Global net-zero emissions occur when the amount of greenhouse gases released by human activities equals the amount removed from the atmosphere. This is often called "net zero." After global net zero is reached, the rate of global warming is expected to slow significantly. However, the warming caused by greenhouse gases already in the atmosphere will continue for some time.

Emissions can refer to all greenhouse gases or only to carbon dioxide (CO₂). Achieving net zero is essential to reduce global warming. This requires greatly reducing emissions, such as by switching from fossil fuels to renewable energy, improving energy efficiency, and stopping deforestation. A small amount of remaining emissions can be balanced by removing carbon dioxide from the atmosphere.

People often use the terms "net-zero emissions," "carbon neutrality," and "climate neutrality" interchangeably. However, these terms can have different meanings in some cases. For example, some standards for carbon neutrality allow a large amount of carbon offsetting. In contrast, net zero standards require reducing emissions to more than 90% and only offsetting the remaining 10% or less to meet 1.5°C climate goals. Organizations often buy carbon credits to balance their leftover emissions.

In the early 2020s, net zero became the main approach for climate action. Many countries and organizations now set net zero goals. As of November 2023, about 145 countries had announced or were considering net zero targets, covering nearly 90% of global emissions. These include some countries that previously resisted climate action. Country-level net zero goals now cover 92% of global GDP, 88% of emissions, and 89% of the world’s population. About 65% of the largest 2,000 publicly traded companies by revenue have net zero targets, and 63% of Fortune 500 companies have similar goals. These targets may result from voluntary actions or government rules.

Net zero claims vary widely in how trustworthy they are. Despite the growing number of commitments, most have low credibility. While 61% of global carbon dioxide emissions are covered by some net zero target, only 7% of emissions are covered by credible targets. This low credibility shows a lack of strong legal rules. It also highlights the need for continued innovation and investment to make reducing emissions possible.

So far, 27 countries have passed laws that include net zero goals or similar targets. However, no country currently has laws that legally require companies based there to achieve net zero. Some countries, like Switzerland, are working on creating such laws.

History and scientific justification

The idea of net-zero emissions began with research in the late 2000s that studied how the atmosphere, oceans, and carbon cycle responded to carbon dioxide (CO₂) emissions. This research showed that global warming will only slow significantly if CO₂ emissions are reduced to net zero. However, existing greenhouse gases in the atmosphere will still cause some warming. Net-zero became an important part of the goals set by the Paris Agreement. This agreement stated that the world must "achieve a balance between human-caused emissions of greenhouse gases and the removal of these gases by natural systems by the second half of this century." The term "net zero" became widely used after the Intergovernmental Panel on Climate Change released its Special Report on Global Warming of 1.5°C in October 2018. This report explained that "reaching and maintaining net zero human-caused CO₂ emissions and reducing other greenhouse gases would stop human-caused global warming over many decades." A scientific review titled "Net-zero emissions energy systems," published in June 2018, was the first to examine the challenges of not only reducing energy-related greenhouse gas emissions but also achieving net-zero emissions overall.

The idea of net-zero emissions is sometimes confused with "stabilization of greenhouse gas concentrations in the atmosphere," a term from the 1992 Rio Convention. These two concepts are different. This is because the carbon cycle naturally absorbs a small amount of human-caused CO₂ into plants and the ocean, even after emissions are reduced to zero. If human-caused CO₂ emissions are reduced to net zero, the amount of CO₂ in the atmosphere would decrease at a rate that matches the slow warming of the deep ocean. This would result in roughly constant global average surface temperatures over decades or centuries. In contrast, stabilizing atmospheric CO₂ concentrations would allow some emissions to continue, but global temperatures would still rise over many centuries due to the ocean's delayed response to warming.

It will be easier to reach net-zero emissions for CO₂ alone than for CO₂ plus other greenhouse gases like methane, nitrous oxide, and fluorinated gases. The net-zero target for non-CO₂ emissions is later because scientists often assume that some of these emissions, such as methane from farming, are harder to eliminate. Short-lived gases like methane do not build up in the climate system as CO₂ does. Therefore, reducing them to zero is not necessary to stop global warming. This is because reducing emissions of short-lived gases causes an immediate drop in the heat they trap in the Earth's atmosphere. However, these gases can cause temperatures to rise quickly in the short term, possibly pushing the temperature increase past the 1.5°C limit earlier. A complete net-zero emissions goal must include all greenhouse gases.

Some targets focus only on reducing CO₂ emissions to net zero. Others aim to reduce all greenhouse gases to net zero. Strong net-zero standards require that all greenhouse gases be included in a specific group's goals. Some authors say that "carbon neutrality" strategies focus only on CO₂, while "net zero" includes all greenhouse gases. However, some publications, such as France's national strategy, use the term "carbon neutral" to mean reducing all greenhouse gases to net zero. The United States has pledged to reach "net zero" emissions by 2050. As of March 2021, it had not yet specified which greenhouse gases would be included in its goal.

Terminology

Countries, local governments, corporations, and financial institutions can make promises to reach net-zero emissions.

In climate change discussions, the terms net zero, carbon neutrality, and climate neutrality are often treated as if they are the same. However, in some cases, they have different meanings. The sections below explain these differences. People often use these terms without clear, official definitions.

Approaches

An actor aiming to reach net-zero emissions may use several methods. These include (1) reducing their own emissions, (2) helping others reduce their emissions, and (3) removing carbon dioxide directly from the air (carbon sinks).

Strong net-zero standards require actors to cut their own emissions as much as possible using science-based methods. If some emissions remain, they must balance them by removing carbon or using offsets. This often involves switching from fossil fuels to clean energy sources. Residual emissions are those that cannot be reduced easily due to technology limits.

Improving energy efficiency is another key way to reduce emissions. Historically, better energy efficiency has been the most effective method. Policies to improve efficiency include setting car fuel standards, encouraging building insulation, and promoting public transportation.

Experts and net-zero frameworks disagree on how much residual emissions are acceptable. Most guidance suggests this should be a small part of total emissions. Factors like industry type and location will influence this. The Science Based Targets initiative says most sectors should reduce residual emissions to below 10% of their baseline by 2050. Sectors with easier alternatives, like power, should aim for even lower levels. Sectors like heavy manufacturing, where emissions are harder to cut, may have higher residual emissions by 2050.

Standards for "carbon neutrality" from the ISO and BSI allow more residual emissions than "net zero" standards. For example, BSI PAS 2060 is a British standard for measuring carbon neutrality. These standards consider carbon neutrality a short-term goal, while net zero is a long-term goal.

To balance leftover emissions, actors can remove carbon dioxide from the air or buy carbon credits that offset emissions. Carbon credits can fund projects like reforestation. Strong standards, like ISO and BSI "net zero" standards, require removal-based offsets that last as long as the emissions they balance. For example, methane lasts about 12 years, so removals balancing methane must last that long. Carbon dioxide lasts 300–1,000 years, so removals balancing it must last much longer.

Carbon credits can also fund projects that prevent emissions, such as improving building energy efficiency or investing in renewable energy. These are called "avoided emissions" offsets. They reduce emissions compared to a baseline but do not remove emissions from the air. Weaker standards, like ISO and BSI "carbon neutrality" standards, allow avoided-emissions credits without requiring long-term durability.

Carbon offsetting has faced criticism. One concern is that it may slow efforts to cut emissions directly. A 2007 report compared carbon offsets to medieval indulgences, suggesting they let people avoid making major changes. Critics also say offsets can support "greenwashing," as seen in a 2021 ruling against Shell.

Weak regulation and challenges in measuring emissions reductions have led to criticism. Some offset programs may not truly balance emissions. The United Nations started a certification process for carbon offsets in 2001 called the Clean Development Mechanism. It aims to support sustainable development and emission reductions while giving industrialized countries flexibility. The UK’s Climate Change Committee warns that reported emissions reductions may not last or may have occurred anyway.

Critics also point out that non-native forest plantations used as carbon offsets can harm local biodiversity and ecosystems.

Most carbon credits in the voluntary market today do not meet UN, UNFCCC, ISO, or SBTi standards for permanent carbon dioxide removal. As a result, significant investment in carbon capture and long-term geological storage will likely be needed to achieve net-zero goals by mid-century.

Implementation

Since 2015, more companies and organizations have promised to reach net-zero emissions. Net-zero means balancing the amount of greenhouse gases (GHG) released into the atmosphere with the amount removed. Many standards have been created to help measure progress toward these goals. Some standards are stronger than others. Weak standards have been criticized for allowing companies to make misleading claims about their environmental efforts. The United Nations (UN), UNFCCC, International Organization for Standardization (ISO), and Science Based Targets initiative (SBTi) support stronger standards.

The "United Nations High-Level Expert Group" has given recommendations to non-state actors, which include cities, local governments, banks, and companies. These recommendations include not funding new fossil fuel projects, supporting strong climate policies, and ensuring that business activities do not harm forests.

About 65% of the 2,000 largest publicly traded companies by revenue have set net-zero goals. Among Fortune 500 companies, 63% have similar goals. These goals can come from either voluntary actions or laws passed by governments.

The Greenhouse Gas Protocol is a widely used set of standards for measuring GHG emissions. These standards follow principles like relevance, completeness, consistency, transparency, and accuracy. They divide emissions into three categories:

• Scope 1 includes direct emissions from a company’s operations, such as burning fuel or using company vehicles.
• Scope 2 includes indirect emissions from using purchased electricity, heat, or steam. At least one-third of global GHG emissions are Scope 2.
• Scope 3 includes emissions from suppliers, customers, and other parts of the supply chain, such as transportation of goods. Scope 3 emissions make up about 75% of emissions reported to the Carbon Disclosure Project, though this varies by industry.

Corporate net-zero goals differ in how much they cover. Some companies only count emissions from their own operations (Scopes 1 and 2) and ignore emissions from customers, which make up 70–90% of oil-related emissions. Strong standards require companies to count all emissions, including Scope 3.

To reach net-zero, organizations are encouraged to set goals for 2050 or earlier. These goals should include short-term targets every 1–5 years. The UN, UNFCCC, ISO, and SBTi recommend reducing emissions by half by 2030. Different industries may have different timelines for reducing emissions.

Many companies claim to aim for net-zero emissions by 2050. These promises are often made at the corporate level. Governments and international groups encourage companies to support national or global net-zero goals. The International Energy Agency says that global investment in low-carbon energy must reach $4 trillion per year by 2030 to meet net-zero goals.

Some experts question whether the world can reach net-zero by 2050. In the European Union, about 29% of companies have set net-zero goals or already achieved them. However, these numbers vary by industry, country, and company size. Companies may be more likely to set goals if they face risks from climate change or if they see climate action as important.

Standards suggest that organizations should choose a starting year (called a "base year") to compare emissions reductions. This year should reflect typical emissions levels. Companies should explain why they chose this year and how they will account for changes over time. Financial institutions should also track emissions from companies they fund, invest in, or insure. Countries should include both emissions from within their borders and emissions from imported goods and services.

Calculating emissions for cities and countries is complex. Products and services made in one place may be used in another. It is important to clarify whether emissions are counted where they are made or where they are used to avoid double counting. Global supply chains and technologies like renewable energy and electric vehicle batteries add to this complexity.

Leading standards allow official groups to certify products as "carbon neutral" but not as "net zero." This is because products can only be labeled net zero if their entire supply chain is on track for net zero. Otherwise, such claims could be misleading.

The International Monetary Fund estimates that policies to reach net-zero by 2050 could increase global GDP by 7%. The cost of reducing emissions by 2050 would be less than 2% of world GDP, while saving costs from climate change could be about 9% of world GDP.

Politics

In the mid-2020s, the idea of achieving net zero became a topic of disagreement among politicians in places like the USA, the European Union, and the UK. As part of discussions about climate change, some people say that leaders must handle difficult and challenging political debates to make the shift toward net zero happen. Others, such as politician Chris Wright, have claimed that net zero goals could be harmful or costly. Some media reports suggest that net zero might raise prices, but others argue these claims do not correctly explain the economic effects of climate change and that reaching net zero is actually less expensive than not taking action.

There are also effects on workers that may cause political issues, as certain industries and areas may face more challenges than others. For example, in the UK, London and the South East have more jobs in the service sector, which are likely to be less affected compared to areas in the Midlands and the North, where heavy industries are more common.

In India, it is said that achieving net zero will mostly depend on how national and state governments work together across different areas of the economy and society.

Some cattle farmers are supporting GWP*, which has been called "dangerous" by others.

Effects

Studies show that countries with high pollution levels that adopt net zero policies often experience better public health. The savings from improved health typically outweigh the expenses of putting these policies into action.

Targets

As of November 2023, about 145 countries have announced or are thinking about setting net zero goals. These goals cover nearly 90% of the world’s greenhouse gas emissions. Some of these countries were not interested in climate action before. Net zero goals now cover 92% of the world’s total money value (GDP), 88% of emissions, and 89% of the world’s people.

According to World Population Review, some countries have net zero or even negative carbon emissions. These countries include Bhutan, Comoros, Gabon, Guyana, Madagascar, Panama, and Suriname. However, the World Resources Institute says all these countries still have more greenhouse gas emissions than they remove. These countries usually have large areas of forests.

Examples of climate-related plans include:
• European Green Deal
• Climate policy of China
• Carbon neutrality in India
• Carbon neutrality in the United States

Many people do not trust net zero goals because there are no rules that require countries to reach them. Most net zero promises are made voluntarily, without being forced. Without rules to check these promises, many are not reliable. In some industries, like steel, cement, and chemicals, it is unclear how to reach net zero using current technology. More research and rules may be needed to make these goals more trustworthy.

Tzeporah Berman, who leads the Fossil Fuel Non-Proliferation Treaty Initiative, has criticized net zero goals made by fossil fuel companies. She says these goals are "delusional and based on bad science."

A group of climate scientists has studied net zero goals. Their research shows that the number of countries with net zero goals in laws or policies grew from 7% in 2020 to 75% in 2023. However, few of these goals meet basic requirements for a strong promise. The UN Race to Zero campaign calls these requirements the "starting line criteria." This means goals must include a plan and proof of actions taken toward reaching the target, not just a statement.

At the 2022 United Nations Climate Change Conference (COP27), a group of experts formed earlier that year by U.N. Secretary-General António Guterres and led by former Canadian Environment Minister Catherine McKenna released a report. The report said that many companies, local governments, regional governments, and financial institutions have made net zero promises that are not real and are just "greenwashing." The report suggested 10 ways to make these promises more trustworthy, such as requiring non-state groups to share clear, proven information (like greenhouse gas reports) that shows they are meeting their goals.

After the report was released, a research group called Net Zero Tracker studied the climate goals of 116 out of 713 regional governments, 241 out of 1,177 cities with more than 500,000 people, and 1,156 out of 2,000 companies in the 25 countries with the most emissions. These companies cover more than 90% of the world’s total money value. The study found that many of these goals are not supported by real actions. More than half of the cities studied had no plan to track or report progress toward their goals.

Challenges

Climate scientists James Dyke, Bob Watson, and Wolfgang Knorr say the idea of net zero has not helped reduce emissions. This is because it allows people to delay reducing emissions now by depending on future, untested technologies like removing carbon dioxide from the air. They explain that assuming these technologies can be used on a large scale gives permission to keep burning fossil fuels and destroy habitats. By studying past climate policies from 1988 to 2021, they found that the net zero idea has allowed people to continue increasing carbon emissions. They said current net zero plans will not stop global warming from reaching 1.5°C because these plans were never meant to. Instead, they were created to protect usual business practices, not the climate. To keep people safe, large and lasting cuts to carbon emissions must happen now. The time for hoping for solutions that do not work is over.

A major reason many net zero claims are not trusted is because they depend heavily on carbon credits. Carbon credits are used to balance emissions by reducing or removing carbon dioxide or other greenhouse gases elsewhere. Many fossil fuel companies have promised to be net zero by 2050, but they continue to increase emissions by extracting and producing fossil fuels. They say they will use carbon credits and technology to capture carbon to keep using fossil fuels. The United Nations has criticized these promises as dangerous examples of making false claims about being environmentally friendly.

Offset projects might also cause harm. Guidelines from ISO say net zero plans should match the United Nations Sustainable Development Goals. This helps support fairness and the global shift to a net-zero economy and future goals. The UNFCCC's Race to Zero campaign says emissions reductions and removals should protect the rights of people most affected by climate change. It also says organizations should explain how they will help communities harmed by climate impacts and the move toward a net-zero economy.