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Business should be thinking about the response to climate change not as a threat but as an opportunity, says Intergovernmental Panel on Climate Change chairman Rajendra Pachauri.

The IPCC is the United Nations body whose task is to report to governments every five years or so on the state of science on climate change, its environmental impacts and what can be done to mitigate it.

Pachauri is visiting New Zealand at a time of vigorous debate between two views. One, espoused by Climate Change Minister David Parker, says that if New Zealand, which is relatively affluent and well endowed with renewable resource, and which trades on a clean, green image, cannot get on top of its carbon emissions, what hope is there for the world. And what sort of signal does it send to countries which face a harsher version of the same dilemmas?

The other view, associated with some of the business lobby groups, says New Zealand is a tiny fraction of the global problem and where doing our bit ends and futile self-sacrifice begins depends on what the rest of world is doing, which at the moment is not much. Better to proceed gingerly.

"I would say Minister Parker's view is a very enlightened one," Pachauri said. "But even from the perspective of NZ business, if you look at this only as a threat or a cost you are taking a very limited view. There are huge opportunities involved."

Companies which grasped that the world is in transition to a low-carbon economy and adapted their practices and technologies accordingly, would be the winners. Laggards risked going out of business. He rejects the idea that the fate of the planet will be decided by China and India, and that neither looks very encouraging at the moment.

"India has 400 million people with no access to electricity. Can any elected government say: 'Look, we have got to cut down on emissions and you guys are going to have to live out your lives in darkness, and so will your children?"'

It would be irresponsible and perhaps self-defeating for developing countries to do exactly what the developed world had done, in terms of the carbon intensity of their development.

But it is the US, whose per capita emissions are 20 times India's, which has to lead, Pachauri said.

"I am optimistic about the United States. There is a groundswell of public opinion and we are seeing some states and Canadian provinces coming together to curb emissions."

And Barack Obama and John McCain favour a cap-and-trade scheme.

"We don't have too much time. I personally feel the next two or three years are going to be absolutely critical," Pachauri said. "If you have a 2 degrees increase [in global average temperature] as the stabilisation target, emissions would need to peak no later than 2015. That's just around the corner."

Other targets the IPCC has considered allow global emissions to peak later, but carry greater environmental risks. The UN framework convention on climate change spelled out the central objective of preventing a "dangerous" level of human interference in the climate system.

Defining what counts is dangerous, Pachauri said, and cannot be decided on the basis of averages.

"It is really a question of looking at the most vulnerable regions of the world ... like small island states and parts of sub-Saharan Africa."

People can have confidence in the IPCC's conclusions, he said.

"The process is so robust - almost to a fault - that I'm not sure there is too much scope for error. Where there are gaps we are very candid in admitting we don't know enough about this subject," he said.

"Given that it is all on the basis of peer-reviewed literature. I'm not sure there is any better process that anyone could have followed.

"Yes there are sceptics but the number has gone down - even if their decibel level has not."