Study suggests that global sea level is less sensitive to high atmospheric carbon dioxide concentrations than previously thought.
From STANFORD’S SCHOOL OF EARTH, ENERGY & ENVIRONMENTAL SCIENCES
Ice sheets may be more resilient than thought, say Stanford scientists
But there may be some good news amid the worry. Sea levels may not rise as high as assumed.
To predict sea level changes, scientists look to Earth’s distant past, when climate conditions were similar to today, and investigate how the planet’s ice sheets responded then to warmer temperatures brought on by increased carbon dioxide in the atmosphere.
In a recently published study in the journal Geology, PhD students Matthew Winnick and Jeremy Caves at Stanford School of Earth, Energy & Environmental Sciences explored these very old conditions and found that sea level might not have risen as much as previously thought – and thus may not rise as fast as predicted now.
To better understand global sea level rise, Winnick and Caves analyzed the middle Pliocene warm period, the last time in Earth’s history, approximately 3 million years ago, when carbon dioxide levels in the atmosphere were close to their present values (350-450 parts per million).
“The Pliocene is an important analogue for today’s planet not only because of the related greenhouse gas concentrations, but because the continents were roughly where they are today, meaning ocean and climate circulation patterns are comparable,” said Winnick.
These similarities are why the Intergovernmental Panel on Climate Change (IPCC), the group responsible for global sea level rise projections, focuses on the mid-Pliocene warm period to inform their computer models.
Previous studies of the mid-Pliocene warm period used oxygen isotope records to determine the volume of Earth’s ice sheets and, by proxy, sea level. Effectively, the oxygen isotope records act as a fingerprint of Earth’s ice sheets. By combining the fingerprint with models of ice sheet meltwater, many previous researchers thought that sea level was likely 82 to 98 feet (25 to 30 meters) higher during the Pliocene.
Such high sea level would require a full deglaciation of the Greenland Ice Sheet and the West Antarctic Ice Sheet, and as much as 30 percent of the East Antarctic Ice Sheet – enough to cover New York City under 50 feet of water. But these estimates arose because the researchers assumed that the Antarctic ice of the Pliocene had the same isotopic composition, that is, the same fingerprint, as it does today – an assumption that Winnick and Caves challenge in their new report.
To understand the isotopic composition of Pliocene ice, Winnick and Caves began in the present day using well-established relationships between temperature and the geochemical fingerprint. By combining this modern relationship with estimates of ancient Pliocene surface temperatures, they were able to better refine the fingerprint of the Antarctic ice millions of years ago. In re-thinking this critical assumption, and by extending their analysis to incorporate ice sheet models, Winnick and Caves recalculated the global sea level of the Pliocene and found that it was 30 to 44 feet (9 to 13.5 meters) higher, significantly lower than the previous estimate.
“Our results are tentatively good news,” Winnick said. “They suggest that global sea level is less sensitive to high atmospheric carbon dioxide concentrations than previously thought. In particular, we argue that this is due to the stability of the East Antarctic Ice Sheet, which might be more resilient than previous studies have suggested.” However, a rise in global sea level by up to 44 feet (13.5 meters) is still enough to inundate Miami, New Orleans and New York City, and threaten large portions of San Francisco, Winnick cautioned.
While the study helps refine our understanding of Pliocene sea level, both Winnick and Caves point out that it’s not straightforward to apply these results to today’s planet. “Ice sheets typically take centuries to millennia to respond to increased carbon dioxide, so it’s more difficult to say what will happen on shorter time scales, like the next few decades,” Winnick said.
“Add that to the fact that CO2 levels were relatively consistent in the Pliocene, and we’re increasing them much more rapidly today, and it really highlights the importance of understanding how sea level responds to rising temperatures. Estimates of Pliocene sea level might provide a powerful tool for testing the ability of our ice sheet models to predict future changes in sea level.”
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So…parts of the east coast of Japan sink more than two feet after big 9.0 whatever earthquake. Hmmm….earthquakes kills 100’s of thousands since 2000…sea level rise kills 0. Is there any common sense left? oops sorry, I referred to the “left”… delete the “left”… there…all fixed.
“Add that to the fact that CO2 levels were relatively consistent in the Pliocene, and we’re increasing them much more rapidly today, and it really highlights the importance of understanding how sea level responds to rising temperatures. Estimates of Pliocene sea level might provide a powerful tool for testing the ability of our ice sheet models to predict future changes in sea level.”
Highlights that CO2 levels during the Pliocene had no influence on sea level and we are not seeing anything out of the ordinary now because much larger volumes of CO2 also has no influence on sea level.
There is no relationship in history of the planet with CO2 and sea level. Not to forget the any excuse for increasing the sea level with the pathetic excuse that is GIA. This value should never be used because they don’t have a clue and so take off 0.3 mm per year for a true value. It takes the awful assumption that no basalt is increasing in the ocean basins from volcanic activity. Nobody on the planet can measure the difference between these and have any clue whether to increase, decrease or leave as it is. Therefore it should be left as it is and any excuse for raising sea levels by tampering.
http://sealevel.colorado.edu/content/what-glacial-isostatic-adjustment-gia-and-why-do-you-correct-it
IMO there is a relationship. When the planet is colder, CO2 is lower and so usually is sea level, but the relationship isn’t causal. Cold water holds more CO2 and cold climate means land ice, which lowers sea level.
Over many millions of years there is no relationship I was meant to say, but there is a tenuous link with the example you have described only during the recent ice ages.
http://i37.tinypic.com/1z3qmg4.jpg
http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/20000000BC.png
Would agree with you if by recent you include the Carboniferous/Permian ice age. CO2 level is less well constrained for the Precambrian Snowball Earth glaciations, but I’ve seen estimates of 100 to 130 ppm then, followed possibly by rapid rise to something on the order of 10,000 ppm (ie, 3160 to 31,600) to 100,000 ppm (ie, 31,600 to 316,000, but probably not at the high end of that range, according to the most recent work).
“Would agree with you if by recent you include the Carboniferous/Permian ice age.”
I would have to include this too because it was the only other ice age period very similar to the recent hundreds of thousands of years and the last few million years. With the continents being in such different positions though it was more likely just coincidence. A broken clock is right twice a day, this was right once in just short of billion years.
http://worldview3.50webs.com/6temp.chart.n.co2.jpg
Extended to 100 million years.
http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/100000000BC.png
Matt,
It wasn’t a coincidence. Ice Houses occur with a pretty regular periodicity, which scientists like Nir Shaviv have suggested is ruled by the solar system’s passage through the spiral arms of the galaxy.
What made the Carboniferous ice age so long-lasting, compared to the Ordovician glaciation, was the position over the South Pole of so much land.
When earth’s climate is cold, naturally CO2 drops. The drop doesn’t cause the cold. Warmunistas confuse cause and effect.
The ice age that should have happened during the Mesozoic was still born because the continents weren’t well positioned for an ice age. However, it did get cold and earth did grow ice. Feathers might possibly have evolved in response to this aborted ice house, as insulation.
Gloria Swansong September 6, 2015 at 6:10 pm
Only a coincidence due to CO2 levels been similar levels back then with many different variables and with one super continent covering the tropics and south pole at the same time. Not a coincidence when ever a large continental land mass covers at least one pole, the Earth will always be ripe for ice ages enabling a huge build up of glacier ice and sea level fall.
Matt,
It’s not a coincidence that CO2 is low during ice ages and ice houses. When the planet is cold, CO2 is low. When it’s warm, CO2 is higher. Cold water holds more gas; warm water holds less and releases it to the air. Physics.
It was a coincidence when the ordovician ice age caused the CO2 levels to drop still above 4000 ppm.
Matt,
Actually, science doesn’t know how much CO2 dropped during the Ordovician ice age. It lacks the needed resolution on available data.
But based upon physics and chemistry, it must have done so.
“Actually, science doesn’t know how much CO2 dropped during the Ordovician ice age. It lacks the needed resolution on available data.
But based upon physics and chemistry, it must have done so.”
Despite the lack of resolution it was still able to give an error range that gave CO2 levels still many times higher than present levels. A drop in CO2 was was recorded depending what source you believe (data or modeled) either from about ~4500 ppm to ~4100 ppm or falls to 10 times present levels (1990’s) or 18 to 8 times present levels (1990’s).
“Although Phanerozoic glaciations usually coincided with times of estimated low atmospheric CO2, the Late Ordovician (440 Ma) glaciation is a significant exception. CO2 levels during that time may have been as much as 10 times greater than present.”
http://onlinelibrary.wiley.com/doi/10.1029/91JD02449/full
“Under the condition of a 4.5% reduction in solar luminosity, permanent snow cover (taken as a key indicator of potential for glaciation) is dramatically different between five experiments. The range of 18X present atmospheric level CO2 (ice free) to 8X (“runaway” icehouse) lies within the uncertainty of previous geochemical estimates of Late Ordovician atmospheric pCO2.”
http://geology.gsapubs.org/content/25/5/447.short
“The analysis of the geologic record has revealed a question concerning how the Late Ordovician glaciation
could have occurred simultaneously with high CO2 levels (10-18x)”
http://www.researchgate.net/profile/Christopher_Barnes3/publication/248809395_Late_Ordovician_glaciation_under_high_atmospheric_CO_2__A_coupled_model_analysis/links/53dd4d910cf2cfac992914fc.pdf
“But based upon physics and chemistry, it must have done so.”
Ice ages always cause the CO2 levels to fall not only based on physics and chemistry, but more importantly biology too.
Matt,
All good.
Warmunistas try to get around the Ordovician ice age not just by pointing to a slightly less powerful sun, but by assuming that science has missed a big drop in CO2 from low resolution during the fairly brief glaciation. That is, they speculate without any evidence that CO2 might have dropped from c. 5000 ppm to 3000 or lower during the glaciation, then bounced back over 4000.
IMO however your figures are reasonable, of CO2 over 4000 ppm even during the glaciation.
Of course, during past warming episodes CO2 concentrations lag temperature increases by 600 to 1,000 years – but they assume that previous warmings were caused by CO2.