Late in August, while the Business Council of Australia was making its ambit claim to limit Australia’s emissions reductions to no more than 10% cuts by 2020, the famous North-west Passage around the north of Canada opened.

A few days later, just as Martin Ferguson was circulating his “softened” emissions trading proposal to big polluters, the North-east passage, around Russia, also opened.

Both these historically and strategically significant events have occurred individually in recent years as the Arctic summer ice has progressively melted. But this is the first time in human history that both passages have been open simultaneously, making the North Polar ice cap an island, and the consequences are far-reaching.

At the end of this week, when Ross Garnaut gives his most critical advice to the Rudd Government – his recommendation as to the short, medium and long-term caps on greenhouse gas emissions for Australia – he must keep those consequences at the forefront of his mind.

As Professor Garnaut well knows, what is happening at the top of our world will flow through to the rest of the planet if we don’t act swiftly and decisively to turn around our emissions and build a new, zero emissions economy across the globe. The Arctic is the driver of several tipping points that, if breached, could send our climate spinning out of control.

The Arctic ice plays a vital role in the Earth’s energy balance through a phenomenon known as albedo. White ice reflects much of the Sun’s energy back into space while dark water absorbs that energy, leading to both local and global warming. As more ice melts, replaced by the dark sea surface, the heating process is dramatically accelerated. We know that the Arctic ice collapse of recent years is already having flow-on effects around the edges of the Greenland ice sheet, and in the Siberian and North American permafrost.

If we trigger the melting of that permafrost, releasing billions of tonnes of methane into the atmosphere, all bets are off as far as warming is concerned. Our planet will head into a runaway heating cycle of 6C and more, leading to widespread inundation, agricultural collapse, loss of drinking water for a third of the global population, and all the consequent geopolitical and security implications.

Is it alarmist to raise this prospect? Given the high scientific likelihood that, if we do not rapidly change the way we power our society, it will come to pass within the lifetime of our children, I don’t think so. Rather it is an alarm call that we would be foolish to sleep through.

What this means for Professor Garnaut, and the Rudd Government, is that any policy framework that seeks to address climate change must actually seek to prevent runaway climate change. We must seek to limit warming by as much and as fast as we still can or else the warming we have already locked in may swiftly overtake us. A policy which seeks to make incremental change, which seeks to cut emissions at the edges, without a plan to completely decarbonise our economy, is not a climate change policy. It may be an economic policy. It may be an election policy. But it is not a policy that seeks to address climate change.

Those who say we should wait for the rest of the world, including some of the world’s poorest people, to act before we do are apparently happy to let global negotiations continue on the road to nowhere where no country moves before the others. We desperately need a circuit-breaker. Coal-dependent Australia making a bold leap into the post-carbon economy could provide such a jolt to the geopolitical debate that a new world becomes possible.

Professor Garnaut and the Government have one clear decision ahead of them. Regardless of the whole array of details which will govern the operations of the emissions trading scheme and make it more or less efficient, the fundamental point is that it must have a cap that is consistent with an environmentally credible limit on emissions.

At one end of the spectrum, the Greens are arguing for an environmentally responsible, challenging, but achievable target of 40% cuts below 1990 levels by 2020, setting Australia on track to zero net emissions by mid century at the latest. At the other end, the Business Council of Australia claims that it cannot countenance a scheme that reduces emissions more than 10% below 2000 levels over that timeframe.

Will the Government side with big business, regardless of the consequences? Will it at least join the Europeans in committing to 30% cuts by 2020? Or will it step up to the mark that it was elected to achieve and choose the path that gives our planet a decent chance?