Monday, 5 January 2009

Caution before taking sceptics seriously

A site shown to me by my recent RMIT minder recently published an article stating that 2008 was an unusually cool year and that it is justification for global warming scepticism.

It is a pity I have been unable to contact John J. Ray, since I could show him by means of decile maps for 2008 that the rainfall over southern Victoria and Tasmania, which has shown alarming declines of 25 percent since 1997, showed not the tiniest improvement this year. In fact, 2008 ranks as the sixth-driest year in Hobart since records began in 1882.

Hobart’s climate has dried out from anthropogenic global warming so much that four of the twelve driest years and none of the thirty-seven wettest years have occurred since 1999. (Indeed, of these thirty-seven wettest years only two – 1985 and 1996 – have occurred since the first “magic gate” was passed in 1976).

Even the claims about 2008 being a cool year are false. Here in Melbourne it was yet again among the warmest ten percent of years since 1910, whilst over Central Australia where the monsoon did not penetrate as between 1997 and 2001 it was similarly warm compared to historic temperature records. Only over the densely-settled area bounded by Nowra, Bundaberg and Moree was 2008 a noticeably cool year: in fact in Sydney, despite rainfall being a little below normal, it was among the coolest ten percent of years since 1910. This would mean that, even if 2008 was still warm over Australia as a whole, it was perceived as a cool year because it was cool over the small densely settled region of the continent.

Such anomalies, noted in the first Annual Climate Statement I read back in 2000, are in fact more common than even the Bureau makes them out to be. They are most notable for the dry years of 1905, 1928 and 1935, which all rank among Australia’s eight driest years on record, but would be perceived as distinctly wet by most Australians (see for instance the Hobart table above).

All in all, rainfall and temperature data for 2008, even if the Eucla and Goldfields have hardly maintained their excessive rainfall of the 1997 to 2006 decade, is no evidence against man-made global warming.

Strangely, one is hearing no claims that it is the “Asian Haze” that has cause the drying of Melbourne’s dams (though I imagine at least some laymen do believe this): it is possible that the “Asian Haze” could reduce rainfall over Victoria and Tasmania, though I cannot believe it could do so to the extent seen since 1997.

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