No Cause For Alarm Over Sea Level Or Ice Sheets
By Professor Cliff Ollier, School of Earth and Environment, University of Western Australia
John Le Mesurier’s recent article in On Line Opinion, “The Creeping Menace”, re-hashes the alarmism about rising sea levels. Much has happened, however, since Al Gore scared the world with visions of metre high seas flooding New York.
First, there is still no proof the Earth is experiencing “dangerous” warming. Temperatures have levelled off since 1998. Many measuring locations are also located in unsuitable areas. Furthermore, the methodologies of averaging temperature are inconsistent and full of problems. This is why “Global Warming” was replaced as a slogan by “Climate Change” (nobody denies that climate changes), and more recently by “Climate Disruption” (which is impossible define or prove).
Second, the increased temperature is supposed to increase sea level mainly by melting the ice-caps, which is impossible. Thermal expansion of the oceans seems to be of little consequence at present because the satellite measurements show the oceans are cooling. Le Mesurier gilds his picture with a few asides on “extreme climatic events” in general and hurricanes in particular. Recent studies, however, show no increase in hurricane activity in the last 40 years.
With regard to sea level, I have come to the view the IPCC and Australian Bureau of Meteorology, run by CSIRO, are unreliable sources of data after critically assessing their statements on this subject for some time. Direct studies of sea level are showing only small rises. You can see the sea level data for yourself for the United States and a few other countries here. Most stations show a rise of sea level of about 2mm per year, but note the considerable variation even within a single state.
Models depend on what is put into them. For example, a 2009 report by the CSIRO for the Victorian Government’s Future Coasts Program on The Effect of Climate Change on Extreme Sea Levels in Port Phillip Bay based its model on temperature projections to 2100 of up to 6.4 degrees. That is the most extreme, fuel intensive, scenario of the IPCC and implies unbelievable CO2 concentration levels in 2100 of approximately 1550 parts per million (expressed in CO2 equivalent). Usage of all known fossil fuel reserves would only achieve half of this and continuation of the current rate of increase in concentration levels would result in only 550ppm by 2100.
In terms of sea levels, the result is a CSIRO predicted rise for Port Phillip Bay by 2100 of 82cm and, with the help of the Bureau of Meteorology, an increase due to wind to 98cm. That is not only well above even the top level projected by the latest IPCC report but is also well above any projections from the last 20 to 100 years.
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 (PDF 1.97MB). For about the past eight years the sea level seems to be virtually constant.
Vincent Gray has reviewed the evidence and finds virtually stable sea levels in the South West Pacific, and he also discusses how the data have been manipulated to suggest rising sea level.
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 20cm higher than the present one. In the 1970s, sea level fell to its present position.” (My italics.)
Incidentally a recent study of coral islands in the Pacific by Webb and Kench showed the islands are actually growing larger despite any possible sea level rise.
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 the Dutch are not alarmed. In the December 11, 2008, issue of NRC/Handelsblad (Rotterdam’s counterpart to The Australian or The Age) Wilco Hazeleger, a senior scientist in the global climate research group at 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.
What about the alleged cause of most of the scary sea level rise – the melting of ice-caps? This idea of rapid loss of ice is based on the concept of an ice sheet sliding down an inclined plane on a base lubricated by meltwater, which is itself increasing because of global warming.
In reality the Greenland and Antarctic ice sheets occupy kilometre-deep basins. If sliding were operative they could only slide into the basin. Virtually all the studies on which alarmist conclusions are based are on the outflowing glaciers around the edges of Greenland where glaciers can flow downhill, and where there is some melting. There is no melting in the interior of ice sheets - it is far too cold.
Glaciers have a budget, with accumulation of snow, conversion to ice, flow of ice, and eventual destruction by melting, ablation or collapse. The centres of the ice sheets, occupying basins, flow only at the base, warmed by geothermal heat and driven by the weight of the overlying ice. There is no direct flow of the near-surface ice in the centre of an ice sheet to the outflow glaciers.
The accumulation of kilometres of undisturbed ice in cores in Greenland and Antarctica show hundreds of thousands of years of accumulation with no gaps in the record caused by melting. The existence of such layers, youngest at the top and oldest at the bottom, enables the glacial ice to be studied through time, a basic source of data on temperature and carbon dioxide in the past.
In the Greenland ice sheet several cores have more than 3km of undisturbed ice which go back in time for over 105,000 years (much less than the Antarctic equivalent). The Vostok cores in Antarctica provide data for the past 414,000 years before the ice starts to be deformed by flow (induced by the weight of the overlying ice and geothermal heat). The Epica core in Antarctica goes back to 760,000 years. The cores show there have been many times when the climate was much warmer than today (e.g. Mediaeval Warm Period). It is fanciful to conclude kilometres of ice can suddenly melt when the records show no melting whatsoever in the ice sheet accumulation areas.
After considering the evidence of three quarters of a million years of documented continuous accumulation, how can we rationally accept that right now the world's ice sheets are collapsing?
The idea of a glacier sliding downhill on a base lubricated by meltwater seemed a good idea when first presented by de Saussure in 1779, but a lot has been learned since then. Not even alpine valley glaciers or the outflow glaciers of Greenland move this way, but by a process called creep, best known from metallurgy. This process explains why the crystals of ice in the snout of a glacier are about a thousand times bigger than the first crystals in the snowfall. Sliding cannot account for this.
Collapse of ice sheets is commonly shown to stir fears of rising sea levels. Yet wherever ice sheets or glaciers reach the sea, the ice floats and eventually breaks off to form icebergs. It is part of the glacial budget: the glaciers never did flow on to the equator. Icebergs have always been with us. Captain Cook saw them on his search for the Great South Land.
Observers frequently seem surprised by the size and suddenness of what they see. In 2007, when a piece of the Greenland ice shelf broke away, the scientists who were interviewed said they were surprised at how suddenly it happened. How else but suddenly would a piece of ice shelf break off? The actual break is inevitably a sudden event - but one that can easily be built into a global warming horror scenario. The point to remember is that the release of icebergs at the edge of an ice cap does not in any way reflect present-day temperature. It takes thousands of years for the ice to move from accumulation area to ice front.
The Hubbard Glacier in Alaska has long been a favourite place for tourists to witness the collapse of an ice front, 10km long and 27m high, sometimes producing icebergs the size of ten-storey buildings. One tourist wrote “Hubbard Glacier is very active and we didn’t have long to wait for it to calve”. Yet the Hubbard Glacier is advancing at 25 metres per year, and has been doing so at least since its discovery in 1895.
Variations in melting or calving around the edges of ice sheets are no indication that they are collapsing, but reflect past rates of snow and ice accumulation in their interior.
Despite alarmist propaganda there is much evidence to suggest that the ice sheets are in good health. For example, one recent paper is entitled “A doubling in snow accumulation in the western Antarctic Peninsula since 1850” (Thomas et al. 2008).
Another reports that “The East Antarctic ice-sheet north of 81.60S increased in mass by 45 ± 7 billion metric tons per year from 1992 to 2003 … enough to slow sea-level rise by 0.12 ±0.002 millimetres per year” (Davis et al. 2005).
Wingham et al. (2006) wrote: “We show that 72 per cent of the Antarctic ice sheet is gaining 27 ± 29 Gt yr-1, a sink of ocean mass sufficient to lower global sea levels by 0.08 mm yr-1.”
Johannessen and colleagues analysed satellite data on the Greenland Ice Sheet from 1992 to 2003. They found an increase of 6.4 ± 0.2 centimetres per year in the vast interior areas above 1500 metres, in contrast to previous reports of high-elevation balance. Below 1500 metres, the elevation-change rate is -2.0 ± 0.9 cm/year.
Of course even if we believe global sea level is rising, it takes another leap of faith to accept that it is caused by minuscule increases in atmospheric carbon dioxide caused by human activity.