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The carbon footprint (or greenhouse gas footprint) serves as an indicator to compare the total amount of greenhouse gases emitted from an activity, product, company or country. Carbon footprints are usually reported in tons of emissions (CO2-equivalent) per unit of comparison; such as per year, person, kg protein, km travelled and alike. For a product, its carbon footprint includes the emissions for the entire life cycle from the production along the supply chain to its final consumption and disposal. Similarly for an organization, its carbon footprint includes the direct as well as the indirect emissions caused by the organization (called Scope 1, 2 and 3 in the Greenhouse Gas Protocol that is used for carbon accounting of organizations). Several methodologies and online tools exist to calculate the carbon footprint, depending on whether the focus is on a country, organization, product or individual person. For example, the carbon footprint of a product could help consumers decide which product to buy if they want to be climate aware. In the context of climate change mitigation activities, the carbon footprint can help distinguish those economic activities with a high footprint from those with a low footprint. In other words, the carbon footprint concept allows everyone to make comparisons between the climate-relevant impacts of individuals, products, companies, countries. In doing so, it helps to devise strategies and priorities for reducing the carbon footprint.
The carbon footprint is commonly expressed as the carbon dioxide equivalent (CO2eq) per unit of comparison. It sums up the total greenhouse gas emissions (not just carbon dioxide) caused by economic activities, events, organizations, services etc. In other definitions, only the carbon dioxide emissions are taken into account but not those of other greenhouse gases, such as methane and nitrous oxide.
To calculate the carbon footprint for different entities, the following methods are used: For organizations, the Greenhouse Gas Protocol is commonly used. It includes three carbon emission scopes (the direct carbon emissions, called Scope 1) and the indirect carbon emissions (Scope 2 and 3). The difference between Scope 2 and 3 is that Scope 3 emissions are those indirect emissions that are derived from the activities of an organization but that stem from sources which they do not own or control. For whole countries, consumption-based emissions accounting can be used to calculate their carbon footprint for a given year. This approach is based on input-output analysis. For example, analysis of global supply chains is possible using consumption-based accounting through input-output analysis assisted by using today’s super-computing capacity. In contrast, countries also prepare national GHG inventories for the UNFCCC. The GHG emissions listed in those national inventories are only from activities in the country itself (called territorial-based accounting or production-based accounting). They do not take into account of production of goods and services (that may be imported) on behalf of residents, which would be called consumption-based accounting.
A strength of comprehensive carbon footprint reporting (including Scope 3 emissions) is that it does away with loopholes of current systems: International transport is currently not included in countries’ GHG inventories for the UNFCCC. Under comprehensive carbon footprint reporting (also called consumption-based carbon accounting), emissions are relegated to final demand, namely to those that consume the goods and services.
A commonly used definition of carbon footprint is as follows: "A measure of the total amount of carbon dioxide (CO2) and methane (CH4) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest. Calculated as carbon dioxide equivalent using the relevant 100-year global warming potential (GWP100)." Carbon footprints are usually reported in tons of emissions (CO2-equivalent) per year.
Carbon footprints are usually reported in tons of emissions (CO2-equivalent) per unit of comparison; such as per year, person (also called per capita), kg protein (when comparing meat products), km travelled and alike.
In the definition of carbon footprint, some scientists include only CO2, but more commonly several of the important greenhouse gases are included. The various greenhouse gases are made comparable by using carbon dioxide equivalents over a relevant time scale, like 100 years. Some organizations use the term greenhouse gas footprint or climate footprint to emphasize that all greenhouse gases are included, not just carbon dioxide.
The Greenhouse Gas Protocol also includes all of the most important greenhouse gases: "The standard covers the accounting and reporting of seven greenhouse gases covered by the Kyoto Protocol – carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PCFs), sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3)."
In comparison, the IPCC in 2022 uses a definition for carbon footprint which only includes carbon dioxide: The carbon footprint is defined there as the "measure of the exclusive total amount of emissions of carbon dioxide (CO2) that is directly and indirectly caused by an activity or is accumulated over the lifecycle stages of a product.": 1796 The IPCC report's authors adopted the same definition that had been proposed in 2007 in the UK. In that publication, only carbon dioxide was included in the definition of carbon footprint, with the justification that other greenhouse gases were more difficult to quantify (due to their differing global warming potentials). They had also stated that an inclusion of all greenhouse gases would make the carbon footprint indicator less practical. One disadvantage of not including methane in the analysis is that some products or sectors that have a high methane footprint (for example livestock) would appear better, less harmful for the climate, than they actually are.
See also: Carbon accounting
The greenhouse gas protocol is a set of standards for tracking greenhouse gas emissions. The standards divide emissions into three scopes (Scope 1, 2 and 3) within the value chain. Those greenhouse gas emissions caused directly by the organization/company itself (e.g. by burning fossil fuels) are referred to as Scope 1. The emissions caused indirectly by an organization, e.g. by purchasing secondary energy sources (e.g. electricity, heat, cooling or steam) and the associated emissions are called Scope 2. Lastly, the indirect emissions associated with upstream or downstream processes are called Scope 3.
Direct or Scope 1 carbon emissions come from sources that are directly from the site that is producing a product or delivering a service. An example for industry would be the emissions related to burning a fuel on site. On the individual level, emissions from personal vehicles or gas burning stoves would fall under Scope 1.
Indirect carbon emissions are emissions from sources upstream or downstream from the process being studied, also known as Scope 2 or Scope 3 emissions.
Scope 2 emissions are the indirect emissions related to purchasing electricity, heat, and/or steam used on site. Examples of upstream, indirect carbon emissions may include: Transportation of materials/fuels, any energy used outside of the production facility, wastes produced outside of the production facility. Examples of downstream, indirect carbon emissions may include: Any end-of-life process or treatments, product and waste transportation, emissions associated with selling the product. The GHG Protocol stipulates calculating upstream as well as downstream emissions. There could be some double counting because upstream emissions of one person's consumption patterns could be someone else’s downstream emissions
Scope 3 emissions are all other indirect emissions derived from the activities of an organization but from sources which they do not own or control. The GHG Protocol's Corporate Value Chain (Scope 3) Accounting and Reporting Standard allows companies to assess their entire value chain emissions impact and identify where to focus reduction activities.
Scope 3 emission sources include emissions from suppliers and product users (also known as the value chain). Transportation of goods, and other indirect emissions are also part of this scope. In 2022 about 30% of US companies reported Scope 3 emissions. The International Sustainability Standards Board is developing a recommendation that Scope 3 emissions be included as part of all GHG reporting.
See also: Carbon accounting
The current rise in global average temperature is more rapid than previous changes, and is primarily caused by humans who are burning fossil fuels. Additional contributions to increasing greenhouse gases in the atmosphere include deforestation as well as agricultural and industrial practices, for example cement production. The two most notable greenhouse gases are carbon dioxide and methane. Greenhouse gas emissions, and hence humanity's carbon footprint has been increasing during the 21st century. The Paris Agreement states that greenhouse gas emissions must be reduced enough so that the global temperature increase is preferably no more than 1.5°C above pre-industrial levels.
The carbon footprint concept allows comparisons between the climate-relevant impacts of individuals, products, companies, countries etc. A carbon footprint label on products could enable consumers to choose those products with a lower carbon footprint if they wanted to contribute to climate change mitigation efforts. For example in the context of meat products, such a label could make it clear that beef has a higher carbon footprint than chicken.
Once the magnitude of the carbon footprint of an organization is known, a strategy can be devised to reduce it. For example, for most businesses the vast majority of emissions do not come from Scope 1 (on site) or Scope 2 (energy supplied directly to the company) activities but from Scope 3 emissions: They come from the extended upstream and downstream supply chain. Therefore, if one ignores the Scope 3 emissions, not all emissions of importance will be detected thus limiting mitigation activities. For large companies (e.g. clothing and automobile) to fully report their carbon footprints would require examination of more than 100,000 supply chain pathways.
The importance of displacement of carbon emissions – also referred to as carbon leakage – has been known for some years. The carbon footprint addresses concerns of carbon leakage unlike the Paris Agreement which does not identify this. Carbon leakage occurs when importing countries (often rich countries) outsource production to exporting countries (often low-income countries). The displacement of impacts is typically from developed to developing countries. For example, countries can make it look like their GHG emissions are reducing by moving dirty industries (those that emit a lot of greenhouse gases) abroad, but when you look at their emissions from a consumption perspective they could be increasing not decreasing.
Carbon leakage and the related international trade has a range of environmental impacts such as increased air pollution, water scarcity, biodiversity loss, raw material usage, and energy depletion.
Scholars have argued that consumption-based accounting (including all Scope 3 emissions) should be used in addition with production-based for shared producer and consumer responsibility. For example, currently countries report on their annual GHG inventory to UNFCCC based on their territorial emissions (also called territorial-based approach or production-based approach). However, it would be beneficial to include consumption-based calculations in the requirements to close loopholes (e.g. to address the challenge of carbon leakage).
Another example is that the Paris Agreement currently does not force countries to include in their national totals the GHG emissions associated with international transport. These emissions are reported separately and not subject to limitation and reduction commitments of Annex 1 Parties under the Climate Convention and Kyoto Protocol. The carbon footprint methodology includes GHG emissions associated with international transport. This means it assigns emissions caused by international trade to the importing country.
The calculation of the carbon footprint of a product, service or sector requires expert knowledge and careful examination of what is to be included. Carbon footprints can be calculated at different scales: for whole countries, for cities, neighborhoods and also for sectors, companies and products. For calculating personal carbon footprints, several free online carbon footprint calculators exist.
Software (such as the "Scope 3 Evaluator") exists that can help companies to report emissions throughout their value chain. The software tools can assist consultants and researchers in modelling global sustainability footprints. In each situation there are a number of questions that need to be answered, for example which activities are linked to which emissions, and which proportion should be attributed to which company. In general, software is essential for the management of corporations but new ways of enterprise resource planning are needed in order to improve corporate sustainability performance.
To achieve 95% carbon footprint coverage, it would be necessary to follow up on 12 million individual supply-chain contributions (based on analyzing 12 sectoral case studies). The Scope 3 calculations can be made easier using input-output analysis, a technique which was originally developed by Nobel-Prize winning economist Wassily Leontief.
Further information: Input–output model and Greenhouse gas inventory § Consumption based accounting
Consumption-based emission accounting (also called consumption-based carbon accounting) traces back the impacts of demand for goods and services to the end consumer. It places responsibility to demand along the global supply chain all the way to the end consumer. In contrast, a production-based approach to calculating GHG emissions is not a carbon footprint analysis: The production-based approach (also called territorial-based approach) only includes impacts physically produced in the country in question. Consumption-based accounting redistributes the emissions from production-based accounting and considers that emissions in another country are necessary for the home country’s consumption bundle.
Consumer-based accounting is based on input-output analysis and is used at the highest levels for any economic research question related to environmental or social impacts. Analysis of global supply chains is possible using consumption-based accounting through input-output analysis assisted by using super-computing capacity.
Input-output analysis (IO) was created by Nobel Prize-winning economist Wassily Leontief to demonstrate the relationship between consumption and production in an economy. It incorporates the entire supply chain, using input-output tables from countries’ national accounts and international data such as UN Comtrade and Eurostat. Input-output analysis has been extended globally to multi-regional input-output analysis (MRIO), aided by innovations and technology enabling the analysis of billions of supply chains. Standards set by the United Nations underpin this analysis.: 280 The analysis enables a Structural Path Analysis which scans and ranks the top supply chain nodes and paths, conveniently listing the hotspots for urgent action. Input-output analysis has increased in popularity because of its ability to interrogate global value chains.
Further information: Life-cycle assessment
In general, Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for assessing allenvironmental impacts associated with the life cycle of a commercial product, process, or service - not just the greenhouse gas emissions. It includes for example also issues of water pollution, air pollution, ecotoxicity and so forth. Some widely recognized procedures for LCA are included in the ISO 14000 series of environmental management standards. A standard called ISO 14040:2006 has the framework for conducting an LCA study. ISO 14060 family of standards provides further sophisticated tools for quantifying, monitoring, reporting and validating or verifying of GHG emissions and removals.
Greenhouse gas product life cycle assessments can also comply with specifications such as Publicly Available Specification (PAS) 2050 and the GHG Protocol Life Cycle Accounting and Reporting Standard.
An advantage of LCA is the high level of detail that can be obtained on-site or by liaising with suppliers. However, LCA has been hampered by the artificial construction of a boundary after which the impact of no further upstream suppliers are considered. This can introduce significant truncation errors. LCA has been combined with input-output analysis (IO), thereby enabling on-site detailed knowledge to be incorporated, where known, while IO connects to global economic databases to incorporate the entire supply chain.
If people only focus on carbon footprints they could ignore or even exacerbate other related environmental issues of concern such as biodiversity loss, ecotoxicity, habitat destruction. These other human impacts on the environment may not be as easily measurable with a single indicator like the carbon footprint. For example, consumers may think that the carbon footprint is a proxy for environmental impact, however there are many examples where this is not correct.: 222 There can in fact be trade-offs between reducing the carbon footprint and environmental protection goals. For example, whilst biofuel is a renewable energy source and can reduce the carbon footprint of energy supply, it can nevertheless pose ecological challenges during its production as it is often produced in monocultures with ample use of fertilizers and pesticides.: 222 Another example are offshore wind parks that could have unintended impacts on marine ecosystems.: 223
The carbon footprint analysis solely focuses on greenhouse gas emissions, unlike a life-cycle assessment which is much broader and looks at all environmental impacts. Therefore, it is useful to stress in communication activities that the carbon footprint is just one in a family of indicators (e.g. ecological footprint, water footprint, land footprints and material footprints), and should not be looked at in isolation. In fact, the carbon footprint can be treated as one component of the ecological footprint.
One example for a suitable tool to put the carbon footprint analysis into a wider perspective is the "Sustainable Consumption and Production Hotspot Analysis Tool "(SCP-HAT) which includes a number of socio-economic and environmental indicators. It offers calculations that are either consumption-based (i.e. following the carbon footprint approach) or production-based. The database of the SCP-HAT tool is underpinned by input-output analysis. This means it includes Scope 3 emissions. The IO methodology is also governed by UN standards: 280 and is based on input-output tables of countries' national accounts and also international trade data such as UN Comtrade, so it is comparable worldwide.
Critics argue that the original aim of promoting the personal carbon footprint concept was to shift responsibility away from the corporations and institutions and onto personal lifestyle choices. For example, the fossil fuel company BP had run a large advertising campaign for the personal carbon footprint in 2005 which helped popularize this concept. This strategy, also employed by other major fossil fuel companies, has been criticized for trying to shift the blame for negative consequences of those industries onto individual choices.
Geoffrey Supran and Naomi Oreskes of Harvard University have argued that concepts such as carbon footprints "hamstring us, and they put blinders on us, to the systemic nature of the climate crisis and the importance of taking collective action to address the problem".
The term carbon footprint has been applied to limited calculations that do not include Scope 3 emissions or the entire supply chain. This can lead to claims of misleading customers with regards to the real carbon footprints of companies or products.
See also: Greenhouse gas emissions
Greenhouse gas emissions (abbreviated as GHG emissions) from human activities strengthen the greenhouse effect, contributing to climate change. Carbon dioxide (CO2), from burning fossil fuels such as coal, oil, and natural gas, is one of the most important factors in causing climate change. The largest emitters are China followed by the US, although the United States has higher emissions per capita. The main producers fueling the emissions globally are large oil and gas companies. Human-caused emissions have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2017 were 425±20 GtC (1539 GtCO2) from fossil fuels and industry, and 180±60 GtC (660 GtCO2) from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2017, coal 32%, oil 25%, and gas 10%.Carbon dioxide (CO2) is the dominant emitted greenhouse gas is themost important greenhouse gas (accounting for more than half of the warming), while methane (CH4) emissions almost have the same short-term impact. Nitrous oxide (N2O) and fluorinated gases (F-gases) play a lesser role in comparison.
The Carbon Trust has worked with UK manufacturers to produce "thousands of carbon footprint assessments". As of 2014 The Carbon Trust state they have measured 28,000 certifiable product carbon footprints.
Plant-based foods tend to have a lower carbon footprint than meat and dairy. In many cases a much smaller footprint. This holds true when comparing the footprint of foods in terms of their weight, protein content or calories. As an example: producing 100 grams of protein from peas emits just 0.4 kilograms of carbon dioxide equivalents (CO2eq). To get the same amount of protein from beef, emissions would be nearly 90 times higher, at 35 kgCO2eq. Only a small fraction of the carbon footprint of food comes from transport and packaging. Most of it comes from processes on the farm, or from land use change. This means the choice of what to eat has a larger potential to reduce carbon footprint than how far the food has traveled, or how much packaging it is wrapped in.
Main article: Greenhouse gas emissions § Emissions by sector
The IPCC Sixth Assessment Report found that global GHG emissions have continued to rise across all sectors, most rapidly in transport and industry. driven by increased global consumption. A key driver of global carbon emissions is affluence, with the IPCC noting that the global wealthiest 10% contribute between about one-third to half (36%–45%) of global GHG emissions. Affluence has been noted by researchers previously as being the key driver of carbon emissions, outpacing the negative impact of population growth and the positive effect of technological developments; continued economic growth mirrors the increasing trend in material extraction and GHG emissions. The IPCC highlighted: “Industrial emissions have been growing faster since 2000 than emissions in any other sector, driven by increased basic materials extraction and production”.
There can be wide variation in emissions for transport of people depending primarily on a) the length of the trip, b) the source of electricity in the local grid, c) the occupancy of public transport and d) in the case of driving — the vehicle and number of passengers. For example, over short to medium distances, walking or cycling are nearly always the lowest carbon way to travel. The carbon footprint of cycling one kilometer is usually in the range of 16 to 50 grams CO2eq per km. For moderate-to-long distances, trains are nearly always the option with the lowest carbon footprint compared to the other options.
Carbon accounting (or greenhouse gas accounting) is a framework of methods to measure and track how much greenhouse gas (GHG) an organization emits. It can also be used to track projects or actions to reduce emissions in sectors such as forestry or renewable energy. Corporations, cities and other groups use these techniques to help limit climate change. Organizations will often set an emissions baseline, create targets for reducing emissions, and track progress towards them. The accounting methods enable them to do this in a more consistent and transparent manner.GHG accounting is often done to address social responsibility concerns, or meet legal requirements. Other motivations include public rankings alongside other companies, financial due diligence, and potential cost savings. GHG accounting methods can help investors better understand the climate risks of companies they invest in. Corporate and community net-zero goals are also aided by accurate accounting methods. There are now many governments around the world that require various forms of reporting, and there is some evidence that programs that require GHG accounting have the effect of lowering emissions. Markets for buying and selling carbon credits also depend on accurate measurement of emissions and emission reductions. These techniques can also help understand the impacts of specific products and services by quantifying their GHG emissions throughout their lifecycle. This can promote more environmentally friendly purchasing decisions.
Main article: List of countries by greenhouse gas emissions per capita
CO2 emissions of countries are typically measured on the basis of production. This accounting method – which is sometimes referred to as territorial emissions – is used for when countries report their emissions, and set targets domestically and internationally, such as the Nationally Determined Contributions. Consumption-based emissions on the other hand are adjusted for trade. To calculate consumption-based emissions we need to track which goods are traded across the world, and whenever a good was imported we need to include all CO2 emissions that were emitted in the production of that good. Consumption-based emissions reflect the consumption and lifestyle choices of a country’s citizens.
According to the World Bank, the global average carbon footprint in 2014 was about 5 metric tons CO2 per person (production based). The EU average for 2007 was about 13.8 tons CO2e per person, whereas for the U.S., Luxembourg and Australia it was over 25 tons CO2e per person. In 2017, the average for the USA was about 20 metric tons CO2e per person. This is one of the highest per capita figures in the world.
The footprints per capita of countries in Africa and India were well below average. To set these numbers into context, assuming a global population around 9–10 billion by 2050 a carbon footprint of about 2–2.5 tons CO2e per capita is needed to stay within a 2 °C target. These carbon footprint calculations are based on a consumption based approach using a Multi-Regional Input-Output (MRIO) database, which accounts for all greenhouse gas (GHG) emissions in the global supply chain and allocates them to the final consumer of the purchased commodities.
Efforts that aim to reduce the carbon footprint of products, services, organizations etc. are a contribution to limit climate change (climate change mitigation).
Main article: Climate change mitigation § Industry
Carbon offsetting can reduce a company's overall carbon footprint by offering a carbon credit. This works by counteracting carbon dioxide emissions with an equivalent reduction of carbon dioxide in the atmosphere. Reforestation, the restocking of existing forests or woodlands that have previously been depleted, is an example of carbon offsetting.
A carbon footprint study using input-output analysis can identify specific and critical areas for improvement because it scrutinizes the entire supply chain. Such an analysis could be used to eliminate the most impactful supply chains, i.e. those with the highest greenhouse gas emissions.
The term carbon footprint was first used in a BBC vegetarian food magazine in 1999, though the broader concept of environmental footprint had been used since at least 1979.
In 2005, the large advertising campaign Ogilvy worked for the fossil fuel company BP to popularize the idea of a carbon footprint for individuals. The campaign instructed people to calculate their personal footprints and provided ways for people to "go on a low-carbon diet".
The carbon footprint is "rooted in the language of ecological footprinting". Unlike the ecological footprint, the carbon footprint is however not expressed in area-based units. The first academic publication about ecological footprints was written by William Rees in 1992. Other related concepts from the 1990s are the "ecological backpack" and Material input per unit of service (MIPS).
To bring global, rigorous oversight to carbon footprint reporting, an International Sustainability Standards Board (ISSB) has formed out of the International Financial Reporting Standards, which will require companies to report on their Scope 3 emissions. The ISSB has taken on board criticisms of other initiatives in its aims for universality, consolidating the Carbon Disclosure Standards Board, the Sustainability Accounting Standards Board and the Value Reporting Foundation. It is complementing the Global Reporting Initiative and is influenced by the Task Force on Climate-Related Financial Disclosures. As of early 2023, Great Britain and Nigeria are already preparing to adopt them.
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