A mega-arid Perth is the key feature

In yesterday’s Yahoo news, they are saying that under present CO₂ conditions the southwestern US state of Arizona, New Mexico, Utah and Nevada would suffer from a much drier climate. This data is based on work from a dried lake bed in New Mexico called the Valles Caldera, which shows that in hotter periods this region of the United States had rainfall even less than those observed since instrumental records began about 125 years ago. it points out that settlements in this area depend greatly upon access to water, and that under projected climate conditions there would be much less water available.

What is problematically overlooked, however, is that the southwest of Western Australia, which has almost no paleoclimate data apart from very specialised research that does not go back even to the Medieval Warm Period (read Climates of the Southern Continents for the best available data) has suffered both from a larger population increase and a greater reduction in rainfall, and yet is not discussed. In fact, though the far southwest of Western Australia has been historically much more humid than any region of the southwest of North America, last year saw almost all this region have its driest year since records began. In fact, the very limited rainfall data going back to 1882 strongly suggest that the observed rainfall in 2010 would not be possible had greenhouse gas levels remained at what they were before the Industrial Revolution.

Even more critically, runoff in southwestern Australia (and Australia generally) shows much more sensitivity to precipitation changes that that in southwestern North America. For example, a decline of forty percent in rainfall (as observed in 2010) has caused runoff into Perth’s dams to decline from 338 gigalitres to just eleven gigalitres, which is a decline of 96.7 percent. In California, by contrast, a decline of 40 percent from normal annual rainfall is a regular occurrence, but never causes runoff to fall below 20 percent of the average. More than that, there is no evidence years so dry as 2010 ever occurred in southwestern Australia even during glacial conditions when most other parts of Australia lost up to ninety percent of their rainfall. This means that at likely future CO₂ levels Perth could have a runoff of a few gigalitres to serve a million people with its formerly renewable groundwater rapidly depleting.

The only solution is for basic necessities in this unique and fragile environment to be realistically priced. Realistically priced would necessarily mean a price that would be able to keep CO₂ levels low enough to maintain the region’s unique ecosystems, and total consumption low enough to keep aquatic systems in order. It is clear that with 2 million people southwestern Australia is quite grossly overpopulated. Based on current runoff levels, that is around 100 litres per person per year or one tenth the accepted minimum of 1000. That would mean prices for energy and water would have to be sufficient to exclude all but the most frugal people.