Canberra Times: If Hurricane Gustav had struck New Orleans with full force, what would that have told us about the scale and speed of climate change? If more of the sea-ice cover in the Arctic Ocean is lost in this year’s summer melting season than last year (which was the worst on record), will that convince people that global warming is a real and present threat? What should people accept as evidence? And what will they accept in practice? For scientists, the most persuasive evidence that …