Wednesday, 27 July 2011

An urban dead sea?

In today’s issue of Time, there is a story of how the excessive use of the Jordan River has reduced the level of the Dead Sea by as much as twenty-seven metres since 1980. It also says that the extraction of potash for the making of fertilisers has contributed significantly to this reduction, which almost rivals that of the Aral Sea in Uzbekistan and Kazakhstan.

Whilst the rains of 2010 and 2011 have eased the problems with the Coorong at least for the moment, in southwestern Australia the situation has got creepily bad to say the least. So altered is Australia’s climate by global warming that in the year from April 2010 to March 2011 the lowest rainfalls were as far south as Corrigin in the heart of the Western Australian wheatbelt.

The map presented here from the Bureau of Meteorology shows that if we make our judgments based on the location of the area of lowest rainfall, then Australia’s rain belts have shifted about eight degrees poleward from their pre-anthropogenic-global-warming location (represented by the year from April 1955 to March 1956 with similar positive SOI values for realistic comparison). Most of the rainfalls observed in the super-monsoon belt today have no parallels even during the wettest years before man-made global warming took over. However, this is not likely to create new species very quickly: it is simply likely to expand monsoonal vineforests at the expense of tropical grasslands. Monsoon forests occur when there are wet and dry seasons and the wet season is longer than the dry season, a situation observed definitely in Darwin today when the wet season of 2010/2011 broke the pre-anthropogenic-global-warming record by a whopping 780 millimetres, or thirty-one inches – more than the average annual rainfall in most of Australia.

The result has been that Perth’s water storages, and indeed all rivers in the southwest of Western Australia, have become the same thing as the Dead Sea. Moreover, because in the pre-anthropogenic-global warming age southwestern Australia’s rivers – even if clearing for grain production made those in drier areas saline – were able to support life, the loss stands much, much larger. The western swamp tortoise has already survived artificially for thirty-five years – its existence depends on levels of runoff not seen in southwestern Australian rivers since 1974 when the CO2 level was 100ppm lower and climatic belts about eight degrees closer to the equator.

Ian Smith, the main CSIRO climatologist, has said that the same trends have occurred in the Middle East, though I do not have rainfall data to say how they compare with what is observed in southwestern Australia. Still, if there is anything in common between them, then we really are faced with the need to restrict water use in hot climates. The trouble is that it is much more economic to farm in hotter climates than in cooler ones because:
  1. more crops can be grown per year, so that even if yields per single crop are lower, total yields on the same amount of land can be higher
  2. higher-value crops can be grown in hotter climates than in cooler ones since the most valuable crops – which of course do not grow naturally in large numbers – are in the more biodiverse hot regions
This creates serious economic problems since cool climates tend to be much less fragile and less greenhouse-intensive to live in than really hot ones. (Even though properly cold climates require large amounts of energy for heating, they always have reliable hydroelectric power to produce it, which hot climates rarely do). Nonetheless, the need to avoid the disasters that have already occurred within an expanding tropical belt is something that really should worry people in cool climates who are willing to realise that a major focus on global environmental concerns means growing local even if it means a less high living standard.

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