Tim Costello/Tim Flannery

Over the past 50 years southern Australia has lost about 20 per cent of its rainfall, and one cause is almost certainly global warming. Similar losses have been experienced in eastern Australia, and although the science is less certain it is probable that global warming is behind these losses too. But by far the most dangerous trend is the decline in the flow of Australian rivers: it has fallen by around 70 per cent in recent decades, so dams no longer fill even when it does rain. Growing evidence suggests that hotter soils, caused directly by global warming, have increased evaporation and transpiration and that the change is permanent. I believe the first thing Australians need to do is to stop worrying about “the drought” – which is transient – and start talking about the new climate.

The cities need drought-proofing by, for example, installing water tanks in all dwellings that can accept them. Because in affected areas the decline in river flow is three times that in rainfall, water tanks that use roofs as catchments are now far more effective than dams for supplying drinking water in cities such as Sydney and Brisbane.

So there you have it.  Way back in 2007 Tim Flannery said that the dams in Australia will no longer fill even when it does rain and that water tanks on roofs were more effective than dams for supplying drinking water in cities such as Sydney and Brisbane.  The line was that Australia’s East Coast cities are running out of water – due to global warming.

I do not need to tell you the main dams in Sydney are over-flowing with water. So Dr Flannery dropped his claim that Australian cities will run out of water due to climate change.  It has been replaced by the claim – in The Angry Summer –  that climate change will lead, inter alia, to “extreme rainfall and damaging flooding”.

 In May 2011, Flannery, when challenged over his 2007 forecast, told AFR journalist Marcus Priest that he “can’t remember everything” he said just four years earlier, but in May 2012, Flannery told the ABC’s Jonathan Green that his previous predictions had been taken “out of context”.