Contraction and Convergence

Contraction and Convergence

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Contraction and Convergence (C&C) is a proposed global framework for reducing greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

 emissions to combat climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

. Conceived by the Global Commons Institute
Global Commons Institute
The Global Commons Institute was founded in the United Kingdom in 1990 by Aubrey Meyer and others to campaign for a fair way to tackle climate change....

 [GCI] in the early 1990s, the Contraction and Convergence strategy consists of reducing overall emissions of greenhouse gases to a safe level (contraction), resulting from every country bringing its emissions per capita
Per capita
Per capita is a Latin prepositional phrase: per and capita . The phrase thus means "by heads" or "for each head", i.e. per individual or per person...

 to a level which is equal for all countries. It is intended to form the basis of an international agreement which will reduce carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 emissions to avoid dangerous climate change
Avoiding Dangerous Climate Change
The related terms "avoiding dangerous climate change" and "preventing dangerous anthropogenic interference with the climate system" date to 1995 and earlier, in the Second Assesment Report of the International Panel on Climate Change and previous science it cites.In 2002, the United Nations...

, carbon dioxide being the gas that is primarily responsible for changes in the greenhouse effect
Greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...

 on Earth. 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. Advocates of Contraction and Convergence stress that negotiations at the United Nations Framework Convention on Climate Change [UNFCCC] are governed sequentially by the 'objective' of the UNFCCC [safe and stable GHG concentration in the global atmosphere] followed by its organising principles ['precaution' and 'equity']. C&C is widely cited and supported

The C&C Proposal

The "contraction" part of Contraction and Convergence model calculates the total amount of carbon being put into the atmosphere as a 'path-integral' or a total 'contraction-event'. Future global emissions will shrink over time and the shape and extent of this [rates/weights/dates] will depend on [a] the final level of atmospheric carbon considered safe, subject [b] to the changing source-sink relationship in future as future atmospherric GHG acculmulation continues.

The "convergence" part structures how the entitlements to emit carbon are shared between the countries or regions of the world. Initially entitlements would reflect current emissions, however subject to a negotiation of 'the rate of convergence' these initial entitlements will converge towards equal per capita entitlements across the planet. An early date of convergence will mean that countries with currently low per capita emissions (which as a rule are poorer countries) will see their entitlements rise while a late date for full convergence would risk curtailing poorer countries' chances of development.

Once convergence is reached then all countries entitlements would continue to fall, subject to the contraction-event required to by UNFCCC-compliant.

Some argue that the per capita focus risks giving an incentive to countries to increase their population to "earn" more entitlements. To answer this, the GCI put a 'population base-year' function in the model for users to choose and specify any date between 2000 and 2050 beyond which no further entitlements would result from population growth.

Acceptable concentration levels

Both the basic concept of Contraction and Convergence and the specific formulas that the Global Commons Institute
Global Commons Institute
The Global Commons Institute was founded in the United Kingdom in 1990 by Aubrey Meyer and others to campaign for a fair way to tackle climate change....

 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 believe that a safe level at which concentrations of greenhouse gases should stabilize is much lower than many suggest. Specifically they believe that suggestions that atmospheric concentrations of carbon dioxide of 550 parts per million by volume (ppmv) would be safe 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 carbon dioxide being stabilized at 350-450 ppmv. GCI's numerical analysis of the unrealistically optimistic 'sink-assumptions' behind the UK Climate Act is here: -


The origin of GCI's intervention dates from 1989 and resulted in a statement published in 1990

The formal calculating model 'Contraction and Convergence' [C&C] was developed over a period of three years in response to the objective and principles of the UNFCCC. Between 1992 and 1995, at the request of the Intergovernmental Panel on Climate Change
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...

, GCI undertook and presented an analysis on the growing trends of expansion and divergence, which revealed the increasing asymmetry in global development between developed
Developed country
A developed country is a country that has a high level of development according to some criteria. Which criteria, and which countries are classified as being developed, is a contentious issue...

 and developing
Developing country
A developing country, also known as a less-developed country, is a nation with a low level of material well-being. Since no single definition of the term developing country is recognized internationally, the levels of development may vary widely within so-called developing countries...

 countries — ultimately observing that it was developing countries that would be worst affected by climate change. C&C was developed by GCI to counteract the adverse effects of these trends.


The application of the framework begins with a full-term contraction budget
A budget is a financial plan and a list of all planned expenses and revenues. It is a plan for saving, borrowing and spending. A budget is an important concept in microeconomics, which uses a budget line to illustrate the trade-offs between two or more goods...

 for global emissions consistent with stabilising atmospheric concentrations of greenhouse gases at a pre-agreed concentration deemed to be safe. In order to help negotiators at the UNFCCC negotiations internationally share this emissions contraction-budget in a way that is less arbitrary and chaotic than it was under 'Kyoto', the C&C model will calculate any rate of linear convergence of all Parties to the global per capita average arising under the chosen contraction rate. This can be on year anywhere between immediate and 'end-of-term' with or without a population base-year as desired. As Prof Ross Garnaut has observed in his 'Review' for the Australian Government , "this rate-of-convergence is the main equity lever" in the negotiations. Practically it means that the sooner the convergence occurs, the faster the gap between under-consumers and over consumers is closed but within the agreed contraction budget.


C&C has wide support as shown here for example
The C&C aspect of the negotiations at COP-3 in Kyoto in 1997 was inconclusive

In 2004 in Milan at COP-9 the UNFCCC Executive, responding to a lack of progress with the 'Kyoto Protocol' negotiations, publicly said, "Stabilization inevitably requires “contraction and convergence” - slide 9: -

In 2009 the Hadley Centre [UKMO] agreed that the rates of C&C projected by GCI to keep within 2 degrees Celsius were better than those projected by the UK Government in its 'Climate Act': -

C&C & COP-15

The C&C aspect of the negotiations at the 2009 United Nations Climate Change Conference
2009 United Nations Climate Change Conference
The 2009 United Nations Climate Change Conference, commonly known as the Copenhagen Summit, was held at the Bella Center in Copenhagen, Denmark, between 7 December and 18 December. The conference included the 15th Conference of the Parties to the United Nations Framework Convention on Climate...

 (COP-15) in Copenhagen in 2009 provoked controversy.

However, these animations of C&C as 'Climate Justice without Vengeance' show transparently the financial implications of negotiating an 'accelerated convergence' which issue remains directly relevant to achieving the 'global climate deal' still sought for at COP-16 and beyond.

The files are available as both *.swf file and flash-self-executable [for both Macs and PCs] and are stable and virus-free: -

See also

  • Mitigation of global warming
    Mitigation of global warming
    Climate change mitigation is action to decrease the intensity of radiative forcing in order to reduce the potential effects of global warming. Mitigation is distinguished from adaptation to global warming, which involves acting to tolerate the effects of global warming...

  • Greenhouse Development Rights
    Greenhouse Development Rights
    Greenhouse Development Rights is a justice-based effort-sharing framework designed to show how the costs of rapid climate stabilization can be shared fairly, among all countries...

  • Carbon rationing
  • Rationing
    Rationing is the controlled distribution of scarce resources, goods, or services. Rationing controls the size of the ration, one's allotted portion of the resources being distributed on a particular day or at a particular time.- In economics :...

External links