Contraction and convergence


in Economics, Politics, Science, The environment

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:

Contraction and convergence graph from the Garnaut Review

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.

{ 12 comments… read them below or add one }

R.K. February 28, 2008 at 9:54 am

That does look like a fair sort of progression. The biggest question that jumps out of that graph is “will it be politically acceptable to force Americans to follow their downward-sloping line during the period when people in China are still trending upward?”

R.K. February 28, 2008 at 9:57 am

This comic will probably serve as a funny reminder of your student days

Milan February 28, 2008 at 11:08 am

The comic is accurate and amusing. Anything about the biochemistry of caffeine has appeal to me.

Milan February 28, 2008 at 11:09 am


Political acceptability is certainly a big problem. That said, contraction and convergence has some hope of (a) solving the problem (b) being feasible and (c) seeming fair.

. February 29, 2008 at 11:34 am

‘Stabilizing climate requires near-zero emissions’
A new climate science paper calls for dramatic action

Avoiding climate catastrophe will probably require going to near-zero net emissions of greenhouse gases this century. That is the conclusion of a new paper in Geophysical Research Letters (subs. req’d) co-authored by one of my favorite climate scientists, Ken Caldeira, whose papers always merit attention. Here is the abstract:

Current international climate mitigation efforts aim to stabilize levels of greenhouse gases in the atmosphere. However, human-induced climate warming will continue for many centuries, even after atmospheric CO2 levels are stabilized. In this paper, we assess the CO2 emissions requirements for global temperature stabilization within the next several centuries, using an Earth system model of intermediate complexity. We show first that a single pulse of carbon released into the atmosphere increases globally averaged surface temperature by an amount that remains approximately constant for several centuries, even in the absence of additional emissions. We then show that to hold climate constant at a given global temperature requires near-zero future carbon emissions. Our results suggest that future anthropogenic emissions would need to be eliminated in order to stabilize global-mean temperatures. As a consequence, any future anthropogenic emissions will commit the climate system to warming that is essentially irreversible on centennial timescales.

. October 29, 2009 at 12:05 pm

World carbon emissions, by country: new data released

The US is no longer number one emitter of carbon dioxide, having been overtaken by China in these latest figures. But when did it happen?

. December 9, 2009 at 3:21 pm

China’s greenhouse gas emissions will peak between 2030 and 2040, the country’s science and technology minister said Monday, as crunch talks on climate change were getting under way in Copenhagen.

Wan Gang said the precise timing of the level would depend on China’s economic growth, rate of urbanization, and level of scientific development.

“There are some uncertainties here, so it is difficult to say whether it will be in the beginning, the end, or the middle, but I can say for sure it will be within that range (of 2030-2040),” he told the Guardian.

China, the world’s largest carbon gas polluter, has promised to make gains in energy efficiency, but has yet to announce a peak date for emissions.”

Aubrey Meyer May 17, 2010 at 11:55 am

Here is a presentation/animation that relates to the [mis]handling of C&C at COP-15 last December: –

As Ross Garnaut correctly said, “the rate of convergence is the main equity-lever [in C&C].”

. April 19, 2011 at 8:35 pm

Hans Rosling and the magic washing machine

What was the greatest invention of the industrial revolution? Hans Rosling makes the case for the washing machine. With newly designed graphics from Gapminder, Rosling shows us the magic that pops up when economic growth and electricity turn a boring wash day into an intellectual day of reading.

. August 11, 2021 at 7:46 pm

Worst polluting countries must make drastic carbon cuts, says Cop26 chief | Cop26: Glasgow climate change conference 2021 | The Guardian

. August 29, 2021 at 4:34 pm

Worst polluting countries must make drastic carbon cuts, says Cop26 chief

Alok Sharma says chance to limit worst impacts of climate breakdown ‘still achievable, but retreating fast’

. October 27, 2021 at 1:54 am

The LMDC argued that its member countries should not be forced onto the same timeline to cut emissions as the industrialized world when they have done little to contribute to historic emissions and may want to use fossil fuels in their own economic development, as wealthier nations have.

This argument is not new. The recognition that different countries have different responsibilities for and capabilities to address climate change is at the heart of the U.N. negotiation process. It was also embedded in the 2015 Paris Agreement, which says that emissions should peak sooner in developed countries than elsewhere. And yet rich countries have delayed taking action to cut their own emissions for more than a decade, and now are demanding that the whole world commit to net-zero. In September, U.S. climate envoy John Kerry went to India to urge Prime Minister Narendra Modi to set a net-zero target. A few weeks ago, U.K. politician and COP26 president Alok Sharma called on G20 countries, some of which are members of the LMDC, like China, Indonesia, and Saudi Arabia, to step up now and set a net-zero target.

The LMDC put forward a different framework. The bloc proposed that rich countries get on the fast track, fully decarbonize by the end of this decade, and “leave the remaining atmospheric space” for carbon emissions to the developing world.

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