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A carbon offset is a reduction in emissions of carbon dioxide or greenhouse gases made in order to compensate for or to offset an emission made elsewhere.〔〔〔〔 Carbon offsets are measured in metric tons of carbon dioxide-equivalent (CO2e) and may represent six primary categories of greenhouse gases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF6).〔Friend, G. (2009). The Truth about Green Business. Upper Saddle River, NJ: FT Press.〕 One carbon offset represents the reduction of one metric ton of carbon dioxide or its equivalent in other greenhouse gases. There are two markets for carbon offsets. In the larger, compliance market, companies, governments, or other entities buy carbon offsets in order to comply with caps on the total amount of carbon dioxide they are allowed to emit. This market exists in order to achieve compliance with obligations of Annex 1 Parties under the Kyoto Protocol, and of liable entities under the EU Emission Trading Scheme. In 2006, about $5.5 billion of carbon offsets were purchased in the compliance market, representing about 1.6 billion metric tons of CO2e reductions.〔(【引用サイトリンク】title=State and Trends of the Carbon Market )〕 In the much smaller, voluntary market, individuals, companies, or governments purchase carbon offsets to mitigate their own greenhouse gas emissions from transportation, electricity use, and other sources. For example, an individual might purchase carbon offsets to compensate for the greenhouse gas emissions caused by personal air travel. Many companies (see list) offer carbon offsets as an up-sell during the sales process so that customers can mitigate the emissions related with their product or service purchase (such as offsetting emissions related to a vacation flight, car rental, hotel stay, consumer good, etc.). In 2008, about $705 million of carbon offsets were purchased in the voluntary market, representing about 123.4 million metric tons of CO2e reductions.〔(Ecosystem Marketplace, New Energy Finance State, of the Voluntary Carbon Markets 2009 )〕 Some fuel suppliers in the UK offer fuel which has been carbon offset such as Fuel dyes. Offsets are typically achieved through financial support of projects that reduce the emission of greenhouse gases in the short- or long-term. The most common project type is renewable energy,〔(【引用サイトリンク】title=Carbon Retirement report: The state of voluntary carbon offsetting in the FTSE 100 )〕 such as wind farms, biomass energy, or hydroelectric dams. Others include energy efficiency projects, the destruction of industrial pollutants or agricultural byproducts, destruction of landfill methane, and forestry projects. Some of the most popular carbon offset projects from a corporate perspective are energy efficiency and wind turbine projects.〔(EcoSecurities, ClimateBiz, Carbon Offsetting Trends Survey 2008 )〕 Carbon offsetting has gained some appeal and momentum mainly among consumers in western countries who have become aware and concerned about the potentially negative environmental effects of energy-intensive lifestyles and economies. The Kyoto Protocol has sanctioned offsets as a way for governments and private companies to earn carbon credits that can be traded on a marketplace. The protocol established the Clean Development Mechanism (CDM), which validates and measures projects to ensure they produce authentic benefits and are genuinely "additional" activities that would not otherwise have been undertaken. Organizations that are unable to meet their emissions quota can offset their emissions by buying CDM-approved Certified Emissions Reductions. Emissions from burning fuel, such as red diesel, has pushed one UK fuel supplier to create a carbon offset fuel named Carbon Offset Red Diesel. Offsets may be cheaper or more convenient alternatives to reducing one's own fossil-fuel consumption. However, some critics object to carbon offsets, and question the benefits of certain types of offsets. Due diligence is recommended to help businesses in the assessment and identification of "good quality" offsets to ensure offsetting provides the desired additional environmental benefits, and to avoid reputational risk associated with poor quality offsets.〔 Offsets are viewed as an important policy tool to maintain stable economies. One of the hidden dangers of climate change policy is unequal prices of carbon in the economy, which can cause economic collateral damage if production flows to regions or industries that have a lower price of carbon—unless carbon can be purchased from that area, which offsets effectively permit, equalizing the price.〔(【引用サイトリンク】url=http://www.carbonoffsetsdaily.com/carbonindustryinterviews/interview-neal-dikeman-co-founder-of-carbonflow-on-web-technologys-role-in-addressing-climate-change-10176.htm )〕 ==Definitions== The World Resources Institute defines a carbon offset as "a unit of carbon dioxide-equivalent (CO2e) that is reduced, avoided, or sequestered to compensate for emissions occurring elsewhere". The Collins English Dictionary defines a carbon offset as "a compensatory measure made by an individual or company for carbon emissions, usually through sponsoring activities or projects which increase carbon dioxide absorption, such as tree planting".〔(【引用サイトリンク】url=http://www.collinsdictionary.com/dictionary/english/carbon-offset )〕 The Environment Protection Authority of Victoria (Australia) defines a carbon offset as: "a monetary investment in a project or activity elsewhere that abates greenhouse gas (GHG) emissions or sequesters carbon from the atmosphere that is used to compensate for GHG emissions from your own activities. Offsets can be bought by a business or individual in the voluntary market (or within a trading scheme), a carbon offset usually represents one tonne of CO2-e". The Stockholm Environment Institute defines a carbon offset as "a credit for negating or diminishing the impact of emitting a ton of carbon dioxide by paying someone else to absorb or avoid the release of a ton of CO2 elsewhere". The University of Oxford Environmental Change Institute defines a carbon offset as "mechanism whereby individuals and corporations pay for reductions elsewhere in order to offset their own emissions". The Encyclopædia Britannica defines a carbon offset as "''any activity that compensates for the emission of carbon dioxide (CO2) or other greenhouse gases (measured in carbon dioxide equivalents ()) by providing for an emission reduction elsewhere.''" A carbon offset is a greenhouse gas (GHG) reduction that is used to counterbalance, or offset, a GHG emission. They are sometimes also referred to as carbon credits, VERs, or CERs.〔(【引用サイトリンク】url=http://www.offsetters.ca/education/reducing-greenhouse-gases/carbon-offsetting )〕 A carbon offset occurs when an individual or organization emits a given amount of GHG emissions but invests in measures that remove the equivalent volume of GHG emissions from the atmosphere or prevent the emissions from taking place at all. Carbon offsets are a financial instrument that represents this reduction in GHG emissions.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Carbon offset」の詳細全文を読む スポンサード リンク
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