The interim version of the Garnaut Review (mentioned earlier) includes a numberless graph illustrating what the principle of contraction and convergence in per capita greenhouse gas emissions would resemble:
A few features are especially notable. The first is the relative trajectories in the opening years. States with very high per capita emissions, like Australia and Canada, would have to reduce emissions sharply right from the outset. Rapidly growing poor states like China would be allowed to grow until per capita emissions are comparable to those in relatively low emission developed states, such as the EU. Gradually, everybody’s per capita emissions become lower and more similar.
This approach becomes a lot more politically feasible when you take these lines to represent emission allocations rather than actual emissions. Developing states would have a choice about how to use the extra space allocated for their development. They could opt to use the allocation for their own emissions, allowing the growth of GHG emitting industry; alternatively, they could sell the allocations to more developed states at a globally established market price. That way, poverty reduction and development goals could be served at the same time as total GHG emissions trend towards a sustainable level. The big advantage of allowing global trading is that it should equalize the international marginal cost of abatement. In simple terms, that means that it will ensure that the emissions that can be avoided at the lowest cost will be addressed first, minimizing the overall cost of mitigation.
The Garnaut Review rightly highlights that it would be incredibly politically difficult to establish such an international regime. At the same time, it is probably also right to say that a general approach that embraces contraction and convergence has the best chance of stabilizing global greenhouse gas emissions at a level that avoids dangerous anthropogenic interference in the climate system, and does so in a way that minimizes total costs and manages the distribution of costs and benefits in an acceptably fair manner.