Frequently Asked Questions About Climate Change Legislation

This page addresses some of the more commonly encountered elements of various policies designed to control greenhouse gas emissions.

1. Questions about climate change policies:
   • a - What is the difference between cap-and-trade and a carbon tax?
   • b - How does cap-and-trade work?
   • c - How much would such policies reduce emissions?
2. What types of emissions are covered?
3. What is a carbon sink?
4. What is a carbon offset?
5. How are carbon allowances given out?
6. What is a safety valve?
7. How are overall emissions measured?
8. What are non-covered entities or sources?
9. What is "leakage?"
10. Are emissions reductions permanent or can they be reversed?
11. What are "banking" and "borrowing" in terms of climate change policy?

Sources and Further Reading

1.a - What is the difference between cap-and-trade and a carbon tax?

While both policies are designed to reduce carbon emissions by putting a price on those emissions, they accomplish that purpose differently. The key difference is in which of two elements is fixed: the price of carbon or the limit on emissions.

In a cap-and-trade system, the limit on carbon emissions is the fixed element, allowing the price of emissions permits to be set by the market. The advantage of a cap-and-trade system is that it permits the choice of a specific limit on emissions rather than leaving the emissions restrictions up to the market itself. The disadvantage is that the price of carbon on which the market settles can be difficult to predict and subject to large fluctuations, making it the less favored option by economists and investors, who prefer a more predictable and stable market. To illustrate the volatility of carbon markets, in 2006 the price of carbon allowances in the European trading system varied between $44.47 and $143.06, with a 70 percent drop in one month alone following regulatory changes (Nordhaus p.38). This represents an extreme case and a better regulated market with improved mechanisms for price control could prevent this type of fluctuation, although some variation will still occur.

With a carbon tax, a specific price is placed upon each unit of carbon emissions. From the perspective of economists, a tax is usually the preferred option because its effects on the market and economy as a whole can be more easily predicted. Like a tax on any other commodity or activity, a carbon tax would create a response to the price, either in the form of emitters finding ways to reduce their emissions or by passing on the cost of their emissions to consumers. As a disadvantage, it is difficult to predict how much the market will reduce emissions as a result of a given tax rate, making the initial tax rate contentious and the outcome for climate policy less certain. Estimates of the price of carbon that would enable the U.S. to meet proposed emissions targets range from $10 to $400 per ton, demonstrating the unpredictable nature of this policy’s effects and why creating a workable plan is politically difficult.

	Carbon Tax	Cap & Trade
Emissions Limit	No set limit	Fixed limit each year - increases incrementally over period the policy is in effect
Price of Emissions	Fixed price per unit of emissions (e.g. $50 per ton)	Varies on market like price of oil or any other tradable commodity
Revenues	Fixed price - revenue depends only on amount of emissions in a given year (e.g. at $10 per ton, tax would raise about $73 billion per year based on current U.S. emissions)*	Depends on how permits are allocated by the government - auction (variable price), fee per permit (fixed price), or given away for free (no revenue unless market transactions are taxed)

* 2007 CO2 emissions in the U.S. - 7,282.4 million metric tons. Source: Energy Information Administration

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1.b - How does cap-and-trade work?

A cap-and-trade system begins with deciding a limit on a particular emission that will be controlled, which is the cap. In the case of climate change, policymakers would set a total cap on greenhouse gas emissions for a given year and issue emissions permits to entities covered under the program, with the total number of permits equal to the amount of the cap. However, since not all industries are as capable as others at reducing their emissions, a cap-and-trade program allows firms to buy permits from other firms if it is cheaper than abating their own excess emissions.

To illustrate, consider a case in which a coal-fired power plant, Plant A, has been issued permits that allow it to emit 900,000 metric tons of carbon equivalent (MTCO₂E) in a given year. However, Plant A expects to emit 1 million MTCO₂E based upon projected demand, leaving a shortfall of 100,000 MTCO₂E that it will have to abate. If the abatement cost for Plant A is about $60 per MTCO₂E, then its total expected cost to abate its excess carbon emissions is about $6 million.

Elsewhere in the electric power market is Plant B, another coal fired power plant that is facing a similar case of excess emissions, although its cost of abatement is only $30 per MTCO₂E because it can more easily make technical upgrades. After making those upgrades, Plant B estimates it could emit only 800,000 MTCO₂E for its projected demand, leaving a surplus of 100,000 MTCO₂E in permits. With a cap-and-trade system, Plant B can pay the money to abate that much, which would cost about $3 million, and sell the extra permits to another plant. If plant A is willing to pay $50 per permit, it pays $5 million to avoid abating its excess emissions for another year, $1 million less than it would have had to pay to abate them now, while Plant B makes an extra $2 million by abating its emissions and selling its extra permits to Plant A. Or, Plant B could sell the permits on the market to another buyer if more is offered.

This example is more simplistic than the real market and uses somewhat unrealistic numbers, but it demonstrates the basic principle behind a cap-and-trade system. In a real system, the various industries covered under the policy buy and sell so often and in such volume that a market for permits is created with a price that varies based upon factors such as the cost of fuel, availability and cost of abatement technology, and demand for the product of emitting industries.

An example of a cap-and-trade system already in effect is the Emissions Trading Scheme (ETS), which the European Union (EU) uses to meet its obligations under the Kyoto Protocol. Under the EU ETS, permits are issued to emitters of greenhouse gases in accordance with the specified activities in the Kyoto Protocol. Starting on January 1, 2005, permits began to be issued for the first trading phase (2005-2007), with 95 percent of them issued for free and the price of the remaining permits determined by the market. That proportion dropped to 90 percent on January 1, 2008 for the second trading phase (2008-2012). If a given activity fails to allocate enough permits to cover its expected emissions for the year, it must pay a fine per ton of excess emissions, an amount which started at 40 euros per ton and increased to 100 euros per ton on January 1, 2008 (Directive 2003/87/EC of the European Parliament and of the Council of 13 October 2003).

The system also has provisions that permit more flexibility than simply purchasing or trading permits. For example, the Kyoto Protocol created a program called the Clean Development Mechanism (CDM), which permits participating nations to offset some of their own emissions with carbon reduction projects in developing nations. By doing so, emitters in developed areas such as the EU can reduce global emissions more cheaply by doing it in a developing country and at the same time contribute to the technological development of that country. The Kyoto Protocol also has a program called the Joint Implementation Plan (JI), which allows Kyoto participants to earn credit toward their emissions reduction targets by contributing to an emissions-reduction or emissions removal (carbon sink) project in another participating nation.

An example of a cap-and-trade system that has been implemented and successfully used in the United States is the Clean Air Markets program the Environmental Protection Agency (EPA) uses to control sulfur dioxide (SO₂) emissions, which cause acid rain. The program was introduced as part of the Clean Air Act Amendments of 1990 and took effect in 1995 with the goal of reducing SO₂ emissions by 10 million tons below 1980 levels. An EPA progress report in 2004 stated that in the first 10 years since initiation of the program, SO₂ emissions had been reduced by 7 million tons below 1980 levels and a subsequent study found that the benefits in 2010 from those reductions would outweigh the costs by a ratio of 40 to 1. The EPA has since included controls for nitrous oxides (NO_X) emissions in the program and has seen similar success.

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1.c - How much would such policies reduce emissions?

The amount that a given policy will reduce emissions depends on the type of control it places on emissions and which types it covers. Cap-and-trade programs place an explicit limit on emissions, which means that the amount by which greenhouse emissions will be reduced is known for every year that the program is in place. The AAAS climate change legislation page provides comparisons of some of the bills proposed in the U.S. Congress and the amounts by which they will reduce emissions. The most aggressive bills seek to reduce emissions to 80 percent below 1990 levels by 2050.

A carbon tax, unlike cap-and-trade, does not have a pre-set limit on emissions and relies on the price placed on each unit of emissions in order to achieve reductions. However, policymakers can set the initial price and adjust it later in order to achieve the emissions goals of the program or lower the price if it is negatively affecting consumers or the economy. Estimates of how much a given price will reduce emissions vary widely, although the economist William Nordhaus estimated, based on IPCC data, that efficiently balancing the costs and benefits of controlling greenhous gas emissions would require an international carbon tax of $17 per ton of carbon starting in 2010 and increasing to $72 per ton by 2050 (Nordhaus p. 31). However, he also pointed out that the governments involved in drafting an agreement would have to sort through difficult issues such as economic burden sharing between poor and rich countries, which could require subsidies or waivers from participation below a given income threshold. Legislation proposed in the United States includes the America’s Energy Security Trust Fund Act of 2007 (H.R.3416), which imposes a $15/ton tax on certain carbon emissions yet to be decided upon and the Save Our Climate Act of 2007 (H.R.2069), which imposes a $10/ton tax on fossil fuels based on their carbon content.

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2 - What types of emissions are covered?

The emissions covered vary with policy, but nearly all of them are measured as an amount of carbon dioxide (CO₂) because their effects on climate are measured in relation to that of CO₂. Because different gases absorb varying amounts of heat and linger in the atmosphere for varying amounts of time, scientists have created a measurement called global warming potential (GWP) that provides a simple means by which to convert emissions of any greenhouse gas into a standard unit with the same effect as CO₂.

For example, methane (CH₄) is about 25 times as potent a greenhouse gas as CO₂, which means that one ton of methane emitted has about the same impact on climate change over a 100-year period, or global warming potential (GWP), as 25 tons of CO₂. Some greenhouse gases, such as HFC-134a, which is used as a refrigerant in many air conditioning systems, has a 100-year GWP of about 1,430 and sulfur hexafluoride (SF₆), which is used in some electrical distribution equipment, has a 100-year GWP of about 22,800. 

The standard unit for carbon emissions used by most regulatory programs is MTCO₂E, or metric tons of CO₂ equivalent. The MTCO₂E of any other greenhouse gas can be obtained by multiplying its actual emissions amount by its GWP. Thus, 100 tons of methane emitted is equal to 2500 MTCO₂E. Some climate change policies proposed in the United States only address carbon dioxide, some delegate the determination of which greenhouse gases to control to the Administrator of the EPA, and others specify which ones will be covered. Information about some of the greenhouse gases most likely to be controlled, which are among the six greenhouse gases included in President Bush’s 2007 executive order, is shown in the table below. If the GWP goes up over time, it means that gas decays in the atmosphere more slowly than CO₂ and if it goes down, that gas decays more quickly than CO₂.

	Lifetime(yrs)	GWP (20 yrs)	GWP (100 yrs)	GWP (500 yrs)
CO2	varies	1	1	1
Methane (CH4)	12	72	25	7.6
Nitrous Oxide (N2O)	114	289	298	153
HFC-134a*	14	3830	1430	435
SF6**	3200	16300	22800	32600

Data Source: IPCC 4th Assessment Report (AR4), 2007. Table 2.14.
* Belongs to a class of chemicals called hydroflourocarbons. There are many varieties, each with unique properties, although the IPCC has data on 11 different types.
** Belongs to a class of chemicals called perflourinated compounds or perflourocarbons, of which the IPCC provides data on 11 types.

The 2006 IPCC Guidelines for National Greenhouse Gas Inventories is cited by the EPA as its reference for the inventories it submits to the United Nations in accordance with the UN Framework Convention on Climate Change (UNFCCC), which the United States ratified in 1992. In addition to the six categories of gases listed above, the IPCC's reporting requirements include nitrogen triflouride (NF₃), triflouromethyl sulphur pentaflouride (SF₅CF₃), halogenated ethers, and other halocarbons not covered by the Montreal Protocol, which includes all ozone-depleting substances.

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3 - What is a carbon sink?

A carbon sink is, very simply, the exact opposite of a carbon source. It is any activity or process that removes carbon dioxide from the atmosphere. In broad terms, there are two types of carbon sinks, natural and artificial. Natural carbon sinks include elements of the Earth’s environment that remove greenhouse gases from the atmosphere as part of a chemical or biological process. Examples include carbon dioxide absorption in the oceans, which constitute the world’s largest carbon sinks by far, carbon dioxide uptake by plants and other living organisms, and absorption of greenhouse gases in other elements of the Earth’s environment such as soil.

Artificial carbon sinks include any human activity that removes greenhouse gases from the atmosphere. That could be direct removal by a machine or chemical process or removal by any intentional manipulation of the Earth’s natural processes. For example, one means by which people have tried to enhance the effectiveness of natural carbon sinks is to simply expand their coverage of the Earth’s surface, such as by planting vast areas of forest. While the actual carbon removal process is natural, the overall impact is different than what would have occurred in the absence of human beings. Overall, land use changes constitute one of the most significant human impacts on the Earth’s balance of carbon sources and sinks, mostly due to deforestation for agriculture.

The effectiveness of a sink depends on what happens to the removed emissions over time, which involves the concepts of reversability and permance. For more on these concepts, see question 10.

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4 - What is a carbon offset?

Many plans to control greenhouse gas emissions include a provision for the use of carbon offsets. Offsets are a means by which a firm can accomplish emissions reductions by contributing to a greenhouse gas reduction activity elsewhere instead of directly reducing its own emissions. That could mean creating a sink by planting more forest, aiding a developing country in reducing its greenhouse emissions by using more efficient technology, or any of a number of other activities that have a net impact of lowering total carbon emissions by the same amount that the activity must lower its own emissions. Programs like this have several benefits in addition to being cheaper for businesses. They produce incentives for farmers and industries in less developed countries to reduce the carbon intensity of their activities as well as providing incentives to protect natural carbon sinks such as the rainforests.

However, while carbon offsets do provide supplementary benefits, making them very appealing to legislators and business advocates, they are subject to a number of potential problems that must be carefully considered. A report from the World Resources Institute (WRI) analyzing the viability of carbon offset programs found five conditions, derived from criteria in the Clean Air Act, which must be met in order for a given carbon offset to be effective.

1. They must be real, meaning they must actually result in the amount of greenhouse gas reduction that is intended. While this seems simple enough, accounting for the total effects of an activity can be difficult, especially with changes in land use. Planting more forest in an area that was previously used for agriculture could improve the take up of carbon dioxide from the atmposphere in that area. However, the same crop may end up being grown in another area that requires more energy intensive farming practices, at least partially negating the effects of the offset from the new forest. This situation is related to the concept of leakage, which is discussed in question 9.
2. They must be additional – meaning that they must make a positive contribution to the world’s net balance of carbon sinks and would not have occurred in the absence of the offset program. This means that to certify an offset under the program, it must be in addition to whatever the world’s agricultural and industrial activities would have done anyway, in the “business as usual” scenario. Like determining whether or not an offset is real, this can be very difficult because it can be hard to tell whether or not a given activity would have happened in the business-as-usual case.
3. They must be verifiable – meaning that they can be monitored and their contribution to emissions reductions accurately verified. This simply reduces the chances that their effects will be overestimated, rendering them not real. There is more on verification in the answer to question 10.
4. They must be permanent – meaning that the emissions offset they claim to produce initially will remain in effect and will not be reduced in strength or reversed. The concepts of reversibility and permanence are addressed in question 10.
5. They must be enforceable – meaning that the agency that certifies them must be able to verify they are real, track their use, and provide for transparency in the program’s operation.

Example of programs that certify carbon credits are the Clean Development Mechanism (CDM) and Joint Implementation Plan (JI), both created under the Kyoto Protocol. The CDM uses a registry of certified emissions reduction (CER) credits that can be used as offsets by nations participating in the Kyoto Protocol in order to meet their greenhouse gas reduction targets. To be qualified as a CER, a project must be approved by the Designated National Authority (DNA) in the nation in which it takes place and subsequently approved by the CDM program authorities at the United Nations. An example of a DNA is Canada’s Clean Development Mechanism and Joint Implementation Office. Under the proposed Lieberman-Warner Climate Security Act of 2008 (S.3036), this function would be performed in the United States by the EPA, which under the bill’s provisions would be required to verify that offsets are real, additional, and permanent and also account for leakage.

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5 - How are carbon allowances given out?

The method by which allowances to emit greenhouse gases are distributed vary by program, however they are typically distributed in one of three ways: they are given out for free by the government or administrative authority, they are sold at a set rate or at their market value, or they are auctioned. In the European Union’s Emissions Trading Scheme (EU ETS), 90 percent of emissions allowances are issued for free by the governments of the participating nations and the remaining allowances are sold at the market rate.

Proposals for cap-and-trade programs in the United States vary, however most of them have at least some percentage of allowances issued for free. Most plans propose to auction the remaining allowances either to provide a source of revenue for the government or provide a means by which the government can return the costs of emissions reduction to consumers. The Lieberman-Warner Climate Security Act of 2008 (S.3036), one of the more commonly mentioned proposals, would initially auction about 28 percent of the allowances, gradually increasing to 85 percent in 2032, with the proceeds being used to reduce the national debt and for a variety of climate change adaptation and mitigation programs. In contrast, the Investing in Climate Action and Protection Act (H.R.6186) would initially auction 94 percent of allowances, eventually increasing to 100 percent, return half the proceeds to consumers in compensation for increases in energy costs, and put the remainder into funding for research and development on low-carbon technology.

The means by which allowances are distributed can have significant consequences for the outcome of the program because it largely determines the cost imposed upon polluters. If too many of the allowances are issued for free, polluters will have less of an incentive to reduce their emissions whereas if too few are given out for free, a cost may be imposed on businesses that is damaging to the economy and that makes emissions reductions too costly to achieve.

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6 - What is a safety valve?

In the context of cap-and-trade legislation, a “safety valve” is a provision that acts as a limit on the cost of emissions allowances. Some cap-and-trade plans include a safety valve provision that would limit the price of emissions allowances in the event that the market price exceeds a given threshold. The proposed Lieberman-Warner Climate Security Act of 2008 (S.3036) would create a “Carbon Market Efficiency Board” which, among other duties, would evaluate the viability of the carbon market and determine if some form of cost relief is needed. The European Union’s Emissions Trading Scheme (EU ETS), which has been in effect since the beginning of 2005, allows the price to be determined purely by the market and does not intervene except in the case of suspected fraud or market distortions.

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7 – How are overall emissions measured?

The greenhouse gas emissions that policies such as the Kyoto Protocol, European Union's Emissions Trading Scheme, and other programs are attempting to control must be measured in some way. To standardize the means by which this is accomplished, the Intergovernmental Panel on Climate Change (IPCC) developed guidelines for national greenhouse gas measurement and reporting that are based upon the definitions, methodology, and reporting requirements of the United Nations Framework Convention on Climate Change (UNFCCC). The national reports are submitted annually, and are now included on the UNFCCC's website. The report also accounts for the differing global warming potential (GWP) of different gases, so that the final number is reflective of an equivalent amount of CO₂, which simplifies the comparison of greenhouse gas emissions across all categories of sources.

As a signatory of the original UNFCCC in 1992, the United States submits greenhouse gas inventories to the UN every year. The Environmental Protection Agency (EPA), which performs the measurements, cites the IPCC's guidlines as its reference and measures the same categories of greenhouse gases and sources as any other UNFCCC member, despite the fact that the United States is not bound by the Kyoto Protocol. The report includes many categories, with sources as obscure as emissions from landfilled yard trimmings and foodscraps, however the primary categories of emissions sources are energy, industrial processes, solvent use, agriculture, land use/land use change and forestry (LULUCF), and waste.

Because the UNFCCC uses 1990 as its baseline year, the reports produced by the EPA and by the reporting agencies of other nations base their measurements on the 1990 level. The inventories look at greenhouse gas-related activities occuring in 1990 and compare changes in all categories of activities covered under the UNFCCC, which essentially addresses any anthropogenic souce of greenhouse gas emissions not covered under the Montreal Protocol for ozone-depleting substances. The reports also include sinks, so that the result of the report is a total inventory of a nation's net greenhouse gas emissions and its comparison to the 1990 level.

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8 – What are non-covered facilities?

In terms of greenhouse gas control policy, a non-covered facility is any source of greenhouse gas emissions that is not covered under a given program. This typically applies to very small sources that are either too inconsequential or too many in number to attempt to account for and control. In the Lieberman-Warner Climate Security Act of 2008 (S.3036), one of the more recent cap-and-trade proposals for the United States, the definition of a covered facility is very explicit, including the amounts of greenhouse gas emissions that qualify it as covered under the program.

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9 – What is “leakage?”

In discussions about the effectiveness of climate change policy, especially in reference to its impact upon global industrial and agricultural activity, policy makers often cite the problem of emissions "leakage." This occurs when an emissions control policy, be it a cap-and-trade program or a carbon tax, provides an incentive for a business in a controlled nation to relocate its activities to another nation where there is no such policy, thereby avoiding having to pay for or control their emissions. In addition to reducing the effectiveness of the climate change policy, it also can hurt the economy of the nation with the policy in place.

Many cap-and-trade policies that have been proposed in the United States and that have already been implemented elsewhere, such as the EU ETS, have provisions that help control for leakage.

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10 – Are emissions reductions permanent or can they be reversed?

The permanence of a greenhouse gas emission reduction project depends on how that reduction is accomplished. Projects to reduce emissions that involve large investments in infrastructure and equipment have much lower chances of being reduced in their effectiveness or reversed because of the amount of money invested. For example, a project to reduce emissions by shifting a power plant from coal to natural gas can be regarded as a permanent change because it is unlikely that the power company would go back to coal after spending a great deal of money to shift to gas.

Conversely, projects that involve less capital intensive practices, such as a simple shift in fuel type without any equipment change, may be more subject to diminishing effectiveness or reversal. If a small generation facility shifted from running on diesel to running on biomass-derived liquid fuel, it would achieve a reduction in greenhouse gas emissions overall, but the operator could easily switch back to diesel, so such projects must be monitored if they are to be counted as creditable emissions reductions. Reversibility and permanence are typically of most concern in areas that may not be easily monitored or covered under a national greenhouse gas registry, especially emissions offset credits.

An example of a system that has been designed to ensure emissions reduction offset credits can be monitored and are not likely to be reversed is the Clean Development Mechanism (CDM) created under the Kyoto Protocol. The CDM allows countries in a cap-and-trade system to invest in emissions reduction projects in developing nations where it will be less expensive. To ensure that emissions reduction projects will not be reversed or diminish in their original level of effectiveness, the CDM requires any such projects to undergo review. A list of approved projects is periodically listed on their website, as are the rejected projects, which include reasons for their rejection. Typically rejection is due to an inability to verify the emissions reductions the submitter claims or inability to monitor them in the future, indicating concern about the potential for reversibility. The European Union's Emissions Trading Scheme (EU ETS) requires all participating nations to have a national greenhouse gas registry so that emissions can be monitored and regulated and several bills proposed in the United States for a cap-and-trade system have similar requirements.

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12 - What are "banking" and "borrowing" in terms of climate change policy?

Some climate change proposals include provisions for banking and borrowing of emissions permits. Essentially, banking and borrowing of permits is a way of using permits like a person would save or borrow money, which helps firms reduce the cost of cutting emissions and allows them flexibility in meeting emissions targets. Banking allows a firm that is covered under an emissions trading system to save any excess permits it has left over at the end of a covered period and use them in the next period or sell them. Instead of expiring, the permits still have value and may still be used, in a similar way to the "rollover" provisions on some cell phone plans that permit customers to save their unused minutes at the end of the month and use them in the next month. The European Union's Emissions Trading Scheme (EU ETS), which is currently in use, allows greenhouse gas emissions permits that are unused at the end of a trading period to be replaced with new ones at no extra cost, essentially permitting banking.

Borrowing is using permits that are scheduled to be issued in a future period in order to meet emissions targets in the current period. The EU ETS does not permit borrowing while the Lieberman-Warner bill proposed in the United States would allow up to 15 percent of emissions to be met with borrowed permits, as long as they do not borrow from a period more than 5 years in the future. Once permits have been borrowed from a future period, they are no longer available when that period is reached, so firms must be sure that they will benefit more from using the permits early and be able to go without them later on.

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Sources and Further Reading

The following information sources were utilitized in the production of this page. For more information on climate change policies and the institutions that develop and study them, see the Center for Science, Technology and Congress Climate Change Information Resources Page or the AAAS Climate Resources Page.

Broekhoff, Derik. "Creating Jobs With Climate Solutions: How Agriculture and Forestry Can Help Lower Costs in a Low Carbon Economy." World Resources Institute, May 21, 2008.

Directive 2003/87/EC of the European Parliament and of the Council of 13 October 2003 establishing a scheme for greenhouse gas emission allowance trading within the Community and amending Council Directive 96/61/EC (Text with EEA relevance)

Environmental Protection Agency (EPA) - Clean Air Act (42 U.S.C. Chapter 85)

Environmental Protection Agency (EPA) - Clean Air Markets

Environmental Protection Agency (EPA) - U.S. Greenhouse Gas Inventory Reports

European Union Emissions Trading Scheme

Foreign Affairs and International Trade Canada: Canada's Clean Development Mechanism and Joint Implementation Office

IPCC. "2006 IPCC Guidelines for National Greenhouse Gas Inventories." United Nations Environmental Programme, Intergovernmental Panel on Climate Change, 2006.

IPCC. "Climate Change 2001: IPCC Third Assessment Report." United Nations Environmental Programme, Intergovernmental Panel on Climate Change, 2001.

Nordhaus, William D. "To Tax or Not to Tax: Alternative Approaches to Slowing Global Warming." Review of Environmental Economics and Policy, Vol.1, Issue 1. (Winter 2007). pp. 26-44. (available in pdf format at the author's homepage)

Peace, Janet and John Weyant. "Insights Not Numbers: The Appropriate Use of Economic Models." Pew Center on Global Climate Change, April 2008.

Pew Center on Global Climate Change. Publications and Reports on various climate change policies

Stern, Nicholas. "The Economics of Climate Change: The Stern Review." Cambridge: Cambridge University Press, 2007. (available in electronic format from HM Treasury)

UNEP. "Handbook for the Montreal Protocol on Substances that Deplete the Ozone Layer." United Nations Environmental Programme, Ozone Secretariat, 7th Edition (2006).

United Nations Framework Convention on Climate Change (UNFCCC)

• Clean Development Mechanism
  • Registered Projects
  • Rejected Projects
• Joint Implementation Plan
• Kyoto Protocol

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Updated December 19, 2008