The Big Question: Is an agreement on climate change in Copenhagen still on the cards?

Why are we asking this now?

Yesterday Gordon Brown, at a meeting of ministers from 17 "major economies" held in London to discuss the talks, warned that countries were not moving fast enough to reach an agreement.

What is at stake?

A global deal to cut the carbon dioxide emissions from power generation, industry, transport and deforestation which, all governments now accept, are causing the atmosphere to heat up, with potentially disastrous consequences for all of us.

That seems like a no-brainer. Why shouldn't all countries agree to that?

While all countries now recognise the problem – a no-brainer is right – they have very differing views about what their role in the solution should be. Cutting CO2 and other greenhouse gases can be done, but not with the wave of a wand. It means redesigning whole economies on a low-carbon model, which involves a lot of effort and a lot of expense; among much else, you have to close down your coal-fired power stations or fit them with costly equipment to capture their CO2 and bury it underground. And the argument at Copenhagen will essentially be about how the effort and the expense should be shared out between nations. If that can be agreed, a deal will be done. If it can't, the world is in for trouble.

So who's arguing?

In the simplest terms, two sides have to come together to do a deal: the rich, mainly western countries of the developed world, such as the US and Britain, and the poorer (but rapidly growing) nations of the developing world, led by China and India. The argument is about responsibility and fairness, and it turns on the fact that most of the CO2 that is in the atmosphere now (and it remains for a century or more) has been put there by the rich countries, who have been pumping the stuff out since the industrial revolution 200 years ago; but most of the extra CO2 that will go into the atmosphere in the future will be put there by the developing nations, who are now embarked on a period of unprecedented, explosive economic growth, much of it powered by burning coal, with the principal purpose of drawing their peoples out of poverty.

Throughout the 20th- century the US was the biggest emitter of carbon dioxide in the world; but in the last two years China has overtaken it, having doubled its carbon emissions from 3bn to 6bn tonnes in a mere decade, and they will continue to grow. So you might say that China, with India, Brazil, Indonesia and their fellow developing economies, are now making the problem worse – and they are; but that the US, with Britain, and Germany and France and the other rich countries, started the problem in the first place – and we did. (And we too are worsening the problem every day, of course, with our own carbon emissions.)

What are the implications for responsibility and fairness?

The principal one is that the rich West has to lead the way in cutting carbon, and this has been recognised by all sides since the first global warming treaty, the UN Framework Convention on Climate Change, signed at the Earth Summit in Rio in 1992. The treaty said that the international community had "common but differentiated responsibilities" with regard to the climate, and this principle was put into effect in the Kyoto Protocol to the treaty, signed in 1997.

Under Kyoto, the rich industrialised countries agreed to cut their carbon emissions by fixed amounts by 2012, but the developing nations were not required to make any cuts at all. They were allowed to carry on with business as usual.

Has anything changed since then?

Yes. First, although most of the rich countries, including Britain, accepted Kyoto, the US Congress would not ratify the treaty, as many US politicians felt it was giving a free ride to countries such as China who were economic competitors; George Bush withdrew the US from Kyoto in 2001. Second, the carbon emissions of China and India and their fellows have mushroomed in a way that no one imagined possible in 1997, and they will represent 90 per cent of all future emissions growth; if unchecked, they will derail all other efforts to control climate change. So the point is, the Chinas and Indias now have to make emissions cuts themselves, or first, the US will not join in a new treaty, and second, the fight to limit atmospheric CO2, and thus future temperature rises, will be lost. But China and India have always argued that they are only growing in the way the West did, and that is true; and now they find the western nations saying: 'don't do what we did, do what we say', which is clearly unfair. The deal at Copenhagen is essentially about what the West can offer to make that unfairness acceptable, and what carbon-cutting actions the Chinese and Indians and other developing countries can take, which will in turn be acceptable to the West.

What might be the offers?

The rich countries have to make clear commitments to cut their own CO2 significantly by 2020, and will have to agree massive financial help – billions and billions of dollars – for the poorer nations to continue their growth in a low-carbon way. For their part, the developing nations will have to agree some sort of numerical targets to cut their own CO2 – something which was once anathema to them, as they saw the imposition of targets on them as a ruse by western competitors to hold back their growth. All sides now have to do things which are demanding.

Then why might the talks fail?

The European Union is signed up to tough emissions cuts and backs a big financial help package; even nations such as Japan and Australia, formerly laggards, have started setting serious CO2 targets. It is the position of the US which is crucial. President Barack Obama has to take something substantial to the table in Copenhagen in December in terms of US domestic action, but the Bill which will define US climate policy is stuck in the Senate, and will not go through until Mr Obama's healthcare package is dealt with, which may not be in time. Can Mr Obama offer something to China and its fellows which Congress will ratify? Maybe. The British Government is optimistic that he will. But if he can't, there will be no deal.

Is that the only threat?

That's the major threat, but it's by no means the only one. This is a treaty whose initial text was 200 pages long and contained 2,000 "square brackets" – points of disagreement. It has to be agreed line by line by 192 countries whose representatives are all playing to different domestic agendas and who might have difficulty agreeing on the colour of an orange. If anybody tells you this is a simple matter, don't listen. It's true we have the technology to solve global warming, but this is not about technology. This is about politics, about the art of the possible. And it's the most difficult piece of politics the world has ever seen.

Could the Copenhagen climate meeting end in failure?

Yes

*The US may fail to come to the table with an adequately serious offer on climate.

*Citing the needs of their people, China and India may make offers of action that the US find inadequate.

*The huge financial agreement that is proposed may unravel because of the differing needs of each nation.

No

*When the time comes, President Obama's US will almost certainly try to offer what is needed.

*China and India are already recognising that they need to act themselves.

*All sides realise that the financial package is an essential part of any finally agreed deal.