Old hands in climate policy know "Contraction and Convergence", for those new to the discussion, here's a BBC article from last year:
This week and next, government representatives attend UN talks in Bonn looking for the next step forward on climate change. In The Green Room this week, Aubrey Meyer argues that the effective and fair model they need already exists.
The impact of climate change, it is generally agreed, will land hardest on the poor.
So perhaps it is time to listen to what people from the poorest continent, Africa, are asking for.
At the climate negotiations in Bonn this week, the Africa Group of Nations has called for the adoption of a concept called Contraction and Convergence - C&C, in the jargon.
They first made their call a decade ago. And with 12 million Africans currently facing drought and famine linked to climate, they have good reason to assert that C&C is right, that it is urgently needed, and ask: "For how long must Africa suffer at the hands of others?"
Contraction and Convergence is the only long-term framework for regulating greenhouse gas (GHG) emissions which does not make carbon dioxide production a luxury that only rich nations can afford.
It creates the social equity which Africa needs, and the carbon reductions which are in all our interests.
Contraction and Convergence is a straightforward model for an international agreement on greenhouse gas emissions.
It sets a safe and stable target for concentrations of greenhouse gases in the atmosphere, and a date by which those concentrations should be achieved, based on the best scientific evidence.
The atmosphere being a "global good", C&C declares that all citizens of the Earth have an equal right in principle to emit, and will actually be given an equal right by this future date, the individual allowance for each citizen being derived from the "safe" global target.
So from the grossly inequitable situation we have now, per capita emissions from each country will "converge" at a far more equitable level in the future; while the global total of emissions will "contract".
That is C&C in a nutshell....MORE