THE public discussion in recent months has narrowed the range of serious debate about greenhouse gas mitigation in Australia. It is a while since any but the fringe dwellers of Australian public policy debate have denied that there is a warming trend. Nor is there now much serious denial that there is a substantial human contribution to that trend.

The excellent Productivity Commission report has settled the question of whether other countries are taking action to reduce the risks of dangerous climate change. It has also played a significant role in what is now a decisive victory for carbon pricing over regulatory intervention in the battle of ideas.

Carbon pricing happens to be the low-cost way to meet national targets, but if some countries want to shoot themselves in the foot by doing things in an expensive way, they are free to do so.

But in this world, in which each country is reducing emissions in its own way, how do we work out what is a fair contribution from each?

The Productivity Commission was not asked, and did not seek, to answer that question. A few commentators who sought to draw an implication that the commission's report contradicted my statement that Australia was a laggard were wide of the mark.