As I've reported, there's been a deal of tension between rich and poor - with the developing world accusing the developed world of forgetting about its needs, as rich nations refuse to cut greenhouse gas emissions enough to stave off "dangerous" climate change (their view).

How much of the rancour turns out to be real and how much synthesized as a political bargaining tool we will find out in Copenhagen - although perhaps not until the last few days of that meeting.

What's certain is that unless the US comes forward with a pledge on reducing its greenhouse gas emissions, there will be no deal of any kind, legally binding or politically binding (whatever those phrases may mean precisely).

If the US does produce a figure, it can realistically be in no other ballpark than a 17-20% reduction from 2005 levels by 2020 - that's roughly what President Obama pledged before the election, and roughly what the Boxer-Kerry bill now going through the Senate would produce.

In a news conference here, US negotiator Jonathan Pershing reckoned this would put the US way ahead of the EU on ambition - the US would cut emissions faster that Europe over the next 11 years.

The reason is that the EU has already cut emissions markedly between 1990 - the baseline that everyone else uses - and today.

And against that baseline, the US pledge will only be about 4% - paltry beside the EU's 20-30% and Japan's 25%.

Mr Pershing may not want the administration to which he belongs to shoulder the burden of making cuts that the Bush government did not... but from the perspective of a developing country many miles away, the US is the US is the US, whoever is in charge at various times.

Is there a formula that everyone could live with? Will the EU consider 4% "comparable" to its own efforts?

Would developing countries accept a US pledge as binding in the absence of Senate legislation - given that on the Kyoto Protocol, the US first signed, then declined to ratify, then withdrew?

Could money and technology bridge the gap?

Is it, indeed, bridgeable?

Mr Pershing said it's not yet been decided whether the US will put forward a target in Copenhagen and one reason for the non-decision - if non-decision it is, rather than a decision that's been taken and is being kept under wraps - is presumably the sticky passage envisaged for the Boxer-Kerry bill.

Republican senators on the influential Environment and Public Works Committee decided to boycott discussions on the bill this week, saying that a full analysis of its financial costs and benefits was needed first.

So committee chair - and bill sponsor - Barbara Boxer pushed it through the committee without debate - a procedure that's apparently rarely used.

However, in a sign that not everything is going swimmingly well, senators John Kerry, Joe Lieberman and Lindsey Graham started working on a "parallel track" towards a bill that can get the 60 votes necessary to pass legislation in the full Senate.

It's likely to include more support for nuclear power and perhaps for the oil and gas industry, while maintaining the cap-and-trade programme that is the current bill's centerpiece.

What this means for prospects of passing climate legislation isn't clear - perhaps not to anyone. But it doesn't exactly sound like a fast track - particularly as the further legislation evolves from the text that the House of Representatives passed in June, the harder it will be to reconcile the two.

A high-level European delegation was in Washington this week and although German Chancellor Angela Merkel's address to Congress asking for more action on climate change was received with applause on the Democrat side, there was reportedly silence on the other side of the house - another indication that not all US lawmakers are convinced that their president is on the right track on climate change.

Other potentially significant moves this week include the meeting of G20 finance ministers - a meeting expressly charged at the last G20 summit in Pittsburgh with putting a new offer of climate finance on the table.

Campaigners are urging them to phase out fossil fuel subsidies as soon as possible. To do so was a pledge made by governments at the G20 summit - it's also an agreed aim under the UN climate convention, which dates all the way back to 1992.

At the time of writing, the finance ministers' meeting is under way but nothing has yet emerged - you can follow my colleague Andrew Walker's reports on the BBC News website and we'll look at it again next week.

A conference will open in the Maldives next week of countries considered especially vulnerable to climate change. Governments invited include Bangladesh, Costa Rica, and a number of Caribbean and Pacific island states.

What they'll come up with is likely to include demands for reducing greenhouse gas emissions further and faster than is currently envisaged under the UN process.

The UN texts, the advice from the Intergovernmental Panel on Climate Change (IPCC) and some of the developed country targets are loosely aimed at keeping the rise in global average temperatures within 2C since pre-industrial times.

The equations are inexact but that may roughly translate to keeping greenhouse gas concentrations below the equivalent of 450 parts per million (ppm) of carbon dioxide.

For the small island developing states (SIDS), that's too much. They want a maximum of 350ppm adopted as the benchmark.

Although on the surface politicians - especially from Europe - are trimming expectations for Copenhagen, behind the scenes they are also encouraging campaigners to step up the pressure in the intervening weeks.

This week, we've had aliens wandering round asking "Where are the leaders?" and barrages of alarm clocks indicating the shortness of time before the summit... and we also have what are probably the first climate hunger strikers.

Anna Keenan and Sara Svensson have vowed to go without food until the Copenhagen summit at least - perhaps beyond, if there is no agreement that meets their satisfaction.

"We're undertaking the hunger strike because we're not seeing much action from governments and we really need it," she told me.

Can their action affect governments and persuade them to amend their positions in the four weeks between now and the start of the Copenhagen talks? Should it?

As always, if you think I've missed any significant developments this week or interesting ones coming up, please post a comment.

It's a story that's been coming for the last few months; now that it's being written, the first cards of the blame game are being played.

Remember the UN climate conference in Bali two years ago, and the road that stretched from there to Copenhagen?

The last-night exhaustion and the tears, the drama of the US being asked to step aside if it wouldn't lead? The glittering promise held out by ministers of a new deal this December - a treaty that would legally bind most countries to do something about curbing their carbon emissions, and fund those about to be beset by effects of climate change?

As October's preparatory conference in Bangkok ended, a complete treaty by the end of the year was already being dismissed in some quarters - even by insiders - as a step too far, given the fundamental divisions that had endured even as governments sought to agree their common vision for the treaty.

There might now only be a framework of an agreement, it was said - but it would have some firm numbers in it, and it would be legally binding.

In the last two weeks, this has unravelled a step further, with politicians and negotiators and officials - and now the UK's Climate Secretary Ed Miliband - acknowledging that achieving anything legally binding is probably too big an ask.

For the developing countries, it's obvious who to blame: the US and the EU.

The US should commit to steep carbon cuts, as envisaged in the Bali Action Plan, they say; the EU should press harder and lean more heavily on its allies in Washington DC.

For those beleaguered Western governments, one answer is to point the finger back at developing countries.

China should pledge more impressive curbs than it has so far, US lead negotiator Todd Stern told a Congressional committee on Wednesday - a notion echoed by Mr Miliband on Thursday.

Developing countries are demanding levels of financial compensation - such as 1% of the industrialised world's GDP - that they know to be unrealistic, said officials here.

Campaign groups, too, are pointing the finger at the US, which they accuse of caving in to corporate lobbying.

Russia and Canada are accused in some circles of less than full commitment to the process - partly from a desire to expand exploitation of oil and gas reserves in places that are now made inaccessible by ice or made unaffordable by the harsh economics of their extraction.

There have been harsh words for Saudi Arabia. The Tcktcktck activist coalition accused the Gulf state of putting its oil interests before the needs of the poor countries with which it's allied in the G77/China bloc, obstructing parts of the negotiations that it found inconvenient.

Wednesday saw a series of events mounted in various developing country capitals to raise the issue, and on Thursday the Saudi delegation was handed a letter outside the talks here saying that "the position of the Saudi Arabian government in the negotiations risks preventing the necessary deal from being made".

For some of the youth caucus, the issue is simple, with the "school report card" they prepared giving pass marks to every bloc from the developing world and failing every industrialised country.

The African countries that staged a walkout on Tuesday would probably concur.

Simplistic? Certainly, according to other developing country delegates who - off the record, of course - found the African action unconstructive - an episode of what Australians term "spitting the dummy".

To some extent, all the blaming and shaming is a political game - another part of the diplomatic manoeuvring which governments use to secure not just a deal they say they need, but the variant of the deal that works best for them.

Does anybody in the Obama administration really expect China to pledge cuts in greenhouse gas emissions when the US has put no numbers on the table at all for 2020?

Does the G77/China bloc really expect the Obama administration to put firm numbers on the table when it only has as much power compared to the Senate as the US political system allows?

There is also a degree of back-covering - getting a bit of retaliation in first, as critics sharpen their knives in the bloody abattoir of national parliamentary politics.

Who is really to blame? Everybody will have their own list; so can guidance be sought in this affair's guiding treatise, the UN Framework Convention on Climate Change?

Perhaps it's worth noting one paragraph...

"The global nature of climate change calls for the widest possible co-operation by all countries and their participation in an effective and appropriate international response, in accordance with their common but differentiated responsibilities and respective capabilities and their social and economic conditions."

...which surely implies that it's up to all parties to achieve the treaty they say they want.

Looks like it's not going to be this year, though... perhaps next?

It looks like the UN climate summit in Copenhagen is shaping up to be another final-night, early-hours, last few seconds kind of affair.

On the surface, what we're witnessing here at the final preparatory session in Barcelona is a stand-off between a pair of adversaries whose positions are both rock solid and un-reconcilable.

Lumumba Stanislaus Di-Aping, the Sudanese diplomat who leads the negotiating team from the G77/China bloc, is adamant that developed nations have to pledge to cut their greenhouse gas emissions by at least 40% (from 1990 levels) by 2020; otherwise there can be no deal.

"Anything less than 40% means Africa's land mass is offered destruction as the only alternative," he said.

And "destruction" included people's livelihoods as well as forests and other ecosystems, he said.

The "at least 40%" demand has raised some eyebrows because it's a deeper cut than the 25-40% figure recommended by the Intergovernmental Panel on Climate Change (IPCC) in order to keep the rise in the average global temperature since pre-industrial times below 2C.

But later, Sweden's chief negotiator Anders Turesson expressed some sympathy for the G77 position.

"It's not unreasonable. We say 30% (the EU target in case of a global deal) is within the span of the IPCC in order to meet a 2C target, but we do also recognise that 2C will provide serious consequences for some countries."

But developed nations - the EU, Australia, Japan, New Zealand, Norway, Canada - have already set out their targets; with or without a big US pledge, it amounts to a lot less than 40%.

So on the surface, no deal is possible in Copenhagen in December, nor in the mooted "child of Copenhagen" conference some time next year that is looking increasingly necessary - nor in any other session thereafter until one side or other drops down from exhaustion.

The same divide appears to be evident when it comes to finance - richer countries paying poorer ones either to help them develop along low-carbon lines, or to help them adapt to impacts of climate change.

Last week, the EU set out its vision for finance. A global pot of 100bn euros per year would be needed by 2020; between a quarter and a half of that would come from the public finances of developed nations, and the EU would pay its fair share.

The EU stopped short of declaring explicitly what that would be; but here, the European Commission's chief negotiator Artur Runge-Metzger clarified that it would be between 5bn and 15bn euros per year - dependent on other developed countries paying their "fair shares" too.

Again, on the surface this is not enough to secure a deal, with various developing country blocs demanding that richer nations contribute 0.5-1% of their GDP, and from public funds too.

Asked how these apparently unbridgeable divides could be bridged, Mr Turesson said it would be wrong to think that final negotiating positions would emerge here in Barcelona, nor in the first week of Copenhagen.

Only when ministers - and possibly heads of government - arrived towards the end of the Copenhagen talks would we really know, he said - and very likely not until the last day, or probably the last night, or the unscheduled early morning beyond the last night.

Later, in a news conference with lead negotiators from the EU, the subject of Canada's emissions reduction target came up - a 20% cut from 2006 levels (or 3% from 1990 levels) by 2020, which the government has declared to be "non-negotiable".

"Negotiators often say things are 'non-negotiable'," said Mr Runge-Metzger. "But if it is really that, why are they here negotiating?"

I asked Mr Di-Aping whether he was sure that no deal was better for the nations he represents than a deal under which developed countries cut their emissions by, say, 30%. He replied by emphasising the arguments lying behind the G77's 40% demand.

I'm sure he wasn't giving away his final negotiating position either, and why would he?

He's probably waiting until the final night in Copenhagen too.

So there are two questions running round my mind.

One is whether it's worth holding the first nine days of that conference. Maybe the thousands of delegates, ministers, aides, campaigners, journalists, caterers and everyone else should spend their time listening to music or watching football with a beer or two before piling in solely for the final night when they'd all be happy and relaxed and thinking of nothing but the good of the planet and its inhabitants.

(Scurrilous I know - and also flawed, because in reality negotiators do have a lot of groundwork to do, including formatting a new draft text that can be used as a basis for the final discussions - but tempting nevertheless.)

The other question is whether this is really the best way to reach a deal that is supposed to have such far-reaching consequences.

After nearly two years of talking, you might think it wouldn't need to come down to another final-night, early-hours, last few seconds kind of affair.

If so, it's looking increasingly likely that you'd be wrong.

"File on final whistle," as editors say to football correspondents - most of whom are much better at it than I am.

So let's look first at the EU summit in Brussels from which environment groups hoped for so much.

Did they get what they were looking for - namely, a big fat firm wad of money to help developing countries curb their greenhouse gas emissions and adapt to climate impacts?

Not really. Broadly endorsing proposals that emerged last month from the European Commission, EU leaders agreed on the size of the pot that will be needed - 100bn euros per year around 2020 - and on roughly what proportion of it should come from public coffers - between a quarter and a half.

(It's envisaged that the rest would come from a global carbon market.)

But the EU is hedging what slice of that public pot it is prepared to stump up, only saying it would shoulder its "fair share" of the burden.

In the international context, there are two issues with this.

One is that if the EU can't put firm numbers on the table, no-one can. The US is hamstrung by domestic political concerns (more of that in a moment), and Japan's new government is not yet in a position to make any pledge.

The more developed developing countries (I trust you know what I mean - there's a case for sorting this nomenclature out once and for all) won't promise a bean until the richer governments have.

And yet most analysts say a Copenhagen deal isn't possible without some firm pledges on finance - so who's going to provide them?

The second issue is the size of the pot. The EU reckons about 100bn euros per year for mitigation and adaptation combined, and that's to be achieved around 2020.

A World Bank report issued last month calculates a need for $75-100bn annually for adaptation alone in the developing world from 2010.

An excerpt from the International Energy Agency's World Energy Outlook released this month estimates $110bn per year for clean energy measures that would put developing countries on the road to emission levels likely to avoid "dangerous" climate change; and that's from 2010 as well.

Put these two estimates together and you get an annual pricetag of about $200bn from next year. The EU's proposing that the developed world provides about 7bn euros next year.

In sporting terminology, that's a mismatch. That's Roger Federer against my cat.

On the surface, the week's most ambitious numbers came from the Brazilian government, which announced a target of cutting deforestation in the Amazon by 80% by 2020.

As deforestation accounts for about half of the country's greenhouse gas emissions, that equates to an emissions cut of 40% between now and 2020 - which looks big, given that it's a developing country with relatively high population and economic growth, and that the target is twice as ambitious as the US Boxer-Kerry bill aims to achieve.

President Lula is due to announce a final target next week, and may confirm the 40% figure.

However, there is a couple of caveats.

First, the 80% figure is only a slight advance on the 70% target announced last year - and the timescale for achieving it is a couple of years longer.

More importantly, estimates of Brazil's deforestation rate have dipped and soared as regularly as a volatile stock over the last few years.

In the year from mid-2006, the monthly rate slowed by 20%. Over the next six months, it apparently rose by a factor of four - a trend attributed to rising commodity prices encouraging farmers to clear land for soya and cattle.

This is clearly something that the government will have to address in order to give its pledge real credibility.

Copenhagen has already hosted a significant climate science meeting this year; and last weekend saw a gathering of 100 legislators drawn from across the major economies.

Brought together under the auspices of Globe - Global Legislators Organisation for a Balanced Environment - the idea was to build avenues of discussion between parliaments other than the ones facilitated by the UN negotiations.

The meeting agreed a set of "key guiding principles" that they said all countries should adopt - setting emissions targets, improving energy efficiency, protecting forests, and so on.

When it comes to influencing the formal UN negotiations, the hand of Globe tends to act very much behind the scenes, so the importance of this agreement is a little hard to assess; but the fact that the principles were originally set out by a member of the Chinese congress and a member of the US Senate working together might be interpreted as significant.

Following on from the discussion in last week's Copenhagen Countdown post about the slim chances of agreeing a comprehensive, detailed treaty this year, there's been some discussion this week about whether anything binding might be possible.

UN Secretary-General Ban Ki-moon suggested that a legally binding agreement might be a step too far. But:

"If we can agree on four political elements, then that could be a hallmark of success on climate change."

UN officials (and reportedly, Danish ministers) have been speaking of a "politically binding" agreement... but some observers have been asking "what is that?"

Outside the strictly political arena, religious leaders emerged to take up the climate cudgels this week - at least in the UK.

On Thursday, the Archbishop of Canterbury hosted a multi-faith (Christian, Jewish, Muslim, Hindu, Sikh, Buddhist, Baha'i, Jain and Zoroastrian) seminar that concluded with a declaration:

"As leaders and representatives of faith communities and faith-based organisations in the UK we wish to highlight the very real threat to the world's poor, and to our fragile creation, from the threat of catastrophic climate change.
 
"We recognise unequivocally that there is a moral imperative to tackle the causes of global warming."

And on Tuesday, UN Secretary-General Ban Ki-moon will speak to what looks like a bigger faith leaders' gathering at Windsor Castle.

How much effect do religious groups have on climate politics? Hard to say, but according to Olav Kjorven of the UN Development Programme:

"The world's faiths joined together in this cause - if viewed in terms of sheer numbers of people - could become the planet's largest civil society movement for change... the decisive force that helps top the scales in favour of a world of climate safety and justice for future generations."

Next week, the US Boxer-Kerry bill is supposed to come before the crucial - and divided - Senate Environment and Public Works committee. Republican members are planning a boycott.

It's one of the key spaces to watch next week.

Another is the meeting of G20 finance ministers in St Andrews, Scotland, at the very end of the week that might produce something more concrete in terms of pledges on money.

But most climate-oriented eyes will be on the UN session in Barcelona, the final week of formal negotiations before the Copenhagen meeting opens.

I'll be there from Wednesday and will be endeavouring to keep you hooked up.

As before, if you think I've left anything significant off this tour d'horizon, please post a comment.

So - a genie to your Aladdin, though emphatically not all-powerful - I thought I'd go along.

Held at Imperial College London - Mr Corbyn's alma mater - the meeting featured presentations from Northern Ireland's famously "climate-sceptical" environment minister Sammy Wilson, botanist and ex-BBC TV nature presenter David Bellamy, and a handful of academics - as well as from Mr Corbyn himself.

(The meeting wasn't endorsed or sponsored by Imperial - I'm sure they'd want me to point that out.)

If you're a practising scientist reading this and are wondering "why did he bother?", by the way, read on... I've an assignment for you at the end.

Like other "sceptical" meetings I've attended, it featured a heady melange of science (some of which would be swiftly dismissed in some quarters as pseudo-science) and politics.

"We're going to refute, totally, the CO2 theory of warming," said Mr Corbyn in his introduction.

"Carbon dioxide is innocent of all accusations relating to global warming," said Hans Schreuder, who runs a website called ilovemycarbondioxide.com.

"I am a denier, and proud to be one," declaimed David Bellamy.

There was much more in this vein, including regular demonisations (and one quite amusing piece of mimickry) of Al Gore, complaints that environmentalism is essentially an anti-technology religion, and - frequently - the contention that governments have embraced CO2-mediated warming as a vehicle for raising taxes.

In fact, according to this meeting, the current rise in CO2 has very little to do with the burning of fossil fuels.

Why it's rising participants were not completely sure, although outgassing of the oceans as they warm could be a reason, some suggested - an extension of the notion that in the past, warming has driven CO2 to higher levels, rather than the other way round.

(The mainstream interpretation of past climatic variation is that greenhouse gas release has amplified warming caused by variations in the Earth's orbit - Milankovitch cycles - resulting in interglacial warm periods; CO2 concentration may lag behind temperature rise, but also contributes to it.)

When asked by my colleague Roger Harrabin (there to report for Radio Four's PM programme) how they felt about indications that CO2 emissions are changing the acidity of the world's oceans - with potentially major implications for the marine food web - speakers were uniformly "relaxed".

Ocean acidification is "utter nonsense" said Piers Corbyn.

Hans Schreuder spoke of the "great misconception" that warmer oceans will carry more CO2. (The mainstream interpretation of acidification isn't that oceans are absorbing more CO2 because they're warmer, by the way, but simply because there is more of it in the atmosphere).

The panel said that if we asked the real experts on this - based in Australia - they would say reefs are in a healthy state.

(I've sent e-mails to some eminent Australian coral scientists asking what they make of this, and I'll post their responses if and when they arrive.)

If there's no truth to CO2-based warming and no need to do anything about it, then why, you might ask, isn't that accepted and understood in the spheres of science, politics and public opinion?

The answer given here is that scientists are desperate to maintain the myth - even through "fraud", according to David Bellamy - in order to perpetuate the "global warming industry" in which they work, while politicians (as noted earlier) see it as a tax-raising exercise.

Environmentalism is a "religion", and the media just want scare stories.

Added to all that is the woefully poor scientific literacy of the UK population. (A climate researcher working at Imperial, who had come to the meeting out of curiosity and who was listening aghast, commented quietly: "And this meeting is a prime example of it".)

Some of the accusations are, frankly, easily dismissed.

Finding no net warming since 1998, the story goes, the "warmers" have since had to abandon the phrase "global warming" as a scary thing and have invented the phrase "climate change" instead.

In that case, why is the organisation set up in 1988 called the Intergovernmental Panel on Climate Change and not the Intergovernmental Panel on Global Warming? Why, the following year, did Margaret Thatcher raise the "problem of global climate change" with the UN, rather than the "problem of global warming" - and call for negotiations leading to "a framework convention on climate change"? Why did the Rio Earth Summit of 1992 adopt a United Nations Framework Convention on Climate Change rather than on Global Warming?

Perhaps someone has been back in a time machine to alter all the documentation.

We've been here before and will doubtless come here again. These issues have been bashed around the world wide web: if you want more - well, surf, fill up, enjoy...

It was a promise of new science from Piers Corbyn that brought me along to the meeting so let's concentrate on that.

In case you haven't come across his work before, Mr Corbyn has developed his own method of weather forecasting based on patterns of solar activity and interactions between the magnetic fields of the Sun and the Earth.

He's not shy about lauding the success of his technique in comparison to methods employed by what you might term "mainstream" forecasters, such as the UK Met Office.

Detractors point out that he has not published scientific papers detailing his methods, meaning that it's impossible for others to verify them; also, that because his company WeatherAction sells these forecasts, he has a commercial interest in promoting his own success and in denigrating competitors.

At the meeting, he explained that the essential ingredients are phenomena that he terms "red strikes" and Swips (solar weather impact periods).

They derive from solar and magnetic phenomena, and are to some degree inherently predictable, he says - some forecasts can be made two years in advance.

He uses historical datasets to make correlations between patterns of strikes and Swips and patterns of weather. His forecasting works by assuming that a certain pattern of strikes and Swips now is likely to produce the same weather pattern as it did in the past.

During the meeting, Mr Corbyn made concrete forecasts relevant to the UK; here they are.

The period from 17-19 November, he says, carries an 85% probability of a storm surge in the North Sea. This will probably lead to snow and blizzards in Scotland and northern England, perhaps a few days later. There are likely to be coastal flood warnings for East Anglia and Holland.

The UK winter, he forecasts, is likely to be cold with some very cold spells. His bete noire, the Met Office, says in an "early indication" that temperatures are likely to be near or above the recent average (3.7C for December), though there is a one in seven chance of a cold one.

So there you are. The forecasts are out; let battle commence.

Mr Corbyn said that this presentation revealed more details of his weather forecasting technique than he has made public before, which is why I've detailed it here - the main interest, for me at least, is the climate stuff.

In his view, climate change ancient and modern can also be laid at the door of solar variability.

He is not the first to make this claim, of course.

Its most prominent champion in recent years has been Danish physicist Henrik Svensmark. He argues that variations in the flux of cosmic rays arriving at Earth - variations caused by the fluctuating solar wind - affect cloud formation, which in turn affects the Earth's temperature.

Several recent scientific papers have poured cold water on the cosmic theory of modern-day climate change; and Piers Corbyn doesn't agree with it either.

One of his arguments is that the cosmic ray mechanism would produce an 11-year cycle of temperature variations, because of the 11-year solar cycle. But when he did a Fourier transform - a mathematical process that draws out frequencies contained in a complex wave - on the often-used HadCRUT dataset of the Earth's temperature, he found that the dominant signal is a warming and cooling with a period of 22 years, not 11.

(This used annual average temperatures; Mr Corbyn tells me he is planning to do the same kind of analysis using records of monthly and daily temperatures.)

A Fourier transform of the temperature dataset shows a strong 22-year cycle, says Piers Corbyn

So what's going on? His explanation is that at the peak of each solar cycle, the polarity of the Sun's magnetic field reverses. So for 11 years it's aligned with the Earth's magnetic field, and for the next 11 it lies in the opposite direction.

This alignment, he believes, largely determines the flux of solar particles into the Earth's atmosphere - and thus the temperature distribution around the planet's surface.

The next ingredient is the Moon. Every 9.3 years, its orbit crosses the elliptic, the apparent path of the Sun across the celestial background - a lunar node. Crossing once in an "upwards" direction and once in a "downwards" direction, the complete cycle takes 18.6 years.

Mr Corbyn says that his analysis shows the main peaks in the temperature record occuring shortly after the concurrence of a lunar node and the maximum of an odd-numbered solar cycle.

Sharp rises are said to occur when solar and lunar components co-incide

His idea of a mechanism for this is a work in progress. But he has calculated that when you combine the two cycles - lunar nodes and the 22-year solar cycle - what comes out is another cycle with a periodicity of about 60 years.

Next, this voyage of discovery takes us to the Pacific Ocean. There you'll find a natural cycle of temperature called the Pacific Decadal Oscillation (PDO), which also appears to have roughly a 60-year periodicity.

Can the PDO affect - or even determine - temperature rises and falls across the Earth?

One "sceptical" US scientist, Roy Spencer of the University of Alabama in Huntsville, thinks it can.

He claims that temperature changes seen over the course of the last century - both during warming and cooling phases - are principally determined by the "phase" of the PDO, with a little involvement from greenhouse gases.

(Cautionary note to climate sceptics planning to seize on Dr Spencer's work as unequivocal proof that man-made climate change is a myth: it uses a computer model! Therefore, by all that sceptics stereotypically hold dear, it cannot be correct, because as you all know: you can't trust models.)

So here is Piers Corbyn's hypothesised connection: he thinks the 60-year cycle derived from combining the periods of the lunar nodes and the 22-year solar cycle drives the PDO; and that the PDO drives global temperatures.

In fact, he holds that such mechanisms drive many, perhaps all natural cycles, including the El Nino Southern Oscillation and North Atlantic Oscillation.

To complete the even longer-term picture, I should add that he has proposed a variant to the traditional Milankovitch cycle picture of Ice Ages; but frankly this blog post is already longer than a Led Zeppelin drum solo and I should attempt some closing thoughts while you're still awake.

You can find a presentation very similar (perhaps identical) to the one he gave at Imperial here [2.5Mb ppt] - the conference site doesn't appear to have presentations posted yet, though organisers suggest it will over the weekend.

After the meeting I had a chat with Joanna Haigh, a solar physicist at Imperial who's published papers on potential links from solar cycles to climate change, and who's known Piers Corbyn on and off for years.

Her reaction: publish the science. Get it out in the peer-reviewed scientific literature, put all the physics in, and let other scientists scrutinise and pick over and debate and criticise - this is the way science advances.

Here's a simple reason why. Even if CO2-mediated warming were wrong, only one out of Henrik Svensmark, Roy Spencer and Piers Corbyn could possibly be right, because they all disagree with each other.

Only the development of properly scrutinised and quantified theories, tested (in the real world where possible) and debated through the traditional avenues of science, could tell which one; and the others would have to be prepared to retire gracefully, as scientists ought to when their pet ideas are proven wrong.

Mr Corbyn tells me he has drafted a paper on some of the climate (as opposed to weather) ideas, though it's not yet been submitted to a journal.

He also says that in one sense it doesn't matter what theories he is developing or how well they're developed; CO2 and other greenhouse gases from human activities cannot be the main driver of warming because they cannot explain a number of features, including the apparent levelling-off of temperatures since the turn of the century.

(It's important to note, of course, that mainstream climate science says this is quite easily explained, with La Nina and (according to some accounts) the cooling phase of the Atlantic Multidecadal Oscillation temporarily blotting out greenhouse warming.)

Did the meeting live up to its billing of "refuting, totally, the CO2 theory of warming"?

Hardly. Because doing that seriously doesn't mean refuting it to my satisfaction, or yours, or that of the audience scattered about the Imperial College lecture theatre on Wednesday; it means convincing the greater community of climate scientists, and that brings us back to... publishing.

What some in the sceptical camp do not appear to appreciate is that published, peer-reviewed science is not only the sole way of establishing and improving theories; it's also, now, the only route to the policymakers they want to influence.

Modern-day ministers and their scientifically-qualified advisers are absolutely not going to listen to half-developed, unpublished theories or complaints about fraud and conspiracies.

As I noted above, many speakers at the meeting labelled mainstream climate science as "politicised". And in one sense it is: whenever a scientist steps away from considering what the data tells you is happening to suggesting what political or social actions sensibly flow from the data, it must be partially politicised.

And why not? I remember at an important HIV/Aids conference back in 2003 interviewing a very feisty French virologist who was gathering signatures from scientists for a petition demanding that governments put more money into providing anti-retroviral drugs for poor countries.

"What is the point of us researching the disease and developing drugs if no-one is going to pay for them to get to the people who need them?" was the basic argument.

Political? You bet.

And for good or bad, that's exactly what politically active climate scientists such as Nasa's Jim Hansen are doing - demanding the action that they think is justified by the science they have developed.

It doesn't automatically negate the worth of the science they do, for virologist or climatologist.

But politics cuts both ways. The timing of this week's meeting is a case in point.

I asked Mr Corbyn whether dropping hints of a new theory of climate change into the mix shortly before the UN summit in Copenhagen was accidental.

He initial answer was that it was "deliberate", before clarifying that the date had first been chosen to mark the first anniversary of the third reading of the UK Climate Change Act; but that when it was pointed out that Copenhagen was just around the corner, he and the other organisers had concluded it was "good timing".

"We are involved in the political debate about climate change," he told me. "The whole regime is suspect and has to be destroyed."

If you really wanted to be cynical, you could argue that enough information on the concept has been released to tantalise the palates of those hungry for a non-CO2 theory, but not nearly enough to allow proper scientific scrutiny.

It does generate a climate projection that is very different from the IPCC's - a "general cooling to 2030 and probably beyond", with temperatures staying below 2002 levels for perhaps a century.

Unlike a weather forecast duel, I don't think policymakers will want to wait until then before deciding whether greenhouse emissions need to be tackled.

Now, doubtless many of you will have views on the science and everything else in this post, and I look forward to reading them.

But the responses I would particularly invite are from working scientists - physicists, climatologists, and those in related fields.

At the beginning of this post, I suggested working scientists might like to read to the end - and here's why.

Piers Corbyn hasn't given you a scientific paper here but I hope I have relayed the main elements, and you can see his presentation for more details.

So please - have a look around. Some of you know about this stuff - orbital precession, solar cycles, Fourier transforms, magnetic dipoles - far, far better than I do. When you have a free moment or two, don't turn to Tetris, but have a play with this box of toys.

The datasets Mr Corbyn used are publically available, as is information on cycles of lunar nodes and such like.

Do the numbers and mechanisms stack up? Is the theory plausible? Compelling? Completely nuts? What do you think?

As of now, does it even qualify as a theory?

I'm certainly not qualified to pronounce judgement - but some of you may be.

I look forward to seeing what you come up with... and so, I'm sure, will everyone anxious to make sure that negotiators in Copenhagen are armed only with the best scientific evidence.

About one-third of the Ecuadorian government's income now derives from oil.

And about one-fifth of its stocks lie in a field that extends under the Yasuni nature reserve, an Andean region that scientists regard as one of the most biodiverse on Earth, with 655 species of tree and plant recorded within a single hectare, not to mention exotic monkeys, frogs and so on.

The same oil field also underlies land traditionally trodden by the Tagaeri and Taromanane indigenous groups who live partially in the Yasuni reserve - groups that have elected to remain apart from modern society, a right granted under Ecuadorian law.

The Tagaeri may now number only about 30 individuals.

Extracting the oil would clearly have major implications for people and nature. Six interconnected drilling platforms would be required; the road network would inevitably lead to logging and increased contact between drillers and indigenous groups - contact that has literally proved lethal to one or other in the past.

Yet not extracting it would mean $7bn of revenue lost.

Two years ago, the government came up with a plan aimed at squaring this particular circle - the Yasuni-ITT Initiative.

The basic idea is that if Western countries are as concerned about greenhouse gas emissions and indigenous rights and biodiversity as they profess to be, they can and should pay Ecuador not to drill here.

The proposal is couched in terms of avoiding emissions from burning the oil. At about 400 million tonnes of CO2, the government estimates this is roughly equivalent to Ecuador's total emissions for 13 years.

(This doesn't factor in any added benefit of avoiding emissions by keeping the forest intact.)

The sum of $350m per year for 10 years - totalling about half of the oilfield's estimated value - was suggested as a reasonable price.

Although drilling is currently banned in the area, Ecuadorian law could allow it in future under a "national interest" clause.

Investing the money in trust fund with some degree of international oversight should ensure that future governments would gain more from perpetuating the fund than they would by ripping up the deal, paying the money back and drilling the oil.

(There's an interesting comparison to be made here, incidentally, to the attitude of governments towards UN negotiations on climate and other environmental matters, where it's assumed that labelling an agreement as "binding" will guarantee action from future regimes - even when one of the lessons of Kyoto is that it won't.

The UK goes further by calling its unilateral 2050 climate target "legally binding" without specifying who will be hung, drawn or quartered in the event of failure.

The Ecuadorian proposal, on the other hand, acknowledges that future governments may go against its wishes and seeks a way of keeping them on track.)

The scheme has gone through several iterations and the current idea for finance is a bit more convoluted, involving the issue of tradeable "Yasunı Guarantee Certificates"; but the basic concept remains the same.

The Yasuni-ITT concept has found favour with a number of governments, including those of Germany, Italy and Norway.

Ecuador's President Rafael Correa is in London this week to promote the initiative. And a paper just out in the journal Biotropica explores its potential and some of the issues it raises.

It's written by a group of conservationists and researchers including Matt Finer of Save America's Forests, who conclude that the Yasuni scheme is "a potentially precedent-setting advance towards avoiding oil and gas development in sensitive areas of megadiverse developing countries".

But as they acknowledge, it also raises a few difficulties and objections.

Firstly, if there is a thirst for fuel, it will be slaked; Ecuador would be rewarded for keeping its oil in the ground, but companies would obtain it from elsewhere, leading to zero net impact on carbon emissions.

An associated issue is that if finance comes through a global carbon market - should the forthcoming Copenhagen climate summit bring such an entity into existence - those who bought carbon credits for protecting the Yasuni reserve would buy the right to emit an equivalent amount of carbon themselves; that's what carbon trading is all about.

The researchers ask whether it's appropriate to spend such a large sum of money on protecting a relatively small region of the world - especially as some would argue that Ecuador has a simple duty to protect areas it has designated as reserves without the need for international aid.

They also ask how much money could guarantee the oil staying put; and one can imagine that if the starkest peak oil forecasts turn out to be true, within decades the price could escalate so much that the rewards of exploiting the field would dwarf income from any trust fund.

And there is a big logistical problem with the Yasuni idea. As yet, no fund, no mechanism exists that can financially reward countries for protecting biodiversity or indigenous peoples, let alone tying that to reducing greenhouse gas emissions.

Despite the progress of research analysing the economic worth of nature, an international mechanism to pay for its protection is years away.

On the climate side, the Kyoto Protocol doesn't allow for trading in carbon credits for what you might call "avoided extraction" of fossil fuels.

A Copenhagen treaty might - although currently it doesn't seem likely.

If it did permit payment for avoided extraction, what doors would that open?

For years, Saudi Arabia has sought financial compensation for the oil and gas it would have to delay selling, or not sell at all, in a carbon-constrained world. The request was made again at the recent round of UN climate negotiations in Bangkok.

If a mechanism were set up to encourage Ecuador to keep 850 million barrels of oil in the ground, how fast might Saudi Arabia sprint out of the blocks in pursuit of dollars relating to its 267 billion barrels?

Ecuador's answer is that funding should be reserved for developing countries in tropical, megadiverse regions.

But that's just Ecuador's view. What if newly autonomous Greenland, say, proposed keeping oil in the ground to preserve habitat for whales and polar bears and protect the traditional way of life of its indigenous Inuit communities?

Should that be barred on grounds of geography? Where does it stop?

Recent reports indicate that Germany is preparing to pledge regular money - $50-70m per year - for the Yasuni fund.

Given as a simple donation, this circumvents some of the issues surrounding the project - though clearly it's not nearly enough to fund the whole thing.

Looking across the entire environmental and social piece, you might conclude that the Yasuni initiative is exactly the kind of scheme needed in a world where species and ecosystems are disappearing at least 100 times the natural rate, where indigenous peoples are increasingly squeezed, and where there is so much apparent concern at the political top table about greenhouse warming.

But if that's the case, how can it best be funded so as to avoid all of the evident pitfalls?

Where do national responsibilities end and become the business of the global community?

Can the developed world afford to back Yasuni, and the other similar bids that will doubtless follow if it is successful?

Or can the developed world afford not to back it?

And no wonder, with the start of the UN climate summit just 45 days away, and various roads to Copenhagen taking routes through all kinds of capital cities and all kinds of fora.

So I thought it would be worth taking a little time at the end of each week as the potentially seminal UN summit approaches to take stock of what's happened and ponder where it might all lead.

What caught the imagination of many commentators this week were comments from UN climate convention executive secretary Yvo de Boer, to the effect that it is now "unrealistic" to expect a full treaty to be negotiated and agreed this year.

"A fully fledged new international treaty... I do not think that is going to happen," he told the Financial Times newspaper.

As he is constantly up close and personal with the main negotiators, Mr de Boer is just about as informed an observer as you can get.

But it's difficult to see why his comments have caused so much consternation among environment groups and political commentators given that government officials and informed observers have been saying the same thing privately (and sometimes publically) for months.

UK Climate Secretary Ed Miliband, speaking just before the Major Economies Forum (MEF) meeting that took place in London on Sunday and Monday, admitted as much.

But he believes something important can still be achieved if it includes three basic elements: numerical mitigation targets for developed nations, agreement (including on figures) on financial support for developing countries, and agreed expressions of "ambition" from the richer developing countries on how they are prepared to curb rising emissions.

For Mr de Boer, the essentials include targets for the rich, defined ambition for the developing world, and a firm timetable for tying up all the loose ends.

As he is also on record as emphasising the necessity of agreement on finances, the hymn-sheets are not demonstrably different.

The framework of a deal is achievable, they are really saying; but not every detail.

Although privately environmental groups might acknowledge that not everything can be done in time for Copenhagen, they're still bound to keep the pressure and expectations as high as they can - which is why WWF's Kim Carstensen condemned talk of not being able to reach a deal as "puzzling outbreak of diplomatic pussyfooting".

From both sides of the wealth divide came calls this week for more ambitious - and binding - proposals on finance for adaptation - money paid by the West to developing countries to help protect their economies and societies against climate impacts.

Connie Hedegaard, Denmark's environment minister and designated chair of the Copenhagen summit, urged the US, Japan and other developed countries to put some serious coin on the table.

And Kenya's Prime Minister Raila Odinga said adaptation money up front was a precondition for his country moving away from fossil fuels.

"We are prepared to forego the dirty way... but to do that we need assistance," he said.

The sting in the tail for Ms Hedegaard is that the EU has yet to agree what it is bringing to the table.

The European Commission has proposed allocating $2-15bn per year from the public purse; but EU finance ministers declined to endorse that at their council meeting this week.

Given the level of EU rhetoric on the subject, some observers contend it's a disgrace that the bloc has not yet decided what it's prepared to offer on this issue - and they believe it's something that could hold up a Copenhagen deal.

Two years ago, the bloc not in favour of a new global climate treaty was unequivocally led by George W Bush's US and John Howard's Australia.

Two elections later, they've both changed tack; but Canada, under Stephen Harper, is emerging as a country that while not explicitly a "Copenhagen-sceptic", is at least making cautionary noises about the desirability of a strong new treaty.

Canadian newspapers this week were quoting Environment Minister Jim Prentice as suggesting the country needed gentler targets than Europe, for example, because of its growing population and energy-intensive economy.

There is also clearly a view that the Alberta tar-sands operation ought to be allowed leeway to progress - something that green groups regard with the same affection that anti-fascist groups retain for Nick Griffin.

Mr Prentice is also quoted as saying that Canada won't finalise its carbon-cutting plans until the US situation becomes clear.

And how soon will that be?

John Kerry, co-sponsor of the climate bill that recently entered the US Senate, said he would try to set a definite timetable for the bill on Monday next.

But five committees have yet to consider it - and some senators vehemently opposed to the legislation, such as Republican James Inhofe, have vowed that they will take as long as they need to take - which, it's feasible to deduce, he interprets as some time well into next year.

Mr Kerry told Mr de Boer earlier this month that a Copenhagen deal was possible even if the Boxer-Kerry bill hasn't passed.

Would developing countries be convinced by a US position and US numbers when the Senate has not authorised them? One wonders...

We also saw this week an agreement between China and India to work together - on clean technology, on curbing emissions, and on the politics of the Copenhagen summit.

This is an important development in that it expressly binds the two Asian giants together in political harmony.

A year or so ago their stances appeared to be diverging, with China relatively open to a deal that constrained its emissions, and India determined to avoid anything that might impact its own economic growth.

Many Chinese officials believe its economic growth and its living conditions will be compromised by climate change - and it appears their arguments have found some favour in Indian ears.

Indian, Chinese and Indonesian action and pledges on energy efficiency and renewable energy brought praise from Mr Miliband at the MEF summit.

But equally clear was the determination of those and other developing nations attending the talks that finance has to be right as a precondition of any deal.

Well... as they say on the BBC's second and third most important media, radio and television; "that's all we've got time for this week".

But have I missed out any vital developments, or misconstrued any of the politics?

If you think I have, please post a comment. Keeping across it all may be too big a job for just one person.

About one-third of species on the threatened list - some winking out of existence in a single season as the disease chytridiomycosis extends its fungal tentacles across the continents; nearly 100 species in captive breeding programmes, often because the risk that wild populations will disappear is considered too high for comfort.

But you probably haven't heard this one; the world's reptiles could be in an equally unhappy situation.

As yet, there isn't a global assessment of reptiles, although the International Union for the Conservation of Nature (IUCN) has begun work on one - more of that in a moment.

In its absence, a group of UK specialists has looked at the data we do have and what it tells us, and asked what we'd see if this limited picture turned out to be representative of the world in general.

You can find it in the journal Diversity.

And it's not pretty. By their analysis, the prospects for reptiles worldwide could be just as bad as for amphibians.

As is often the case in these matters, there's more data from Europe than from less developed parts of the world; and the UK is especially rich in studies (though not in the number of reptile species), thanks to the long tradition of amateur naturalists.

The first finding these researchers made as they trawled the scientific literature was that both reptiles and amphibians appear to be less well-studied than birds or mammals.

Between 2005 and 2009, one scientific paper was written for every 11 amphibian or reptile species. Mammals and birds notched up one paper for every four species.

Globally, only 5% of reptile species are classed as threatened.

But only 16% of species have been properly assessed; and when you ask what proportion of those assessed species are threatened, it turns out to be the same as for amphibians - about 30%.

In Europe, where Red Lists have been compiled for both amphibians and reptiles, the proportion of threatened species is again the same across both groups.

So on the face of it, it looks as though quite an important global conservation issue is being neglected here; and you might well ask "why?"

I had a quick chat with John Wilkinson of the UK charity Amphibian and Reptile Conservation, one of the researchers on this study, to get some ideas.

One very simple fact, he points out, is that reptiles are just more difficult to study.

Many frogs come out to mate spectacularly once a year; and when they're in the throes of mating, there's not much that will make them stop and run away and hide.

So it's relatively easy for researchers to study a site from season to season and get a quick handle on population changes.

(That's not true of all amphibians, of course - the enigmatic caecilians being a good counter-example.)

Reptiles, on the other hand, don't generally go in for such spectacular seasonal manifestations, and just finding them can be an issue, let alone combing the relatively large patches of land they might inhabit to assess numbers.

Even the UK's enthusiasts have not generated the same amount of data for reptiles as for amphibians, he says.

Whereas the year's first spawning of frogs is anticipated and documented and used as a marker for the arrival of spring, there's nothing comparable with reptiles.

In the developing world, conservation groups are now funding regular research trips aimed at finding new amphibian species - and sometimes they pay off spectacularly.

Perhaps something similar is needed now for reptiles.

For a comprehensive picture to emerge, we should look to the global assessment - these are regarded in the field as being just about as definitive as you can get.

But the chances of it arriving any time soon look pretty remote. Simon Stuart, chair of the IUCN Species Survival Commission, tells me they just don't have the $2-3m needed to do it.

In the meantime, IUCN and the Zoological Society of London plan to release an analysis of 1,500 species in a few months' time, which they think might provide a more accurate indication of global status than anything we have at present.

Does it - should it - make you feel a little uncomfortable that the world's reptiles might be under threat just as much as amphibians, currently the most threatened group of all - and we just don't know?

While these readers agree that the BBC is biased; what they don't agree about is in which direction it's biased.

Too much "scepticism", or not enough? In the pay of the oil barons, or told what to think by "Europe"? Too scary, or not scary enough?

All these accusations turn up as regularly in my mailbox as they do for my colleagues and in the comments section of this blog and others.

Regular readers of this blog will know that I've tried to steer discussion away from "BBC bias" in months gone by, mainly because I think what's happening "out there" matters more than what's happening "in here".

Whether the Greenland icecap is disintegrating, why biodiversity loss is not being curbed, why industrial fishing is not more efficiently regulated - these are surely bigger questions to ask and more interesting topics for an environment forum than endless debates about BBC reporting.

So you might ask why I'm raising the issue now.

There are two reasons: one is that in the run-up to the UN Copenhagen summit, climate change is moving ever closer to the centre of the political stage, and readership and scrutiny of our coverage is bound to escalate - and I wanted to get this train of thought done and dusted before we reach Copenhagen, because there's going to be no time to discuss it then.

The second reason is that I'd like to respond to a recent blog post by the Daily Telegraph's Damian Thompson, who reported what he described as a "U-turn" in the BBC's climate coverage in an article by my colleague Paul Hudson last week: "Whatever happened to global warming?"

Anyone who monitors BBC coverage regularly will see, first of all, that we do not have and have never had a line on the issue:

We covered the Stern Review when it was published, reporting what it contained and analysing what it meant. We examined it critically and talked to economists who didn't rate it as a piece of work.

We reported the UK government's Climate Projections, which purport to provide a local-level picture of climate change in the future - and reported why some scientists reckoned that the projections couldn't be reliable.

We reported pieces of science suggesting that sea levels would rise higher than the Intergovernmental Panel on Climate Change projected, and pieces of science forecasting there would be no net warming over the next 10 years.

Within the BBC, there are many different people covering climate change.

On this website, you can read articles relating to the issue written by Jonathan Amos, Tom Feilden, Pallab Ghosh, Roger Harrabin, Matt McGrath, James Morgan, Sarah Mukherjee, James Painter, Paul Rincon, David Shukman, Susan Watts - that's just a selection - and by Paul Hudson, and by me.

These days, the issue is covered by journalists with expertise and backgrounds in science, in business, and in Westminster politics, as well as by those with expertise in one particular region of the world.

It's also worth making the point that, as a general rule, the BBC allows the correspondent to identify what the story is. You are the person on the ground who's done the research - it's your field of expertise - and so, by and large, you get to decide what's important about the story and how it should be told.

That's not to say that editors don't scrutinise and shape coverage - they do - but they don't dictate it.

What are we accused of? Here's an example:

A few weeks ago, the US National Snow and Ice Data Center announced that this year's summer ice minimum had not fallen below those of the last two years, but that the overall longer-term trend was still downwards.

Given the constraint that our news headlines have to be between 31 and 33 characters long, I thought "Pause in Arctic's melting trend" was a pretty decent effort, encapsulating both the immediate finding and how it sat in the longer-term picture.

Not a bit of it. It attracted complaints of bias both because "there is no long-term melting trend" and because "it isn't a pause or any such thing": perfect symmetry.

A headline can't be biased in both directions at once. Any bias here has to be in the eye of the beholder.

So here's the nub. In the run-up to Copenhagen, you're not all going to agree with everything the BBC writes or broadcasts - that's impossible. And let's be honest - journalists are not infallible, in the BBC or anywhere else.

But biases and party lines? I don't think so - but please feel free to disagree. So let's have that discussion here, and now.

PS: Another blog post this week - by the Guardian's Leo Hickman - queried why Paul's article appeared as a BBC News website story, when it was first conceived as a blog post.

On this occasion, we commissioned a piece from Paul which in fact overlapped with what he was already doing for the blog.

On most occasions, we'd just link straight to the blog (as we do to this one). But regardless of format, the editorial standards are the same across the News site, blogs and news stories included, as Steve Herrmann describes in a recent post at The Editors blog.

It's worth it because the UK has been one of the developed world's champions when it comes to curbing emissions, having cut greenhouse gas output by about 16% since 1990.

So here's the rub: if the UK has been relatively successful but is still being told it has not done enough - and told that by its own advisors, the Committee on Climate Change (CCC), rather than by green campaigners - what does that say about everyone else?

According to UN data, the UK stands in bronze medal position behind Norway and Germany (among OECD countries) in the table of emission slashers, and at opposite poles from back markers such as Spain, Portugal, Greece and New Zealand, which have all seen emissions rise by more than 20% over the same period - 50% in the case of Spain.

(I'm using here UN data up to 2006, the last year for which comparisons are readily available - it's likely that the recession will have made every nation's figures a bit lower, but is unlikely to have changed the overall picture.)

In large part, Germany and the UK have cut emissions through chance. German re-unification forced the closure and refurbishment of old, inefficient industry in the former Soviet sector, while the advent of North Sea gas (combined with some other domestic political concerns) in the UK prompted a large-scale transition from coal to less carbon-intensive natural gas.

A point that this week's CCC report brings out is that most UK reductions since the "dash for gas" have been achieved in greenhouse gases other than carbon dioxide.

Government figures show that methane release is down 53%, mostly from cleaning up landfill practices. Nitrous oxide (NOX) emissions have been cut by 47% - most of that reduction occurring in a brief blitz in the late 1990s when emissions from production of adipic acid - a precursor to nylon and other polymers - fell dramatically.

The CCC pegs this as a problem because, clearly, you can't keep making cuts here for ever. We've seen with the Montreal Protocol that when an industry comes on side with a policy initiative, changes can be made rapidly: this is what happened with nitrous oxide in the chemical industry in the late 1990s.

But methane and NOX emissions from agriculture have proved less tractable. And even if you could eliminate all methane and NOX emissions overnight, you can only make double the carbon cuts achieved already with these gases because their emissions have already been halved.

By comparison, carbon dioxide emissions from power stations - closely tied to economic performance - have risen slightly from the late 1990s when the "dash for gas" ended.

If landfill methane and industrial NOX were "low-hanging fruit" that the UK has now picked, other nations are in a similar situation.

France already has a low-carbon portfolio of electricity generation because of its long-standing reliance on nuclear energy.

Germany's high recycling levels leave it with fewer possibilities than the UK in terms of cutting landfill emissions.

And when it comes to the EU as a whole - still the main political driving force in global moves to agree a new climate treaty - the biggest greenhouse gas reduction of all has come from the former Soviet bloc's economic meltdown in the years after 1990, which is unlikely to be repeated.

The Committee on Climate Change makes the point that if the UK is to go much further in reducing its greenhouse gas footprint, it now has to begin making serious cuts in carbon dioxide emissions from every sector of society - housing, industry, power generation and transport.

The size of the "step change" they're advocating can be seen from the words used by chief executive David Kennedy, talking about making energy use in the home more efficient across the country.

Rather than just "sending low-energy lightbulbs though the post or targeting pensioners for cavity wall insulation" - a phrase that he managed to utter without sounding dismissive - a nationwide plan was needed, he said, that would go from street to street transforming the nation's housing stock.

The graphs of forecasts show no carbon savings from loft or cavity wall insulation beyond about 2015, because every cavity wall and loft in the country would have been done by then.

The UK government says that it is already planning a "step change" though the Low Carbon Transition Plan that it published in June.

Opinions are divided on how well that plan stacks up against government targets, and in particular against the pledge to cut greenhouse gas emissions by 34% from 1990 levels by 2020.

Like other European nations, the UK's main emission-cutting tool is the EU-wide carbon market, aimed at incentivising companies to change their ways and penalising those that do not.

If a new treaty is agreed at the UN climate summit in Copenhagen in December, it is certain to contain measures aimed at developing a global carbon market.

The idea is that carbon prices should then drive emissions downwards worldwide. The market will channel clean development money to countries that need it, and levies on trading are likely to be used to raise funds to help the poorest nations adapt to climate impacts.

The CCC's conclusion is that the market alone cannot deliver the scale of carbon cuts that the UK has signed up to - a "step change" away from reliance on the market and towards greater direction and greater regulation is a must, it says.

The EU as a whole is signed up to a 20% cut from 1990 levels - a 30% cut if there is a global agreement.

Japan has pledged 25% by 2020; Australia and the US could yet end up adopting targets that require significant and rapid action to achieve, even if they don't look terribly ambitious in the eyes of campaigners when related to 1990 levels.

Japan's emissions now stand 6% above 1990 levels, partially because it plucked its own low-hanging fruit - energy efficiency - in response to the oil crisis of the 1970s.

As a few recent analyses (including one from the World Resources Institute) have shown, the degree of "ambition" shown in the pledges of developed nations in the lead-up to the Copenhagen summit are not enough to bring carbon cuts of the 25-40% scale that the Intergovernmental Panel on Climate Change (IPCC) suggests are necessary to "avoid dangerous climate change".

The conclusion from the CCC's report provides part of the explanation.

For most countries, a "step change" in ambition would require a "step change" in policies - policies that would, for most, mean making the first painful bites into the nether regions of national carbon emissions.

A little wincing at the prospect seems to me entirely natural.

The company behind the plan, E.On, says nothing of the sort - it blames its decision on reduced electricity demand caused by the recession.

The plant - intended to replace an older one that has to come out of service in six years' time because of EU restrictions on sulphur and nitrous oxide emissions - isn't merited until 2016 given new market conditions, it says.

So where does the truth lie? Has campaign power really turned off the juice?

As usual in these issues, the picture is a bit more complex than either side is painting it.

Yes, electricity demand is down this year - by about 8% from last year, according to the government.

And that doesn't only affect what happens this year. When E.On first mooted the project back in 2006, projected demand - and so their forecasts of revenue from the plant - would have been higher than they are now.

On the other hand, there's no doubt that as Bryony Worthington writes in The Guardian, E.On's name has attracted a certain amount of the brown stuff over this plan - and although that may not decide a commercial company's decision, it can influence it, particularly when economic factors are pushing in the same direction.

A third factor concerns competitions for funding for carbon capture and storage (CCS).

Energy and Climate Secretary Ed Miliband declared in April that no new coal-fired stations would be built in the UK unless they included a demonstration CCS capability.

Up to four new plants would be permitted with CCS - and a competition would decide which applicants would receive funding to assist them.

In parallel, the European Commission is also going to supply funding for six demonstration-scale CCS plants across the EU.

Liberal Democrat MEP Chris Davies, who has encouraged European action on CCS, is suggesting Kingsnorth will not be the UK's successful contender, and that "within a week", the commission will unveil a rival project near Doncaster in the north of England as a winner.

The UK government, meanwhile, does not know when it will announce the results of its own CCS competition.

These are other factors pushing E.On towards a Kingsnorth delay.

On the global stage, though, the decision means very little.

As the International Energy Agency announced this week, the recession will almost certainly reduce energy demand across the world (and therefore greenhouse gas emissions) this year.

Its conclusions on the investment question, though, are mixed.

The problematic economy may stall investment in new "dirty" infrastructure through reducing demand; but it may also curb forays into cleaner technologies, because companies will have less money to spend.

In Europe, carbon is trading at about 13 euros per tonne - way below the levels needed to stimulate heavy investment in technologies that will curb emissions, according to many studies.

But the presumption has to be that under business as usual, when the red line of economic growth starts pointing upwards, any delayed investment in coal-fired stations will crank up again.

A single decision in one relatively prosperous nation is unlikely to have any bearing on investment decisions far afield - particularly in less developed nations, and especially in those that are currently exploiting their own coal reserves.

With enough coal in the world to last for centuries, this is why you'll often hear politicians and officials maintain that there can be no climate change solution that does not include coal.

Yet the very real practical issues with CCS remain - no-one has yet shown that it can work on a commercial scale, and even if it can, it's likely to hike the cost of generation significantly.

The Kingsnorth decision helps to raise discussion of the coal conundrum; but it doesn't solve it.

Which is why parties keen to see meaningful brakes applied to the world's carbon emissions are far better off looking to Copenhagen than to Kingsnorth.

Chief exhibit is the discussion surrounding the sheaf of articles on "planetary boundaries" offered up by Nature a couple of weeks ago - and thanks to simon-swede and manysummits, among others, for ploughing into the material and having a look at what it means.

In case anyone hasn't read through the previous thread where such comments are homed, Johan Rockstrom of the Stockholm Resilience Centre (an interesting title in itself) and a group of other concerned researchers offered up the concept that there are boundaries to various aspects of our exploitation of the Earth's resources beyond which it would be prudent not to venture.

Examples include: our output rate of greenhouse gases, nitrogen and phosphorus fertilisers, and ozone-depleting chemicals; our toll on biodiversity; the proportion of the Earth's surface taken for farming and settlement; the supply of freshwater - that sort of thing.

Dr Rockstrom orders these into seven boundaries, and concludes that for some of them, humanity has already overstepped.

In addition to all the comments you've already posted on the last thread here, this raised a couple of questions in my mind.

The first is whether "planetary boundaries" takes us forward - as manysummits argues - from the whole "limits to growth" discussion that will be familiar to anyone who's touched on sustainability concerns over the last four decades; the second, whether it's useful.

More than 200 years ago, Thomas Malthus gave us the first simple limits to growth argument, noting "the difficulty of subsistence" that "must necessarily be severely felt by a large portion of mankind" if the human population continued to grow "unchecked".

So here we have limits in one dimension, basically - hunger.

In the 20th Century, "limits to growth" thinking has become much more sophisticated, encompassed many more issues, and used computer models in an attempt to quantify various aspects of the future.

But it still largely talks in terms of how natural constraints limit humanity's capacity to grow - economically, or just in terms of population size - rather than turning that around and asking how humanity's expansion affects nature.

The "planetary boundaries" notion is different in that it sets out limits for nature, rather than for us. Then it looks at what breaching those boundaries will mean for nature - and for us.

It is based more in ecology than economics - and also, thanks to the revolution in environmental science during the last 20 years, based more in evidence - in the observation of rivers and oceans and forests and the atmosphere that now pour back real-world data as never before.

The notion that there are planetary boundaries is perhaps obvious, but as the journal Nature argues, attempting formally to set out where they are ought to be a useful exercise - if only so that other researchers come along and argue against it, and thought progresses.

Already, others are arguing against it.

In companion articles in the same journal, for example, climate scientist Myles Allen argues that the 350ppm boundary proposed by Rockstrom for the atmospheric concentration of carbon dioxide has "relatively little support" in the scientific literature, that it may take centuries to achieve even if emissions decline rapidly, and that it represents an "unnecessary distraction" from existing political targets such as the G8-endorsed 2C.

I wonder, too, whether it's reasonable to think in terms of a boundary for biodiversity loss.

Many of the arguments for preserving the wonderful totality of life on Earth are primarily ethical in character; and an argument that we need to keep the rate of species loss below 10 times the background rate perhaps misses the point that ideally, it wouldn't be anything more than the background rate.

I see now that I've got ahead of myself. In chewing over my first question - how does the planetary boundaries idea take us forward? - I've started to look at whether it's likely to be useful in understanding the many dimensions and drivers of environmental decline, and in curbing it.

Here, we are into the realms of speculation, of course. My suspicion is that even if discussions take off immediately, it'll be a heck of a long time before some of the boundaries are consensually drawn.

It might be possible to analyse some of them quantitatively - the impacts of ocean acidification on food supply, perhaps - but others are likely to prove much less tractable.

And as we are seeing now in the run-up to the Copenhagen climate summit - as we are likely to see next year as the global goal of curbing biodiversity loss comes up for review - turning science into political action is still the elusive ingredient in this whole picture.

In the middle of contemplating this big, airy, conceptually-driven look at environmental ills and solutions, I neglected to mark a birthday last week.

It is the birthday of something at the other end of the scale from planetary boundaries - not a grand conceptualisation, and not something concentrating on the problem, but something aimed at providing localised solutions.

I even missed the doubtless delicious lunch that went with it - in order to attend meetings planning how the BBC will cover the Copenhagen summit, for Pete's sake! The sacrifices I make for you...

The birthday in question was that of certified seafood. It is 10 years since the Marine Stewardship Council (MSC) was created with a mandate to slow the decline of marine life by assisting the discerning customer to finance its protection.

I see the MSC label in some of the shops where I buy food. The organisation now calculates that about 7% of the world's capture fisheries are certified as sustainable, from longline-caught Norwegian haddock to the western Australian rock lobster.

When I interviewed MSC chief Rupert Howes two years ago for a BBC World Service radio series on sustainable fisheries, the figure was 6%. So it's going up, but slowly - although the tentacles of certification are gathering more fleets to its bosom, the vast majority remain outside.

And it's not difficult to see why. Being certified as sustainable means abiding by a heap of what any frontiersman of the deep would viscerally classify as "red tape" - restricting catches to a scale aimed at ensuring the fishery can persist forever, filling in the paperwork needed so the origin of a batch of food can be traced, using gear designed to keep bycatch as low as possible, and so on.

And some of these - more expensive gear, smaller catches, more bureaucracy - will impact a fisherman's profitability, right?

Wrong. To mark its birthday, the MSC commissioned a number of journalists to interview fishermen taking part in the scheme; and among the findings are that MSC certification can make fishermen richer.

Some Australian fishermen reported restaurants would pay between 30% and 50% more for certified fish. Even supermarkets (and Walmart, among others, is signed up) are paying more.

In one sense, I've always liked the certification concept, whether it's for fish or flowers or timber.

If I want to have my goods produced sustainably, I can - and the certifying body takes away from me the unfeasibly huge task of finding out for myself how sustainable it is.

I look for the logo, I pay my price premium and everyone's happy. And if I'm not bothered, if I just want the cheapest I can find and hang the health of the stock, then I can do that that too.

But that also tells you that certification can never be all of the solution.

So, 7% of the market is currently certified as sustainable. What's the limit - 10%, 12%, 20%? No-one knows - but I'd wager a sustainable salmon dinner with a feast of organic croutons on top that it's a lot less than 100%.

Certification can bring other benefits. The MSC cites examples of fisheries where the government has liked the extra profits and sustainability of the certification regime so much that it's imposed it on all its fleets.

But many fisheries, one suspects, will always slip through the sustainability net if certification is all there is.

Industrial fishing brings us up hard against limits to growth.

Trawlers breached the limit of the Grand Banks cod stock in the early 1990s; whether it will ever grow again is still a moot point.

And we are depleting some stocks of their largest fish so spectacularly that we have imposed a new biological limit on their growth - species are becoming smaller, and reproducing earlier, than before our intervention.

So I'll wish the MSC a belated Happy Birthday, and hope they celebrated with - well, fishcakes, I suppose, with candlefish on top.

Perhaps they are shedding a little light on the burning issue of how to stay within the planetary boundaries that nature imposes.

Thus came the initial reaction from Todd Stern, the chief US climate envoy, after China's President Hu Jintao told the special session of UN heads of government that he would set mandatory targets for improving "carbon intensity".

(In other words, between now and 2020, Chinese factories and power stations and everything else will become more efficient - making more stuff while producing less and less carbon dioxide per unit of stuff.)

Mr Hu's speech was trailed as potentially ground-breaking by no less a figure than the UN's chief climate official, Yvo de Boer, who said China could "become the front-runner" in climate diplomacy.

Did Mr Hu deliver?

"It depends..."

We don't know how big the carbon intensity targets will be, for one thing. Mr Hu described them as "notable"; if they're not notable enough, they will simply be swamped by economic growth.

(The current Five-Year Plan, running from 2006 to 2010, has a goal of improving carbon intensity by 20% during the course of the five years).

Mr Hu also re-affirmed the target of providing 15% of China's primary energy mix by 2020 from non-fossil-fuel sources - renewables and nuclear - and of re-foresting tracts of his country.

And that's about it.

His speech was heard by several key audiences.

One consisted of the other world leaders sitting in the UN chamber - and they seemed appreciative, although the clapometer didn't whizz round as far for him as for Japan's incoming Prime Minister Yukio Hatoyama as he re-affirmed a pledge to slash emissions by about a third over the next 11 years.

An important sub-set of that UN chamber audience was the wider G77 bloc of developing countries with whom China is allied on most issues, and certainly on this one.

Mr Hu made a large nod to them by referencing the needs of least developed countries (LDCs) and African nations for financial and technical support in adopting low-carbon technologies and protecting themselves against impacts of climate change.

Then there was an audience back home - all the technocrats and bureaucrats and other agents of the Chinese government who have been charged over the last few decades with growing the national economy, and who have succeeded in that task very well - perhaps too well for the country's ecological health.

Mr Hu appeared to be telling them that now they have a second key task - de-carbonising the economy while continuing to grow it.

But in the short term, his most important audience lay a few hundred kilometres southwest of UN headquarters, in Washington DC.

Some time this month, the US Senate is due to start debating the Waxman-Markey Bill, which would set emissions caps for various bits of the economy and establish a nationwide carbon market.

Senatorial scepticism on the Kyoto Protocol was a leading reason why the treaty did not deliver what it once promised; the same scepticism in regard of the UN climate process now could substantially scupper the negotiations taking place in Copenhagen in December.

And the main reason for senatorial scepticism this time round - as last - is that leading developing nations such as China aren't "doing enough".

No-one seriously expects developing countries to accept numerical cuts in their greenhouse gas emissions.

But many richer nations believe calculations (stemming from the Intergovernmental Panel on Climate Change) that the more successful ones, including China, must curb the growth in their emissions by about 30% from the "business as usual" trajectory by 2020 or thereabouts.

One senses that anything like 30% would be acceptable to Mr Obama's administration - but the Obama administration is not the US Senate.

If Mr Hu's words are heard in the Senate as a firm commitment to take firm action, swift passage of a strong form of Waxman-Markey becomes more likely, which in turn makes a Copenhagen deal more likely. The reverse is also true.

So how will they regard it? We shall see.

One canard that really has to be slain at some point is the notion that any of these pledges, by China or any other country, are really mandatory in the sense that you or I would understand the word.

It's mandatory that you obey the speed limit when driving, otherwise you'll be up before a judge and might lose your licence. It's mandatory that you fill in a tax return or else you're liable for a fine. It's mandatory that you feed the pet tortoise otherwise it'll die and the kids won't speak to you for a week.

But in all the fine words of the UN climate convention and Kyoto Protocol, in the language likely to come out of Copenhagen, in the UK's "legally-binding" commitment to cut emissions by 80% by 2050 and so far in China's adoption of "notable" carbon intensity targets, there is no sanction - nothing - that compels or even strongly persuades countries to meet their targets.

Mandatory? Not according to the Oxford English Dictionary definition ("binding", "obligatory", "compulsory", "not discretionary"...)

So what has come out of this UN special session, a personal initiative of Secretary-General Ban Ki-moon?

Too soon to tell, perhaps - but I don't think there is any chance that two years ago, you could have had the UN chief, US president, Chinese president, Japanese prime minister and the leader of a low-lying island state such as the Maldives all in the same room and all singing from broadly the same hymnsheet ("vital issue", "time running out", "need to make a deal", etc etc etc).

Whether that's enough to give UN negotiations the kick they appear to need is another matter.

"It depends..." - on a lot of things, including what lies behind the word "notable".

No, me neither.

At first I thought he must be the mannish hero of some cheap boys' novella - a Pimpernel in the face of organised crime, a Zorro jumping on the cat-stroking villainry of world domination, a musketeer with liberty carved into his very eyeballs.

Somewhat disappointingly, in one sense, it's a fish.

And I know this: if trawlers used to catch 60 tonnes of them in a single hour back in the 1970s and now they catch only one tonne in an hour, something has happened to the alfonsin that he must consider entirely the opposite of splendid.

You or I might get to eat a splendid alfonsin (also known as splendid alfonsino, which is even more heroic); but we're unlikely to see one alive, as they generally live on or near the ocean floor at depths that can reach 1.3km.

For a long while after the dawn of commercial fishing, such species remained out of reach, out of sight and out of mind.

No more. As more accessible stocks dwindled, and demand continued to rise with the growing human population and affluence, ever more well-equipped fishing vessels began to target these deep-ocean species with a range of methods, the most destructive of which entails dragging five-tonne pieces of iron at the front of trawls over the sea floor - fine, if it's just sand and silt, but not so great if it's a deep-sea coral reef.

Three years ago, following a heap of pushing and prodding and repeated false starts, the UN General Assembly eventually acknowledged the possibility that soon some of these species might vanish out of sight forever unless steps were taken to protect them.

Deep-water bottom-dwellers are often slow to grow and slow to reproduce. The orange roughy can live to at least 149.

This makes them highly vulnerable to overfishing, unlike species that reproduce with great fecundity when they're barely out of the fry stage.

Conservation groups pressed the UN for a straightforward moratorium on bottom-trawling except in places where good management regimes were already established.

Enough member governments demurred to force a weakening, but what emerged was, by the standards of these things, not a bad set of measures: scroll down to "A/RES/61/105" at this research guide.

Governments promised to protect vulnerable marine ecosystems (VMEs), either by themselves or through regional fisheries management organisations (RFMOs). Where no competent RFMO existed, they would create one.

Countries would bar vessels that flew their flags from bottom-fishing in international waters where it had not been proven that no harm would come to VMEs. The precautionary principle was everywhere and most of these rules had to be put in place pretty quickly, by the end of 2008.

That 2006 resolution also instructed the UN secretary general to monitor the situation and provide a status report. It had to be ready for this year's UN General Assembly, which opens in the middle of next week.

At this moment, officials from UN member governments are in New York poring over the secretary-general's report [329Kb pdf].

It's unlikely that any of the bottom-trawling countries will find much to keep them awake at nights.

The main reason is encapsulated in a couple of sentences so strangely juxtaposed in sentiment that they could belong to different centuries; you'll find them on page seven.

The first states that submissions for the report were solicited, and did in fact arrive, from member governments, RFMOs and non-governmental organisations - which in this case mainly means conservation groups such as the Deep Sea Conservation Coalition (DSCC).

The second states that the people compiling the report based it on submissions from governments and RFMOs, as well as unspecified "other relevant information".

So - er - what happened to the rest of the submissions?

The DSCC's take on this is that "the secretary general's report collated the information received on what has been done, but in doing so does not clearly show what has not been done".

For an example of what the coalition means, let's take the area managed by the North East Atlantic Fisheries Commission (NEAFC).

The report says that NEAFC decided to prohibit gillnets and entangling nets (which work pretty much as their name suggests) in water deeper than 200m; very good. It also agreed to "reduce all deep-water fishing effort" by one-third.

According to the DSCC, what the report omits is that gillnets and entangling nets are a minor source of catches, the majority coming from trawls - which are not banned; and that under the effort-reduction measure, the reported catch actually rose from 20,000 tonnes in 2004 to 90,000 tonnes in 2007.

And so on; there is more, much more of this.

The secretary general's report is long (67 pages), detailed and acronym-dense, and unless you readily know your PECMAS from your SIODFA you'll not find it easy going; nor will you the detailed DSCC submission [597Kb pdf].

But what it really boils down to is this. The UN resolution three years ago said, in a nutshell, "don't fish the sea bottom unless you know you can do it sustainably".

What seems to have happened in many areas of the world is that member governments have put into place regimes that say "we don't have any information to say that's not sustainable, so we'll presume it's okay to continue".

Lobbyists for fishermen may at this point wish to express concern about livelihoods; two things are worth bearing in mind.

Firstly, all governments signed up to this; anyone who doesn't like it should complain to them.

Secondly, the resolution doesn't ban bottom-fishing; it just says don't do it unless you know it won't destroy deep-sea ecosystems, such as ocean vents, or the very fish stocks you're trying to catch.

UN member states don't have to accept the secretary general's report. They're discussing it this week, and it will come up again during the General Assembly (agenda item 77b, in case you're interested).

If they're serious about making fishing sustainable, they might ask how it is that catches can rise by a factor of more than four under measures that are supposed to cap them.

They might ask why it is that in the entire north west Pacific, fishing nations have agreed to protect just one part of one seamount among many that are likely to support vulnerable ecosystems.

They might ask why protocols designed to encourage captains to move on when they realise they're having an "encounter" with a vulnerable marine ecosystem stipulate they can bring up 100kg of live coral or 1,000kg of sponges before realisation has to dawn.

Then again, they might not ask any of this; in which case, we had better enjoy the splendour of the alfonsin and all its cousins while we still can.

The occasion: that on the 22nd birthday of the Montreal Protocol on Substances that Deplete the Ozone Layer, every UN member country has ratified the treaty - the first time that's happened with any international environmental agreement.

The latest adherent is East Timor, whose Prime Minister Xanana Gusmao declared his country's pride in "joining the rest of the world in the fight against the depletion of the ozone layer and the effort towards its recovery".

Having played a leading role in East Timor's push for independence, Mr Gusmao knows a thing or two about fighting long fights; and that's just as well, as it is far from clear how long the journey to ozone "recovery" is going to take.

This graph from the World Meteorological Organization (WMO), which collects and collates data on the Antarctic ozone "hole", makes clear that although the exact size of the hole varies from year to year, it's stubbornly resistant to going away.

This is despite the fact that within months, the Montreal Protocol's list of banned chemicals will rise to 100 - all the variants of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrobromofluorocarbons (HBFCs) and so on whose stratospheric chemical offspring gnawed away the ozone layer as their usage soared in the determinedly white-coated years following World War II.

Why the ozone hole has not started to recover, as scientists initially believed it would, is a complex and only partially understood issue.

Firstly, not all ozone-depleting chemicals were phased out at the same time, with developing countries given longer to change over; a few substances, such as the fumigant methyl bromide, are still in use.

A second factor was the development of a thriving international black market.

Some companies in developing countries that were permitted to continue manufacturing and using CFCs found it more profitable to export them to western nations where they were officially banned.

At one point, the Environmental Investigation Agency estimated that CFCs ranked second only to drugs in their value to the black market stallholders of Miami.

Those days are almost over. The big industrial consumers such as refrigeration plants have largely switched to other chemicals, a process encouraged by chemical manufacturers such as Dupont.

The original bad boys, CFCs, are out of circulation (apart from possibly a few "essential uses") next year.

But many of these substances persist in the atmosphere for decades. And it appears that man-made global warming is increasing their impact.

More heat trapped in the lower atmosphere means that less permeates up to the stratosphere - which is cooling as a result.

That encourages the chemical reactions that take ozone molecules apart.

Climate change is increasing water vapour concentrations in the stratosphere above the poles. That means more polar stratospheric clouds, which again speeds ozone destruction.

The current best estimates are that the hole will be back to its pre-CFCs size by about 2050.

Paradoxically, though, the Montreal Protocol has helped to curb climate change, as some of the heavy ozone-depleting molecules are also among the most potent greenhouse gases that humanity has invented.

A recent study concluded that the treaty has had more impact on greenhouse gas emissions than the Kyoto Protocol would do even if all its targets are implemented - which currently looks unlikely.

However, a companion study calculated that use of popular ozone-friendly replacements, HFCs, is likely to increase so fast (for air-conditioning and other applications) that they could become major contributors to global warming in the coming decades - perhaps contributing 20% of the man-made greenhouse by 2050.

That analysis prompted a number of countries, led by Mauritius and Micronesia, to suggest using the mechanisms of Montreal to regulate HFCs - an initiative that has just received backing from the three nations of North America.

As with all of the protocol's phase-outs, it will need industry support to be successful.

The Montreal Protocol is widely hailed as a treaty that has worked - and by some measures, it has, with an internationally-endorsed political process, backed up by technical and financial help for countries that needed it, leading to a phase-out of the chemicals of concern.

Unep reckons that by curbing damage to the ozone layer, it has prevented 1.5 million cases of melanoma, about 20 million other cancers, and 130 million eye cataracts.

But it's worth reflecting that if 2050 turns out to be about right, it will have taken humanity more than a century to create, understand, discuss, regulate and solve a relatively small-scale and tractable environmental problem.

What does that timescale imply for our capacity to solve biodiversity decline, ocean acidification, climatic change, the spread of deserts, and the other symptoms of our swelling human population?

Raise a glass, if you will, in Montreal and Nairobi; but a swift sobriety ought perhaps to follow.