A 2002 Essay on Global Warming Part 1

Larsen B Ice Shelf Collapse

From my pre-blog archives first published online in April 2002 (edited)

Over the last five years there have been various reports of warmer polar circles, ice thinning, and the ice caps shrinking. All these reports have been guarded with the usual curious scientific reserve. The reports always appear to be ultra-conservative with their predictions. And usually hedge their bets by saying that there is no evidence that the phenomenon observed is due to global warming and may be part of a natural process or cycle. However the basic science of a ‘greenhouse’ planet is well established – without the greenhouse effect there would be no life on earth. This combined with the steadily increasing amounts of greenhouse gases man has returned to the atmosphere over the last two hundred years means the atmospheric temperatures must be warming up, no matter how slowly, and regardless of whether it can be recognised above normal variation or not.

The most recent developments have been the huge icebergs breaking off the Larsen B ice shelf on the West Antarctic Peninsula… There are a number of new theories relevant to this occurrence and the future of mankind. One is that the ice shelves are like a ‘cork in the bottle’ that stops the ice sheets that cover the land from travelling rapidly to the sea and melting. Were the West Antarctic Ice shelf to melt then sea levels would be raised around the world by 5 metres. Current estimates give a probability of this event occurring at only 1 in 20 chance in the next 200 years.

Another is the new thesis that environmental changes (and extinctions) can occur rapidly and almost in a human time scale (ie about 100 years). Many of the current scientific calculations like the estimate of probability for a melting West Antarctic ice sheet above may be based on the false assumptions – that the changes will be gradual rather than catastrophic and that the rising sea levels will be caused by thermal expansion of the sea and not by melting Antarctic ice sheets. Note the current estimates that predict a sea level rise of about .4 to 1.4m over the next 100 years are based on the thermal expansion of the oceans alone and are not inclusive of any ice melting over land.

Meanwhile anecdotal evidence reported in the (mainly electronic) media of what appears to have been a fairly cool summer has meant uninformed commentators, from sundry radio jocks, and even on the ABC, have been claiming that the ‘greenhouse’ and global warming are all bullshit, or words to that effect. What they have failed to recognise is that global warming is measured in world averages. Some places may actually get colder and there may be also wide seasonal variations. For example there may be cooler summers with the other seasons warmer, or there may be diurnal variation with warmer nights and the days the same, leading to higher average temperatures. Apparently the Victorian summer, despite its lack of scorching hot days, was about average. What may be cause for some alarm is that the breakup of Larsen B ice shelf was caused by variations of this kind – local warming which had a “strong and immediate effect”.

(to be continued)