KEY POINTS:
Delegates to the Bali climate change conference barely had time to pack their bags before the White House issued a statement expressing "serious concerns" about the deal to which its representatives, along with those of 186 other countries, had just agreed.
It was a salutary reminder that for all the progress made at Bali the geopolitics of climate change remain excruciatingly difficult.
A chorus of relief greeted a last-minute United States "U-turn" which prevented the conference from breaking up as an acrimonious failure. We should be grateful for that.
The process of negotiating a post-2012 treaty can now begin and a deadline of 2009 has been agreed. We should be grateful for that too.
The parties have committed to the "consideration" by all developed countries of quantified emission objectives and "comparability of efforts" among them.
The optimistic view, exemplified by Climate Change Minister David Parker, focuses on the "all" and the "comparability" and sees it as an undertaking by the US to join the rest of the developed world in adopting emission reduction targets.
The cynical view focuses on the weasel word "consideration" and notes that the US was also a key player at the Kyoto conference 10 years ago but never ratified the Kyoto Protocol.
Which brings us back to President George W. Bush and his serious concerns.
"The problem of climate change cannot be adequately addressed through commitments by developed countries alone. Major developing countries must also act," he said.
This is undoubtedly true. But it is equally undeniable that it is both unseemly and futile to expect major developing economies - code for China and India - to undertake any kind of economic sacrifice in the cause of curbing climate change when the largest and richest emitter of all is free-riding.
That is what most needs to change.
The US needs to step up and take responsibility for its contribution to global warming.
It is not all that needs to happen, but it is what needs to happen next.
Halfway through the two years the world has given itself to negotiate a new treaty the US will elect a new president.
He or she will be more progressive than Bush on climate change - it is scarcely possible to be less so. But American concerns about climate policy handing China another competitive advantage will not magically dissipate with Bush.
The risk is that the climate treaty will become entangled in a broader rivalry between the US and China.
It could become hostage to American concerns that have everything to do with trade imbalances and the loss of manufacturing jobs, the currency peg and the role of sovereign wealth funds, and nothing to do with the poor old planet.
A more optimistic view goes like this: The US is no exception to the rising international tide of popular concern about climate change. The fate of John Howard across the Tasman is a warning to politicians who underestimate that.
An increasing number of large US corporations are alive to the opportunities of leading the switch to cleaner technologies for generating electricity and propelling vehicles which will inevitably succeed the 19th century ones we currently rely on, and the risks of being left behind in that process.
Meanwhile nobody needs to explain to China or India about the potentially calamitous consequences for them of untrammelled global warming.
Or that economic growth at any environmental cost is a self-defeating policy.
Or that it is foolish to become hooked on oil just as it becomes really scarce and expensive.
So there ought to lie the basis for a deal in Copenhagen in two years' time.
It is just that the Bali road map to Copehagen leads through some pretty challenging terrain.
Negotiators will work on a regime for providing incentives for avoided deforestation in developing countries - a source of emissions comparable to the world's entire vehicle fleet.
There is also a mandate to work on sector-specific agreements, seen by some as the best hope of avoiding "leakage", where emissions-intensive activities merely migrate from countries with tough emission rules to those which have none.
Part of the price of an agreement at Bali was for the European Union to drop its insistence on the need for developed countries to commit to cutting their emissions by 25 to 40 per cent from 1990 levels by 2020.
It was supported by New Zealand, but with the caveat that it was only meaningful in the context of a long-term goal all parties had signed up to.
This support could be seen as disingenuous.
New Zealand's gross emissions are 25 per cent above 1990 levels right now; there is not the remotest possibility of reducing them to 25 per cent below that level in little more than a decade, especially when half of them arise from the metabolic functions of ruminants.
True, post-1990 forests provide an offset that should reduce our net emissions by 2012 to 12 or 13 per cent above 1990 levels. But by 2020 the surge of planting in the early and mid-1990s will be nearing harvesting age and the forests will turn from a sink to a source, adding to the emissions for which the country is accountable.
So New Zealand will inevitably be looking for special treatment in the context of any collective target for developed countries.
Instead of a quantified range by a certain date, the Bali road map ends up referring only to the need for deep cuts in emissions as a matter of urgency.
There is only a footnote referring to those passages in the United Nations Intergovernmental Panel on Climate Change's fourth assessment report this year which spell out what deep and urgent really mean.
Cuts of 25 to 40 per cent by developed countries by 2020 and 80 to 95 per cent by 2050 are what the IPCC reckons is necessary to stabilise the level of greenhouse gases in the atmosphere at 450 parts per million CO2-equivalent, which in turn ought to limit the increase in the average global temperature to 2C above pre-industrial levels.
A less ambitious goal of 3C of warming would still require developed country emissions to fall to 10 to 30 per cent below 1990 levels by 2020.
And it would be more likely to be above the threshold for dangerous climate change.
