The Copenhagen summit is to prevent dangerous global warming, and for countries to stop the growth in greenhouse gas emission. Who should make the cuts? Industrialised nations such as the US, UK, Japan and others have emitted by far more carbon, and still continue to emit vast amounts per person, so these countries have a responsibility to make the deeper cuts.
However, emissions from emerging economies such as China and India are surging, and any global limit on emissions needs to be applicable to these nations too. Yet per person, these nations have small carbon footprints and millions of people in deep poverty - 400 million Indians live without electricity, for instance. So China, India, Brazil, South Africa and others can argue that they need to be allowed to continue to pollute for a while as they improve their citizens’ lives.
Balancing the responsibilities for cuts is a key part of the negotiations in Copenhagen. There is an argument that in the long term, a low-carbon economy will be cheaper than a fussil-fuelled one. But time is short and there will be costs in the near term. Everyone agrees that the poorer nations need urgent help. Citizens in places from Haiti to Sudan to Bangladesh have done virtually nothing to pollute the atmosphere, but are bearing the worst impacts of floods and droughts. Richer nations will need to pay billions from now - some call it reparation for damage to the earth's climate. It will also cost a lot to build the global clean energy infrastructure that is essential to staunch the carbon from the coal and gas power stations, a large contributor of global emissions.
For the first emerging economies such as India, the ideal is to skip the high-carbon growth phase entirely and go straight to renewables and perhaps nuclear power. EU has suggested that $100bn a year from 2020 would cover the global climate change bill. But estimates from development groups reach up to four times that amount. Finding a figure that all nations accept is the second key part of the negotiations. In theory, buying permits to pollute from those who can cut their emissions most cheaply is attractive - maximum bang for buck and a flow of cash to pay for investments. However, from one perspective, this kind of offsetting simply looks like paying poorer people to clear up the mess left by the rich, who can then continue to pollute.
Also, if carbon trading is to cut real emissions, the cap set in the market has to be tight, and to date, political imperatives have overridden those of the planet. Nevertheless, carbon trading will remain at the heart of any treaty sealed in Copenhagen, as it was in the Kyoto treaty.
About 40 per cent of all the carbon emitted by human activity has come from razing forests. Stopping deforestation, in principle, cheap and simple, does not cut them down. But paying people, via carbon credits - not to fell trees, soon becomes complex. Who really owns the trees? Were they going to be chopped down anyway? And how do you verify what actually happens? Finding a solution to these issues is one of the strongest hopes for the Copenhagen summit.
Poor countries could be paid for the first time to protect the forests they depend on. Many new jobs would be created. It could stimulate community forest management and eco-tourism. Protecting the forest would lead to better erosion control, water quality and biodiversity. Negotiations at the UN's climate summit in Copenhagen will use language that is full of technical jargon and confusing acronyms. Rising sea levels, increased droughts, floods and heat waves, and changing seasonal weather patterns mean that countries will have to adopt to protect ordinary citizens, businesses and infrastructure such as transportation, energy and water supply, to prevent the worst effects of climate change having an impact on the economy.
Adaptation is the term used to refer to such preparation and includes measures such as protecting coastal areas by building sea walls, reforestation to try to prevent flooding, increasing water conservation and changing crops to varieties that flourish in warmer climates. Mitigation simply means actions to reduce global warming, by cutting greenhouse gas emissions and protecting carbon sinks such as the Amazon rainforest which absorbs carbon dioxide.
Negotiations held in September in Barcelona were grim: all now acknowledge that no legal deal is possible in Copenhagen. If so, then a total collapse would leave 20 years of negotiations in tatters and the world unprotected against the ravages of global warming.