Cheat Sheet: Contraction and Convergence

Sounds painful.

It will very likely prove to be so.

So what is it exactly?

It's a model for stabilising carbon emissions at safe or at least safer levels and is designed to be equitable so that the developed countries that caused the bulk of the problem have to take the greatest action to mitigate the risk of climate change.
How's it work then?

Basically a global carbon budget is set based on the concentration of greenhouse gases in the atmosphere that scientists deem safe and the date by which we have to reach that level. That budget includes a figure for the amount the world can safely emit to achieve that stabilisation goal and that figure is divided by the expected population in the target year to get a per capita emission entitlement. Each country can then work out their national allocation based on the size of their population.

So everyone in the world would have the same emissions limit?

That's the idea. In theory the system would be extremely equitable as the world's poorest countries would actually be able to increase their emissions per capita as they continue to develop, while the richer countries who are predominantly responsible for the high greenhouse gas concentrations in the atmosphere would have to make the biggest investments to bring their per capita emissions down. The overall effect would be that total emissions would contract as each country's emissions converge towards a common per person target – hence contraction and convergence.

Sounds fair.

Yes, it should be. In theory the per capita emission allocations become a tradeable commodity so it would also provide a mechanism for wealth redistribution as those poorer countries with emissions far below their allocated level would be able to sell their excess allotted credits to richer countries. Poorer countries then could use this revenue stream to fund projects to protect against climate change and install low carbon technologies. The richer countries that caused the bulk of climate change would effectively pay for the countries worst effected by it to cope, but without the inefficiencies of an aid programme.

Is C&C likely to be implemented?

Well, since it was developed in the early-nineties by Aubrey Meyer at the Global Commons Institute the concept has been supported by a raft of different political groups and environmentalists, including the African Group of Nations and the UN.

That doesn't really answer the question, is it likely to be implemented?

Well, the concept is gaining traction but if we're honest it is unlikely to come into effect any time soon. While it is hard to argue with the model in principle – everyone owns the atmosphere and everyone should have an equal right to pollute it – there is plenty to argue about in how best to set the budget and how to divvy up the annual emission allocations. Some scientists reckon we need to stabilise greenhouse gas concentrations at less than 450ppm and ideally closer to 350ppm by 2030, others including the International Panel on Climate Change put the figure at 550ppm by 2050. Predicting population growth is also likely to be a subject of considerable debate, as is the topic of the best way to police each country's emission caps.

Would it be cynical to suggest such a long-winded debate would prove pretty convenient for those countries required to deliver the deepest emission cuts?

Well if we're being cynical the chance of getting a global agreement around any system that commits the developed world to a far more dramatic reduction in emissions than China and India is unlikely as long as the US and to a lesser extent Europe refuse to hand the Asian powerhouses anything that may resemble a competitive advantage.