CLIMATE change has always been driven by the sun, the earth’s orbit and plate tectonics, at least that is what many so-called sceptic would argue.
In a new paper in this week’s journal Nature Tim Naish and colleagues conclude that there is a relationship between the past collapse of West Antarctic ice shelf and the earth’s orbit. In the same issue of Nature there is an article by David Pollard who, with Robert De Conto, ran a five-million-year computer simulation of the ice sheet and concluded that if surrounding waters increase by 5 degrees Celsius, it could melt in one thousand years or so.
So, the loss of the West Antarctic ice shelf from warming is a thing to worry about on a thousand-year, rather than hundred-year, time frame.
Add to this new information suggesting that Greenland’s once galloping glaciers have slowed, and it seems there is going to need to be a reduction in the official estimates of sea level rise which have been fairly modest anyway – modest at least relative to claims by Al Gore.
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Notes
Modelling West Antarctic Ice Sheet Growth and Collapse Through the Past Five Million Years. David Pollard and Robert M DeConto. Nature Vol 458, March 19, 2009
Obliquity-paced Pliocene West Antarctic ice sheet oscillations. Tim Naish et al, Nature Vol 458, March 19, 2009
Heaven and Earth by Ian Plimer http://jennifermarohasy.com/blog/2009/03/heaven-and-earth-new-book-by-ian-plimer/
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
“CLIMATE change has always been driven by the sun, the earth’s orbit and plate tectonics, at least that is what many so-called sceptic would argue. ”
Biological influences have also played an important part in climate, but I don’t know that anyone would argue with that list, other than it is incomplete. Are AGW proponents supposed to be unaware of the role of the sun and Milankovich cycles?
SJT,
I thought you thought that scientific modellers knew what they were doing. Or is that only AGW modellers?
On a related topic, I would be keen to know if anyone can comment on the meaning of this article about Antarctic ice…
“Kiwis solve global warming riddle”
http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10562595
Just how did they come up with their 5C figure?
They said they ran a 5 million year simulation. Why did they only make a claim for 1000 years? Did they simply look for a 1000 year stretch somewhere in the simulation and claim it is the reality for 5C water temperature increase?
Not a big deal even if it happens. Vostok and the Pole (1300 km apart) have average summer temperatures of -30C and -25C respectively. Winter is 30-35C colder. They have never experienced temperature as high as -12C in record history. Not much melting at those temperatures. An extra 5C might even allow them to pick up more ice due to increased evaporation at the coast.
“SJT,
I thought you thought that scientific modellers knew what they were doing. Or is that only AGW modellers?”
I was referring to Jennifer’s claim that only ‘sceptics’ think that there are other climate forcings besides CO2.
As for models, Jennifer has posted many topics here that say models are useless. It suits her to believe them when they agree with something she thinks. Not the first time, either.
In this radio interview Pollard says the likely time is 2-3 thousand years.
http://www.npr.org/templates/story/story.php?storyId=102066621&ft=1&f=1001
“But Pollard’s study indicates that the West Antarctic ice sheet won’t melt away too rapidly. He figures that will take at least 1,000 years, and more likely 2,000 to 3,000 years.”
Sun yes; plate tectonics no.
Plate tectonics is a myth.
“In the oral session, except for one presentation that was clearly pro plate tectonics, and another one that did not address the issue of global and large scale geology specifically, there was general consensus that subduction, and therefore plate tectonics, is mechanically impossible.” — Stavros T. Tassos (seismologist/geoscientist) and Karsten M. Storetvedt (geophysicist), November 2007
“Subduction is a myth.” — Samuel W. Carey, geologist, 1988
“People don’t want to see it. They believe in subduction like a religion.” — Samuel W. Carey, geologist, 1981
“Subduction exists only in the minds of its creators.” — Samuel W. Carey, geologist, 1976
Am I missing something here? The implication seems to be that this will melt after 1000 years, and that until that 1000 years is up, nothing will have melted, so no problem?
“As for models, Jennifer has posted many topics here that say models are useless. It suits her to believe them when they agree with something she thinks. Not the first time, either.”
All sensible people are very sceptical about all models. Even this one and it’s a sceptical model.
“Am I missing something here? The implication seems to be that this will melt after 1000 years, and that until that 1000 years is up, nothing will have melted, so no problem?”
Read up on it a bit more. More like 7000 years.
He says up to 3,000 years, but I repeat, he’s not saying that there won’t be any melting or sea level rise, that’s the time he gives for it to be all gone.
He also says
He is also only talking about one source of sea level rise, there are others.
Jenifer
Melting is probably only a bit player when the West Antarctic Ice Sheet (WAIS) collapses. leading to an increases in ocean level (7 feet?). The WAIS is prevented and associated glaciers are held back from sliding into the ocean by the Ross Ice Shelf, which is up to a half mile thick and close to the size of France. Recently the Andrill program, working from a Ross Shelf site, obtained strata samples dating from the present back to about 5 million years ago. During this period of time they found evidense that the shelf had collapsed or melted away about 70 times. With the shelf gone, major portions of the WAIS and its glaciers then begin to travel oceanwards. This should result in a much more rapid rise of ocean level than would be the case with melting. I won’t try guessing as to how much faster.
Steve Schapel
hat newspaper article is sort of about the Andrill program, only it seems to have been written by someone who was very ill-informed. The time period of the samples obtained have nothing to do with covers the two and a half million years of the earth’s current glacial period and then extends beyond that for a few more million years. The atmospheric CO2 level is thought to have been fairly constant — down to about 200 ppm during glaciation and up to 280 to 300 during interglacial periods. I recall reading a newspaper about the program where one of the scientists said that his best guess was that it would take a temperature invrease of two to three degrees to bring about the next collapse. This left me puzzled as to how, during the “ice house” conditions of the earth that have prevailed during at least the past few million years, the sun could have ome up with the extra heat needed to bring about these collapses — and to have done this 70 times, and apparently only during interglacial periods.
The comprehensive Mirny ice core data shows, repeatedly, that warming comes around a mean of about 800 years before CO2 increase. So, warming is the driver and CO2 the consequence. Unless the time measurements of this Ross ice shelf study is able to separate this small difference relative to a scale of millions of years then it is wrong to ascribe CO2 as the primary cause of warming. If it can separate it then why would the results be in total conflict with the Russian data.