The mammalian blastocyst hatches before implantating into the endometrial lining of the womb. Once implanted the embryo will continue its development through the next stages of gastrulation, neurulation, and organogenesis. Gastrulation is the formation of the three germ layers that will form all of the different parts of the body. Neurulation forms the nervous system, and organogenesis is the development of all the various tissues and organs of the body.
A newly developing human is typically referred to as an embryo until the ninth week after conception, when it is then referred to as a fetus.
In other multicellular organisms, the word "embryo" can be used more
broadly to any early developmental or life cycle stage prior to birth or hatching.
Etymology
First attested in English in the mid-14c., the word embryon derives from Medieval Latinembryo, itself from Greekἔμβρυον (embruon), lit. "young one", which is the neuter of ἔμβρυος (embruos), lit. "growing in", from ἐν (en), "in" and βρύω (bruō), "swell, be full"; the proper Latinized form of the Greek term would be embryum.
This section
is about is a summary of embryonic development in all types of animals,
including humans. For information specific to human embryonic
development, see Human embryonic development.
Embryos (and one tadpole) of the wrinkled frog (Rana rugosa)Mouse and snake embryos
In animals, fertilization begins the process of embryonic development
with the creation of a zygote, a single cell resulting from the fusion
of gametes (e.g. egg and sperm).
The development of a zygote into a multicellular embryo proceeds
through a series of recognizable stages, often divided into cleavage,
blastula, gastrulation, and organogenesis.
Cleavage is the period of rapid mitotic cell divisions that occur
after fertilization. During cleavage, the overall size of the embryo
does not change, but the size of individual cells decrease rapidly as
they divide to increase the total number of cells. Cleavage results in a blastula.
Depending on the species, a blastula or blastocyst stage embryo can appear as a ball of cells on top of yolk, or as a hollow sphere of cells surrounding a middle cavity.
The embryo's cells continue to divide and increase in number, while
molecules within the cells such as RNAs and proteins actively promote
key developmental processes such as gene expression, cell fate
specification, and polarity. Before implanting into the uterine wall the embryo is sometimes known as the pre-implantation embryo or pre-implantation conceptus. Sometimes this is called the pre-embryo a term employed to differentiate from an embryo proper in relation to embryonic stem cell discourses.
Gastrulation is the next phase of embryonic development, and
involves the development of two or more layers of cells (germinal
layers). Animals that form two layers (such as Cnidaria) are called diploblastic, and those that form three (most other animals, from flatworms
to humans) are called triploblastic. During gastrulation of
triploblastic animals, the three germinal layers that form are called
the ectoderm, mesoderm, and endoderm. All tissues and organs of a mature animal can trace their origin back to one of these layers. For example, the ectoderm will give rise to the skin epidermis and the nervous system, the mesoderm will give rise to the vascular system, muscles, bone, and connective tissues, and the endoderm will give rise to organs of the digestive system and epithelium of the digestive system and respiratory system.
Many visible changes in embryonic structure happen throughout
gastrulation as the cells that make up the different germ layers migrate
and cause the previously round embryo to fold or invaginate into a
cup-like appearance.
Past gastrulation, an embryo continues to develop into a mature
multicellular organism by forming structures necessary for life outside
of the womb or egg. As the name suggests, organogenesis is the stage of
embryonic development when organs form. During organogenesis, molecular
and cellular interactions prompt certain populations of cells from the
different germ layers to differentiate into organ-specific cell types.
For example, in neurogenesis, a subpopulation of cells from the
ectoderm segregate from other cells and further specialize to become the
brain, spinal cord, or peripheral nerves.
The embryonic period varies from species to species. In human
development, the term fetus is used instead of embryo after the ninth
week after conception, whereas in zebrafish, embryonic development is considered finished when a bone called the cleithrum becomes visible.
In animals that hatch from an egg, such as birds, a young animal is
typically no longer referred to as an embryo once it has hatched. In viviparous
animals (animals whose offspring spend at least some time developing
within a parent's body), the offspring is typically referred to as an
embryo while inside of the parent, and is no longer considered an embryo
after birth or exit from the parent. However, the extent of development
and growth accomplished while inside of an egg or parent varies
significantly from species to species, so much so that the processes
that take place after hatching or birth in one species may take place
well before those events in another. Therefore, according to one
textbook, it is common for scientists to interpret the scope of embryology broadly as the study of the development of animals.
Flowering plants (angiosperms) create embryos after the fertilization of a haploid ovule by pollen. The DNA from the ovule and pollen combine to form a diploid, single-cell zygote that will develop into an embryo. The zygote, which will divide multiple times as it progresses throughout embryonic development, is one part of a seed. Other seed components include the endosperm,
which is tissue rich in nutrients that will help support the growing
plant embryo, and the seed coat, which is a protective outer covering.
The first cell division of a zygote is asymmetric, resulting in an embryo with one small cell (the apical cell) and one large cell (the basal cell).
The small, apical cell will eventually give rise to most of the
structures of the mature plant, such as the stem, leaves, and roots.
The larger basal cell will give rise to the suspensor, which connects
the embryo to the endosperm so that nutrients can pass between them.
The plant embryo cells continue to divide and progress through
developmental stages named for their general appearance: globular,
heart, and torpedo. In the globular stage, three basic tissue types
(dermal, ground, and vascular) can be recognized. The dermal tissue will give rise to the epidermis or outer covering of a plant, ground tissue will give rise to inner plant material that functions in photosynthesis, resource storage, and physical support, and vascular tissue will give rise to connective tissue like the xylem and phloem that transport fluid, nutrients, and minerals throughout the plant. In heart stage, one or two cotyledons (embryonic leaves) will form. Meristems (centers of stem cell
activity) develop during the torpedo stage, and will eventually produce
many of the mature tissues of the adult plant throughout its life. At the end of embryonic growth, the seed will usually go dormant until germination. Once the embryo begins to germinate (grow out from the seed) and forms its first true leaf, it is called a seedling or plantlet.
Plants that produce spores instead of seeds, like bryophytes and ferns, also produce embryos. In these plants, the embryo begins its existence attached to the inside of the archegonium on a parental gametophyte from which the egg cell was generated.
The inner wall of the archegonium lies in close contact with the "foot"
of the developing embryo; this "foot" consists of a bulbous mass of
cells at the base of the embryo which may receive nutrition from its
parent gametophyte. The structure and development of the rest of the embryo varies by group of plants.
Since all land plants create embryos, they are collectively referred to as embryophytes
(or by their scientific name, Embryophyta). This, along with other
characteristics, distinguishes land plants from other types of plants,
such as algae, which do not produce embryos.
Creating and/or manipulating embryos via assisted reproductive technology (ART) is used for addressing fertility concerns in humans and other animals, and for selective breeding in agricultural species. Between the years 1987 and 2015, ART techniques including in vitro fertilization (IVF) were responsible for an estimated one million human births in the United States alone. Other clinical technologies include preimplantation genetic diagnosis (PGD), which can identify certain serious genetic abnormalities, such as aneuploidy, prior to selecting embryos for use in IVF. Some have proposed (or even attempted - see He Jiankui affair) genetic editing of human embryos via CRISPR-Cas9 as a potential avenue for preventing disease; however, this has been met with widespread condemnation from the scientific community.
ART techniques are also used to improve the profitability of
agricultural animal species such as cows and pigs by enabling selective
breeding for desired traits and/or to increase numbers of offspring.
For example, when allowed to breed naturally, cows typically produce
one calf per year, whereas IVF increases offspring yield to 9–12 calves
per year. IVF and other ART techniques, including cloning via interspecies somatic cell nuclear transfer (iSCNT), are also used in attempts to increase the numbers of endangered or vulnerable species, such as Northern white rhinos, cheetahs, and sturgeons.
Cryoconservation of plant and animal biodiversity
Cryoconservation of genetic resources
involves collecting and storing the reproductive materials, such as
embryos, seeds, or gametes, from animal or plant species at low
temperatures in order to preserve them for future use. Some large-scale animal species cryoconservation efforts include "frozen zoos" in various places around the world, including in the UK's Frozen Ark, the Breeding Centre for Endangered Arabian Wildlife (BCEAW) in the United Arab Emirates, and the San Diego Zoo Institute for Conservation in the United States.
As of 2018, there were approximately 1,700 seed banks used to store and
protect plant biodiversity, particularly in the event of mass
extinction or other global emergencies. The Svalbard Global Seed Vault
in Norway maintains the largest collection of plant reproductive
tissue, with more than a million samples stored at −18 °C (0 °F).
Fossilized animal embryos are known from the Precambrian, and are found in great numbers during the Cambrian period. Even fossilized dinosaur embryos have been discovered.
Greenhouse gas inventories are emission inventories of greenhouse gas emissions that are developed for a variety of reasons. Scientists use inventories of natural and anthropogenic
(human-caused) emissions as tools when developing atmospheric models.
Policy makers use inventories to develop strategies and policies for
emissions reductions and to track the progress of those policies.
Regulatory agencies and corporations also rely on inventories to
establish compliance records with allowable emission rates. Businesses,
the public, and other interest groups use inventories to better
understand the sources and trends in emissions.
Unlike some other air emission inventories, greenhouse gas
inventories include not only emissions from source categories, but also
removals by carbon sinks. These removals are typically referred to as carbon sequestration.
Greenhouse gas inventories typically use Global warming potential (GWP) values to combine emissions of various greenhouse gases into a single weighted value of emissions.
Examples
Some of the key examples of greenhouse gas inventories include:
National governments that are Parties to the UNFCCC and/or the Kyoto Protocol are required to submit annual inventories of all anthropogenic greenhouse gas emissions from sources and removals from sinks.
The Kyoto Protocol includes additional requirements for national
inventory systems, inventory reporting, and annual inventory review for
determining compliance with Articles 5 and 8 of the Protocol.
Project developers under the Clean Development Mechanism of the Kyoto Protocol prepare inventories as part of their project baselines.
Greenhouse gas emissions accounting is measuring the amount of greenhouse gases (GHG) emitted during a given period of time by a polity, usually a country but sometimes a region or city. Such measures are used to conduct climate science and climate policy.
There are two main, conflicting ways of measuring GHG emissions: production-based (also known as territorial-based) and consumption-based. The Intergovernmental Panel on Climate Change
defines production-based emissions as taking place “within national
territory and offshore areas over which the country has jurisdiction”. Consumption-based emissions take into account the effects of trade, encompassing the emissions from domestic final consumption and those caused by the production of its imports.
From the perspective of trade, consumption-based emissions accounting
is thus the reverse of production-based emissions accounting, which
includes exports but excludes imports (Table 1).
The choice of accounting method can have very important effects on policymaking, as each measure can generate a very different result.
Thus, different values for a National greenhouse gas Emissions
Inventory (NEI) could result in a country choosing different optimal mitigation activities, the wrong choice based on wrong information being potentially damaging. The application of production-based emissions accounting is currently favoured in policy terms as it is easier to measure,
but it is criticised in the literature principally for its inability to
allocate emissions embodied in international trade/transportation and
the potential for carbon leakage.
Over the last few decades emissions have grown at an increasing rate from 1.0% yr−1 throughout the 1990s to 3.4% yr−1 between 2000 and 2008. These increases have been driven not only by a growing global population and per-capita GDP, but also by global increases in the energy intensity of GDP (energy per unit GDP) and the carbon intensity of energy (emissions per unit energy).These drivers are most apparent in developing markets
(Kyoto non-Annex B countries), but what is less apparent is that a
substantial fraction of the growth in these countries is to satisfy the
demand of consumers in developed countries (Kyoto Annex B countries). This is exaggerated by a process known as Carbon Leakage
whereby Annex B countries decrease domestic production in place of
increased importation of products from non-Annex B countries where
emission policies are less strict. Although this may seem the rational
choice for consumers when considering local pollutants, consumers are
inescapably affected by global pollutants such as GHG, irrespective of
where production occurs.
Although emissions have slowed since 2007 as a result of the global
financial crisis, the longer-term trend of increased emissions is likely
to resume.
Today, much international effort is put into slowing the
anthropogenic release of GHG and resulting climate change. In order to
set benchmarks and emissions targets for - as well as monitor and
evaluate the progress of - international and regional policies, the
accurate measurement of each country's NEI becomes imperative.
A comparison of the production-based and consumption-based national emissions inventories (NEI).
Criteria
Production-based NEI
Consumption-based NEI
Emissions covered
Administered territory
Global
Allocation
Domestic production
Domestic consumption
Allocation of trade
Includes exports, not imports
Includes imports, not exports
Mitigation focus
Domestic activities including exports
Domestic activities and imports (exports excluded)
As production-based emissions accounting is currently favoured in
policy terms, its methodology is well established. Emissions are
calculated not directly but indirectly from fossil fuel usage and other
relevant processes such as industry and agriculture according to 2006
guidelines issued by the IPCC for GHG reporting.
The guidelines span numerous methodologies dependent on the level of
sophistication (Tiers 1–3 in Table 2). The simplest methodology combines
the extent of human activity with a coefficient quantifying the
emissions from that activity, known as an ‘emission factor’. For example, to estimate emissions from the energy sector (typically contributing over 90% of CO2
emissions and 75% of all GHG emissions in developed countries) the
quantity of fuels combusted is combined with an emission factor - the
level of sophistication increasing with the accuracy and complexity of
the emission factor. Table 2 outlines how the UK implements these guidelines to estimate some of its emissions-producing activities.
Table 2. Some emissions producing activities and methods used
to estimate emissions. IPCC tier represents one of three tiers, each
tier indicating an additional layer of sophistication. These tiers
indicate which method of emissions calculations is used from the IPCC
1996 Guidelines.
Activity
GHG
IPCC Tier
Method used to estimate emissions
Public electricity and heat production
CO2
2
An emissions factor is applied to fuel consumption data from DUKES.
Some data are also collected from individual point sources at generation
facilities. The emissions factors are UK specific factors obtained by
sampling average UK carbon content of fuels.
Road transportation
CO2, CH4, N2O
3
Emissions from road transport are estimated from a combination of
total fuel consumption data taken from the Digest of UK Energy
Statistics and fuel properties, and from a combination of drive related
emission factors and road traffic data on fuel use, car type, miles
driven, road types, and fuel type from the Department for Transport.
Domestic aviation
CO2, CH4, N2O
3
Data from the Department for Transport and Civil Aviation Authority
on aircraft movements is broken down by aircraft type at each UK
airport. The model takes into account the lengths of time spent on
different parts of an aircraft's take off and landing cycle and
different types of aircraft used in the UK.
Refrigeration and air conditioning equipment
HFC
2
Data on the numbers of UK domestic and commercial refrigerators is
obtained from the UK Market Transformation Programme and activity data
supplied by industry. Data on mobile air conditioning systems is
obtained from the UK Society of Motor Manufacturers and Traders.
Once the numbers and size of refrigerators is known, an emissions
factor which was derived to reflect UK refrigeration fluids applied to
estimate emissions
Enteric fermentation is a digestive process in ruminant animals which produces methane.
Emissions are estimated from animal production data from the June
agricultural census. Emissions factors for milk producing cattle, lambs
and deer are calculated using a tier 2 approach which takes into account
the sizes, ages and types of UK animals.
Agricultural soils
N2O
1 and 2
The method involves estimating the contributions from the use of
inorganic fertilizer, biological fixation of nitrogen by crops,
ploughing in crop residues, cultivation of organic soils, spreading
animal manure on land, and manures dropped by animals grazing in the
field using data from DEFRA
and the British Survey of Fertiliser Practice. For some of these areas
IPCC default methods are used and for other UK specific methods are
used.
Wastewater handling
CH4, N2O
2
The estimate is based on the work of Hobson et al. (1996) who
estimated emissions of methane for the years 1990–95. Subsequent years
are extrapolated on the basis of population. Sewage disposed to landfill
is included in landfill emissions
Emissions from burning wood are counted against the country where the
trees were felled rather than the country where they are burnt.
Consumption-based
emissions accounting has an equally established methodology using
Input-Output Tables. These "display the interconnection between
different sectors of production and allow for a tracing of the
production and consumption in an economy"
and were originally created for national economies. However, as
production has become increasingly international and the import/export
market between nations has flourished, Multi-Regional Input-Output
(MRIO) models have been developed. The unique feature of MRIO is
allowing a product to be traced across its production cycle,
"quantifying the contributions to the value of the product from
different economic sectors in various countries represented in the
model. It hence offers a description of the global supply chains of
products consumed". From this, assuming regional- and industry-specific data for CO2
emissions per unit of output are available, the total amount of
emissions for the product can be calculated, and therefore the amount of
emissions the final consumer is allocated responsibility for.
The two methodologies of emissions accounting begin to expose
their key differences. Production-based accounting is transparently
consistent with GDP, whereas consumption-based accounting (more complex
and uncertain) is consistent with national consumption and trade.
However, the most important difference is that the latter covers global
emissions - including those ‘embodied’ emissions that are omitted in production-based accounting - and offers globally based mitigation options. Thus the attribution of emissions embodied in international trade is the crux of the matter.
Figure 1 and Table 3 show extent of emissions embodied in
international trade and thus their importance when attempting emissions
reductions. Figure 1 shows the international trade flows of the top 10
countries with largest trade fluxes in 2004 and illustrates the
dominance of trade from developing countries (principally China, Russia
and India) to developed countries (principally USA, EU and Japan). Table
3 supports this showing that the traded emissions in 2008 total 7.8
gigatonnes (Gt) with a net CO2 emissions trade from developing to developed countries of 1.6 Gt.
Table 3 also shows how these processes of production, consumption
and trade have changed from 1990 (commonly chosen for baseline levels)
to 2008. Global emissions have risen 39%, but in the same period
developed countries seem to have stabilized their domestic emissions,
whereas developing countries’ domestic emissions have doubled. This
‘stabilization’ is arguably misleading, however, if the increased trade
from developing to developed countries is considered. This has increased
from 0.4 Gt CO2 to 1.6 Gt CO2 - a 17%/year average growth meaning 16 Gt CO2
have been traded from developing to developed countries between 1990
and 2008. Assuming a proportion of the increased production in
developing countries is to fulfil the consumption demands of developed
countries, the process known as carbon leakage becomes evident. Thus,
including international trade (i.e. the methodology of consumption-based
accounting) reverses the apparent decreasing trend in emissions in
developed countries, changing a 2% decrease (as calculated by
production-based accounting) into a 7% increase across the time period. This point is only further emphasized when these trends are studied at a less aggregated scale.
Table 3. Allocation of global emissions to Annex
B and non-Annex B countries separated into domestic and internationally
traded components.
Component
1990 (Gt CO2)
2008 (Gt CO2)
Growth (%/y)
Annex B
Domestic
Annex B Domestic (Bdom)
11.3
10.8
-0.3
Trade component
Annex B to Annex B (B2B)
2.1
2.2
0.2
Annex B to non-Annex B (B2nB)
0.7
0.9
1.8
Production
Annex B production (Bprod = Bdom + B2B + B2nB)
14.2
13.9
-0.1
Consumption
Annex B consumption (Bcons = Bdom + B2B + nB2B)
14.5
15.5
0.3
Non-Annex B
Domestic
Non-Annex B domestic (nBdom)
6.2
11.7
4.6
Trade component
Non-Annex B to Annex B (nB2B)
1.1
2.6
7.0
Non-Annex B to non-Annex B (nB2nB)
0.4
2.2
21.5
Production
Non-Annex B production (nBprod = nBdom + nB2B + nB2nB)
7.7
16.4
5.9
Consumption
Non-Annex B consumption (nBcons = nBdom + B2nB + nB2nB)
7.4
14.8
5.3
Trade totals
Traded emissions (B2B + B2nB + nB2B + nB2nB)
4.3
7.8
4.3
Trade balance (B2nB − nB2B)
-0.4
-1.6
16.9
Global emissions (Bprod + nBprod = Bcons + nBcon)
21.9
30.3
2.0
Figure 2 shows the percentage surplus of emissions as calculated by
production-based accounting over consumption-based accounting. In
general, production-based accounting proposes lower emissions for the EU and OECD countries (developed countries) and higher emissions for BRIC
and rest of the world (developing countries). However,
consumption-based accounting proposes the reverse with lower emissions
in BRIC and RoW, and higher emissions in EU and OECD countries. This led Boitier to term EU and OECD ‘CO2 consumers’ and BRIC and RoW ‘CO2 producers’.
The large difference in these results is corroborated by further analysis. The EU-27
in 1994 counted emissions using the consumption-based approach at 11%
higher than those counted using the production-based approach, this
difference rising to 24% in 2008. Similarly OECD countries reached a
peak variance of 16% in 2006 whilst dropping to 14% in 2008. In
contrast, although RoW starts and ends relatively equal, in the
intervening years it is a clear CO2 producer, as are BRIC with an average consumption-based emissions deficit of 18.5% compared to production-based emissions.
Peters and Hertwich
completed a MRIO study to calculate emissions embodied in international
trade using data from the 2001 Global Trade Analysis Program (GTAP).
After manipulation, although their numbers are slightly more
conservative (EU 14%; OECD 3%; BRIC 16%; RoW 6%) than Boitier the same trend is evident - developed countries are CO2 consumers and developing countries are CO2
producers. This trend is seen across the literature and supporting the
use of consumption-based emissions accounting in policy-making
decisions.
Tools and standards
ISO 14064
The ISO 14064 standards (published in 2006 and early 2007) are the most recent additions to the ISO 14000
series of international standards for environmental management. The ISO
14064 standards provide governments, businesses, regions and other
organisations with an integrated set of tools for programs aimed at measuring, quantifying and reducing greenhouse gas emissions. These standards allow organisations take part in emissions trading schemes using a globally recognised standard.
Local Government Operations Protocol
The
Local Government Operations Protocol (LGOP) is a tool for accounting
and reporting greenhouse gas emissions across a local government's
operations. Adopted by the California Air Resources Board (ARB) in September 2008 for local governments to develop and report consistent GHG inventories to help meet California's AB 32 GHG reduction obligations, it was developed in partnership with California Climate Action Registry, The Climate Registry, ICLEI and dozens of stakeholders.
The California Sustainability Alliance also created the Local Government Operations Protocol Toolkit,
which breaks down the complexities of the LGOP manual and provides an
area by area summary of the recommended inventory protocols.
Know IPCC Format for GHG Emissions Inventory
The data in the GHG emissions inventory is presented using the
IPCC format (seven sectors presented using the Common Reporting Format,
or CRF) as is all communication between Member States and the
Secretariat of the United Nations Framework Convention on Climate Change
(UNFCCC) and the Kyoto Protocol.
Advantages of consumption-based accounting
Consumption-based
emissions accounting may be deemed superior as it incorporates embodied
emissions currently ignored by the UNFCCC preferred production-based
accounting. Other key advantages include: extending mitigation options,
covering more global emissions through increased participation, and
inherently encompassing policies such as the Clean Development Mechanism (CDM).
Extending mitigation options
Under
the production-based system a country is punished for having a
pollution intensive resource base. If this country has pollution
intensive exports, such as Norway where 69% of its CO2 emissions are the result of production for export,
a simple way to meet its emissions reductions set out under Kyoto would
be to reduce its exports. Although this would be environmentally
advantageous, it would be economically and politically harmful as
exports are an important part of a country's GDP. However, by having appropriate mechanisms in place, such as a harmonized global tax, border-tax adjustment or quotas, a consumption-based accounting system could shift the comparative advantage towards a decision that includes environmental factors.
The tax most discussed is based on the carbon content of the fossil
fuels used to produce and transport the product, the greater the level
of carbon used the more tax being charged. If a country did not
voluntarily participate then a border tax could be imposed on them.
This system would have the effect of embedding the cost of
environmental load in the price of the product and therefore market
forces would shift production to where it is economically and
environmentally preferable, thus reducing GHG emissions
Increasing participation
In addition to reducing emissions directly this system may also alleviate competitiveness
concerns in twofold ways: firstly, domestic and foreign producers are
exposed to the same carbon tax; and secondly, if multiple countries are
competing for the same export market they can promote environmental
performance as a marketing tool.
A loss of competitiveness resulting from the absence of legally binding
commitments for non-Annex B countries was the principal reason the US
and Australia, two heavily emitting countries, did not originally
ratify the Kyoto protocol (Australia later ratified in 2007).
By alleviating such concerns more countries may participate in future
climate policies resulting in a greater percentage of global emissions
being covered by legally binding reduction policies. Furthermore, as
developed countries are currently expected to reduce their emissions
more than developing countries, the more emissions are (fairly)
attributed to developed countries the more they become covered by
legally bound reduction policies. Peters
argues that this last prediction means that consumption-based
accounting would advantageously result in greater emissions reductions
irrespective of increased participation.
Encompassing policies such as the CDM
The CDM is a flexible mechanism set up under the Kyoto Protocol with the aim of creating ‘Carbon Credits’ for trade in trading schemes such as the EU ETS. Despite coming under heavy criticism (see Evans, p134-135; and Burniaux et al.,), the theory is that as the marginal cost of environmental
abatement is lower in non-Annex B countries a scheme like this will
promote technology transfer
from Annex B to non-Annex B countries resulting in cheaper emissions
reductions. Because under consumption-based emissions accounting a
country is responsible for the emissions caused by its imports, it is
important for the importing country to encourage good environmental
behaviour and promote the cleanest production technologies available in
the exporting country.
Therefore, unlike the Kyoto Protocol where the CDM was added later,
consumption-based emissions accounting inherently promotes clean
development in the foreign country because of the way it allocates
emissions. One loophole that remains relevant is carbon colonialism
whereby developed countries do not mitigate the underlying problem but
simply continue to increase consumption offsetting this by exploiting
the abatement potential of developing countries.
Disadvantages of consumption-based accounting
Despite
its advantages consumption-based emissions accounting is not without
its drawbacks. These were highlighted above and in Table 1 and are
principally: greater uncertainty, greater complexity requiring more data
not always available, and requiring greater international
collaboration.
Greater uncertainty and complexity
Uncertainty
derives from three main reasons: production-based accounting is much
closer to statistical sources and GDP which are more assured; the
methodology behind consumption-based accounting requires an extra step
over production-based accounting, this step inherently incurring further
doubt; and consumption-based accounting includes data from all trading
partners of a particular country which will contain different levels of
accuracy. The bulk of data required is its second pitfall as in some countries
the lack of data means consumption-based accounting is not possible.
However, levels and accuracy of data will improve as more and better
techniques are developed and the scientific community produce more data
sets - examples including the recently launched global databases: EORA
from the University of Sydney, EXIOPOL and WIOD databases from European
consortia, and the Asian IDE-JETRO. In the short term it will be important to attempt to quantify the level of uncertainty more accurately.
Greater international co-operation
The
third problem is that consumption-based accounting requires greater
international collaboration to deliver effective results. A Government
has the authority to implement policies only over emissions it directly
generates. In consumption-based accounting emissions from different
geo-political territories are allocated to the importing country.
Although the importing country can indirectly oppose this by changing
its importing habits or by applying a border tax as discussed, only by
greater international collaboration, through an international dialogue
such as the UNFCCC, can direct and meaningful emissions reductions be
enforced.
Sharing emissions responsibility
Thus far it has been implied that one must implement either production-based accounting or consumption-based accounting.
However, there are arguments that the answer lies somewhere in the
middle i.e. emissions should be shared between the importing and
exporting countries. This approach asserts that although it is the final
consumer that ultimately initiates the production, the activities that
create the product and associated pollution also contribute to the
producing country's GDP. This topic is still developing in the
literature principally through works by Rodrigues et al., Lenzen et al., Marques et al. as well as through empirical studies by such as Andrew and Forgie.
Crucially it proposes that at each stage of the supply chain the
emissions are shared by some pre-defined criteria between the different
actors involved.
Whilst this approach of sharing emissions responsibility seems
advantageous, the controversy arises over what these pre-defined
criteria should be. Two of the current front runners are Lenzen et al. who say “the share of responsibility allocated to each agent should be proportional to its value added” and Rodrigues et al.
who say it should be based on “the average between an agent's
consumption-based responsibility and income-based responsibility”
(quoted in Marques et al.).
As no criteria set has been adequately developed and further work is
needed to produce a finished methodology for a potentially valuable
concept.
Trends
Measures
of regions' GHG emissions are critical to climate policy. It is clear
that production-based emissions accounting, the currently favoured
method for policy-making, significantly underestimates the level of GHG
emitted by excluding emissions embodied in international trade.
Implementing consumption-based accounting which includes such emissions,
developed countries take a greater share of GHG emissions and
consequently the low level of emissions commitments for developing
countries are not as important.
Not only does consumption-based accounting encompass global emissions,
it promotes good environmental behaviour and increases participation by
reducing competitiveness.
Despite these advantages the shift from production-based to
consumption-based accounting arguably represents a shift from one
extreme to another.
The third option of sharing responsibility between importing and
exporting countries represents a compromise between the two systems.
However, as yet no adequately developed methodology exists for this
third way, so further study is required before it can be implemented for
policy-making decisions.
Today, given its lower uncertainty, established methodology and
reporting, consistency between political and environmental boundaries,
and widespread implementation, it is hard to see any movement away from
the favoured production-based accounting.
However, because of its key disadvantage of omitting emissions embodied
in international trade, it is clear that consumption-based accounting
provides invaluable information and should at least be used as a
‘shadow’ to production-based accounting. With further work into the
methodologies of consumption-based accounting and sharing emissions
responsibility, both can play greater roles in the future of climate
policy.
The
carbon footprint can be used to compare the climate change impact of
many things. The example given here is the carbon footprint (greenhouse gas emissions) of food across the supply chain caused by land use change, farm, animal feed, processing, transport, retail, packing, losses.
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 (CO2-equivalent) per unit of comparison. Such units can be for example tonnes CO2-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 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 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 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 (CO2eq) 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 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 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 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 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.
Definition
Comparison of the carbon footprint of protein-rich foods
A formal 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)."
Scientists report carbon footprints in terms of equivalents of tonnes of CO2 emissions (CO2-equivalent). They may report them per year, per person, per kilogram of protein, per kilometer travelled, and so on.
In the definition of carbon footprint, some scientists include only CO2. 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.
In comparison, the IPCC definition of carbon footprint
in 2022 covers only carbon dioxide. It defines the carbon footprint 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." 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 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 the climate than they actually are.
Overview of Greenhouse Gas Protocol scopes and emissions across the value chain, showing upstream activities, reporting company and downstream activities.
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. Greenhouse gas emissions caused directly by the organization such as by burning fossil fuels are referred to as Scope 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 carbon emissions (Scope 1)
Direct or Scope 1 carbon emissions come from sources on 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 (Scope 2)
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 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 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
Other indirect carbon emissions (Scope 3)
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 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 carbon footprint concept makes comparisons between 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 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 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 a consumption perspective.
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 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 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.
Underlying concepts for calculations
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. 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 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 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 based on input-output analysis
Consumption-based vs. production-based CO₂ emissions per capitaProduction vs. consumption-based CO₂ emissions for the United StatesProduction vs. consumption-based CO₂ emissions per capita for China
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, 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 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 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 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 analysis: The full life cycle includes a production chain
(comprising supply chains, manufacture, and transport), the energy
supply chain, the use phase, and the end of life (disposal, recycle)
stage.
Life cycle assessment (LCA) is a methodology for assessing all environmental impacts associated with 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 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.
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 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 the entire supply chain.
Problems
Shifting responsibility from corporations to individuals
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 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".
Relationship with other environmental impacts
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 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 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 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 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 is comparable worldwide.
Differing boundaries for calculations
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.
Carbon dioxide is the main greenhouse gas resulting from human activities. It accounts for more than half of warming. Methane (CH4) emissions have almost the same short-term impact. Nitrous oxide (N2O) and fluorinated gases
(F-gases) play a lesser role in comparison. Emissions of carbon
dioxide, methane and nitrous oxide in 2023 were all higher than ever
before.
By products
Carbon footprint of EU diets by supply chain
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.
Food
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 (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.
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 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,” the IPCC said.
Transport
Comparison to show which form of transport has the smallest carbon footprint
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 is usually in the range of 16 to 50 grams CO2eq per km. For moderate or long distances, trains nearly always have a lower carbon footprint than other options.
By organization
Carbon accounting
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.
The main reasons for GHG accounting are to address social responsibility
concerns or meet legal requirements. Public rankings of companies,
financial due diligence and potential cost savings are other reasons.
GHG accounting methods help investors better understand the climate risks of companies they invest in. They also help with net zero emission
goals of corporations or communities. Many governments around the world
require various forms of reporting. There is some evidence that
programs that require GHG accounting help to lower emissions. Markets for buying and selling carbon credits
depend on accurate measurement of emissions and emission reductions.
These techniques can help to understand the impacts of specific products
and services. They do this by quantifying their GHG emissions
throughout their lifecycle (carbon footprint).
CO2 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 the world. Whenever a product is imported, all CO2
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 CO2 per person, measured on a production basis. The EU average for 2007 was about 13.8 tonnes CO2e per person. For the USA, Luxembourg and Australia it was over 25 tonnes CO2e per person. In 2017, the average for the USA was about 20 metric tonnes 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. Per capita emissions in India are low for its
huge population. But overall the country is the third largest emitter of
CO2 and fifth largest economy by nominal GDP in the world.[91] Assuming a global population of around 9–10 billion by 2050, a carbon footprint of about 2–2.5 tonnes 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. This database accounts for all greenhouse gas (GHG) emissions in the global supply chain and allocates them to the final consumer of the purchased commodities.
Sign at demonstration: "Go vegan and cut your climate footprint by 50%"
Climate change mitigation
Efforts to reduce the carbon footprint of products, services and
organizations help limit climate change. Such activities are called
climate change mitigation.
Carbon offsetting can reduce a company's overall carbon footprint by providing it with a carbon credit.
This compensates the company for carbon dioxide emissions by
recognizing an equivalent reduction of carbon dioxide in the atmosphere.
Reforestation, or restocking existing forests that have previously been depleted, is an example of carbon offsetting.
A carbon footprint study can identify specific and critical areas for improvement. It uses input-output analysis and scrutinizes the entire supply chain. Such an analysis could be used to eliminate the supply chains with the highest greenhouse gas emissions.
History
The term carbon footprint was first used in a BBC vegetarian food magazine in 1999, though the broader concept of ecological footprint, which encompasses the carbon footprint, had been used since at least 1992, as also chronicled by William Safire in the New York Times.
In 2005, fossil fuel company BP hired the large advertising campaign Ogilvy
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 derived from the ecological footprint, which encompasses carbon emissions.
The carbon footprint follows the logic of ecological footprint
accounting, which tracks the resource use embodied in consumption,
whether it is a product, an individual, a city, or a country. While in the ecological footprint, carbon emissions are translated into areas needed to absorb the carbon emissions, the carbon footprint on its own is expressed in the weight of carbon emissions per time unit. William Rees wrote the first academic publication about ecological footprints in 1992. Other related concepts from the 1990s are the "ecological backpack" and material input per unit of service (MIPS).
Trends and similar concepts
The International Sustainability Standards Board
(ISSB) aims to bring global, rigorous oversight to carbon footprint
reporting. It was formed out of the International Financial Reporting
Standards. It 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.
It consolidates the Carbon Disclosure Standards Board, the
Sustainability Accounting Standards Board and the Value Reporting
Foundation. It complements the Global Reporting Initiative. It is
influenced by the Task Force on Climate-Related Financial Disclosures.
As of early 2023, Great Britain and Nigeria were preparing to adopt
these standards.
The concept of total equivalent warming impact (TEWI) is the most used index for carbon dioxide equivalent (CO2) emissions calculation in air conditioning and refrigeration
sectors by including both the direct and indirect contributions since
it evaluates the emissions caused by the operating lifetime of systems. The Expanded Total Equivalent Warming Impact method has been used for an accurate evaluation of refrigerators emissions.
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