In October 2006 Flannery quoted a US Navy study stating that, there may be, "no Arctic icecap in Summer in the next five to 15 years. He also quoted NASA's Professor James Hansen, "arguably the world authority on climate change" who said, "we have just a decade to avert a 25-metre rise of the sea". In February 2007, as he explained how increased soil evaporation impacts on runoff, he said "even the amount of rain that falls isn't actually going to fill our dams and our river systems" and in June 2007, he said that, "Adelaide, Sydney and Brisbane, water supplies are so low they need desalinated water urgently, possibly in as little as 18 months".