New Zealanders who live in cities can help reduce climate change by using less fossil fuel for transport, Dr Ralph Chapman says.
He's an environmental economist who now teaches at Victoria University and spoke at the Whanganui Science Forum last week. He knows how governments view climate change, after working in New Zealand's Treasury for 12 years and in the Ministry for the Environment for 10.
He's just written a short book called Time of Useful Consciousness: Acting Urgently on Climate Change.
"Time of useful consciousness" is a term used by airlines to describe the time left before oxygen runs out when a pilot can still save an aircraft in trouble. It's now that time for climate change, Dr Chapman said.
In Paris nations are trying to agree to curb emissions and limit climate change to 2C - a temperature rise that would be difficult, but manageable.
However Dr Chapman said there was a 35 per cent chance temperatures would actually rise 4C, which would be catastrophic, and governments would unravel under the pressure. Worldwide the temperature has risen by 1C already.
The prospect of further rises has insurance companies, re-insurers and the World Bank worried. The number of earthquakes they have to pay for is relatively steady, but the number of droughts, fires, floods and storms is growing.
For the past 10,000 years there have been 180 to 300 parts per million of carbon dioxide in the atmosphere. Now there are 400, and rising.
It's already certain ice will melt and sea levels will rise, with low-lying cities like Miami and New Orleans doomed.
Carbon emissions from burning coal and oil have to be limited. New Zealand's National-led Government has gone to this month's Paris climate talks proposing to limit this country's emissions to 50 per cent of 1990 levels by 2050.
Dr Chapman said that was inadequate.
"Government is committed to a path taking the world to over 3C - unmanageable climate change. That's the government you elected."
The UN is asking developed nations to limit emissions by 85 per cent to 90 per cent in that time. China and the US, previously reluctant, have made stronger commitments than New Zealand.
Central government is focused on growth, jobs and income and its environment ministry "doesn't have the guts" to protect the environment.
"It's up to councils to take the lead, in the absence of commitment from central government."
Surveys have shown 16 per cent of people are not concerned about climate change, and 13 per cent deny that human activity causes it.
"That means that 60 to 70 per cent are concerned. Public opinion is pretty on the ball about this, at least in principle."
But Dr Chapman said decisions about climate change were made by people who would not face the worst problems it will cause. They tended to be people over 50, men rather than women and wealthy leaders of government and business.
Cities must get more compact, with people using public transport or by walking and cycling. That would cut carbon emissions from transport - 40 per cent of New Zealand's total.
Carbon should cost emitters $100 to $200 a tonne, he said, because the consequences cost that much. But New Zealand's emissions trading scheme, now being reviewed, puts carbon at $7 a tonne.
Flying to Europe and back creates four to five tonnes of carbon, as much as a whole year of car travel. Dr Chapman has mixed feelings about tourism.
"It's exploiting cheap travel, and travel isn't cheap. Travel should be expensive, if it's paying its real price."