Monday, 26 January 2009

The future climate of Melbourne

Twenty-five days with no rain in Melbourne and only dreadful hot weather in sight have really hit hard on me.

Along with a repeat of the super-powerful 1999/2000 tropical wet season – nearly as much rain has fallen in Camooweal as during the big wet of January 1974 – it is clear that what Australia will have, even from this year, is a climate unlike anything known from instrumental or paleoclimate records even in recent global-warming affected years.

What would surprise most people is that under this new climate Melbourne – Australia’s second-largest population centre – will rather than a very temperate climate be the most arid place in the entire continent. Reduced reflection form the centre of the continent will allow a deeper monsoon displaced as far south as the cycle of the Sun – or approximately as far as Alice Springs – and this will drench the majority of the continent during the summer months almost every year in a manner beyond even that of January 1974.

However, for southern Victoria, Tasmania and adjacent areas of South Australia, this extended monsoon will bring hot north winds with a consistency unknown in the instrumental record. As the old tropical air crosses the Great Divide, it will be left dry and incredibly hot. More than that, it is known that the Hadley circulation or subtropical high has already shifted seven degree south since 1979 (probably about ten degrees since global warming took hold of our climate in 1967) and can be expected to have its centre around Bass Strait year-round from this year, with the result that the last cold fronts will have passed southern Australia in 2008.

The consequences will be threefold for southern Victoria and adjacent areas:
1) entire absence of their once-reliable rain-bearing winds, so that the winters will be as rainless as in, say, Burketown historically.
2) entire absence of relieving cool changes – even dry ones – in the summer. This will permit, instead of a record over 150 years of five successive days over 40˚C in Melbourne, an average of twenty to thirty in succession every summer.
3) forest trees adapted to fire will never recover because the bone-dry weather will allow annual summer fires to ultimately kill off seedlings, leading to the extinction of not only the wet-adapted tall eucalypts like Mountain Ash, but even to species adapted to a subhumid climate like that of the Western Plains

My mother told me yesterday that the extinction of the tall eucalypts and cool-climate rainforests would not be a crime to compare with what the USSR did to the Aral Sea. It is hard to agree given how unique such species as mountain ash, snow gum and the numerous heathland wildflowers that typify the native flora of southern Australia are. It has grown clear to me that Australia’s masses are not going to cause a reduction in the greenhouse emissions of a nation that should be allowed, not twelve times the world’s average per capita emissions, but as a reflection of its fragile ecology and sensitive hydrology no more than five percent of the average. Thus, it is time Australia was internationally regarded as a “rogue” state akin to Cuba, Iran and Sudan. At least that might make Australia’s people and others think about how awful their environmental record already is and will prove in the future on present trends.

No comments: