Last Interglacial period was derived from the Antarctic Ice Sheet, “reemphasizing the concern that both the Antarctic and Greenland Ice Sheets may be more sensitive to warming temperatures than widely thought.”
“The central question we asked was, ‘What are the warmest 5,000 years we can find for all these records, and what was the corresponding sea level rise during that time?'” McKay said.
Evidence for elevated sea levels is scattered all around the globe, he added. On Barbados and the Bahamas, for example, notches cut by waves into the rock six or more meters above the present shoreline have been dated to being 125,000 years old.
“Based on previous studies, we know that the sea level during the Last Interglacial was up to 8.5 meters higher than today,” McKay explained.
“We already knew that the vast majority came from the melting of the large ice sheets in Greenland and Antarctica, but how much could the expansion of seawater have added to that?”
Given that sea surface temperatures were about 0.7 degrees warmer than today, the team calculated that even if the warmer temperatures reached all the way down to 2,000 meters depth – more than 6,500 feet, which is highly unlikely – expansion would have accounted for no more than 40 centimeters, less than a foot and a half.
“That means almost all of the substantial sea level rise in the Last Interglacial must have come from the large ice sheets, with only a small contribution from melted mountain glaciers and small ice caps,” McKay said.
According to co-author Bette Otto-Bliesner, senior scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., getting the same estimate of the role ocean expansion played on sea level rise increases confidence in the data and the climate models.
“The models allow us to attribute changes we observe in the paleoclimate record to the physical mechanisms that caused those changes,” Otto-Bliesner said. “This helps tremendously in being able to distinguish mere correlations from cause-and-effect relationships.”
The authors cautioned that past evidence is not a prediction of the future, mostly because global temperatures during the Last Interglacial were driven by changes in the Earth’s orbit around the sun. However, current global warming is driven by increasing greenhouse gas concentrations.
The seasonal differences between the northern and the southern hemispheres were more pronounced during the Last Interglacial than they will be in the future.
“We expect something quite different for the future because we’re not changing things seasonally, we’re warming the globe in all seasons,” McKay said.
“The question is, when we think about warming on a global scale and contemplate letting the climate system change to a new warmer state, what would we expect for the ice sheets and sea levels based on the paleoclimate record? The Last Interglacial is the most recent time when sea levels were much higher and it’s a time for which we have lots of data,” McKay added.
“The message is that the last time glaciers and ice sheets melted, sea levels rose by more than eight meters. Much of the world’s population lives relatively close to sea level. This is going to have huge impacts, especially on poor countries,” he added.
“If you live a meter above sea level, it’s irrelevant what causes the rise. Whether sea levels are rising for natural reasons or for anthropogenic reasons, you’re still going to be under water sooner or later.”
Reference:
McKay, N., J. T. Overpeck, and B. Otto-Bliesner (2011). The role of ocean thermal expansion in Last Interglacial sea level rise. Geophys. Res. Lett., doi:10.1029/2011GL048280, in press. A version of the accepted paper is available online at the Geophysical Research Letters site: http://www.agu.org/journals/gl/papersinpress.shtml
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Update: Leif Svalgaard has the full paper here. Thanks Leif.
Another issue is that if you look at the world’s sea level gauges, you can only get about 2.0 mm/year of sea level rise or less. The satellite measurements are “adjusted and calibrated to select tide gauges”.
Only a small minority of the gauges are over 3.0 mms/year – even the infamous Charleston North Carolina is essentially flat since 1990 despite the sinking coastline of about 1.0 mm/year (from glacial isostatic rebound).
http://tidesandcurrents.noaa.gov/sltrends/trends/8665530.png
http://tidesandcurrents.noaa.gov/sltrends/sltrends.html
Jack Green says:
July 19, 2011 at 11:43 am
… NASA’s research into Ceres and Vesta have shown that earths orbit changes are because of these two bodies and could explain Climate changes in the past.
http://hotair.com/archives/2011/07/18/video-nasa-dawn-reaches-vesta/
From your link:
… The new calculations show that Ceres and Vesta gravitationally interact with themselves and with the other planets of the solar system. Because of these interactions, they are continuously pulled or pushed slightly out of their initial orbit. The calculations show that, over time, these effects do not average out. Consequently, their orbits are chaotic, meaning that we cannot predict their positions over long periods.
Hot Air indeed! I don’t believe NASA would write such simplistic nonsense.
The ephemerides constructed for the Dawn project used the measured masses of 24 asteroids and modeled the masses of 276 others as well as the highly accurate known masses of Pluto, the 8 planets, the moon and the Sun. In other words, NASA modelled the interactions of 311 solar system objects to do the navigation for Dawn.
They know exactly what the interactions are between Ceres, Vesta and 309 other solar system objects. By now, of course, that will have an improved measurement of Vesta’s mass and probably some idea of its non-spherical gravitational field.
Looks to me like we lose New Orleans and Miami / Palm Beach…. as those are largely democratic areas, the presidential election ought to tilt Republican, so “What’s the problem?” 🙂
Really, though: 3 feet? Someone is smoking something…
Bill,
Thank you for your comments as always.
One peccadillo, however: Its Charleston, SOUTH Carolina. 😉 Not “North.” Us native Carolinians are quick to clarify the difference.
The real sinking, however, from glacio-isostatic adjustment (and other factors such as stting on the edge of a 35-million-year-old impact crater) is occurring in the more heavily populated coastal region 400 miles to the north, around Virginia and Maryland.
And there may be more than sinking going on here. It may just be a gradual redistribution of the water masses in the means and over time across the globe, as Morner writes about.
And there may be a factor related to changes in speed and positioning of the Gulf Stream current in the means, and over time, too.
Not to mention we live here on soft squishy coastal plain sediments and also at the end of some pretty powerful rivers.
The James River which courses just a few miles to my north, scours out one of the largest “natural” harbors in the world, with a consistently deep channel never in need of dredging, one mile across and 50 to 70 feet deep.
And so, 10 miles to the east of this harbor, when the Chesapeake Bay Bridge Tunnel tide gauge registers over 6 mm in annual rise, such readings are to be taken with a grain of salt…and alot of grains of sand and sediment.
But the CBBT reading is not alone. If you point and click Ocean City, MD, its 5.48 mm per year.
http://tidesandcurrents.noaa.gov/sltrends/sltrends.html
My own area which has 1.7 million people, 4.44 mm/year.
Many things are at play here. And certainly cause for concern those populated areas who are under the gun.
However…what is the emergency?
http://curryja.files.wordpress.com/2011/07/post-glacial_sea_level.png
Natural Sea Level Variability.
As climate varies…in that nebulous range that so many, many informed specialists on here indicate, so does the ocean, and so does the ocean’s “level”.
So what is the emergency? There is none.
Except that we risk extinction if we continue to be muddled by groupthink and hysteria and all sorts of CAGW nonsense.
Hey Overpeck**!
Nothing to worry about. Move on.
Chris
Norfolk, VA, USA
Kevin Vaughan:-)
FYI The BBC is funded by a combination of huge taxpayer grantsdoled out by the Guvment,laregly these days todo the Guvment’s bidding, & a Pole-tax known as the BBC Licence Fee levied upon each & every household, unless one is an Old Aged Pensioner over the age of about 85when it becomes free of charge.
Tom t says:
July 19, 2011 at 10:09 am
They are right, sea level will rise by up to 3ft. The key is that “up to”. It is like stores when they say “save up to 90%”, when in fact you will be luck to find anything even 20% off.
You’ve nailed that sucker well & truly.The UK Guvment back in 2003-4 wanted to introduce a new drink-driving limit down from 80mg/100ml of alcohol:breath, to 50mg/100ml. This was an EU directive as part of the big Guvment Euro-super state, the PDREU. Of course Big Guvment knew the British people would never tolerate this, not because they believe in drink-driving, but because it would have been seen quite rightly as yet another podgy EU finger interference in British life. So what did Big Guvment do? They commissioned a recently elevated Peer of the Realmto undertake a study fr loads of dosh of course,that concluded after a suitable period,that “up to 160 lives per year could be saved”. Somebody was quick to point out that the term “up to” had to include the figure “0” to make sense!
“The authors cautioned that past evidence is not a prediction of the future, mostly because global temperatures during the Last Interglacial were driven by changes in the Earth’s orbit around the sun. However, current global warming is driven by increasing greenhouse gas concentrations.”
Is this not a HUGE assumption ?
and another example of the bunch making the noise having never lived near the ocean.
ITS ABOUT THIS THING CALLED TIDES!!!!
they come, they go, we get a 1M rise in sealevel at the local beach then wait about 12 hours and it will be down about the same.
then there is the fall extreme high tide. its usually about twice the normal high tide.
but WAIT we also have the spring Extreme High tide. thats about 300% of the normal high tide.
the reason that i don’t quote figures is that the amount differs according to the geographic location of where you look.
people that live/work in areas affected by tides normally view the alarmists that claim a couple of feet of rise in sealevel is comming as another excercise by idiots because they see more activity in a year than these nitwits predict in a century.
ARRRRRRRRRRGH.
C
“If sea levels rose to where they were during the Last Interglacial Period, large parts of the Gulf of Mexico would be under water.”
I hate to break it to him, but 100% of the Gulf is “underwater”, always has been and always will be.
He should have said “large parts of the land bordering the Gulf”. Imprecise writing implies imprecise thinking.
“The study combined paleoclimate records with computer simulations”
So there you have it in a nutshell, this study is based on the two things that they can’t seem to get right. Paleo and computer models.
Next patient please!