Posted 1 July 2009
"Firstly, shelf ice is floating, because it is less dense than seawater. When floating ice melts, there is no change in sea level. This is a bit of elementary physics known as Archimedes’ Principle. Secondly, the breakup of ice shelves is normal and inevitable. Ice caps grow by precipitation in the uplands, flow at depth, and at the ice front the ice either melts or breaks off as icebergs. The ice never simply keeps flowing to the equator. Icebergs are produced in both times of climate warming and times of cooling, so they tell us nothing of climate change." Dr Cliff Ollier explains elementary physics
Ice-sheets and sea level
by Cliff Ollier
May 31, 2009
As the world has been getting cooler since 1998 the global warming alarmists have to scare us with other things. A favourite is rising sea level, allegedly caused by rapid melting of the ice caps of Antarctica and Greenland.
For example, a prepared statement by Barrie Pittock and Andrew Glikson claims that “New studies … indicate the Greenland and west Antarctica ice caps would, if atmospheric CO2-equivalent concentrations reached 450 ppm, very likely melt rapidly, raising sea-level on the scale of metres per century”.
Similarly, in a letter of 27 March 2009 to Kevin Rudd, James Hansen wrote “Global climate is near critical tipping points that could lead to loss of all summer sea ice in the Arctic … initiation of ice sheet disintegration in West Antarctica and Greenland with progressive, unstoppable global sea level rise …”
A recent Australian scare-story relates to the Wilkins Ice shelf. The Australian of April 29 reported “a 13-month old photograph was published this month to support the view that a catastrophic melting of Antarctic ice was imminent.” Together with the suspect use of an old photo, "Mr Garrett [Minister for the Environment] claimed the break-up of the Wilkins ice shelf in West Antarctica indicated sea level rises of 6m were possible by the end of the century, and that ice was melting across the continent.”
My letter was published by the paper the next day:
Your front-page article states that Peter Garrett claimed the break-up of the Wilkins ice shelf in West Antarctica indicated sea level rises of 6 metres were possible. His claim includes two basic errors. Firstly, shelf ice is floating, because it is less dense than seawater. When floating ice melts, there is no change in sea level. This is a bit of elementary physics known as Archimedes’ Principle.
Secondly, the breakup of ice shelves is normal and inevitable. Ice caps grow by precipitation in the uplands, flow at depth, and at the ice front the ice either melts or breaks off as icebergs. The ice never simply keeps flowing to the equator. Icebergs are produced in both times of climate warming and times of cooling, so they tell us nothing of climate change.
Incidentally, Peter Garrett was on evening TV on 30 April. When questioned about his 6 metre sea level rise prediction, he gave his sources as IPCC and CSIRO. Yet by 2007 even the IPCC had reduced its estimate to between 18cm and 59 cm.
Very large ice bergs have been breaking off and leaving Antarctica long before the global warming scare. Geoffrey Blainey’s The Tyranny of Distance reported "In the southern summer of 1854 - 55 an enormous island of ice was afloat in the relatively warm latitude of 40 degrees south, just south west of the island of Tristan de Cunha.”
Doubts on the extreme claims arise from studies of the real state of affair in the ice regions, and real studies of sea level.
The head of the Australian Antarctic Division’s glaciology program reported recently that: "sea ice losses in West Antarctica over the past 30 years have been more than offset by increases in the Ross Sea region, just one sector of East Antarctica.”
The Department of Atmospheric Sciences at the University of Illinois provides data on sea ice anomalies. On 22 May 2009 global sea ice was 2.6% ABOVE the 1979-2000 average.
Satellite data from 1982 to 2003 (published in the Journal of the Royal Society) showed that the Antarctic icesheet is growing higher from precipitation at about 5 mm/yr which would LOWER sea level.
Direct studies of sea level are showing only small rises. You can get sea level data for the United States and a few other countries, from satellite imagery here
Most show a rise of sea level of about 2 mm per year, but there is considerable variation. An unusually high reading is from Chesapeake Bay, Virginia, at 6.05 ±1.14 mm/yr. Even this is only 1.98 feet in 100 years, and no cause for alarm.
Similar figures are reported elsewhere, such as Reykjavik, Iceland 2.34 mm/yr; Bermuda 2.04 mm/yr; Murmansk, Russia 3.92 mm/yr.
In Scandinavia, which is rising in response to loss of the old ice sheet the sea level is falling: Goteborg, Sweden -1.3 mm/yr; Oslo, Norway -4.53 mm/yr.
Two favourites of sea level alarmists are Tuvalu and the Maldives. Sea level measurements for Tuvalu (and 10 other stations) between 1992 and 2006 are available on Fig. 13 on the Australian Bureau of Meteorology website.
For about the past eight years the sea level seems to be virtually constant.
Sea level in the Maldives was studied in enormous detail by the doyen of sea level scientists, Niklas Axel-Mörner. His team determined the sea level curve over the past 5,000 years based on evidence of morphology, stratigraphy, biology and archaeology supported by extensive C14 dating, and found that “All over the Maldives there is evidence of a sub-recent sea level some 20 cm higher than the present one. In the 1970s, sea level fell to its present position.” (my italics).
Holland is very low and would be particularly vulnerable to any large rise of sea level. It is also a world leader in coastal study and engineering, and they are not alarmed. In a piece in the December 11, 2008, issue of NRC/Handelsblad (Rotterdam’s counterpart to the New York Times) Wilco Hazeleger, a senior scientist in the global climate research group at KNMI (the Royal Netherlands Meteorological Institute) wrote:
In the past century the sea level has risen twenty centimetres. There is no evidence for accelerated sea-level rise. It is my opinion that there is no need for drastic measures. Fortunately, the time rate of climate change is slow compared to the life span of the defense structures along our coast. There is enough time for adaptation.
Our politicians (and some scientists) should base their opinions on real observations instead of alarming us with nightmares of catastrophic sea level rise based on false models of ice caps.
Of course even if we believed sea level is rising, it takes another leap of faith to accept that it results from minuscule increases in atmospheric carbon dioxide caused by human activity.
1. “here” = http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml
2. “website” = http://www.bom.gov.au/ntc/IDO60101/IDO60101.200809.pdf