Australia will start to get an idea of where it is going on climate change, later this week.

That will happen when Professor Ross Garnaut’s draft report on the nation’s options is published.

It will be published on Friday.

Professor Garnaut’s final report won’t be released until September.

Garnaut is making no secret of the fact that climate change science is still far from mature.

But he is  also saying that the costs of waiting until it is will, almost certainly, be higher than those of starting to act now.

He compares the state of public knowledge now with that which existed, when Columbus sailed west, several centuries ago, searching for China.

Garnaut admitted, too, that even the best climate change scientists we have now differ, even with each other, on important points.

He concedes, too, that Galileo’s case shows that one person can be right, when many others are wrong.

But he says uncertainty is no excuse for inaction.

And Garnaut warns that, in current circumstances, the “business as usual” option must be rated as “high risk.”

“This has no close precedent,” he said.

The professor’s draft report, though, is expected to provide the first real guide to the approach to climate change, that the Rudd government is likely to take.

This will be a rough – and expensive – ride.