By Richard Black
Environment correspondent, BBC News website
If you thought that climate change was just an occasional staging post on the eternal global tour of international diplomacy, think so no more.
Presidents Hu and Bush have been on opposite sides of the table
Within the last few months the climate circus has stopped at the G8 in Heiligendamm, the UN climate convention (UNFCCC) in Vienna, and UN HQ in New York (twice) - not to mention triple dips into the prediction pot of the Intergovernmental Panel on Climate Change (IPCC).
Over the next few months, the pace hots up. After Apec - the Asia-Pacific Economic Co-operation forum - there is the Gleneagles clean energy dialogue in Berlin, UN HQ (again), the Washington White House, and finally, in December, the UN climate convention's annual summit, this time amidst Bali's lush beauty.
Did I miss a few out? I hope so.
It would be nice to leave room for some content in this article among the dizzy succession of geographical name-checks and the welter of organisational initials, which is beginning to resemble the alphabet soup of heavyweight boxing.
"There's a complex picture emerging," observes John Ashton, the British government's international climate change envoy.
"I would draw an analogy with other international negotiations, for example on arms control. What you saw was that when it became clear that this was something the world needed to do something about, you saw a proliferation of different conversations in various fora.
"That's what we're seeing now with climate change."
So is the complexity a good or a bad thing?
Bad, it appears, to some, notably the governments of Malaysia, China and the Philippines which opposed Australian and US moves to get a climate resolution from the Sydney Apec meeting.
"It is unfortunate that people who are talking about climate change like the US are not even members of the Kyoto Protocol," Malaysia's trade minister Rafidah Aziz said during the preliminary skirmishes.
"If you want to talk about climate change, please join in with the rest of the global community to make commitments... there's no point talking outside of the [Kyoto Protocol] forum."
In other words, keep it simple, Sydney.
The Apec formula, as originally proposed by Australian premier John Howard with Washington's blessing, envisaged developed and developing nations alike signing up to goals - not on reducing greenhouse gas emissions however, but on improving "energy intensity".
Brought first into the political arena by President Bush, the intensity concept is basically a measure of how efficiently your economy uses energy - the ratio of wealth created to energy expended.
"Clean" technologies such as nuclear energy are an Apec priority
It is a concept that environmental groups find deeply troubling.
"Even with the proposed target (of a 25% improvement in intensity by 2030), we would see a net increase in emissions from the region," comments Tony Mohr, climate change campaigner from the Australian Conservation Foundation (ACF).
"Intensity improves, but the economy grows as well. And that's the problem with intensity targets."
In the run-up to the Apec summit, the Australian government's Bureau of Agricultural and Resource Economics (Abare) produced a report forecasting that under business as usual, emissions from Apec nations would grow by 130% between now and 2050.
With the deployment of technologies such as renewables, nuclear, clean coal and energy efficiency, Abare calculated it would be feasible to reduce that emissions figure by 49%.
So hang on, let's do the maths... 49% of 230%... subtract the original 100%... and what Abare is projecting, what Mr Howard and Mr Bush believe acceptable, is a rise in greenhouse gas emissions of about 15% by 2050.
And the rise is that small only if all these clean technologies are developed and rolled out smoothly across the region, which even Abare admits is a path strewn with social and economic hurdles - it could have added technical ones, too.
The rise could be much bigger.
Writing about this Apec meeting has given me a distinct feeling of deja vu; and I know why. It is because when I covered the inaugural ministerial meeting of the Asia-Pacific Partnership for Clean Development and Climate in Sydney some 18 months ago - and apologies for thickening the alphabet soup still further - exactly the same arguments appeared.
Then, as now, we had major Asian economies at the table. Then, as now, the Howard and Bush governments argued that technology and voluntary deals could bring emissions down. Then, as now, we had an Abare report showing that when they talked of bringing emissions down, they actually meant allowing emissions to rise.
The climate world is certainly on twin tracks when it comes to the meaning of apparently simple words.
There is a green sales pitch for Mr Howard's Apec push, though, and it is this.
Under Kyoto, developing countries do not have any firm targets for reducing emissions. At least under the proposed Apec agreement, they would have a target for something.
Being cynical for a moment, perhaps that is why China, Malaysia and the rest want to stick to the Kyoto track, and focus on developing a successor agreement when the protocol's existing targets expire in 2012.
Kyoto brings no targets for developing nations; but it does bring revenue, through the Clean Development Mechanism (for clean technologies, usually) and through funds to help them adapt to the impacts of climate change.
A "Kyoto-2" treaty, the focus of the Vienna talks, would provide an even bigger pot.
"I think there was a general concern (in Vienna) that funds for adaptation need to rise quite dramatically, and a recognition that the mechanisms in place to fund adaptation have been insufficient," said Angela Ledford-Anderson, vice-president for climate programmes at the National Environmental Trust in Washington DC.
The details of any Kyoto-2 treaty are still in embryonic form, and will in all probability have barely progressed to the foetal stage before the big UN climate forum in Bali at the end of the year, to which Vienna was the official prelude.
If you will permit a mixed liquids metaphor, the alphabet soup appears to be muddying the waters.
"There was a reluctance among many parties to go into too much detail and a reluctance to commit until the events of the next few months, the various conversations in different fora, have taken place," observes Ms Ledford-Anderson.
But on the biggest issue - a new set of emissions targets for when the current set expires in 2012 - something of a consensus did emerge at Vienna, to many observers' surprise.
The aspiration that developed countries should aim to cut their emissions by 25-40% by 2020 is far from a deal, but it already looks very different from the Apec/Asia-Pacific Partnership/Bush vision.
So how should we judge all these different fora, philosophies and processes?
"We should keep our eyes on the big picture, and the big picture is the level of ambition," suggests John Ashton, emphasising that the Vienna targets derive from the scientific necessity to cut emissions as determined by the IPCC.
"At the moment, (the US and Australian initiatives) are not ambitious enough - but they're not unique in that, the problem we all face is how we bridge the gap between where we are now and where we need to get."
Environment protestors have been prominent at the Apec venue
There is no doubt that climate politics is entering a complex phase. No longer is it the case that nations are either for Kyoto or against it; Japan, for example, is for Kyoto, and yet also for the Asia-Pacific Partnership which comes with a very different level of ambition.
And no longer are the arguments just about cutting emissions. Funds for adaptation, clean technology rollout, and financing mechanisms are considered by many of the players, certainly by the developing world's superpowers.
Energy security, leverage, avoided deforestation, sequestration... the list is almost as long as Angela Merkel's climate travel itinerary.
But amidst these swirling, evanescent mists it is possible to discern two familiar philosophical pillars.
In one, governments commit to common policies based on the science which, rightly or wrongly, they have endorsed through their membership of the IPCC, and which the Stern Review has declared affordable.
In the other, they subject business-as-usual to only slight voluntary curtailments that will not distort its basic high-carbon shape.
Both have high-profile, powerful backers. The myriad conversations, processes and journeys of the next four months should tell us much about which is likely to prove dominant.