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Contraction and Convergence

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Contraction and Convergence (C&C) is a proposed global framework for reducing greenhouse gas emissions to combat climate change. Conceived by the Global Commons Institute in the early 1990's, the Contraction and Convergence strategy consists of reducing overall emissions of greenhouse gases to a safe level, 'Contraction', where the global emissions are reduced because every country brings emissions per capita to a level which is equal for all countries, 'Convergence'.

It is intended to form the basis of an international agreement which will reduce carbon emissions to avoid climate change. It is expressed as a simple mathematical formula. This formula can be used as a way for the world to stabilize carbon levels at any level. The supporters of Contraction and Convergence anticipate that future negotiations would focus solely on what that final level should be.

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The theory

The Contraction part of Contraction & Convergence concentrates on the total amount of Carbon being put into the atmosphere. This lays down an annual fall of global emissions - how great that fall would be would depend on the final level of atmospheric carbon considered safe.

The Convergence part lays down how the entitlements to emit carbon are distributed between the countries of the world. Initially these entitlements would reflect current emissions to reflect the difficulty in making the transition. However these initial entitlements will converge towards equal per capita emissions across the planet. The year when entitlements reach equality would be subject to negotiation. An early date would mean that initially countries that currently have low per capita emissions (which as a rule are poorer countries) would see their entitlements rise. A late date for full convergence would risk curtailing poorer countries' chances of development. Once convergence had reached then all countries entitlements would continue to fall, that is to say contract.

The per capita element risks giving an incentive to countries to increase their population to "earn" more entitlements. Hence there it's desirable to set maximum populations beyond which no further entitlements would be gained and indeed Global Commons Institute advocates this.

Acceptable concentration levels

Both the basic concept of Contraction and Convergence and the specific formulas that the Global Commons Institute advocate can be adapted to both very moderate restrictions on Carbon Emissions through to much more drastic measures depending on what final level of greenhouse gases concentration is deemed to carry an acceptable level of risk.

However supporters of Contraction and Convergence such as the Climate Justice Project believe that a safe level at which concentrations of greenhouse gases should stabilize is much lower than other estimates suggest. Specifically they believe that suggestions by the IPCC that atmospheric concentrations of CO2 of 550 ppmv would be okay are wrong. This they consider runs the risk of entering a phase of runaway “climate feedback”, where one change sparks off another with unpredictable results. They advocate erring on the side of caution, with atmospheric concentrations of CO2 being stabilized at 350-450 ppmv.

In order to reach these targets for, say, the UK, individuals would have to cut their personal emissions by between 60% and 90%.


Contraction and Convergence was developed, over a period of 3 years, in response to the UNFCCC's 1992 call for an equitable distribution of carbon emission rights among individual states or groups of states, in proportion to their population, with planned progress towards that objective by an agreed date. Between 1992 and 1995, at the request of the Intergovernmental Panel on Climate Change, the Global Commons Institute (GCI) discovered and presented an analysis on the growing trend of 'Expansion and Divergence', which revealed the increasing effect of global development and the asymmetry in development between developed and developing countries—ultimately suggesting that it was developing countries that would be worst affected by climate change. Contraction and Convergence was developed by the GCI to counteract the negative effects of this trend.


The implementation of the framework begins with a full-term contraction budget for global emissions consistent with stabilising atmospheric concentrations of greenhouse gases at a pre-agreed concentration maximum deemed to be safe.


Contraction & Convergence has the support of key government spokespersons in the Group of African Nations, in India and in China [1]. it is also favored by the European Commission[citation needed] and many other government bodies[citation needed]. In 1998 it was endorsed by the European Parliament[citation needed]. It is supported by many campaigners and groups from George Monbiot and Mayer Hillman to Scientists for Global Responsibility and the Royal Institute of British Architects (RIBA).


This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Contraction_and_Convergence". A list of authors is available in Wikipedia.
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