No cause for alarm

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.