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So it is to be between 10% and 20% below 1990 levels by 2020, and it will cost all of us an estimated $30 a week extra: but bear in mind this is a target for New Zealand's negotiating position at the international climate change conference in December.
This means the final target could be higher or lower, or none at all if the conference collapses in failure. After all, the United Nations' Intergovernmental Panel on Climate Change believes a 25% to 40% cut is needed from developed countries as a whole by 2020, with an 80% minimum reduction by mid-century.
New Zealand's offer is very conditional: other countries must play their part to New Zealand's satisfaction. All the critics of the Government's climate change policy are unhappy, as might be expected.
One of the most active, Greenpeace, intends to continue its campaign for its relatively extreme position of requiring cuts of 40% - and never mind the cost or the economic damage this might cause.
It says the Government's initially low range comes nowhere near what science says is necessary. The Greens want a public campaign to force the target to be raised, and the Labour Party thinks it is too low to be taken seriously by anyone, including by our trading partners.
The problem with these censorious arguments, however, is that while they might have theoretical virtue, governments have to deal with political realities.
The public have to be persuaded to accept that the target can be met by reducing domestic emissions, storing carbon in forests through more tree planting and purchasing emission reductions from other countries, rather than by much more onerous means.
There will also be an emissions trading scheme covering all sectors, although details have yet to be announced.
As it stands, it is likely the public will be aggrieved by the likely direct cost to them, for the sole study quoted in reports this week suggested a 15% reduction would result in a drop in disposable income from $49,000 a year to $47,650 in 2020.
Petrol prices could rise by between 3.7 cents a litre and 12.3 cents a litre, depending on the price of carbon. Not surprisingly, many business groups urged the Government to aim for less than 10% in its target; so did the Treasury, doubtless fearful of the economic impact of anything higher.
Even meeting the new target, assuming it stands, will be difficult and costly, because New Zealand already exceeds the 1990 levels by 24%, according to John Key. But meeting it will certainly change people's behaviour in the ways they use fuels for heating and transport, and generally by acting in sustainable ways.
The debate will proceed now at least with some sort of finite skeleton: moral and environmental imperative versus economic cost.
The Government argues that it has taken a line which balances the environmental need with the economic pressures, but there must remain a concern that the lower target strategy might cause problems with New Zealand's internationally promoted "clean, green" image, especially if the talk gets very tough in Copenhagen and the post-failure search begins for scapegoats.
The nightmare of a transportation premium being imposed on our exports cannot be far from the minds of ministers.
But on the brighter side, now that a target range has been preferred, efforts to continue the search for and development of renewable energy technologies will accelerate, while the urgent research and development on the science of agriculture-based emissions might, if it succeeds, prove to be a saviour for our agricultural sector.
The conditional target the Government has set gives it a great deal of negotiating room; indeed, one of the conditions, that major developing countries (China and India) take action "commensurate with their responsibilities", could be read as a back-out clause.
And there will be argument about why the United States - considered by some critics to be the world's worst polluter - has not been added to the list.
But the critics need reminding that the New Zealand offer is but an opening bid, like those of several other first world countries such as Australia (14%), Canada (3%) and the US (no change from 1990).
There is an argument that New Zealand's emissions are far too small in a relative sense to have any significant bearing on climate change, and that therefore we should ignore international demands and protocols.
Once again, however, New Zealand has no realistic choice but to respond, in a sense because of its very smallness, but also because half of our emissions come from agriculture, and that represents a Damoclean threat other countries might use against us now that climate change and international trade are becoming inextricably linked.