Over the next year, John Key faces a choice between his – and New Zealand's – international reputation on one hand and National's support base on the other as he wrestles with reducing our carbon footprint

If you use the language of the Prime Minister's favourite past-time to describe his political style, you'd say he's got a great short game. Short-term, or at least term-to-term, he's proven himself a master reading the public's appetites and knowing his political limits.

Call it poll-driven or short-sighted, but it's been darn effective both in managing the immediate economic crises his government's faced and winning votes. As I've written about Bill English before, this government has been defined as much by what it hasn't done as what it has. But there's a flip-side to this, laid bare at the G20 this weekend.

One of the defining marks of the Key years has been a refusal to engage with long-term issues; "kicking the can down the road", as some like to call it. His modus operandi has been to say, if I don't have to face up to it now, I'll leave it for some other PM. You can see it in his refusal to engage on the retirement age, cutting contributions to the Cullen Fund, public transport and of course climate change.

But he can't keep kicking the climate can down the road as he has done. His golfing buddy Barack Obama called Tony Abbott out this weekend at the G20 in Australia in a pretty unsubtle way. You might he he shirt-fronted Abbott, talking of the risk of the Great Barrier Reef disappearing before he and his grand-kids had a chance to see it.

Obama said the Asia-Pacific region had more to lose from climate change than any other part of the world and said all countries needed to act and act decisively. You could argue Key was as shirt-fronted by that as Abbott was.

Our Emissions Trading Scheme is now a joke, emissions are up 20 percent under National and by the Ministry of the Environment's own estimates say we are nowhere near on track to meet our own goal of cutting emissions to 50 percent of 1990 emissions by 2050.

Key has settled on a safe series of political spin lines regarding climate change – New Zealand is too small to make a difference, nothing matters unless the big emitters change, we're doing our bit through the global alliance, we already use a lot of renewable energy, and we have a unique footprint that's got more to do with farming than fuel.

He's evolving the argument behind that last point, saying that because we produce food for the world – and the world does need more food – other countries should give us an free pass and not insist we cut emissions as much as them.

All of these lines work at home; Key's political calculation is that anyone who truly cares about these issues is probably voting Green anyway, so for at least another term or three there's little political cost to him in ignoring the problem. But it'll be less acceptable abroad.

In truth, Key's reluctance to move comes down to the economy and his government's failure to "re-balance" it. Because we are so over-dependent on dairy – and agriculture more generally – making a difference to our emissions would come at a high cost to our farmers, and therefore the country.

Because Key and Co don't like to look long-term, they've failed to see a) the economic need of transitioning to a more blatantly green economy and b) the economic opportunity of being a market leader in this area. The deal between China and the US this month looks like an opportunity missed for this country; China has to spend what in technical terms you might call a gazillion dollars to ensure its emissions peak by 2030. That will mean a lot more non-coal-fired plants; if we had taken the Greens' advice six years ago and put the power of the state and market behind our own renewables energy we'd be in a great position to reap the profits.

That's all by-the-by now, but the very real problem for Key is that Obama is determined action on climate change will be a legacy of his presidency and with China moving on the issue, the time could be ripe for real action.

The next focal point for world decision-making is at the United Nations climate change conference in November next year and the pressure will be on for substantive action. Obama has already said the Copenhagen conference failed because leaders were still negotiating when they arrived, whereas the talking should be done by then and they should arrive merely to ratify. That means hard talking – and cabinet agreeing a new reduction target – early next year.

So Key and his cabinet face some tough choices.

On Sunday the Prime Minister all-but ruled out moving agriculture into our ETS while he's in power, which will make it hard to seriously cut emissions given that, as he says, we have a unique footprint with close to half of our emissions coming from methane.

He tried out this line about being a food-basket for the world, but it will be a hard sell. Lots of countries, America and China included, can argue they produce more food than we do and America exports tonnes more to the world. So why should we be able to hide at the back of the class and not be called out? Can we actually hide at such an event now we're on the Security Council? And are we prepared to sacrifice our reputation for moral leadership?

It seems international pressure means we will have to come up with a better target and will actually have to do something to achieve it, rather than heading in the wrong direction as we have under National. But farmers and much of the National Party base will be fighting that all the way.

So what's Key to do? Is his decision determined by his golfing buddy and international reputation or his support base and fourth-term dream?

Or, dare I hope, by a sense of responsibility to his grand-children's generation, so eloquently described by Obama in Brisbane on Saturday.