Fall

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The Oxford Principles for Net Zero Aligned
Carbon Offsetting
September 2020

The Oxford Principles for Net Zero Aligned Carbon
Offsetting
Executive Summary
As part of their climate strategies, many companies, organisations, cities, regions and financial
institutions are relying on voluntary carbon offsetting—payment to receive credit for a certified
unit of emission reduction or removal carried out by another actor. Current best practice helps
to reduce some of the well-known risks associated with existing offsets (e.g. improper carbon
accounting, re-release of stored carbon, negative unintended impacts on humans or
ecosystems, etc.), but is unlikely to deliver the types of offsetting needed to ultimately reachnet zero emissions. The Oxford Principles for Net Zero Aligned Carbon Offsetting (the “Oxford
Offsetting Principles”) presented here outline how offsetting needs to be approached to ensure
it helps achieve a net zero society.
1. Cut emissions, use high quality offsets, and regularly revise offsetting strategy as bestpractice evolves
A host of carbon offsetting best practices have been developed over the past decades.
Adherents to these principles must first observe these best practices, which can be grouped as:•

Prioritise reducing your own emissions - Minimise the need for offsets in the first place.

•

Ensure environmental integrity - Use offsets that are verifiable and correctly accounted forand have a low risk of non-additionality, reversal, and creating negative unintended
consequences for people and the environment.

•

Maintain transparency - Disclose current emissions, accounting practices, targets to reachnet zero, and the type of offsets you employ.

2. Shift to carbon removal offsetting
Most offsets available today are emission reductions, which are necessary but not sufficient toachieve net zero in the long run. Carbon removals scrub carbon directly from the atmosphere.
Users of offsets should increase the portion of their offsets that come from carbon removals,
rather than from emission reductions, ultimately reaching 100% carbon removals by midcentury to ensure compatibility with the Paris Agreement goals. Creating demand for carbon
removal offsets today will send the necessary market signal to increase supply.
3. Shift to long-lived storage
The transition from emission reductions to carbon removals as outlined in Principle 2 above iscritical for achieving net zero, but doesn’t address the question of how carbon is stored. Shortlived storage involves methods that have a higher risk of being reversed over decades. Longlived storage refers to methods of storing carbon that have a low risk of reversal over centuries
to millennia, such as storing CO2 in geological reservoirs or mineralising carbon into stable
forms. Short-lived storage offsets help buy time to reduce emissions and invest in long-lived

The Oxford Principles for Net Zero Aligned Carbon Offsetting

1

storage, but they are not a long-term solution for achieving balance between sinks and sources.
It is therefore critical that investment in scaling and improving the technologies that enablelong-lived storage begins now. Creating demand for long-lived offsets today sends a signal tothe market to grow the supply of such offsets.
4. Support the development of net zero aligned offsetting
The market for the high-quality offsets needed to meet Principles 2 and 3 is immature and inneed of early-adopters to support its evolution. Users of these principles can develop themarket for net zero aligned offsetting by:•

Using long-term agreements - give the certainty required by offset project developers tocreate net zero offsets.

•

Forming sector-specific alliances - work collaboratively with peers to develop the market
for net zero aligned offsets.

•

Supporting the restoration and protection of a wide range of natural and semi-natural ecosystems
in their own right - not only will this secure the ecosystem goods and services on whichhumans depend, including resilience to the impacts of climate change, but willcontribute to carbon storage over the long term. While carbon offsetting can help to fundsome of this work, such efforts should fundamentally be supported for the benefits andvalues they create, not purely for the purpose of carbon offsetting.

•

Adopting and publicising these Principles, and incorporate them into regulation and standardsetting for approaches to offsetting and net zero.

The Oxford Principles for Net Zero Aligned Carbon Offsetting

2

The Oxford Principles for Net Zero Aligned Carbon
Offsetting*
Myles Allen1,2, Kaya Axelsson1,3, Ben Caldecott2,3, Thomas Hale2,4, Cameron Hepburn2,3, Conor
Hickey3, Eli Mitchell-Larson*1,5, Yadvinder Malhi1, Friederike Otto1, Nathalie Seddon6, & Steve
Smith2,3
1 Environmental Change Institute, University of Oxford
2 Oxford Martin School, University of Oxford

3 Smith School of Enterprise and the Environment, University of Oxford
4 Blavatnik School of Government, University of Oxford
5 Saïd Business School, University of Oxford

6 Nature-based Solutions Initiative, Department of Zoology, University of Oxford* Corresponding author: eli.mitchell-larson@chch.ox.ac.uk

To meet the Paris Agreement’s objective of “holding the increase in the global averagetemperature to well below 2°C above preindustrial levels and pursuing efforts to limit thetemperature increase to 1.5°C above pre-industrial levels” we must rapidly move toward net
zero carbon dioxide (CO2) emissions by mid-century. This means substantially reducing
emissions (“sources”) and balancing any residual emissions with removals (“sinks”) on an
ongoing basis.1
Many countries and “non-state actors”, such as cities, regions, companies, organisations andfinancial institutions, are pledging to achieve net zero emissions. While some actors can feasibly
eliminate all of their emissions to reach “absolute zero”, some actors will have residual
emissions. For example, emissions from biological processes in agriculture, some industrial
processes, and fossil fuel combustion for aviation will likely be difficult to eliminate fully by
2050. A number of actors therefore include “carbon offsets” within their climate strategy. Theseare purchased credits representing a certified unit of emission reduction or carbon removal
carried out by another actor.
A number of critically important questions emerge for the users of offsets. How can offsetting
be made a credible means of achieving net zero? What types of offsets should be used andwhen? How can actors purchasing offsets, and stakeholders holding them accountable, avoid
the risk of greenwashing? How can users catalyse the cost-effective supply of the right kind of
offsets at scale?
The Oxford Principles for Net Zero Aligned Carbon Offsetting are designed to help clarify
these questions, particularly for non-state actors who want to design and deliver rigorous
voluntary net zero commitments and develop high quality carbon markets.

*

The Oxford Principles for Net Zero Aligned Carbon Offsetting were devised through collaboration with experts
across the University of Oxford. The Principles incorporate expertise from the Blavatnik School of Government,
Environmental Change Institute, Nature-based Solutions Initiative, Oxford Martin School, Oxford Sustainable
Finance Programme, Saïd Business School, School of Geography and the Environment, and the Smith School ofEnterprise and the Environment.

The Oxford Principles for Net Zero Aligned Carbon Offsetting3

We urge offset buyers to adopt and integrate the Oxford Offsetting Principles into theiractivities. We also encourage regulators and standard setters to reflect them in the design ofoffsetting systems and net zero standards. Observing these Principles will help ensure thatusers avoid buying low-quality offsets and that their decarbonisation plans are compatible withachieving net zero.
The Oxford Offsetting Principles are intended to be used by a variety of stakeholders:•

Corporations and organisations designing and delivering credible plans for achieving
net zero.

•Financial institutions for the same purpose, as well as to assess the plans of investees
and borrowers. This can inform risk and impact analysis, as well as engagement andstewardship activities.

•

Civil society to gauge which organisations are aligning with the Paris Agreement,
revealing leaders and laggards.

•

Initiatives and networks that promote net zero target setting and disclosure by non-state
actors, who can align their requirements with the Oxford Offsetting Principles.

•

Regulatory and standard setting bodies to create voluntary or mandatory rules or otherpolicy interventions that drive the economy toward net zero, including enabling
investments that can support the realisation of the Oxford Offsetting Principles on a
global basis.

•

Researchers and academic institutions to address their own emissions, or to guideresearch to fill time-sensitive knowledge gaps in the carbon offsetting space.

The Oxford Principles for Net Zero Aligned Carbon Offsetting

4Principle 1: Cut emissions, use high quality offsets, and regularly revise
offsetting strategy as best practice evolves
A number of best practices have been developed to set international consensus on what
constitutes credible carbon offsetting. Adherents to these principles must first and foremost
observe these best practices for all purchased offsets, as summarised in the Stockholm
Environment Institute’s comprehensive introduction to the topic and other similar guides.2 Bestpractice generally covers the following areas:
Prioritise reducing your own emissions and scaling up removals, minimising the need for
offsets to achieve net zero
Cutting emissions and scaling up removals can take many forms and is often sector specific.
Actors can benchmark themselves against peers to help determine if they have maximised all
reduction opportunities. This can be done informally, for example an airline emulating or
exceeding the fleet upgrades of its peers or a law firm comparing its emission intensity against
similar firms. Formal frameworks for benchmarking emissions are also available,3 as areindustry-specific associations focused on climate action.
The amount of net emissions that remain and must therefore be offset will be specific to theorganisation, based on available technologies, strategic goals in terms of equity and inclusivity,
and their own financial strength. Criteria should be revisited frequently, since emissions thatwere previously considered hard-to-reduce may become easier to reduce due to newtechnologies, falling costs, or new incentives. Many initiatives exist to help organisations to do
this, including: Climate Action 100+, LEED, Net Zero Asset Owners Alliance, Oxford Martin
Principles for Climate-Conscious Investment, RE100, Science Based Targets initiative, and The
Investor Agenda.
Use offsets that are verifiable and correctly accounted for, have a low risk of nonadditionality, reversal, and creating negative unintended consequences
Verifying offsets ensures that the emission reduction or carbon removal actually takes place,and that all forms of double-counting, including double-claiming of the emission reduction
benefit, are avoided. Forward-selling, and any time gap between the purchase of the offset andthe successful execution of the emission reducing or carbon removing activity must be
minimised, and mechanisms to ensure that the environmental benefits from an offset are
actually delivered must be strong. Care must be taken to ensure offset providers are properly
converting the climate impacts of non-CO2 climate pollutants into CO2 terms according to theiractual warming impact, particularly for short-lived greenhouse gases like methane.4
Offsets should also be additional, meaning they represent an emission reduction or carbon
removal relative to a counterfactual baseline that would not have taken place but for theoffsetting activity.5,6 Additionality can be difficult to determine and verify, and ultimately
involves some degree of subjectivity since the counterfactual world in which the offsetting
activity was not performed cannot be observed directly.

The Oxford Principles for Net Zero Aligned Carbon Offsetting5Permanence refers to how long a greenhouse gas stays out of the atmosphere, whether stored
in a physical reservoir or whose emission was deferred through avoidance.7 In the case ofphysically storing carbon in a reservoir (e.g. a forest, or a geological sink), the risk of reversalof that carbon back into the atmosphere must be acknowledged and accounted for in theoffsetting plan. For example, afforestation or reforestation generates carbon removal carbon
offsets, but if forests are subsequently cut down or destroyed by pests, fire, or other natural
disturbances the stored carbon is reversed and the carbon offset must be invalidated.
Potential unintended negative consequences associated with nature-based offsetting could
include but are not limited to loss of livelihood to farmers or those from local communities who
rely on forest products, loss of agricultural land, violations of local community land rights,
decreased biodiversity in low-diversity tree plantations or from tree-planting on biodiverse andnaturally low tree cover habitats such as grasslands, savannas, and peatlands, unanticipatedchanges to hydrological or nutrient cycles and other adverse impacts on the social andecological resilience of landscapes. High quality nature-based offsets can embed additional
value, such as enhancements to biodiversity, local incomes, climate-change resilience andsafeguarding community rights.
Disclose current emissions, accounting practices and targets to reach net zero
Disclosure includes all emissions within an organisation’s sphere of influence, often
categorised according to the Greenhouse Gas Protocol framework for reporting emissions8:•

Scope 1 emissions are direct emissions from owned or controlled sources e.g. company
vehicles.

•Scope 2 emissions are indirect emissions from the generation of purchased energy e.g.
purchased electricity.

•

Scope 3 emissions are all other indirect emissions that occur in the value chain, including
both upstream and downstream emissions e.g. emissions associated with the use of
products or services sold or used by an organisation.

Organisations must disclose the accounting practices they use to measure emissions andconvert the climate impacts of short-lived gases (e.g. methane) into carbon dioxide (a long-livedgas) equivalent terms.
Following current best practice is crucial for all actors but, as we outline below, it is just the
point of departure.

The Oxford Principles for Net Zero Aligned Carbon Offsetting

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Principle 2 – Shift to carbon removal offsetting
An immediate transition to 100% carbon removals is not necessary, nor is it currently feasible,
but organisations must commit to gradually increase the percentage of carbon removal offsets
they procure with a view to exclusively sourcing carbon removals by mid-century.
Most offsets available today are emission reductions, which are necessary but not sufficient tomaintain net zero in the long run. Carbon removals scrub carbon directly from the atmospherewhich can counteract ongoing emissions after net zero is achieved, as well as create thepossibility of net removal for those actors who choose to remove more carbon than they emit.
Figure 1 provides a simplified classification of offsets and guidance on how to assess thesedifferences.
Figure 1: Taxonomy of Carbon Offsets
How is the offset generated?
CarbonremovalEmission
reduction

Is carbon stored?

Yes

No

Yes
How is carbon stored?

I

III

II
Avoided emissions,or emission reduction
without storage

Forward-looking,counterfactual
baseline:• Renewable energy• Cleaner cookstoves

Clear retrospective
emissions data:• N2O abatement• Methaneabatement

Emissions reduction
with short-lived
storage• Avoided damage toecosystems• Changes to ag
practices that retain
already-stored carbon
Less permanent
Higher risk of reversal

IV

V

Emissions reduction
with long-lived
storage

Carbon removalwith short-lived storage• CCS on industrial
facilities• CCS on fossil-fuelpower plant• Afforestation &reforestation• Soil carbon
enhancement• Ecosystem restoration

More permanent
Lower risk of reversal

Less permanent
Higher risk of reversal

Carbon removalwith long-lived
storage• DACCS• BECCS• Mineralisation• Enhanced
weathering
More permanent
Lower risk of reversal

Figure 1 – This simplified classification scheme shows five types of carbon offset based on whether carbon isstored, and the nature of that storage. Carbon removal is defined as the act of taking CO2 out of the air andpermanently storing it. For all forms of carbon removal, whether nature-based solutions or technologicallymediated processes, carbon must be stored. Principle 2 addresses the distinction between emission reduction andcarbon removal. For offsets that involve storing carbon, a further distinction is made as to whether that storage islikely to be short-lived (on the order of decades) or long-lived (on the order of centuries to millennia). Principle 3
addresses the distinction between short-lived and long-lived storage. Note that avoided emissions (Type I) should
not be considered superior to Types II-V on the basis of permanence, since such emissions may only be temporarily
avoided. The marginal quantity of fossil fuel whose use is avoided by such an offset might get purchased andconsumed by someone else (carbon leakage), or it may remain in the ground for years, only to be extracted andemitted at a later date when prices and other conditions change (intertemporal carbon leakage). Avoided
emissions can therefore also suffer from poor “permanence” if the reduction is not enduring. Figures 1 & 2
prepared by Eli Mitchell-Larson.

The Oxford Principles for Net Zero Aligned Carbon Offsetting

7

Offsets eventually need to come exclusively from carbon removals, but emission reductions
will remain crucial for decades. Emission reductions include avoided emissions, for example
the deployment of renewable energy to replace planned fossil fuel power plants, programmes
to update inefficient cook stoves, and the destruction of potent greenhouse gases like methaneand nitrous oxide before they reach the atmosphere. In other cases, the emission reduction
requires physically storing the carbon whose emission was averted, for example, installing
Carbon Capture and Storage (CCS) on industrial point sources or gas power stations. Paying
someone to avoid damage to natural and semi-natural ecosystems, an offset class that suffersfrom hard-to-prove additionality and concerns over carbon leakage, is technically a form ofemission reduction in which carbon is stored – in this case within the preserved ecosystemitself. For such offsets, it is critical that the storage employed is sufficiently permanent (seePrinciple 3) whether in biological carbon reservoirs through avoided damage to natural andsemi-natural ecosystems, or in geological reservoirs as with CCS.
In contrast, carbon removals are offsets generated by projects that remove carbon dioxide
directly from the atmosphere. Examples include biological carbon sequestration (planting trees,soil carbon enhancement, etc.), bioenergy with carbon capture and storage (BECCS), direct air
capture with geological storage (DACCS), or converting atmospheric carbon back into rockthrough remineralisation. High-quality emission reductions have exactly the same effect on theatmosphere as carbon removals in the near term. But carbon removals have a critical advantage
over emission reductions because they scrub emissions from the atmosphere. As a result, they
will eventually play a hugely important role in stabilising atmospheric concentrations of carbon
dioxide, and potentially even reducing them after net zero is achieved.
Users of offsets must increase the portion of their offsets that come from carbon removals,
rather than from emission reductions, ultimately reaching 100% carbon removals by midcentury to ensure compatibility with the Paris Agreement goals. Creating demand for carbon
removal offsets today will send a signal to the market to increase supply.

The Oxford Principles for Net Zero Aligned Carbon Offsetting

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Principle 3: Shift to long-lived storage
Offsets increasingly need to come from activities that store carbon permanently, with very low
risk of re-release into the atmosphere. Whereas Principle 2 concerned the distinction between
emissions reduction and carbon removals (orange and blue pathways in Figure 1), Principle 3
addresses the importance of shifting from short-lived storage to long-term storage (lighter anddarker box shading in Figure 1).
Short-lived storage refers to methods of storing carbon which have an uncertain or higher riskof being reversed within decades. These include many biological storage methods likeafforestation, reforestation and soil carbon enhancement. Such methods are capable of storingcarbon for millennia, provided that land use and environmental conditions do not change.
However, challenging conditions such as changing political priorities, economic pressures, fire,disease and risks associated with climate change itself, all conspire to increase the risk that thistrapped carbon will be re-emitted in the near-to-medium term. Provided offsetting in high-risk
regions and situations (whether for climate, geopolitical, or other factors) is avoided orapproached with appropriate caution, ecosystem-based carbon storage can be low-risk over thelong term.
Figure 2: Example net zero aligned offsetting trajectory

Percent breakdownof offset portfolio

100%

0%

Avoided emissions & emission
reductions with short-lived storage

I & II

r
bon
Car

em

h
hs
wit
l
a
ov
IV

Em

is s i

on

du
s re

ed
-l i v
ort

e
rag
sto

ngh lo
t
i
w

live

age
tor
s
d

n
ctio III

Carbon removal with long-lived storage

V

2020

2030

2040

2050

Figure 2 - An illustrative breakdown showing the percentages of different types of offsets that could be used toaddress unmitigable emissions between 2020 and 2050. It is not intended to be prescriptive, but shows one
plausible pathway an offsetting plan that is compatible with Principles 2 & 3 could follow, showing the shift awayfrom emissions reductions (orange colours) toward carbon removal (blue colours) and the shift away from shortlived storage (above the diagonal line) to long-lived storage (below the diagonal line).

The Oxford Principles for Net Zero Aligned Carbon Offsetting

9Long-lived storage refers to methods of storing carbon which have low risk of reversal overcenturies to millennia. This includes storing CO2 in geological reservoirs or mineralising carbon
into stable forms. While robust monitoring and verification is still needed to ensure the CO2
added to these stores does not leak out, they are generally much more inert and secure thanbiological storage methods.
The duration of storage does not map directly onto the carbon removal-emission reduction
distinction. Some carbon removal offsets can suffer from short-lived storage (e.g. someafforestation or soil carbon projects), and conversely some emission reduction offsets offer very
long-term storage (e.g. carbon capture equipped on a cement plant with subsequent geologicalstorage). Offsets that constitute both a carbon removal and offer long-lived storage do exist (e.g.
DACCS), but are challenging to procure due to their early stage, limited supply, and, for thetime being, high costs.9,10 It is critical that investment in scaling and improving the technologies
that enable long-lived storage begins now. A net zero aligned portfolio of offsets must increase
the portion of carbon removals over emission reductions, and the portion of long-lived
storage over short-lived storage, over time (see Figure 2 above).

The Oxford Principles for Net Zero Aligned Carbon Offsetting

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Principle 4: Support the development of net zero aligned offsetting
Principle 1 reaffirms the need to reduce first, offset with high-quality offsets second, andcontinually revise one’s offsetting strategy as best practices evolve. Principles 2 and 3 introduce
a new framework for proactively evolving the mix of carbon offsets in one’s portfolio toward
an end-state compatible with achieving net zero. However, while some carbon removal andlong-lived storage options to meet Principles 2 and 3 exist today, volumes must rise and costmust decline to make this long-term transition more feasible are not yet in place.
What explicit actions can buyers and sellers of offsets take in the short to medium term tosupport net zero aligned offsetting? What early impacts should users of offsets aim to bringabout? Organisations can use their buying power and political and social credibility to drive
meaningful change today in the following ways:•

Market signalling. Adopting the Oxford Offsetting Principles and publicising theiradoption can create demand for offsets that are net zero aligned, thus motivating
investment and project creation. Currently there are too few offsets employing longlived storage. There are also too many offsets with short-lived storage and low integrityon other metrics such as additionality (see Principle 1). Creating demand for long-lived
storage will help accelerate their deployment to deliver the necessary supply over the
long-term.

•

Aggregating demand and supply. Organisations adopting the Oxford Offsetting
Principles have an opportunity to be more proactive than simply signalling demand. For
example, users could individually or collectively enter into long-term offset purchaseagreements, similar to the power purchase agreements which supercharged solar andwind deployment. Such agreements provide long-term guaranteed revenue streams thatallow developers to finance carbon projects upfront, and they provide price certainty foroffset users. These could be designed as Contracts-for-Difference or could have different
call or put option characteristics to provide a credible price signal to suppliers tomotivate investment, while giving buyers flexibility and value for money. An exampleof how this can work includes the recently announced Woodland Carbon Guarantee
Scheme11.

•

Forming sector-specific alliances. Each sector has its own unique considerations aroundabsolute emissions reductions it can take before using offsets, and additional goals it
may wish to accomplish through offsetting. Users of offsets can build partnerships andcollaborate across their sector(s) to leverage shared opportunities and set out sectorspecific offsetting rules and commitments consistent with the Oxford Offsetting
Principles. They can also advocate for industry bodies to take clearer and stronger
stances on climate policy and offsetting standards. Note that these Principles areprimarily buyer-facing, but offset sellers and carbon project developers have anenormously important role to play, and can adopt the spirit of the principles by actively
advocating that their customers shift their demand in the manner described in Principles
2 and 3.

The Oxford Principles for Net Zero Aligned Carbon Offsetting11•

Support the restoration and protection of a wide range of natural and semi-natural
ecosystems in their own right. Not only will this secure the ecosystem goods andservices on which humans depend, including resilience to the impacts of climate change,
but will contribute to carbon storage over the long term. Nature based solutions may
well be needed to balance carbon released from natural feedbacks under a warming
scenario, even as we do achieve a net zero balance of long-term emissions andremovals12. Ecosystems can provide a wide range of other social and environmental
benefits beyond carbon, including biodiversity13,14. For these reasons, the protection andrestoration of ecosystems must be rapidly scaled up, irrespective of any carbon benefits
they may or may not provide. While carbon offsets can help to fund some of this work,
such efforts should be valued and funded for the broad suite of benefits and values theycreate, not incidentally through carbon offsetting. Carbon offsetting can be one of thesevalues and in some cases can help facilitate the broad range of values, but safeguards
should be employed such that carbon offsetting does not pre-empt other ecological andsocial values, and conversely that the pursuit of ecological and social values does notundermine the professed carbon benefits.

•

Incorporating the Principles into regulations and standards. A wide range of voluntary
and regulatory standards currently govern both approaches to offsetting and how net
zero is defined. Going forward, actors adopting the Principles should work to ensurethat such regulations and standards evolve to reflect a science-based approach tooffsetting and net zero, as defined in the Principles.

These are just some of the immediate ways in which organisations can work to ensure that theoffsetting market develops in a way that can deliver net zero alignment. There are a variety ofenabling conditions that can and should be pursued simultaneously, from supporting newmarketplaces, standards, and relevant certifications, to conducting research and development
to increase the quality and quantity of high-quality sustainable offsets. An offsetting strategyaligned with the aim of achieving net zero at a global scale must include ways to support these
conditions.

The Oxford Principles for Net Zero Aligned Carbon Offsetting

12References
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costs, barriers and potential. Energy Strategy Reviews 22, 61–81 (2018).
11. Forestry Commission. Woodland Carbon Guarantee. GOV.UK
https://www.gov.uk/guidance/woodland-carbon-guarantee (2020).
12. Lowe, J. A. & Bernie, D. The impact of Earth system feedbacks on carbon budgets andclimate response. Philosophical Transactions of the Royal Society A: Mathematical, Physical andEngineering Sciences 376, 20170263 (2018).
13. Chausson, A. et al. Mapping the effectiveness of nature-based solutions for climate change
adaptation. Global Change Biology 22 (2020).
14. Seddon, N. et al. Understanding the value and limits of nature-based solutions to climatechange and other global challenges. Philosophical Transactions of the Royal Society B: Biological
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