net zero emissions
Global net zero emissions describes the state where emissions of carbon dioxide due to human activities and removals of these gases are in balance over a given period. It is often called simply net zero. In some cases, "emissions" refers to emissions of all greenhouse gases, and in others  it refers only to emissions of carbon dioxide (CO2).To reach net zero targets requires actions to reduce emissions. One example would be by shifting from fossil fuel energy to sustainable energy sources. Organizations often offset their residual emissions by buying carbon credits. People often switch between the terms net zero emissions, carbon neutrality, and climate neutrality with the same meaning.: 22–24  However in some cases, these terms have different meanings from each other. Some standards bodies allow more use of offsets for carbon neutral certification than for net zero certification.    
In the last few years, net zero has become the main framework for climate ambition. Both countries and organizations are setting net zero targets. Today more than 140 countries have a net zero emissions target. They include some countries that were resistant to climate action in previous decades. Country-level net zero targets now cover 92% of global GDP, 88% of emissions and 89% of the world population. 65% of the largest 2,000 publicly traded companies by annual revenue have net zero targets. Among Fortune 500 companies the percentage is 63%. Company targets can result from both voluntary action and government regulation.
Net zero claims vary enormously in how credible they are. Most have low credibility. This is despite the increasing number of commitments and targets. While 61% of global carbon dioxide emissions are covered by some sort of net zero target, credible targets cover only 7% of emissions. This low credibility reflects a lack of binding regulation. It is also due to the need for continued innovation and investment to make decarbonization possible.To date, 27 countries have enacted domestic net zero legislation. These are laws that legislatures have passed which contain net zero targets or equivalent. There is currently no national regulation in place that legally requires companies based in that country to achieve net zero. Several countries including Switzerland are developing such legislation.

History and scientific justification
The idea of net zero came out of research in the late 2000s into how the atmosphere, oceans and carbon cycle were reacting to CO2 emissions. This research found that global warming will only stop if CO2 emissions are reduced to net zero. Net zero was basic to the goals of the Paris Agreement. This stated that we must "achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century". The term "net zero" gained popularity after the Intergovernmental Panel on Climate Change published its Special Report on Global Warming of 1.5 °C (SR15) in 2018, This report stated that "Reaching and sustaining net zero global anthropogenic [human-caused] CO2 emissions and declining net non-CO2 radiative forcing would halt anthropogenic global warming on multi-decadal timescales (high confidence)."The idea of net zero emissions is often confused with "stabilization of greenhouse gas concentrations in the atmosphere". This is a term that dates from the 1992 Rio Convention. The two concepts are not the same. This is because the carbon cycle continuously sequesters or absorbs a small percentage of cumulative historical human-caused CO2 emissions into vegetation and the ocean. This happens even after current CO2 emissions are reduced to zero. If the concentration of CO2 in the atmosphere were kept constant, some CO2 emissions could continue. However global average surface temperatures would continue to increase for many centuries due to the gradual adjustment of deep ocean temperatures. If CO2 emissions that result directly from human activities are reduced to net zero, the concentration of CO2  in the atmosphere would decline. This would be at a rate just fast enough to compensate for this deep ocean adjustment. The result would be approximately constant global average surface temperatures over decades or centuries.It will be quicker to reach net-zero emissions for CO2 alone rather than CO2 plus other greenhouse gases like methane, nitrous oxide and fluorinated gases. The net-zero target date for non-CO2 emissions is later partly because modellers assume that some of these emissions such as methane from farming are harder to phase out. Emissions of short-lived gases such as methane do not accumulate in the climate system in the same way that CO2 does. Therefore there is no need to reduce them to zero to halt global warming. This is because reductions in emissions of short-lived gases cause an immediate decline in the resulting radiative forcing. Radiative forcing is the change in the Earth's energy balance that they cause. However, these potent but short-lived gases will drive temperatures higher in the short term. This could possibly push the rise in temperature past the 1.5 °C threshold much earlier. A comprehensive net-zero emissions target would include all greenhouse gases. This would ensure that we also urgently reduce non-CO2 gases.

Terminology
Countries, local governments, corporations, and financial institutions may all announce pledges for achieving to reach net zero emissions. In climate negotiations we refer to these groups as actors.In climate change discussions we often use the terms net zero, carbon neutrality, and climate neutrality as if they mean the same thing.: 22–24  In some contexts, however, they have different meanings from each other. The sections below explain this. People often  use these terms without rigorous standard definitions.

Implementation
Since 2015, there has been significant growth in the number of actors pledging net zero emissions. Many standards have emerged that interpret the net zero concept and aim to measure progress towards net zero targets.: 38   Some of these standards are more robust than others. Some people have criticized weak standards for facilitating greenwashing.: 38  The UN, UNFCCC, International Organization for Standardization (ISO), and the Science Based Targets initiative (SBTi) promote more robust standards.

Types of greenhouse gas
Some targets aim to reach net zero emissions only for carbon dioxide. Others aim to reach net zero emissions of all greenhouse gases. Robust net zero standards state that all greenhouse gases should be covered by a given actor's targets.Some authors say that carbon neutrality strategies focus only on carbon dioxide, but net zero includes all greenhouse gases.  However some publications, such as the national strategy of France, use the term "carbon neutral" to mean net reductions of all greenhouse gases. The United States has pledged to achieve "net zero" emissions by 2050. As of March 2021 it had not specified which greenhouse gases will be included in its target.

Scopes of emissions sources
The Greenhouse Gas Protocol is a group of standards that are the most common in GHG accounting. These standards reflect a number of accounting principles. They include relevance, completeness, consistency, transparency, and accuracy. The standards divide emissions into three scopes:

Scope 1 covers all direct GHG emissions within a corporate boundary (owned or controlled by a company). It includes fuel burned by the company, use of company vehicles,  and fugitive emissions.
Scope 2 covers indirect GHG emissions from consumption of purchased electricity, heat, cooling or steam. As of 2010, at least one third of global GHG emissions are Scope 2.
Scope 3 emission sources include emissions from suppliers and product users (also known as the "value chain"). Transportation of goods, and other indirect emissions are also part of this scope.  Scope 3 emissions these were estimated to represent 75% of all emissions reported to the Carbon Disclosure Project, though that percentage varies widely amongst business sectors.Corporate net zero targets vary in how widely they cover emissions related to the company's activities. This can greatly affect the volume of emissions that are counted. Some oil companies, for instance, claim that their operations (Scopes 1 and 2) produce net zero emissions. These claims do not cover the emissions produced when the oil is burned by its customers,  which are 70 - 90% of oil-related emissions. This is because they count as Scope 3 emissions.Robust net zero standards require Scope 3 emissions to be counted, but "carbon neutrality" standards do not.

Approaches
A given actor may plan to achieve net zero emissions through a combination of approaches. These would include (1) actions to reduce their own emissions, (2) actions to directly remove carbon dioxide from the atmosphere, and (3) purchasing carbon credits.

Reducing emissions
Robust net zero standards require actors to reduce their own emissions as much as possible following science-based pathways. They must then balance their residual emissions using removals and offsets.: 12  This typically involves shifting from fossil fuels to sustainable energy sources. Residual emissions are emissions that are not practical to reduce for technological reasons.Experts and net zero frameworks disagree over the exact percentage of residual emissions that may be allowed. Most guidance suggests this should be limited to a small fraction of total emissions.  Sector-specific and geographical factors would determine how much. The Science Based Targets initiative says that residual emissions across most sectors should fall between 5-10% of an organization's baseline emissions. It should be even lower for some sectors with competitive alternatives like the power sector. Sectors such as heavy manufacturing where it is harder to mitigate emissions will probably have a higher percentage of residual emissions by 2050.The ISO and British Standards Institution (BSI) publish "carbon neutrality" standards that have higher tolerance for residual emissions than "net zero" standards. For example, BSI PAS 2060 is a British standard for measuring carbon neutrality. According to these standards, carbon neutrality is a short-term target, and net zero is a longer-term target.

Carbon removals and offsets
To balance residual emissions, actors may take direct action to remove carbon dioxide from the atmosphere and sequester it. Alternatively or in addition they can buy carbon credits that "offset" emissions. Carbon credits can be used to fund carbon removal projects such as reforestation.    
Strong standards such as the ISO and BSI "net zero" standards only allow removal-based offsets that have the same permanence as the greenhouse gases that they balance. We call this concept "like for like" removals.  Permanence means that removals must store greenhouse gases for the same period as the lifetime of the GHG emissions they balance. For example, methane has a lifetime of around 12 years in the atmosphere. Carbon dioxide lasts between 300 and 1,000 years. Accordingly, removals that balance carbon dioxide must last much longer than removals that balance methane.   
Carbon credits can also fund initiatives that aim to avoid emissions. One example would be energy efficiency retrofits or renewable energy projects. Avoided emissions offsets result from actions that reduce emissions relative to a baseline or status quo. But they do not remove emissions from the atmosphere. Weak standards such as ISO and BSI "carbon neutrality" standards allow organizations to use avoided-emissions carbon credits. They do not specify how permanent or durable a credit must be.Carbon offsetting has been critizied on several fronts. One important concern is that offsets may delay active emissions reductions.  In a 2007 report from the Transnational Institute, Kevin Smith likened carbon offsets to medieval indulgences. He said they allowed people to pay "offset companies to absolve them of their carbon sins." He said this permits a "business as usual" attitude that stifles required major changes. Many people have criticized offsets for playing a part in greenwashing. This argument appeared in a 2021 watchdog ruling against Shell.Loose regulation of claims by carbon offsetting schemes combined with the difficulties in calculating greenhouse gas sequestration and emissions reductions has also given rise to criticism. This argument is that this can result in schemes that do not adequately offset emissions in reality. There have been moves to create better regulation. The United Nations has operated a certification process for carbon offsets since 2001. This is called the Clean Development Mechanism. It aims to stimulate "sustainable development and emission reductions, while giving industrialized countries some flexibility in how they meet their emission reduction limitation targets." The UK Government's Climate Change Committee says reported emissions reductions or removals may have happened anyway or. not last into the future. This is despite an improvement in standards globally and in the UK.There has also been criticisms of non-native and monocultural forest plantations as carbon offsets. This is because of their "limited—and at times negative—effects on native biodiversity" and other ecosystem services.Most of the carbon credits on the voluntary market today do not meet UN, UNFCCC, ISO or SBTi standards for permanent carbon dioxide removals. So significant investment in carbon capture and permanent geological storage will probably be necessary to achieve net-zero targets by mid-century.

Timeframe
To achieve net zero, actors are encouraged to set net zero targets for 2050 or earlier. Long-term net zero targets should be supplemented by interim targets for every one to five years. The UN, UNFCCC, ISO, and SBTi all say that organizations should prioritize early, front-loaded emissions reduction. They say they should aim to halve emissions by 2030. Specific emissions reduction targets and pathways may look different for different sectors. Some may be able to decarbonize more quickly and easily than others.

Comprehensive accounting
The guidance from standards institutions says that organizations should choose a base year to measure emissions reductions against. This should be representative of their typical greenhouse gas profile. They should explain the choice of baseline and how they will acount for changes in conditions since the baseline. Financial organizations should also include emissions within their portfolio. This should include all organizations they have financed, invested in, or insured. Countries and regions should include both territorial emissions released within their boundaries and consumption emissions related to products and services imported and consumed within their boundaries)Cities and countries pose a challenge when it comes to calculating emissions. This is because the production of products and services within their boundaries might be linked to either internal consumption or exports. At the same time the population also consumes imported products and services. So it is important to state explicitly whether emissions are counted at the location of production or consumption. This helps to prevent double counting. The lengthy manufacturing chains of a globalised market might make this challenging. There are additional challenges with looking at renewable energy systems and electric vehicle batteries. This is because the necessary embodied energy and other effects of raw material extraction are often significant when measuring life-cycle emissions. However the local emissions at the place they are used may be small.

Equity and impact
The concept of net zero has attracted criticism for the impact it could have on equity and distribution. The use of removals or carbon credits for offsetting has been particularly controversial. This is because of the possibility that offset projects themselves could have harmful effects.  The ISO Net Zero Guidelines say that net zero strategies should align with the United Nations Sustainable Development Goals.This is in order to "support equity and global transition to a net zero economy, and any subsequent UN global goals which supersede the 2030 SDGs." The UNFCCC's Race to Zero campaign says emissions reductions and removals should "safeguard the rights of the most vulnerable people and communities". It says that organizations should disclose how they will support communities affected by climate impacts and climate transition.

Alignment with the global net zero goal
The United Nations High-Level Expert Group on the Net Zero Emissions Commitments of Non-State Entities has made several recommendations for non-state actors. Non-state actors include cities, regional governments, financial institutions, and corporations. One of these is not financing new fossil fuel development. Another is supporting strong climate policy. And another is ensuring that business activities and investments do not contribute to deforestation.: 12–13

Standards for products
Leading standards and guidance allow official accreditation bodies to certify products as carbon neutral but not as net zero. The rationale behind this is that until organizations and their supply chains are on track for net zero, allowing a product to claim to be net zero at this point would be disingenuous and lead to greenwashing.

Credibility
More and more nations and private and public-sector organizations are committing to net zero. But the credibility of these claims remains low. There is no binding regulation requiring a transition to net zero. So the overwhelming majority of net zero commitments have been made on a voluntary basis. The lack of an enforcement mechanism surrounding these claims means that many are dubious. In many sectors such as steel, cement, and chemicals, the pathway to reaching net zero in terms of technology remains unclear. Further investment in research and innovation and further regulation will probably be necessary if net zero claims are to become more credible.
A consortium of climate scientists has tracked net zero commitments. Their research found that  net pledges drafted in law or policy documentation have grown from 7% of countries in 2020 to 75% in 2023. However, very few have met the minimum requirements for a "decent pledge". The UN Race to Zero campaign calls them "starting line criteria". This states that they must have a "plan and published evidence of action taken towards reaching the target" besides a stated pledge,

The role of carbon credits
One of the main reasons for the low credibility of many net zero claims is their heavy reliance on carbon credits. Carbon credits are often used for offsetting. They reduce or remove emissions of carbon dioxide or other greenhouse gases in order to compensate for emissions made elsewhere. Many fossil fuel companies have made commitments to be net zero by 2050. At the same time they continue to increase greenhouse gas emissions by extracting and producing fossil fuels. They claim that they will use carbon credits and carbon capture technology in order to continue extracting and burning fossil fuels. The UN has condemned such pledges as dangerous examples of greenwashing.

2050 deadline
Many companies often claim a commitment to reach net zero emissions by the year 2050. These promises are often made at the corporate level. Both governments and international agencies encourage businesses to contribute to a national, or international, net zero pledge. The International Energy Agency says that global investment in low carbon substitutes for fossil fuels needs to reach US$4 trillion  annually by 2030 for the world to get to net zero by 2050. At the national level, US President Joe Biden has published strategies towards net zero and encouraged Americans to help the United States reach net zero. Biden has signed an executive order for government agencies to reach net zero by 2050. Many companies have made net zero pledges by 2050. They include German train manufacturer Siemens, American automaker Ford, and Taiwanese electronics manufacturer Foxconn. In addition, the magazine Forbes has released a list of US companies that have made the most progress towards net zero with 2050 or earlier goals. As of September 2023, the companies topping this list are Moody's, MSCI, and Northrop Grumman.Some groups have raised concerns that net zero cannot be achieved worldwide by 2050. Energy company ExxonMobil has said this would be highly unlikely because it would require high losses in living standards. given the high loss in standards of living that humanity would sacrifice in order to attain net zero. Others, such as Bloomberg's editorial board and investment banker Mark Carney, have stated that net zero is only possible with nuclear power.

Criticism
Climate scientists James Dyke, Bob Watson, and Wolfgang Knorr argue that the concept of net zero has been harmful for emissions reductions. This is because it allows actors to defer present-day emissions reductions by relying on future, unproved technological fixes. Examples are carbon offsetting, carbon dioxide removal and geoengineering. "The problems come when it is assumed that these [technological fixes] can be deployed at vast scale. This effectively serves as a blank cheque for the continued burning of fossil fuels and the acceleration of habitat destruction," they said. By tracing the history of previous failures in climate policy at reducing emissions from 1988 to 2021, they said they "[arrive] at the painful realisation that the idea of net zero has licensed a recklessly cavalier 'burn now, pay later' approach which has seen carbon emissions continue to soar". They concluded: "Current net zero policies will not keep warming to within 1.5 °C because they were never intended to. They were and still are driven by a need to protect business as usual, not the climate. If we want to keep people safe then large and sustained cuts to carbon emissions need to happen now. [...] The time for wishful thinking is over."In March 2021, Tzeporah Berman, chair of the Fossil Fuel Non-Proliferation Treaty Initiative, argued that the Treaty would be a more genuine and realistic way to achieve the goals of the Paris Agreement than the net zeron approach. She described net zero as "delusional and based on bad science".In his 2021 report, Dangerous Distractions, economist Marc Lee said that net zero had the potential to be a dangerous distraction that reduced political pressure to reduce emissions.  "A net zero target means less incentive to get to 'real zero' emissions from fossil fuels, an escape hatch that perpetuates business as usual and delays more meaningful climate action," he said. "Rather than gambling on carbon removal technologies of the future, Canada should plan for a managed wind down of fossil fuel production and invest public resources in bona fide solutions like renewables and a just transition from fossil fuels," he said.

See also
Carbon footprint
Carbon Neutral Cities Alliance
Carbon Neutrality Coalition
Carbon neutrality in India
Carbon neutrality in the United States
European Green Deal
Low-carbon economy

References


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