humbug2

HUMBUG #2: ICE SURGES, SEA-LEVEL AND THE FOURTH ESTATE
Sleepy Melbourne (where I live) is the sporting capital of Australia. It is home to the Grand Final (Aussie Rules football), the Australian Open (tennis), and the Australian Grand Prix (Formula One cars and 500cc bikes). It hosted the Summer Olympics in 1956, well before its sporting rival Sydney (2000) got its turn. I can’t swear to their veracity, but I have heard assertions that Melbourne’s three new moveable-roof sports stadia, accommodating indoor/outdoor crowds of 52,000, 15,000 and 10,000 respectively, are unmatched in cities elsewhere - and at least, by Sydney. While Melbourne is on the move sporting-wise, traditionalists still point instead to Melbourne’s sand-belt, which contains several of the world’s finest remaining century-old, natural-style, golf courses.

But the locals don’t know or don’t care about a much more commendable distinction. Melbourne is a city of newspaper readers. The credit is largely due to the influence (right around Australia, I suspect) over the past century - remember, the Australian nation is only 100 years old this year - of three great newspaper-owning families (Packer, Fairfax and Murdoch).

With a population of less than 4 million, three daily papers are available in Melbourne. The blue-collar Herald Sun tabloid dominates, with daily average sales of about 550,000 copies. The white collar market is shared by two broadsheets: the local sales of a national paper, The Australian, at a little over 100,000, and The Age at just under 200,000. It is The Age which has cornered Melbourne’s “ain’t it awful” market.

Under the headline “Alarm bells sound over shrinking glacier” and the subheading “scientists show for the first time that Antarctic ice is melting”, The Age reports (3 February 2001, p 22) surging of the Pine Island Glacier - in an article by Tim Radford reprinted from the Guardian, an enthusiastic bearer of bad tidings on things environmental.

The press report begins:
For the first time, scientists have detected ominous signs of the ice thinning in west Antarctica.
The continent’s biggest glacier, which has been systematically measured for the last eight years, has lost a 10-metre thickness of ice and retreated five kilometres inland.
If the thinning continues at that rate, the entire glacier could disappear into the ocean within a few hundred years.
There have been fears for more than a decade that the west Antarctic ice sheet could be unstable.
The region holds enough ice to raise sea levels by five metres; flooding coastal cities such as London, New York, Tokyo and Calcutta.

What has caused our impending doom? The article tells us that:
The scientists said the discovery added weight to the argument that small changes at the coast of the continent - such as the effects of global warming - could be transmitted swiftly inland, leading to an acceleration of sea level rise.

But let’s step back for a moment.

The Antarctic is not warming in summer (see Figure 5, originally from Jim Angell at NOAA), when ice might melt. Furthermore, we have a global coverage by polar orbiting satellites extending back to the late 1970’s; and for that time, at least, we know that no significant trends are apparent in Antarctic sea-ice extent.

Better still, what did the original paper (Shepherd et al 2001), the source paraphrased by the Guardian, actually say? I quote here from its abstract:
The Pine Island Glacier (PIG) transports 69 cubic kilometers of ice each year from ~10% of the West Antarctic Ice Sheet (WAIS). It is possible that a retreat of the PIG may accelerate ice discharge from the WAIS interior. .... The thinning cannot be explained by short-term variability in accumulation and must result from glacier dynamics.
and from the body of the paper:
..... the time scale for the thinning process is that of an ice dynamic fluctuation ....

Radford’s shoddy and slanted analysis doesn’t mention the findings of the crucial paper by Conway et al (1999). These authors tell us that, in the region of the Ross Embayment (see Figure 6), the grounding line of the West Antarctic Ice Sheet has retreated 1300 km along the foot of the Transantarctic Mountains since the Last Glacial Maximum, mostly in the past 8,000 years. Unlike the much larger ice sheet on East Antarctica, the WAIS is founded on a submerged continental shelf; and, perhaps destabilised by rising sea-level, has lost 2/3 of its volume since the LGM. The WAIS has contributing about 11 metres to total sea-level rise since the LGM of some 130 metres (the larger part of the rise originated from melting of the ice sheets on North America and Eurasia).

Collapse of the WAIS was in progress prior to the industrial revolution.

There are two conclusions to be drawn here:
* The WAIS collapse is nothing to do with greenhouse - but it needs watching, nevertheless.
* As a source of climate-change information, the popular press is unreliable.

Reference
Conway, H. et al 1999, “Past and future grounding-line retreat of the West Antarctic Ice Sheet”, Science v 286 pp 280-3.
Shepherd, Andrew et al 2001, “Inland thinning of Pine Island Glacier, West Antarctica”, Science v 291 pp 862-4.

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