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131-543: A carbon footprint (or greenhouse gas footprint ) is a calculated value or index that makes it possible to compare the total amount of greenhouse gases that an activity, product, company or country adds to the atmosphere . Carbon footprints are usually reported in tonnes of emissions ( CO 2 -equivalent ) per unit of comparison. Such units can be for example tonnes CO 2 -eq per year , per kilogram of protein for consumption , per kilometer travelled , per piece of clothing and so forth. A product's carbon footprint includes
262-445: A x and a r are not necessarily constant over time. While the absorption of infrared radiation by many greenhouse gases varies linearly with their abundance, a few important ones display non-linear behaviour for current and likely future abundances (e.g., CO 2 , CH 4 , and N 2 O). For those gases, the relative radiative forcing will depend upon abundance and hence upon the future scenario adopted. Since all GWP calculations are
393-402: A greenhouse gas would absorb over a given time frame after it has been added to the atmosphere (or emitted to the atmosphere). The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing ". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide (CO 2 ), which is taken as
524-411: A production-based approach to calculating GHG emissions is not a carbon footprint analysis. This approach is also called a territorial-based approach. The production-based approach includes only impacts physically produced in the country in question. Consumption-based accounting redistributes the emissions from production-based accounting. It considers that emissions in another country are necessary for
655-529: A carbon footprint addresses concerns of carbon leakage which the Paris Agreement does not cover. Carbon leakage occurs when importing countries outsource production to exporting countries. The outsourcing countries are often rich countries while the exporters are often low-income countries . Countries can make it appear that their GHG emissions are falling by moving "dirty" industries abroad, even if their emissions could be increasing when looked at from
786-603: A comparison to CO 2 which is non-linear, all GWP values are affected. Assuming otherwise as is done above will lead to lower GWPs for other gases than a more detailed approach would. Clarifying this, while increasing CO 2 has less and less effect on radiative absorption as ppm concentrations rise, more powerful greenhouse gases like methane and nitrous oxide have different thermal absorption frequencies to CO 2 that are not filled up (saturated) as much as CO 2 , so rising ppms of these gases are far more significant. Carbon dioxide equivalent (CO 2 e or CO 2 eq or CO 2 -e) of
917-464: A consumption perspective. Carbon leakage and related international trade have a range of environmental impacts. These include increased air pollution , water scarcity , biodiversity loss , raw material usage, and energy depletion. Scholars have argued in favour of using both consumption-based and production-based accounting. This helps establish shared producer and consumer responsibility. Currently countries report on their annual GHG inventory to
1048-411: A given year to that year's total emissions. The annual airborne fraction for CO 2 had been stable at 0.45 for the past six decades even as the emissions have been increasing. This means that the other 0.55 of emitted CO 2 is absorbed by the land and atmosphere carbon sinks within the first year of an emission. In the high-emission scenarios, the effectiveness of carbon sinks will be lower, increasing
1179-416: A global scale, the warming effects of one or more greenhouse gases in the atmosphere can also be expressed as an equivalent atmospheric concentration of CO 2 . CO 2 e can then be the atmospheric concentration of CO 2 which would warm the earth as much as a particular concentration of some other gas or of all gases and aerosols in the atmosphere. For example, CO 2 e of 500 parts per million would reflect
1310-594: A graph. Because the GWP of a greenhouse gas depends directly on its infrared spectrum, the use of infrared spectroscopy to study greenhouse gases is centrally important in the effort to understand the impact of human activities on global climate change . Just as radiative forcing provides a simplified means of comparing the various factors that are believed to influence the climate system to one another, global warming potentials (GWPs) are one type of simplified index based upon radiative properties that can be used to estimate
1441-400: A greenhouse gas would absorb over a given time frame after it has been added to the atmosphere (or emitted to the atmosphere). The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing ". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide (CO 2 ), which is taken as
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#17327974625661572-427: A low concentration in the atmosphere. The values given in the table assume the same mass of compound is analyzed; different ratios will result from the conversion of one substance to another. For instance, burning methane to carbon dioxide would reduce the global warming impact, but by a smaller factor than 25:1 because the mass of methane burned is less than the mass of carbon dioxide released (ratio 1:2.74). For
1703-408: A mix of atmospheric gases which warm the earth as much as 500 parts per million of CO 2 would warm it. Calculation of the equivalent atmospheric concentration of CO 2 of an atmospheric greenhouse gas or aerosol is more complex and involves the atmospheric concentrations of those gases, their GWPs, and the ratios of their molar masses to the molar mass of CO 2 . CO 2 e calculations depend on
1834-539: A molecule of X remains in the box. τ {\displaystyle \tau } can also be defined as the ratio of the mass m {\displaystyle m} (in kg) of X in the box to its removal rate, which is the sum of the flow of X out of the box ( F out {\displaystyle F_{\text{out}}} ), chemical loss of X ( L {\displaystyle L} ), and deposition of X ( D {\displaystyle D} ) (all in kg/s): If input of this gas into
1965-510: A more consistent and transparent manner. CO 2 emissions of countries are typically measured on the basis of production . This accounting method is sometimes referred to as territorial emissions. Countries use it when they report their emissions, and set domestic and international targets such as Nationally Determined Contributions . Consumption -based emissions on the other hand are adjusted for trade. To calculate consumption-based emissions analysts have to track which goods are traded across
2096-412: A much shorter atmospheric lifetime than carbon dioxide, its GWP is much less over longer time periods, with a GWP-100 of 27.9 and a GWP-500 of 7.95. The carbon dioxide equivalent (CO 2 e or CO 2 eq or CO 2 -e or CO 2 -eq) can be calculated from the GWP. For any gas, it is the mass of CO 2 that would warm the earth as much as the mass of that gas. Thus it provides a common scale for measuring
2227-414: A much shorter atmospheric lifetime than carbon dioxide, its GWP is much less over longer time periods, with a GWP-100 of 27.9 and a GWP-500 of 7.95. The contribution of each gas to the enhanced greenhouse effect is determined by the characteristics of that gas, its abundance, and any indirect effects it may cause. For example, the direct radiative effect of a mass of methane is about 84 times stronger than
2358-464: A number of questions that need to be answered. These include which activities are linked to which emissions, and which proportion should be attributed to which company. Software is essential for company management. But there is a need for new ways of enterprise resource planning to improve corporate sustainability performance. To achieve 95% carbon footprint coverage, it would be necessary to assess 12 million individual supply-chain contributions. This
2489-445: A process known as water vapor feedback. It occurs because Clausius–Clapeyron relation establishes that more water vapor will be present per unit volume at elevated temperatures. Thus, local atmospheric concentration of water vapor varies from less than 0.01% in extremely cold regions and up to 3% by mass in saturated air at about 32 °C. Global warming potential (GWP) is an index to measure how much infrared thermal radiation
2620-438: A quantity of gas is calculated from its GWP. For any gas, it is the mass of CO 2 which would warm the earth as much as the mass of that gas. Thus it provides a common scale for measuring the climate effects of different gases. It is calculated as GWP multiplied by mass of the other gas. For example, if a gas has GWP of 100, two tonnes of the gas have CO 2 e of 200 tonnes, and 9 tonnes of the gas has CO 2 e of 900 tonnes. On
2751-454: A reference gas. Therefore, the GWP has a value of 1 for CO 2 . For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered. For example, methane has a GWP over 20 years (GWP-20) of 81.2 meaning that, for example, a leak of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As methane has
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#17327974625662882-454: A reference gas. Therefore, the GWP has a value of 1 for CO 2 . For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered. For example, methane has a GWP over 20 years (GWP-20) of 81.2 meaning that, for example, a leak of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As methane has
3013-408: A single number. Scientists instead say that while the first 10% of carbon dioxide's airborne fraction (not counting the ~50% absorbed by land and ocean sinks within the emission's first year) is removed "quickly", the vast majority of the airborne fraction – 80% – lasts for "centuries to millennia". The remaining 10% stays for tens of thousands of years. In some models, this longest-lasting fraction
3144-468: A specific timescale. Thus, if a gas has a high (positive) radiative forcing but also a short lifetime, it will have a large GWP on a 20-year scale but a small one on a 100-year scale. Conversely, if a molecule has a longer atmospheric lifetime than CO 2 its GWP will increase when the timescale is considered. Carbon dioxide is defined to have a GWP of 1 over all time periods. Methane has an atmospheric lifetime of 12 ± 2 years. The 2021 IPCC report lists
3275-585: A starting amount of 1 tonne of methane, which has a GWP of 25, after combustion there would be 2.74 tonnes of CO 2 , each tonne of which has a GWP of 1. This is a net reduction of 22.26 tonnes of GWP, reducing the global warming effect by a ratio of 25:2.74 (approximately 9 times). The values provided in the table below are from 2007 when they were published in the IPCC Fourth Assessment Report . These values are still used (as of 2020) for some comparisons. A substance's GWP depends on
3406-710: A strategy to reduce it. For most businesses the vast majority of emissions do not come from activities on site, known as Scope 1, or from energy supplied to the organization, known as Scope 2, but from Scope 3 emissions, the extended upstream and downstream supply chain . Therefore, ignoring Scope 3 emissions makes it impossible to detect all emissions of importance, which limits options for mitigation. Large companies in sectors such as clothing or automobiles would need to examine more than 100,000 supply chain pathways to fully report their carbon footprints. The importance of displacement of carbon emissions has been known for some years. Scientists also call this carbon leakage . The idea of
3537-491: A variety of Atmospheric Chemistry Observational Databases . The table below shows the most influential long-lived, well-mixed greenhouse gases, along with their tropospheric concentrations and direct radiative forcings , as identified by the Intergovernmental Panel on Climate Change (IPCC). Abundances of these trace gases are regularly measured by atmospheric scientists from samples collected throughout
3668-569: A wider perspective. It includes a number of socio-economic and environmental indicators. It offers calculations that are either consumption-based, 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. It is based on input-output tables of countries' national accounts and international trade data such as UN Comtrade, and therefore it
3799-520: Is a CO 2 molecule. The first 30 ppm increase in CO 2 concentrations took place in about 200 years, from the start of the Industrial Revolution to 1958; however the next 90 ppm increase took place within 56 years, from 1958 to 2014. Similarly, the average annual increase in the 1960s was only 37% of what it was in 2000 through 2007. Many observations are available online in
3930-535: Is a level which the Intergovernmental Panel on Climate Change (IPCC) says is "dangerous". Greenhouse gases are infrared active, meaning that they absorb and emit infrared radiation in the same long wavelength range as what is emitted by the Earth's surface, clouds and atmosphere. 99% of the Earth's dry atmosphere (excluding water vapor ) is made up of nitrogen ( N 2 ) (78%) and oxygen ( O 2 ) (21%). Because their molecules contain two atoms of
4061-434: Is also cooling the upper atmosphere, as it is much thinner than the lower layers, and any heat re-emitted from greenhouse gases is more likely to travel further to space than to interact with the fewer gas molecules in the upper layers. The upper atmosphere is also shrinking as the result. Anthropogenic changes to the natural greenhouse effect are sometimes referred to as the enhanced greenhouse effect . This table shows
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4192-489: Is an asymmetry in electric charge distribution which allows molecular vibrations to interact with electromagnetic radiation. This makes them infrared active, and so their presence causes greenhouse effect . Earth absorbs some of the radiant energy received from the sun, reflects some of it as light and reflects or radiates the rest back to space as heat . A planet's surface temperature depends on this balance between incoming and outgoing energy. When Earth's energy balance
4323-407: Is another way to compare gases. While GWP estimates infrared thermal radiation absorbed, GTP estimates the resulting rise in average surface temperature of the world, over the next 20, 50 or 100 years, caused by a greenhouse gas, relative to the temperature rise which the same mass of CO 2 would cause. Calculation of GTP requires modelling how the world, especially the oceans, will absorb heat. GTP
4454-626: Is as follows: "A measure of the total amount of carbon dioxide (CO 2 ) and methane (CH 4 ) 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)." Scientists report carbon footprints in terms of equivalents of tonnes of CO 2 emissions ( CO 2 -equivalent ). They may report them per year, per person, per kilogram of protein, per kilometer travelled, and so on. In
4585-515: Is as large as 30%. Estimates in 2023 found that the current carbon dioxide concentration in the atmosphere may be the highest it has been in the last 14 million years. However the IPCC Sixth Assessment Report estimated similar levels 3 to 3.3 million years ago in the mid-Pliocene warm period . This period can be a proxy for likely climate outcomes with current levels of CO 2 . Greenhouse gas monitoring involves
4716-427: Is based on analyzing 12 sectoral case studies. The Scope 3 calculations can be made easier using input-output analysis. This is a technique originally developed by Nobel Prize-winning economist Wassily Leontief . Consumption-based emission accounting traces the impacts of demand for goods and services along the global supply chain to the end-consumer. It is also called consumption-based carbon accounting. In contrast,
4847-439: Is because it is often produced in monocultures with ample use of fertilizers and pesticides . Another example is offshore wind parks , which could have unintended impacts on marine ecosystems . 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
4978-774: Is calculated is to be found in the IPCC's 2001 Third Assessment Report. The GWP is defined as the ratio of the time-integrated radiative forcing from the instantaneous release of 1 kg of a trace substance relative to that of 1 kg of a reference gas: G W P ( x ) = a x a r ∫ 0 T H [ x ] ( t ) d t ∫ 0 T H [ r ] ( t ) d t {\displaystyle {\mathit {GWP}}\left(x\right)={\frac {a_{x}}{a_{r}}}{\frac {\int _{0}^{\mathit {TH}}[x](t)\,dt}{\int _{0}^{\mathit {TH}}[r](t)\,dt}}} where TH
5109-506: Is comparable worldwide. 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. Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect . This contributes to climate change . Carbon dioxide (CO 2 ), from burning fossil fuels such as coal , oil , and natural gas ,
5240-403: Is mostly due to the rapid growth and cumulative magnitude of the disturbances to Earth's carbon cycle by the geologic extraction and burning of fossil carbon. As of year 2014, fossil CO 2 emitted as a theoretical 10 to 100 GtC pulse on top of the existing atmospheric concentration was expected to be 50% removed by land vegetation and ocean sinks in less than about a century, as based on
5371-558: Is one of the most important factors in causing climate change. The largest emitters are China followed by the United States. The United States has higher emissions per capita . The main producers fueling the emissions globally are large oil and gas companies . Emissions from human activities 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
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5502-401: Is published in the same IPCC tables with GWP. Another metric called GWP* (pronounced "GWP star" ) has been proposed to take better account of short-lived climate pollutants (SLCPs) such as methane. A permanent increase in the rate of emission of an SLCP has a similar effect to that of a one-time emission of an amount of carbon dioxide, because both raise the radiative forcing permanently or (in
5633-507: Is shifted, its surface becomes warmer or cooler, leading to a variety of changes in global climate. Radiative forcing is a metric calculated in watts per square meter, which characterizes the impact of an external change in a factor that influences climate. It is calculated as the difference in top-of-atmosphere (TOA) energy balance immediately caused by such an external change. A positive forcing, such as from increased concentrations of greenhouse gases, means more energy arriving than leaving at
5764-837: Is that they absorb the wavelengths of radiation that a planet emits , resulting in the greenhouse effect . The Earth is warmed by sunlight, causing its surface to radiate heat , which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). The five most abundant greenhouse gases in Earth's atmosphere, listed in decreasing order of average global mole fraction , are: water vapor , carbon dioxide , methane , nitrous oxide , ozone . Other greenhouse gases of concern include chlorofluorocarbons (CFCs and HCFCs ), hydrofluorocarbons (HFCs), perfluorocarbons , SF 6 , and NF 3 . Water vapor causes about half of
5895-490: Is the amount of energy per unit area, per unit time, absorbed by the greenhouse gas, that would otherwise be lost to space. It can be expressed by the formula: R F = ∑ i = 1 100 abs i ⋅ F i / ( l ⋅ d ) {\displaystyle {\mathit {RF}}=\sum _{i=1}^{100}{\text{abs}}_{i}\cdot F_{i}/\left({\text{l}}\cdot {\text{d}}\right)} where
6026-450: 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 no further impacts of upstream suppliers are considered. This can introduce significant truncation errors . LCA has been combined with input-output analysis. This enables on-site detailed knowledge to be incorporated. IO connects to global economic databases to incorporate
6157-401: Is the key driver of carbon emissions. It has a bigger impact than population growth. And it counters the effects of technological developments. Continued economic growth mirrors the increasing trend in material extraction and GHG emissions . “Industrial emissions have been growing faster since 2000 than emissions in any other sector, driven by increased basic materials extraction and production,”
6288-489: Is the level the United Nations' Intergovernmental Panel on Climate Change (IPCC) says is "dangerous". Most greenhouse gases have both natural and human-caused sources. An exception are purely human-produced synthetic halocarbons which have no natural sources. During the pre-industrial Holocene , concentrations of existing gases were roughly constant, because the large natural sources and sinks roughly balanced. In
6419-499: Is the most important greenhouse gas overall, being responsible for 41–67% of the greenhouse effect, but its global concentrations are not directly affected by human activity. While local water vapor concentrations can be affected by developments such as irrigation , it has little impact on the global scale due to its short residence time of about nine days. Indirectly, an increase in global temperatures cause will also increase water vapor concentrations and thus their warming effect, in
6550-421: Is the time horizon over which the calculation is considered; a x is the radiative efficiency due to a unit increase in atmospheric abundance of the substance (i.e., Wm kg ) and [x](t) is the time-dependent decay in abundance of the substance following an instantaneous release of it at time t=0. The denominator contains the corresponding quantities for the reference gas (i.e. CO 2 ). The radiative efficiencies
6681-469: Is therefore more comprehensive. This comprehensive carbon footprint reporting including Scope 3 emissions deals with gaps in current systems. Countries' GHG inventories for the UNFCCC do not include international transport. Comprehensive carbon footprint reporting looks at the final demand for emissions, to where the consumption of the goods and services takes place. A formal definition of carbon footprint
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#17327974625666812-507: Is to be included. Carbon footprints can be calculated at different scales. They can apply to whole countries, cities, neighborhoods and also sectors, companies and products. Several free online carbon footprint calculators exist to calculate personal carbon footprints. Software such as the "Scope 3 Evaluator" can help companies report emissions throughout their value chain. The software tools can help consultants and researchers to model global sustainability footprints. In each situation there are
6943-523: Is used by regulators. Water vapour does contribute to anthropogenic global warming, but as the GWP is defined, it is negligible for H 2 O: an estimate gives a 100-year GWP between -0.001 and 0.0005. H 2 O can function as a greenhouse gas because it has a profound infrared absorption spectrum with more and broader absorption bands than CO 2 . Its concentration in the atmosphere is limited by air temperature, so that radiative forcing by water vapour increases with global warming (positive feedback). But
7074-705: Is usually in the range of 16 to 50 grams CO 2 eq per km. For moderate or long distances, trains nearly always have a lower carbon footprint than 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
7205-461: Is wrapped in. The IPCC Sixth Assessment Report found that global GHG emissions have continued to rise across all sectors. Global consumption was the main cause. The most rapid growth was in transport and industry. A key driver of global carbon emissions is affluence . The IPCC noted that the wealthiest 10% in the world contribute between about one third to one half (36%–45%) of global GHG emissions. Researcheres have previously found that affluence
7336-726: The Kyoto Protocol , in 1997 the Conference of the Parties standardized international reporting, by deciding (see decision number 2/CP.3) that the values of GWP calculated for the IPCC Second Assessment Report were to be used for converting the various greenhouse gas emissions into comparable CO 2 equivalents. After some intermediate updates, in 2013 this standard was updated by the Warsaw meeting of
7467-568: The UN Framework Convention on Climate Change (UNFCCC, decision number 24/CP.19) to require using a new set of 100-year GWP values. They published these values in Annex III, and they took them from the IPCC Fourth Assessment Report , which had been published in 2007. Those 2007 estimates are still used for international comparisons through 2020, although the latest research on warming effects has found other values, as shown in
7598-539: The UNFCCC based on their territorial emissions. This is known as the territorial-based or production-based approach. Including consumption-based calculations in the UNFCCC reporting requirements would help close loopholes by addressing the challenge of carbon leakage. The Paris Agreement currently does not require countries to include in their national totals GHG emissions associated with international transport. These emissions are reported separately. They are not subject to
7729-441: The UNFCCC . The GHG emissions listed in those national inventories are only from activities in the country itself. This approach is called territorial-based accounting or production-based accounting. It does not take into account production of goods and services imported on behalf of residents. Consumption-based accounting does reflect emissions from goods and services imported from other countries. Consumption-based accounting
7860-610: The carbon dioxide emissions are taken into account. These do not include other greenhouse gases , such as methane and nitrous oxide . Various methods to calculate the carbon footprint exist, and these may differ somewhat for different entities. For organizations it is common practice to use the Greenhouse Gas Protocol . It includes three carbon emission scopes. Scope 1 refers to direct carbon emissions. Scope 2 and 3 refer to indirect carbon emissions. Scope 3 emissions are those indirect emissions that result from
7991-406: The climate effects of different gases. It is calculated as GWP times mass of the other gas. The global warming potential (GWP) is defined as an "index measuring the radiative forcing following an emission of a unit mass of a given substance, accumulated over a chosen time horizon, relative to that of the reference substance, carbon dioxide (CO 2 ). The GWP thus represents the combined effect of
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#17327974625668122-526: The greenhouse effect is heavily driven by water vapor , human emissions of water vapor are not a significant contributor to warming. The annual "Emissions Gap Report" by UNEP stated in 2022 that it was necessary to almost halve emissions. "To get on track for limiting global warming to 1.5°C, global annual GHG emissions must be reduced by 45 per cent compared with emissions projections under policies currently in place in just eight years, and they must continue to decline rapidly after 2030, to avoid exhausting
8253-458: The life cycle of a commercial product , process , or service. It is not limited to the greenhouse gas emissions. It is also called life cycle analysis. It includes water pollution , air pollution , ecotoxicity and similar types of pollution. Some widely recognized procedures for LCA are included in the ISO 14000 series of environmental management standards. A standard called ISO 14040:2006 provides
8384-478: The value chain . Transportation of good, 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 to include Scope 3 emissions in all GHG reporting. The current rise in global average temperature is more rapid than previous changes. It is primarily caused by humans burning fossil fuels . The increase in greenhouse gases in
8515-535: The 100-year GWP scale as the standard in international agreements. The Kigali Amendment to the Montreal Protocol sets the global phase-down of hydrofluorocarbons (HFCs), a group of high-GWP compounds. It requires countries to use a set of GWP100 values equal to those published in the IPCC's Fourth Assessment Report (AR4). This allows policymakers to have one standard for comparison instead of changing GWP values in new assessment reports. One exception to
8646-562: The 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 GtC (2575 GtCO 2 ), of which 484±20 GtC (1773±73 GtCO 2 ) from fossil fuels and industry, and 219±60 GtC (802±220 GtCO 2 ) from land use change . Land-use change , such as deforestation , caused about 31% of cumulative emissions over 1870–2022, coal 32%, oil 24%, and gas 10%. The Carbon Trust has worked with UK manufacturers to produce "thousands of carbon footprint assessments". As of 2014
8777-551: 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. The protein output of peas and beef provides an example. Producing 100 grams of protein from peas emits just 0.4 kilograms of carbon dioxide equivalents (CO 2 eq). To get
8908-486: The GWP as 83 over a time scale of 20 years, 30 over 100 years and 10 over 500 years. The decrease in GWP at longer times is because methane decomposes to water and CO 2 through chemical reactions in the atmosphere. Similarly the third most important GHG, nitrous oxide (N 2 O), is a common gas emitted through the denitrification part of the nitrogen cycle . It has a lifetime of 109 years and an even higher GWP level running at 273 over 20 and 100 years. Examples of
9039-444: The GWP definition excludes indirect effects. GWP definition is also based on emissions, and anthropogenic emissions of water vapour ( cooling towers , irrigation ) are removed via precipitation within weeks, so its GWP is negligible. When calculating the GWP of a greenhouse gas, the value depends on the following factors: A high GWP correlates with a large infrared absorption and a long atmospheric lifetime. The dependence of GWP on
9170-480: The GWP100 standard exists: New York state ’s Climate Leadership and Community Protection Act requires the use of GWP20, despite being a different standard from all other countries participating in phase downs of HFCs. The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO 2 and evaluated for
9301-464: The IPCC said. There can be wide variations in emissions for transport of people. This is due to various factors. They include the length of the trip, the source of electricity in the local grid and the occupancy of public transport. In the case of driving the type of vehicle and number of passengers are factors. Over short to medium distances, walking or cycling are nearly always the lowest carbon way to travel. The carbon footprint of cycling one kilometer
9432-631: The USA, Luxembourg and Australia it was over 25 tonnes CO 2 e per person. In 2017, the average for the USA was about 20 metric tonnes CO 2 e 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. Per capita emissions in India are low for its huge population. But overall the country is the third largest emitter of CO 2 and fifth largest economy by nominal GDP in
9563-412: The United Nations underpin this analysis. The analysis enables a Structural Path Analysis. This scans and ranks the top supply chain nodes and paths. It conveniently lists hotspots for urgent action. Input-output analysis has increased in popularity because of its ability to examine global value chains . Life cycle assessment (LCA) is a methodology for assessing all environmental impacts associated with
9694-414: The activities of an organization but come from sources which they do not own or control. For countries it is common to use consumption-based emissions accounting to calculate their carbon footprint for a given year. Consumption-based accounting using input-output analysis backed by super-computing makes it possible to analyse global supply chains . Countries also prepare national GHG inventories for
9825-452: The argument that other greenhouse gases were more difficult to quantify. This is because of their differing global warming potentials. They also stated that an inclusion of all greenhouse gases would make the carbon footprint indicator less practical. But there are disadvantages to this approach. One disadvantage of not including methane is that some products or sectors that have a high methane footprint such as livestock appear less harmful for
9956-469: The atmosphere into bodies of water (ocean, lakes, etc.), as well as dissolving in precipitation as raindrops fall through the atmosphere. When dissolved in water, carbon dioxide reacts with water molecules and forms carbonic acid , which contributes to ocean acidity . It can then be absorbed by rocks through weathering . It also can acidify other surfaces it touches or be washed into the ocean. The vast majority of carbon dioxide emissions by humans come from
10087-531: The atmosphere is also due to deforestation and agricultural and industrial practices . These include cement production . The two most notable greenhouse gases are carbon dioxide and methane . Greenhouse gas emissions, and hence humanity's carbon footprint, have been increasing during the 21st century. The Paris Agreement aims to reduce greenhouse gas emissions enough to limit the rise in global temperature to no more than 1.5°C above pre-industrial levels. The carbon footprint concept makes comparisons between
10218-427: The atmosphere, terrestrial ecosystems , the ocean, and sediments . These flows have been fairly balanced over the past 1 million years, although greenhouse gas levels have varied widely in the more distant past . Carbon dioxide levels are now higher than they have been for 3 million years. If current emission rates continue then global warming will surpass 2.0 °C (3.6 °F) sometime between 2040 and 2070. This
10349-459: The atmospheric fraction of CO 2 even though the raw amount of emissions absorbed will be higher than in the present. Major greenhouse gases are well mixed and take many years to leave the atmosphere. The atmospheric lifetime of a greenhouse gas refers to the time required to restore equilibrium following a sudden increase or decrease in its concentration in the atmosphere. Individual atoms or molecules may be lost or deposited to sinks such as
10480-501: The atmospheric lifetime and GWP relative to CO 2 for several greenhouse gases are given in the following table: formula (years) (Wm ppb , molar basis). Estimates of GWP values over 20, 100 and 500 years are periodically compiled and revised in reports from the Intergovernmental Panel on Climate Change . The most recent report is the IPCC Sixth Assessment Report (Working Group I) from 2023. The IPCC lists many other substances not shown here. Some have high GWP but only
10611-423: The balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound or absorption by bodies of water). The proportion of an emission remaining in the atmosphere after a specified time is the " airborne fraction " (AF). The annual airborne fraction is the ratio of the atmospheric increase in
10742-609: The blame for negative consequences of those industries on to individual choices. Geoffrey Supran and Naomi Oreskes of Harvard University argue 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". A focus on carbon footprints can lead people to ignore or even exacerbate other related environmental issues of concern. These include biodiversity loss , ecotoxicity , and habitat destruction . It may not be easy to measure these other human impacts on
10873-502: The box ceased, then after time τ {\displaystyle \tau } , its concentration would decrease by about 63%. Changes to any of these variables can alter the atmospheric lifetime of a greenhouse gas. For instance, methane's atmospheric lifetime is estimated to have been lower in the 19th century than now, but to have been higher in the second half of the 20th century than after 2000. Carbon dioxide has an even more variable lifetime, which cannot be specified down to
11004-401: The burning of fossil fuels , with remaining contributions from agriculture and industry . Methane emissions originate from agriculture, fossil fuel production, waste, and other sources. The carbon cycle takes thousands of years to fully absorb CO 2 from the atmosphere, while methane lasts in the atmosphere for an average of only 12 years. Natural flows of carbon happen between
11135-405: The burning of fossil fuels . Additional contributions come from cement manufacturing, fertilizer production, and changes in land use like deforestation . Methane emissions originate from agriculture , fossil fuel production, waste, and other sources. If current emission rates continue then temperature rises will surpass 2.0 °C (3.6 °F) sometime between 2040 and 2070, which
11266-474: The carbon footprint as the "measure of the exclusive total amount of emissions of carbon dioxide (CO 2 ) that is directly and indirectly caused by an activity or is accumulated over the lifecycle stages of a product." The IPCC report's authors adopted the same definition that had been proposed in 2007 in the UK. That publication included only carbon dioxide in the definition of carbon footprint. It justified this with
11397-579: The carbon footprint concept allows everyone to make comparisons between the climate impacts of individuals, products, companies and countries. It also helps people devise strategies and priorities for reducing the carbon footprint. The carbon dioxide equivalent (CO 2 eq) emissions per unit of comparison is a suitable way to express a carbon footprint. This sums up all the greenhouse gas emissions. It includes all greenhouse gases, not just carbon dioxide. And it looks at emissions from economic activities, events, organizations and services. In some definitions, only
11528-404: The carbon footprint is just one in a family of indicators (e.g. ecological footprint , water footprint , land footprint , and material footprint), and should not be looked at in isolation. In fact, carbon footprint can be treated as one component of ecological footprint. The "Sustainable Consumption and Production Hotspot Analysis Tool" (SCP-HAT) is a tool to place carbon footprint analysis into
11659-417: The carbon footprint. They depend 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 . For climate change mitigation activities, the carbon footprint can help distinguish those economic activities with a high footprint from those with a low footprint. So
11790-436: The climate impacts of individuals, products, companies and countries. A carbon footprint label on products could enable consumers to choose products with a lower carbon footprint if they want to help limit climate change . For meat products, as an example, such a label could make it clear that beef has a higher carbon footprint than chicken. Understanding the size of an organization's carbon footprint makes it possible to devise
11921-665: The climate than they actually are. The greenhouse gas protocol is a set of standards for tracking greenhouse gas emissions. The standards divide emissions into three scopes (S cope 1, 2 and 3) within the value chain . Greenhouse gas emissions caused directly by the organization such as by burning fossil fuels are referred to as S cope 1 . Emissions caused indirectly by an organization, such as by purchasing secondary energy sources like electricity, heat, cooling or steam are called Scope 2 . Lastly, indirect emissions associated with upstream or downstream processes are called Scope 3 . Direct or Scope 1 carbon emissions come from sources on
12052-479: The definition of carbon footprint, some scientists include only CO 2. But more commonly they include several of the notable greenhouse gases . They can compare various greenhouse gases 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 includes all of
12183-550: The differing times these substances remain in the atmosphere and their effectiveness in causing radiative forcing." In turn, radiative forcing is a scientific concept used to quantify and compare the external drivers of change to Earth's energy balance . Radiative forcing is the change in energy flux in the atmosphere caused by natural or anthropogenic factors of climate change as measured in watts per meter squared. As governments develop policies to combat emissions from high-GWP sources, policymakers have chosen to use
12314-454: The direct measurement of atmospheric concentrations and direct and indirect measurement of greenhouse gas emissions . Indirect methods calculate emissions of greenhouse gases based on related metrics such as fossil fuel extraction. There are several different methods of measuring carbon dioxide concentrations in the atmosphere, including infrared analyzing and manometry . Methane and nitrous oxide are measured by other instruments, such as
12445-431: The emissions for the entire life cycle . These run from the production along the supply chain to its final consumption and disposal. Similarly, an organization's carbon footprint includes the direct as well as the indirect emissions that it causes. The Greenhouse Gas Protocol (for carbon accounting of organizations) calls these Scope 1, 2 and 3 emissions . There are several methodologies and online tools to calculate
12576-464: The entire supply chain. Critics argue that the original aim of promoting the personal carbon footprint concept was to shift responsibility away from corporations and institutions and on to personal lifestyle choices. The fossil fuel company BP ran a large advertising campaign for the personal carbon footprint in 2005 which helped popularize this concept. This strategy, employed by many major fossil fuel companies, has been criticized for trying to shift
12707-470: The environment with a single indicator like the carbon footprint. Consumers may think that the carbon footprint is a proxy for environmental impact. In many cases this is not correct. There can be trade-offs between reducing carbon footprint and environmental protection goals. One example is the use of biofuel , a renewable energy source and can reduce the carbon footprint of energy supply but can also pose ecological challenges during its production. This
12838-410: The final consumer of the purchased commodities. Efforts to reduce the carbon footprint of products, services and organizations help limit climate change. Such activities are called climate change mitigation. Greenhouse gas Greenhouse gases ( GHGs ) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases
12969-524: The framework for conducting an LCA study. ISO 14060 family of standards provides further sophisticated tools. These are used to quantify, monitor, report and validate or verify 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
13100-453: The gas concentration decays over time in the atmosphere. This is often not precisely known and hence the values should not be considered exact. For this reason when quoting a GWP it is important to give a reference to the calculation. The GWP for a mixture of gases can be obtained from the mass-fraction-weighted average of the GWPs of the individual gases. Commonly, a time horizon of 100 years
13231-446: The greenhouse effect, acting in response to other gases as a climate change feedback . Human activities since the beginning of the Industrial Revolution (around 1750) have increased carbon dioxide by over 50% , and methane levels by 150%. Carbon dioxide emissions are causing about three-quarters of global warming , while methane emissions cause most of the rest. The vast majority of carbon dioxide emissions by humans come from
13362-423: The home country's consumption bundle. Consumer-based accounting is based on input-output analysis. It 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 with input-output analysis assisted by super-computing capacity. Leontief created Input-output analysis (IO) to demonstrate
13493-434: The indirect emissions related to purchasing electricity, heat, or steam used on site. Examples of upstream carbon emissions include transportation of materials and fuels, any energy used outside of the production facility, and waste produced outside the production facility. Examples of downstream carbon emissions include any end-of-life process or treatments, product and waste transportation, and emissions associated with selling
13624-506: The industrial era, human activities have added greenhouse gases to the atmosphere, mainly through the burning of fossil fuels and clearing of forests. The major anthropogenic (human origin) sources of greenhouse gases are carbon dioxide (CO 2 ), nitrous oxide ( N 2 O ), methane and three groups of fluorinated gases ( sulfur hexafluoride ( SF 6 ), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs, sulphur hexafluoride (SF 6 ), and nitrogen trifluoride (NF 3 )). Though
13755-493: The 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, thereby assigning 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
13886-455: The limited remaining atmospheric carbon budget ." The report commented that the world should focus on broad-based economy-wide transformations and not incremental change. Several technologies remove greenhouse gas emissions from the atmosphere. Most widely analyzed are those that remove carbon dioxide from the atmosphere, either to geologic formations such as bio-energy with carbon capture and storage and carbon dioxide air capture , or to
14017-828: The most important contributions to the overall greenhouse effect, without which the average temperature of Earth's surface would be about −18 °C (0 °F), instead of around 15 °C (59 °F). This table also specifies tropospheric ozone , because this gas has a cooling effect in the stratosphere , but a warming influence comparable to nitrous oxide and CFCs in the troposphere . K&T (1997) used 353 ppm CO 2 and calculated 125 W/m total clear-sky greenhouse effect; relied on single atmospheric profile and cloud model. "With Clouds" percentages are from Schmidt (2010) interpretation of K&T (1997). Schmidt (2010) used 1980 climatology with 339 ppm CO 2 and 155 W/m total greenhouse effect; accounted for temporal and 3-D spatial distribution of absorbers. Water vapor
14148-503: The most important greenhouse gases. "The standard covers the accounting and reporting of seven greenhouse gases covered by the Kyoto Protocol – carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), hydrofluorocarbons (HFCs), perfluorocarbons (PCFs), sulfur hexafluoride (SF 6 ) and nitrogen trifluoride (NF 3 )." In comparison, the IPCC definition of carbon footprint in 2022 covers only carbon dioxide. It defines
14279-511: The number of years (denoted by a subscript) over which the potential is calculated. A gas which is quickly removed from the atmosphere may initially have a large effect, but for longer time periods, as it has been removed, it becomes less important. Thus methane has a potential of 25 over 100 years (GWP 100 = 25) but 86 over 20 years (GWP 20 = 86); conversely sulfur hexafluoride has a GWP of 22,800 over 100 years but 16,300 over 20 years (IPCC Third Assessment Report). The GWP value depends on how
14410-439: The potential future impacts of emissions of different gases upon the climate system in a relative sense. GWP is based on a number of factors, including the radiative efficiency (infrared-absorbing ability) of each gas relative to that of carbon dioxide, as well as the decay rate of each gas (the amount removed from the atmosphere over a given number of years) relative to that of carbon dioxide. The radiative forcing capacity (RF)
14541-718: The product. The GHG Protocol says it is important to calculate upstream and downstream emissions. There could be some double counting . This is 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 they are from sources 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. These are also known as
14672-508: The projections of coupled models referenced in the AR5 assessment. A substantial fraction (20–35%) was also projected to remain in the atmosphere for centuries to millennia, where fractional persistence increases with pulse size. Values are relative to year 1750. AR6 reports the effective radiative forcing which includes effects of rapid adjustments in the atmosphere and at the surface. Atmospheric concentrations are determined by
14803-788: The range-resolved infrared differential absorption lidar (DIAL). Greenhouse gases are measured from space such as by the Orbiting Carbon Observatory and through networks of ground stations such as the Integrated Carbon Observation System . The Annual Greenhouse Gas Index (AGGI) is defined by atmospheric scientists at NOAA as the ratio of total direct radiative forcing due to long-lived and well-mixed greenhouse gases for any year for which adequate global measurements exist, to that present in year 1990. These radiative forcing levels are relative to those present in year 1750 (i.e. prior to
14934-450: The relationship between consumption and production in an economy. It incorporates the entire supply chain. It uses input-output tables from countries' national accounts. It also uses international data such as UN Comtrade and Eurostat . Input-output analysis has been extended globally to multi-regional input-output analysis (MRIO). Innovations and technology enabling the analysis of billions of supply chains made this possible. Standards set by
15065-407: The same amount of protein from beef, emissions would be nearly 90 times higher, at 35 kgCO 2 eq. 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
15196-605: The same element , they have no asymmetry in the distribution of their electrical charges , and so are almost totally unaffected by infrared thermal radiation, with only an extremely minor effect from collision-induced absorption . A further 0.9% of the atmosphere is made up by argon (Ar), which is monatomic , and so completely transparent to thermal radiation. On the other hand, carbon dioxide (0.04%), methane , nitrous oxide and even less abundant trace gases account for less than 0.1% of Earth's atmosphere, but because their molecules contain atoms of different elements, there
15327-470: The same mass of carbon dioxide over a 20-year time frame. Since the 1980s, greenhouse gas forcing contributions (relative to year 1750) are also estimated with high accuracy using IPCC-recommended expressions derived from radiative transfer models . The concentration of a greenhouse gas is typically measured in parts per million (ppm) or parts per billion (ppb) by volume. A CO 2 concentration of 420 ppm means that 420 out of every million air molecules
15458-421: The site that is producing a product or delivering a service. An example for industry would be the emissions from burning a fuel on site. On the individual level, emissions from personal vehicles or gas-burning stoves are Scope 1. Indirect carbon emissions are emissions from sources upstream or downstream from the process being studied. They are also known as Scope 2 or Scope 3 emissions. Scope 2 emissions are
15589-416: The soil as in the case with biochar . Many long-term climate scenario models require large-scale human-made negative emissions to avoid serious climate change. Negative emissions approaches are also being studied for atmospheric methane, called atmospheric methane removal . Global warming potential Global warming potential ( GWP ) is an index to measure how much infrared thermal radiation
15720-404: The soil, the oceans and other waters, or vegetation and other biological systems, reducing the excess to background concentrations. The average time taken to achieve this is the mean lifetime . This can be represented through the following formula, where the lifetime τ {\displaystyle \tau } of an atmospheric species X in a one- box model is the average time that
15851-458: The start of the industrial era ). 1990 is chosen because it is the baseline year for the Kyoto Protocol , and is the publication year of the first IPCC Scientific Assessment of Climate Change . As such, NOAA states that the AGGI "measures the commitment that (global) society has already made to living in a changing climate. It is based on the highest quality atmospheric observations from sites around
15982-501: The subscript i represents a wavenumber interval of 10 inverse centimeters . Abs i represents the integrated infrared absorbance of the sample in that interval, and F i represents the RF for that interval. The Intergovernmental Panel on Climate Change (IPCC) provides the generally accepted values for GWP, which changed slightly between 1996 and 2001, except for methane, which had its GWP almost doubled. An exact definition of how GWP
16113-418: The table. and Annex III of the 2021 IPCC WG1 Report (years) GWP over time up to year 2022 Year 1750 Year 1998 Year 2005 Year 2011 Year 2019 Mole fractions : μmol/mol = ppm = parts per million (10 ); nmol/mol = ppb = parts per billion (10 ); pmol/mol = ppt = parts per trillion (10 ). The IPCC states that "no single atmospheric lifetime can be given" for CO 2 . This
16244-479: The tables above. Though recent reports reflect more scientific accuracy, countries and companies continue to use the IPCC Second Assessment Report (SAR) and IPCC Fourth Assessment Report values for reasons of comparison in their emission reports. The IPCC Fifth Assessment Report has skipped the 500-year values but introduced GWP estimations including the climate-carbon feedback (f) with a large amount of uncertainty. The Global Temperature change Potential (GTP)
16375-440: The time-scale chosen, typically 100 years or 20 years, since gases decay in the atmosphere or are absorbed naturally, at different rates. The following units are commonly used: For example, the table above shows GWP for methane over 20 years at 86 and nitrous oxide at 289, so emissions of 1 million tonnes of methane or nitrous oxide are equivalent to emissions of 86 or 289 million tonnes of carbon dioxide, respectively. Under
16506-424: The top-of-atmosphere, which causes additional warming, while negative forcing, like from sulfates forming in the atmosphere from sulfur dioxide , leads to cooling. Within the lower atmosphere, greenhouse gases exchange thermal radiation with the surface and limit radiative heat flow away from it, which reduces the overall rate of upward radiative heat transfer. The increased concentration of greenhouse gases
16637-428: The wavelength of absorption is more complicated. Even if a gas absorbs radiation efficiently at a certain wavelength, this may not affect its GWP much, if the atmosphere already absorbs most radiation at that wavelength. A gas has the most effect if it absorbs in a "window" of wavelengths where the atmosphere is fairly transparent. The dependence of GWP as a function of wavelength has been found empirically and published as
16768-602: The world. It excludes water vapor because changes in its concentrations are calculated as a climate change feedback indirectly caused by changes in other greenhouse gases, as well as ozone, whose concentrations are only modified indirectly by various refrigerants that cause ozone depletion . Some short-lived gases (e.g. carbon monoxide , NOx ) and aerosols (e.g. mineral dust or black carbon ) are also excluded because of limited role and strong variation, along with minor refrigerants and other halogenated gases, which have been mass-produced in smaller quantities than those in
16899-425: The world. Assuming a global population of around 9–10 billion by 2050, a carbon footprint of about 2–2.5 tonnes CO 2 e 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. This database accounts for all greenhouse gas (GHG) emissions in the global supply chain and allocates them to
17030-408: The world. Its uncertainty is very low." The natural flows of carbon between the atmosphere, ocean, terrestrial ecosystems , and sediments are fairly balanced; so carbon levels would be roughly stable without human influence. Carbon dioxide is removed from the atmosphere primarily through photosynthesis and enters the terrestrial and oceanic biospheres. Carbon dioxide also dissolves directly from
17161-494: The world. Whenever a product is imported, all CO 2 emissions that were emitted in the production of that product are included. Consumption-based emissions reflect the lifestyle choices of a country's citizens. According to the World Bank, the global average carbon footprint in 2014 was about 5 tonnes of CO 2 per person, measured on a production basis. The EU average for 2007 was about 13.8 tonnes CO 2 e per person. For
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