Copenhagen Countdown: 10 days
This was the week that saw the heavyweights come to town.
The EU had said it, UN climate convention chief Yvo de Boer had said it: without something firm on the table from China and US, together responsible for about 40% of the world's greenhouse gas emissions, it would be very difficult to reach agreement of any kind at the Copenhagen summit.
Unsurprising, then, that EU leaders and Mr de Boer applauded the announcements - within a 24-hour period - of commitments by both countries to constrain emissions, the latter saying the pledges "can unlock two of the last doors to a comprehensive agreement".
Depending on what impact the recession turns out to have had on US emissions, the target of a 17% cut from 2005 levels by 2020 may turn out to be a cut of about 12% from current levels; and it's only a few percent down from 1990 levels, the commonly-used baseline.
I've raised the question of whether developing countries will regard this as satisfactory before; and it's also unclear whether the US will put anything forward on finance, the other key ingredient of any Copenhagen deal.
China's target of reducing carbon intensity by 40-45% by 2020 has received more plaudits than the US pledge, though Reuters' Chris Buckley raises an intriguing question in an analysis article from Beijing, asking how willing China will be to see this plan independently verified - something that industrialised nations are liable to demand, in the end, as part of a legally-binding global climate treaty.
These two pronouncements were evidently facilitated by President Obama's recent visit to Beijing.
Indian Prime Minister Manmohan Singh's visit to Washington this week, however, doesn't appear to have borne quite such meaty fruit.
The two governments signed a memorandum of understanding on climate change, clean energy and energy security - but nothing formal on curbing emissions.
As India's environment minister Jairam Ramesh acknowledged on Friday, China's announcement of a numerical pledge now leaves India as the only major greenhouse gas emitter not to put any firm numbers on the table:
"We've to think hard about our climate strategy now and look for flexibility... to avoid being isolated at Copenhagen."
Mr Ramesh is intending to put a carbon intensity pledge forward next week, according to the Times of India; though it'll be less ambitious than China's, as befits its lower per-capita GDP and emissions figures.
Chinese and US leaders didn't come forward with the travel plans that some had been hoping for.
Mr Obama will go to Copenhagen - but only en route to collect his Nobel Peace Prize in Oslo, meaning he'll not be there for the long and winding final hours when deals are done. And President Hu Jintao will not, as far as we know, be attending, leaving Prime Minister Wen Jiabao to lead China's delegation.
One explanation would be that both leaders are keeping their political powder dry for whenever and wherever a new treaty can be signed.
In the US itself, the "Climategate" issue - the batch of e-mails and documents apparently stolen from the Climatic Research Unit at the UK's University of East Anglia - appears to be emerging as an issue of some significance, at least in the Senate, where the Boxer-Kerry bill on capping and trading carbon emissions is being considered by a number of committees.
James Inhofe, a long-time "sceptic" and the ranking Republican senator on the crucial Environment and Public Works Committee, said:
"...lawmakers have an obligation to determine the extent to which the so-called 'consensus' of global warming, formed with billions of taxpayer dollars, was contrived in the biased minds of the world's leading climate scientists."
Mr Inhofe sees the issue as not only lethal for the Boxer-Kerry bill, but at least highly toxic for the Environmental Protection Agency (EPA) as it prepares to mandate action by businesses and public bodies based on a finding that carbon dioxide causes "endangerment".
Climategate - which, among mainstream media, we reported first here on the BBC News website - has also surfaced as an important ingredient of the political debate in Australia, where the government is desperate to pass cap-and-trade legislation through the Senate before the Copenhagen conference begins.
The issue is proving thorny enough to have split the opposition Liberal party, some of whose senators have rebelled against leader Malcolm Turnbull's pledge to support the measure; and the government is planning to have another go at passing the bill on Monday.
It could even lead to a general election, with Mr Turnbull warning that the party risks annihilation if the rebels hold sway:
"We would be wiped out... the vast majority of Australians want to see action on climate change."
As far as I've been able to ascertain, climate politics elsewhere remains unimpressed by allegations that the CRU documents undermine the very basis of the forthcoming negotiations; but it's a question that I will be asking when the Copenhagen talks open.
With the governments in Canberra and Washington DC now firmly signed up to chasing a deal in Copenhagen, some of the pressure that used to fall on the Howard and Bush administrations is now finding its way to Canada.
The government's target for Copenhagen is uncannily similar to the US figure - a 20% cut from 2006 levels by 2020, equating to about 3% from 1990 levels - an indication of how keen the Canadian government is to avoid losing competitiveness against its southern neighbour.
Environmental groups say this is woefully inadequate and - with support from former UK International Development Secretary Clare Short - are urging that Commonwealth Heads of Government, meeting this weekend in Trinidad, should expel Canada from the organisation because its climate inaction threatens other member countries.
Whatever the chances are of that happening, the meeting will also be a chance to see what Commonwealth leaders make of UK Prime Minister Gordon Brown's call on Friday for a $10bn fund to be established pretty much immediately to help developing countries constrain emissions and adapt to climate impacts.
This is the same size of pot that Yvo de Boer has been saying needs to be on the table at Copenhagen.
UN agencies recommend - and most parties appear to accept - that the eventual fund will need to disburse sums at least an order of magnitude bigger every year, but this is viewed as start-up money that can be deployed immediately - not only restraining emissions, but acting as a sign of good faith that industrialised governments are serious about a Copenhagen deal.
Amazon nations held a summit this week where all agreed this sort of money was essential to achieving a Copenhagen agreement.
But there was something of a mixed message from Brazil's President Luiz Inacio Lula da Silva.
A couple of weeks ago he pledged to cut Brazil's carbon emissions by 36% by 2020, principally through reducing deforestation; but at the Manaus meeting he appeared to be saying this could only happen if Western countries made it happen:
"Let no gringo [foreigner] ask us to let an Amazonian starve to death under a tree... we want to preserve [the forests], but [other countries] have to pay for that preservation."
For the penultimate time, I type this phrase: if you think I've missed anything of significance that's happened over the last week, please post a comment.