Asa Wahlquist, rural writer | October 10, 2008
THE drought affecting southern Australia is officially the worst on record.
Victoria has recorded the driest year in history. In April, vines were removed from Merbein vineyard due to the drought. Pic: Graham Crouch
David Jones, the head of climate analysis at the Bureau of Meteorology, said the drought affecting south-west Western Australia, south-east South Australia, Victoria and northern Tasmania "is now very severe and without historical precedent".
Dr Jones said Victoria had had "the driest multi-year period on record, but also by far the hottest".
He said the rainfall deficiencies were the largest on record.
"If you look at Victoria, where the effect has been particularly severe, in the last 12 years we have now missed out on two years of rainfall, which is an extraordinary result,” he said.
“Across Victoria as a whole, if you add up how much rainfall has been missed in 12 years, it is now up around 1300mm or four feet of rainfall, a very, very large rainfall deficit."
In contrast, much of northern Australia is experiencing well above average rainfall, with a record high rainfall across the Top End, the Kimberley and parts of Cape York Peninsula.
Dr Jones said the current dry started in 1996 in Victoria, while the Murray-Darling Basin moved into drought in late 2001.
He said temperatures were running at about one degree "above any previous comparable drought. That is substantially hotter, and that one degree is a global warming signal."
He said the data suggests that for every one degree of warming, there is a 15 per cent decline in run-off, or river flow, in the Murray-Darling Basin.
"Those numbers are what we are seeing. They are perhaps larger than we would have expected from a theoretical basis, but it is clearly a whole sequence of changes are happening in our catchment in response to the climate change," Dr Jones said.
He said a similar drying pattern had been observed in Europe's Mediterranean, and the south-west in the USA.
"There are currently some very severe droughts in those regions, and also substantial rainfall declines."
He said the current dry was at the extreme end of what the climate models had predicted.
The most dramatic effects have been felt by Melbourne.
Melbourne recorded its driest September on record.
"If one looks at the history of data we have for Melbourne, we have rainfall records going 150 years. We simply have not seen anything like what we currently have, not even close," he said.
The previous longest dry for Melbourne was the six years from 1979 to 1984.
"Starting in 1997 we have had 11 years, nearly 12 years" of dry conditions.
