When activists and journalists can't get hold of government documents, you know things have turned serious.

OK, I'm exaggerating a bit. But it is a trend that you notice as a reporter; the more things actually matter - the closer events move to what governments really hold to be important, rather than what might seem important from some agenda or fancy formal title - the closer they guard information.

So it's interesting just how little has leaked out this week about the contents of two contrasting visions presented to a gathering of "select" countries in Copenhagen - visions that put forward radically different versions of the political deal that might be done over the next two weeks (given that discussions on the formal treaty text aren't expected now to approach conclusion).

In one corner were the Danish hosts, with a formulation that reportedly repeated the attempt made at July's G8 summit to get major developing countries to adopt the goal of halving global greenhouse gas emissions by 2050, and accept 2020 as the date by which they should peak.

It was turned down in July, and it's been turned down again.

An analysis presented at last year's UN summit in Poznan calculated that if developed nations vowed 80% cuts by 2050 - which most subsequently have, at the G8 summit - population growth in the developing world meant developing countries would have to make per-capita cuts of about 60% by 2050 in order to meet the global 50% target.

And it's too much for developing countries to countenance. Although a 50% target wouldn't be legally binding in any meaningful sense, it would indicate that major developing economies were preparing to accept emissions cuts when their main contention is that Western nations continue to proffer too little.

Details of what precisely is in the counter-proposal - put forward by the BASIC group (Brazil, South Africa, India and China) - are even more sketchy.

They are thought to include a rejection of any binding constraints on emissions for developing countries, opposition to international verification of those constraints, opposition to the notion of trade tariffs on countries unwilling to curb emissions, and the continuation of emission reductions from developed nations under the Kyoto Protocol rather than any new framework, which is anathema to the US.

The BASIC nations are said to be prepared to walk out of the Copenhagen chamber if these demands are not met, presumably accompanied by other developing countries.

But as I said, discovering exactly what is written on these pieces of paper is a task that's been beyond just about everyone outside tight government circles - an indication that the real powerplay has begun.

The waters muddied further when the Danish government denied having put a proposal forward - despite the fact that Reuters journalists had seen a text of what appeared to be such a document, and that developing country delegates had commented on what appeared to be such a document.

On Thursday, India became the last major player to put a proposal on the table, vowing to cut carbon intensity by 20-25% by 2020.

Initial reports suggested the figure was conditional on international financial support, but Environment Minister Jairam Ramesh made it clear that it is unilateral and independent of anything that anyone else might offer at Copenhagen.

As to what will be on offer financially, the US said this week that it would pay its "fair share" of the $10bn per year fund that various people (including UK Prime Minister Gordon Brown, French Prime Minister Nicolas Sarkozy and UN climate convention executive secretary Yvo de Boer) think is needed now, to show developing countries that the West is serious about helping others and to begin putting money into "no-brainer" issues such as reducing deforestation.

What does a "US fair share" look like? Senator John Kerry reckons $3bn; like every other ingredient of these negotiations, you can bet that the Obama administration has a figure in mind, but in the best traditions of summit brinkmanship, has no intention of revealing it just yet.

Something that has intrigued runes-readers this week is the last-minute change of travel plans by President Obama himself.

Having initially decided to slot in a quick Copenhagen visit in the middle of the first week, en route to picking up his Nobel peace Prize in Oslo, it now appears he will be there for the summit's final hours - which led Rajendra Pachauri, head of the Intergovernmental Panel on Climate Change (IPCC), to opine:

"This is a very significant development, which in substance and symbolism greatly enhances the prospects of a satisfactory agreement at Copenhagen."

Dr Pachauri has been busy on another front during the week as well, calling for an investigation into the so-called "ClimateGate" affair - the hack, or leak, of e-mails and other documents from the Climatic Research Unit (CRU) at the University of East Anglia, repository of one of the important records of global temperatures.

The university has commissioned an independent review into the issue, the most important of its terms of reference being to determine whether there is evidence of suppression or manipulation of data at odds with acceptable scientific practice which "may therefore call into question any of the research outcomes".

The fact that the review is in the most embryonic of stages has not held some observers back from asserting that the issue either undermines the entire fabric of climate science, or that it makes no difference at all to the overall picture and is simply the latest and nastiest in a long line of smear tactics from "sceptics".

But during the week we had the first sign that it might influence the Copenhagen negotiations, with Saudi Arabia's lead negotiator Mohammad Al-Sabban telling the BBC that:

"It appears from the details of the scandal that there is no relationship whatsoever between human activities and climate change."

This has been condemned in some quarters - not least by the UK government - as manifestly untrue, and mere "nonsense". Gordon Brown told The Guardian newspaper:

"We mustn't be distracted by the behind-the-times, anti-science, flat-earth climate sceptics."

In the meantime, it will be interesting to see how Mr Al-Sabban's comments play out inside the wider bloc of developing countries, which includes many governments very convinced by the science of rising sea levels and scorched farmland, and very keen to see a strong deal in Copenhagen.

The ClimateGate issue appears to have gained more political traction in the US Senate, where Republicans maintain it's the "last nail in the coffin" for the Boxer-Kerry bill, which aims to limit national emissions.

Senator James Inhofe, the leading opponent, revealed this week that he too would be in Copenhagen to make sure people know "there is no way that the US is going to ratify any kind of treaty that is anything at all like Kyoto".

Since my last post, the Australian opposition Liberal Party has elected a new leader, the overtly climate-sceptical Tony Abbott, following a rift over whether to support or block the government's cap-and-trade bill in the Senate.

Prime Minister Kevin Rudd plans to have another go at passing the bill next year. But it does mean that he - like Mr Obama - will not have a guarantee of domestic legislation in his hand when he arrives in Copenhagen.

OK - if I've missed anything of note over the past seven days, do post a comment.

I've another request, too - if you can restrain yourselves from plastering this thread with stuff about ClimateGate, please do.

There are more than 700 comments on the previous thread, the vast majority related to it. I know from e-mails that some readers find endless picking over of climate science repetitive and boring - and when they do, they don't read through the comments. Fresh, pertinent and interesting are my suggestions.

See you next from Copenhagen - or should that be the Emerald City? We've spent so long getting there, it almost feels like it...