Does the Cancun outcome give real hope for curbing climate change? Views diverge...
Within the last week we've run here on the BBC News website two articles by people knowledgeable about climate change that reach widely differing conclusions about the outcome of this year's UN climate summit.
Last week, Kevin Anderson, head of the UK's Tyndall Centre for Climate Change Research, wrote that the outcome offers small comfort:
"There is currently nothing substantive to suggest we are heading for anything other than a 4C rise in temperature, possibly as early as the 2060s... it is hard to find any scientist seriously engaged in climate change who considers a 4C rise within this century as anything other than catastrophic..."
Yet this week, Achim Steiner, head of the UN Environment Programmes, argues that the outcome "has put the world back on track" to combatting climate change - although he acknowledges the speed of travel will leave many frustrated.
Both are entirely reasonable deductions bearing in mind the standpoints from which each approaches the issue - Professor Anderson from science, Mr Steiner from politics.
In Cancun itself, even though many national delegations would probably have agreed with Professor Anderson's diagnosis, they went for the only politically feasible deal on the table - an agreement cleverly constructed by the Mexican hosts that allowed every nation to head home claiming at least a partial victory.
Every nation, that is, except Bolivia, which remained apart. Its objections were noted; but that's all, the Mexicans deciding that if every other country wanted the accord, that was consensus enough to move forward.
The Bolivians were incensed enough by this that there's talk of legal action - although it's not clear who they would sue. The UN overall? The UN climate convention? The Mexican government?
Thoughts are being drawn from lawyers expert in UN lore over what "consensus" means. Does it have to mean, in this case, all governments - or is all but one OK?
The question has a political angle as well. In the Bali summit of 2007, the single government holding out against the proposed deal was the US; if they had not in the end come round, would the Indonesian hosts have been as willing to "note" US objections and move on declaring consensus as the Mexicans were to work around Bolivian objections?
Bolivia's Evo Morales was the darling of some activists - but is the country right?
The Bolivia situation is also causing a good deal of angst among the pressure groups and think tanks which are trying to outline the strategy they'll pursue next year in the run-up to the UN summit in Durban.
According to the picture of climate science outlined by the Intergovernmental Panel on Climate Change (IPCC), the Bolivians are right: the Cancun agreement is too weak on emission cuts and, as things stand, the world probably will see temperatures rise beyond the 2C or 1.5C levels that most nations say they want.
Major effects are likely, not least on the icefields and water supplies of South America itself.
On the other hand, the Cancun agreement does explicitly acknowledge that fact.
It is also an agreement that explicitly requires more of the governments that signed it.
Furthermore, it starts to operationalise things that many developing countries and NGOs hold dear, such as finance for climate adaptation and a mechanism for paying countries to tackle deforestation.
And it is, politically, the only game in town, approved by governments of many nations at least as climate-vulnerable as Bolivia.
Which takes us back to the Kevin Anderson / Achim Steiner divergence.
My suspicion is that the strategy emerging will be to see Bolivia as the "conscience" of the UN climate convention. To swing behind the Bolivians and condemn the rest of the world for its "consensus" - as some groups are advocating - would surely close avenues of co-operation that many will want to pursue.
But there are other big questions to be addressed as well.
First and foremost is the question of "legal form", as it's known within the climate convention.
At one end of the spectrum of possibilities sits a legally-binding treaty. At the other is "pledge and review" - where each country says what it's going to do, unilaterally, and then looks back five or 10 years later to see whether the pledges were met.
The first of those options would follow the model of the Kyoto Protocol; the second concept is entrenched in the Copenhagen Accord, the minimalist document that emerged from 2009's ill-starred summit in the Danish capital.
The Cancun agreement attempts to be neutral on the question, setting the legal form of any new agreement to one side. To have done otherwise would probably have wrecked any chance of consensus at the summit.
There are elements that go further than "pledge and review" - for example, agreement that some kind of international system (very sketchy on detail at the moment) will be in place for monitoring and assessing countries' performance against their targets.
International environmental treaties are traditionally unpopular on Capitol Hill
Nevertheless, chunks of language appear to have been imported directly from the Copenhagen Accord.
And although there are elements that require movement in a genuinely multilateral way - for example, the management of the new Green Fund - there is no indication that industrialised nations are required to negotiate their pledges upwards in order to meet the "emissions gap" they have themselves identified.
The US administration, meanwhile, has indicated once again that it will not countenance anything legally-binding in the near term unless China does likewise.
But bearing in mind the traditional hostility of the other US government, the Senate, to ratifying UN environmental treaties, there must be considerable doubt as to whether the US would in fact sign up to a legally-binding treaty even if Tuvalu, Togo, Tanzania and the rest of the developing world were prepared to.
And China, India, Saudi Arabia (and perhaps Bolivia) will certainly not accept legally-binding emission curbs unless the US, Japan and others do likewise.
So should the push still be for a legally-binding treaty? Or should movers and shakers take the line that the scale of the cuts is more important than the legal form of a new agreement, and work with governments to increase their ambition?
The position of Japan perhaps exemplifies the dilemma.
Clearly it is not going to accept further emission cuts under the Kyoto Protocol when its current commitment period closes at the end of 2012.
Yet in terms of the scale of what it has pledged - a 25% emissions cut from 1990 levels by 2020 - it is ahead of virtually every other country.
In Cancun, it and the other Kyoto refuseniks (with Russia and Canada to the fore) negotiated a clever little deal whereby pledges made by developed countries inside and outside the Kyoto Protocol will be entered in the same register.
That permits them to claim that pledges are equivalent, whether made under the protocol or not.
In fact, one possible pathway for the year ahead sees these three nations formally withdrawing from the Kyoto Protocol, as they are legally allowed to do - a pathway that could well lead to other developed nations doing the same.
Another pathway sees them staying within it after 2012 - ensuring access, perhaps, to its "flexible mechanisms" - but putting their emission pledges outside it.
So is Japan to be condemned for putting a roadblock in the way of a legally-binding treaty, or congratulated for pledging deep emission cuts in what is already a very energy-efficient economy?
China, and other developing nations, are pursuing their own clean development plans
Is there any point in pushing the legally-binding option given the very real political obstacles?
The issue is painted more clearly still by comparing the situations of Canada and Spain.
A few years ago, both were way off track to meeting their Kyoto targets.
Canada decided not to try; Spain embarked on a major renewable energy drive, has been buying carbon credits by the bucketful, and fully intends to meet its Kyoto goal.
The difference between them has nothing to do with the legal form of an international agreement; it is entirely a question of divergent political directions. The Canadian situation also shows that the notion that emission pledges can truly be considered legally-binding is highly questionable (as discussed here in the run-up to Copenhagen).
Yet most developing countries and many other players are deeply wedded to the idea of a legally-binding deal, and the idea of abandoning the goal would be anathema to many - perceived as an admission of defeat.
Another strategic issue concerns the Green Fund.
Lots of work needs to be done - mainly outside the UN climate convention - in order to make it work as envisaged.
Finance ministers will ultimately have to commit money from national coffers, and agree on "innovative finance" mechanisms that will probably be resisted tooth-and-claw by elements of the business community.
Yet the sum that industrialised countries mean to raise - $100bn per year by 2020 - is not, according to estimates from bodies such as the World Bank and the International Energy Agency, enough for the twin tasks of helping the developing world "green" its energy sector and protect itself against climate impacts.
So should the strategy be to work with governments to fully operationalise the Green Fund, or push the point that more cash is needed?
One thing that is clear is that neither scientists such as Kevin Anderson nor pressure groups need any more to tell rich governments "our research shows you need to do more".
The wording of the Cancun agreement instead allows the message to be "you agree you need to do more - and you've said how much - and here's how we think you can close the gap that you've identified and say you're worried about".
For people who follow the politics of the climate in all its intricacies, the road to the Durban summit a year from now promises to be a fascinating one.
Kevin Anderson and the Bolivians are right - the Cancun outcome does not solve the problem of man-made climate change.
But Achim Steiner and the other nations are also right - it does open the door to the climate agreement that the science says is needed.
And that was a door that a year ago, in the chilling winds of Copenhagen, seemed firmly closed.