Climate glossary

Turn your knowledge and awareness into action by getting to grips with the keywords, concepts and solutions central to tackling climate change.

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The planting of trees in an area where there has not previously been a forest. Afforestation is a popular focus for many carbon offsetting and carbon removal projects.

An umbrella term relating to the study, production and use of plants through agriculture for a variety of purposes including food, fuel and fibres. Agronomy encompasses several sciences and research areas such as meteorology, biology, ecology, biotechnology and soil sciences.

An igneous volcanic rock, formed when molten lava cools. Basalt is a type of silicate rock, a mineral compound made from silicon and oxygen which is central to natural weathering. It’s also highly abundant – basalt is the most common rock found in the oceanic crust – and is safe to spread on farmland, making it the perfect choice for UNDO’s enhanced rock weathering process.

The basalt we source at UNDO is a by-product of aggregate and mining industries, meaning we don’t use additional energy to produce it. Basalt has many environmental co-benefits. It’s packed with micro and macronutrients to maintain soil fertility, improve its pH, and aid in crop growth and resilience.

A chemical compound formed when carbonic acid (rainwater combined with atmospheric carbon dioxide) mineralises upon interacting with rock formations on Earth. Bicarbonate ions are stored in the soil or washed out to sea, where they play an important part in the carbon cycle and in maintaining a healthy pH level in both land and water.

In enhanced rock weathering, bicarbonate ions form much quicker than they normally would, because a much smaller and finer size of rock is used. This ensures that bicarbonate ions are locked away in the soil or sea within a matter of decades, rather than the millennia the natural process normally takes.

A carbon-rich liquid, created through heating biomass such as agricultural waste in an oxygen-free environment. In the carbon removal industry, bio oil is created and then injected deep underground, where it sinks and solidifies, locking the carbon in place.

A high-carbon content product created through burning biomass (organic matter such as wood and leaves) without the presence of oxygen. When biochar is spread on soil, the majority of its carbon content is released into the earth and sequestered. Biochar is chiefly produced as a soil amendment, but it’s increasingly being used in carbon removal processes.

The different forms of life (plants, animals, fungi, insects, bacteria, etc.) in any given area or environment. Protecting Earth’s biodiversity is crucial to ensure its ecosystems continue to thrive. Biodiversity is negatively affected by extractive human activities such as overfishing, land clearing (deforestation) and poaching.

A term used to describe carbon captured and stored specifically by coastal and marine ecosystems and organisms, including seagrasses, mangroves and marshes. Blue carbon management methods are sometimes employed in the process of carbon dioxide removal.

An insurance mechanism that allows carbon removal projects to compensate in cases of carbon reversal. Project developers allocate a certain number of carbon credits to the buffer pool over time. In the event of the project suffering a release of carbon dioxide back into the atmosphere that outweighs the amount of carbon they have sequestered, the developer would retire or cancel an equivalent amount of credits in the buffer pool to account for the loss.

Buffer pools are maintained by accreditation platforms such as Gold Standard and Verra.

For a full understanding, keep scrolling down for definitions of carbon credits, carbon removal, carbon reversal, Gold Standard and Verra.

The act of preventing carbon from being released into the atmosphere through reducing emissions. A company switching to renewable energy or an individual walking instead of driving are both methods of carbon avoidance.

The maximum amount of CO₂ emissions Earth can tolerate while ensuring that warming stays below a certain threshold. Earth’s carbon budget follows the Paris Agreement, which aims to ensure global warming does not rise beyond 1.5°C.

A process whereby carbon dioxide or an equivalent greenhouse gas is captured, treated and transported to be sequestered in a storage facility or geological formation. Carbon capture usually takes place at the source of the emission, such as a factory or power plant. It is a climate change mitigation technique that also aims to slow the move away from fossil fuel dependency in order to keep transition costs at a minimum.

The final stage in the life cycle of a carbon credit. A carbon credit must be retired in order for its owner to claim the emissions reduction represented by the credit. Once retired, a carbon credit cannot be resold or reused.

Retirement takes place at different points depending on the type of credit issued. If a credit has been purchased to compensate for emissions that have already taken place, then it is retired immediately upon purchase. If a credit has been purchased to contribute towards climate impact which has not yet taken place, then it will only be retired once the impact has occurred.

Refers to the year in which carbon emissions were either avoided, reduced or removed from the atmosphere. Carbon credits are subsequently independently verified and made available for use once issued by the relevant carbon standard. Carbon credits should always be denoted with the vintage year – which might even be in the future – and this also has an impact on the price.

Measurable, verifiable emissions reductions generated by carbon offsetting and carbon removal projects. Carbon credits can be acquired by businesses and individuals via support of climate projects like UNDO, and play an important part in the reduction of global emissions. There are two types of carbon credits: avoidance credits and removal credits.

Avoidance credits come from supporting emissions reduction projects that look at preventing emissions before they occur, rather than addressing greenhouse gases that have already been released into the atmosphere.

Removal credits are generated through support of projects that remove existing emissions of carbon dioxide and other greenhouse gases from the atmosphere. At UNDO, we are focused on providing high-quality removal carbon credits, through ensuring our projects meet the highest possible certification standards.

One carbon credit represents that one metric tonne of CO₂ or equivalent greenhouse gas has been avoided or removed.

A unit to measure the environmental impact of all greenhouse gases. By using this measurement, scientists and others in the climate space can talk about the impact of gases such as methane and nitrous oxide by using a singular unit which is expressed in terms of the equivalent amount of carbon dioxide emissions these gases represent.

The total number of greenhouse gases emitted by the actions of a business, country, individual or other entity or action. Measuring your own carbon footprint by using an online calculator can be a useful way to keep track of your personal emissions and work towards reducing them.

A process whereby companies invest in climate projects that are related to their products or industry and specifically target emissions within their supply chain.

As a response to stringent climate policies, a company may choose to move their production abroad to a country with less ambitious climate measures. The additional emissions that are often the result of such a move are referred to as carbon leakage.

A marketplace where carbon credits are traded. There are two types of carbon markets: compliance and voluntary.

Compliance carbon markets are created in response to a regional, national or international policy requirement. The first example of such a market was initiated by the Kyoto Protocol, and involved signatories committing to mandatory emissions reduction targets to be partially fulfilled through the purchase of carbon offsets.

Voluntary carbon markets enable organisations to buy and sell carbon offsets and credits on a voluntary basis to, for example, become carbon-neutral certified or meet other environmental goals. Offsets purchased on the voluntary carbon market are not bought to adhere to legally binding emissions reduction obligations.

A company can become carbon negative by offsetting more emissions than they produce over a certain amount of time, usually through the purchase of carbon credits or by supporting offsetting and removal projects.

A certification to denote that a company offsets the same amount of emissions it produces. Carbon-neutral certification is valid for one year and is governed by an internationally recognised standard. It can be applied to a specific part of a company’s operational output (such as emissions relating to a particular product or aspect of activity like delivery and distribution) or to the company’s entire operation.

Where companies invest in projects, not necessarily related to their products or industry, that reduce or remove emissions of carbon dioxide outside of their supply chain.

Sometimes also referred to as carbon dioxide removal or CDR, carbon removal is the process of removing carbon dioxide from the atmosphere after it has been released and safely sequestering it for a long period of time. There are many different methods of carbon removal; some are nature-based (like enhanced rock weathering) and others depend more heavily on mechanical machinery. The Intergovernmental Panel on Climate Change (IPCC) has identified carbon removal technology as a key factor in keeping global warming under 1.5°C.

The release of sequestered carbon dioxide back into the atmosphere. Carbon reversal is an inherent risk for many carbon removal technologies. Reversal can be unavoidable (due to disease in trees, fire or other natural disasters) or avoidable (due to, for example, mismanagement of land).

Unavoidable carbon reversals can be counteracted by the project developer contributing to a ‘buffer pool,’ a reserve of carbon credits that acts as an insurance policy and is usually maintained by the accreditation body to which the project is registered.

Avoidable carbon reversals are compensated by the project developer retiring an equivalent amount of carbon offset credits to make up for the loss of climate benefits incurred by the re-release of carbon dioxide.

The capture and long-term storage of atmospheric carbon dioxide in plants, soil, rocks and oceans.

An area or substance that, as part of its natural process, removes carbon dioxide from the atmosphere and stores it for an indefinite period of time as part of the natural carbon cycle. Examples of carbon sinks include peat bogs, mangroves and wetlands.

Any source or process, natural or otherwise, from which CO₂ is emitted into the atmosphere. The burning of fossil fuels constitutes an artificial carbon source, while the process of plant deterioration is an example of a natural source of carbon emission.

A weak acid formed when rainwater combines with atmospheric carbon dioxide. Carbonic acid plays an important part in the weathering process, reacting with soil and rocks to create bicarbonate ions.

Generally, climate change is defined as the long-term change of Earth’s climate on a global or regional level. In common use, however, climate change mainly refers to the scientifically proven negative influence of human activities on the planet’s climate patterns.

Human-influenced climate change is sometimes called ‘anthropogenic climate change’.

Often used interchangeably with ‘climate change’, this phrase is considered to place a heavier emphasis on the seriousness of the many environmental threats the planet faces.

A movement, pioneered by activists and leaders in the Global South, that advocates for the fair distribution of resources and wealth to help developing nations deal with the impact of climate change. Climate justice combines social inequality and human rights, demanding that historically marginalised communities be central in shaping the global response to climate change.

A term used to refer to positive secondary effects arising from climate change mitigation measures. For example, when an individual chooses to walk or cycle instead of driving, the co-benefit is that they may lead a more active, healthy lifestyle as a result.

Enhanced rock weathering has many co-benefits, including improved soil health and ocean deacidification. Co-benefits are increasingly considered in climate research and policy and are recognised in the Paris Agreement as an important aspect of signatories’ emissions reductions plans.

Yearly conventions held by the United Nations Framework Convention on Climate Change, where member states gather to discuss the progress made towards dealing with climate change and upholding the Paris Agreement.

The process through which an entity, typically a business or industry, seeks to lower its carbon footprint by various carbon avoidance or carbon removal initiatives.

The wide-scale removal of trees and plant life from historically forested areas. Deforestation occurs when the trees themselves are the sought-after resource, but also for the purpose of clearing land for other uses such as farming and mining.

A carbon removal technology, sometimes referred to as ‘Direct Air Capture and Storage’ (DACS), that captures and stores carbon dioxide from the atmosphere using an engineered, mechanical system. Air is typically drawn in through large fans which separate the carbon dioxide and sequester it underground.

A carbon removal technology that extracts CO₂ from seawater through a process combining electricity and chemistry. The process takes place within two treatment cells. Water is drawn into the first cell, where protons, released by reactive electrodes, acidify the water and convert inorganic bicarbonate content into molecular carbon dioxide to be safely collected. The water is then moved into the second cell with a reversed voltage, where it is alkalised before being released. The collected CO₂ is then sequestered elsewhere, such as within geological formations under the sea bed, or chemically converted for use in other industries.

Electrochemical ocean capture is an emerging form of carbon removal, with research ongoing into how it can be scaled and integrated with existing machinery. It has the co-benefit of contributing to ocean deacidification, while also making seawater more available to sequester CO₂ as a natural carbon sink.

A nature-based carbon removal technology that accelerates the geological process of rock weathering to permanently lock away CO₂ from the atmosphere. Rock weathering is a natural process whereby carbon dioxide combines with rainwater as it falls through the atmosphere, interacts with rock formations it lands on and mineralises to form solid bicarbonate ions which are safely stored in the soil or washed out to sea.

In enhanced rock weathering, a much smaller and finer form of rock is used, meaning that a cycle that normally takes millions of years takes just decades instead.

Read more about how UNDO does enhanced rock weathering here.

A social-justice movement critical of the way marginalised communities are more exposed to environmental issues – such as air pollution, hazardous water waste and extraction of resources – and their associated health impacts.

While climate justice deals more generally with the disproportionate effect of climate change on marginalised groups, environmental justice focuses predominantly on the unfair proximity of specific places and communities to infrastructures and procedures relating to fossil fuel industries, such as mining, waste disposal and oil drilling.

A framework used to determine a company’s performance in areas concerning sustainability and social responsibility, often used by investors when assessing the non-financial risks associated with a business’ operations. ESG consists of three pillars, each covering different matters.

The Environmental pillar assesses, among other things, a company’s emissions, use of resources and positive sustainability activities. 

The Social pillar looks at things like labour practices, supply chain standards and employee development. Governance covers topics such as shareholder rights, corporate responsibility and diversity at board level.

Hydrocarbon-containing materials found in Earth’s crust that are extracted and burned as fuel. Fossil fuels are derived from organic matter such as the remains of dead animals and plants that have usually decomposed over millions of years. The most common fossil fuels are coal, oil and gas. The burning of these fuels releases vast amounts of carbon dioxide into the atmosphere and is a leading cause of climate change.

A unit of measurement, equal to one billion tonnes, used to quantify emissions. The phrase ‘gigatonne-scale’ is frequently used in reference to carbon removal, as this is the ideal scale for carbon removal to reach for the worst effects of climate change to be avoided. The IPCC has stated that we need to remove ten gigatonnes of CO₂ per year by 2050 to keep global temperatures from rising above 1.5°C.

Gigatonnes, and tonnes more widely, fall under the metric system, while the ‘ton’ is an imperial measurement. A tonne can sometimes be referred to as a ‘metric ton’ to avoid confusion with similarly named units of measurement in the imperial system.

The long-term heating of Earth’s surface due to human activities since the beginning of the Industrial era. Global warming is caused by the release of greenhouse gases that trap heat in the atmosphere, leading to a temperature increase of around 0.2°C per decade.

‘Global warming’ was, for a long time, the primary term used to refer to Earth’s changing climate. However, it has its own distinct definition and shouldn’t be used interchangeably with ‘climate change’, which refers more broadly to both human and non-human causes of changing weather patterns.

A voluntary carbon offset programme focused on progressing the United Nations Sustainable Development Goals (SDGs) and ensuring that projects benefit their neighbouring communities.

An umbrella term to refer to gases including carbon dioxide, methane and nitrous oxide that trap heat in the atmosphere that cannot be dispelled, resulting in rising global temperatures.

A marketing strategy employed by companies or organisations looking to position themselves or their products as more environmentally conscious than they are.

A politically neutral, intergovernmental body of the United Nations, tasked with advancing scientific knowledge on climate change to aid in the creation of governmental policies to tackle the issue. To this end, the IPCC produces reports detailing options, often referred to as pathways, for halting the rate at which climate change is progressing.

A non-profit organisation offering accreditation to platforms and businesses operating in the voluntary carbon market. ICROA defines standards to ensure carbon credits and offset programmes are of the highest quality and are providing valuable impact., a leading carbon crediting platform specialising in carbon removal technology, recently became the first crediting programme with a focus on carbon removal to have their standard accredited by ICROA. A methodology for quantifying carbon removal from Enhanced Rock Weathering is the most recent to be added to the PURO portfolio. UNDO was part of a working group of scientists, environmentalists and industry experts that worked closely with to develop this methodology, so we’re very excited to see it endorsed by ICROA.

An independent, non-governmental organisation that develops, publishes and sells international standards across fields such as food safety, agriculture, healthcare and manufacturing. Its ISO 14000 branch covers standards relating to environmental management, providing companies with standards to implement to measure and improve their environmental impact and performance.

A social-justice framework that protects workers’ rights in the context of economic uncertainty caused by climate change, ensuring an equitable shift to sustainable energy and production that prioritises the needs of those whose livelihoods depend on the fossil fuel industry.

An international treaty that was effective between 1997 and 2020, compelling member states to commit to reducing greenhouse gas emissions. While it is a separate treaty rather than a successor, the Paris Agreement, adopted in 2015, is now the primary international treaty on climate change.

A methodology assessing the environmental performance of a product, service or process across its entire life cycle. An LCA takes into account the potential impact of, for instance, extraction of raw materials, energy use during manufacture, usage, eventual disposal and recycling possibilities. The International Organization For Standardization (ISO) offers guidance on conducting LCAs.

In the case of carbon removal technology, a life cycle analysis would take into account how the technology is powered (if it uses renewable energy, for example) as well as the environmental impact of storing and sequestering the CO₂.

A practice whereby crushed limestone, known as agricultural lime, is spread on farmland with the purpose of improving the quality of the soil. Limestone is rich in calcium and magnesium. It increases the soil’s pH, reduces acidity and boosts the absorption of key nutrients, improving overall crop yield.

Spreading crushed basalt rock on farmland has similar positive effects on soil health, raising the pH and reducing acidity. We estimate that by spreading basalt every three to five years, farmers can reduce the need for liming, saving money in the process.

A multi-step process employed to verify the positive impact of a climate project or mitigation method with the purpose of producing carbon credits. First, the project or mitigation activity is carefully measured in terms of its impact in lowering carbon emissions over a specific period of time. This data is then reported to an accredited third party, which verifies the data and converts it into carbon credits.

A unit of measurement equal to one million tonnes. Like gigatonne, megatonne is used to quantify greenhouse gas emissions and discuss carbon removal targets.

As with gigatonnes and tonnes in general, the megatonne is a metric, rather than imperial, measurement.

A type of experiment, normally conducted outdoors, which examines organisms and/or the natural world within a controlled environment. Mesocosm experiments are typically medium in scope and are seen as a bridge between laboratory experiments and field studies, which have micro and macro focuses respectively.

The natural process whereby organic matter is converted over time into mineral nutrients. In the carbon removal industry, ‘mineralisation’ also refers to the act of injecting CO₂ into rock for permanent storage.

A state achieved when the amount of greenhouse gas emissions is balanced by the amount of emissions that are removed. In order for a company to achieve net-zero status, emissions must be reduced – not just offset or neutralised – across all areas of the business. Net zero is typically seen as a long-term goal for organisations and industries. The Paris Agreement denotes that in order to stay below the 1.5°C warming threshold, we must globally reach net-zero emissions by 2050.

When atmospheric CO₂ is absorbed by the world’s oceans, their pH reduces and they become more acidic. Ocean acidification leads to environmental challenges such as bleached coral reefs and the poor health of fish populations. 

Enhanced rock weathering produces bicarbonate ions that are washed out to sea, where they contribute to the deacidification process. These ions are necessary for the formation of shells and skeletons in many marine creatures, organic matter which eventually falls to the ocean floor, forming carbonate rocks that store carbon for millions of years.

In carbon removal, permanence refers to the length of time for which carbon dioxide is sequestered. Different methods of removal offer different lengths of time and their permanence can be affected by external conditions and factors. For example, afforestation and reforestation generally sequester CO₂ for around 100 years, and can be impacted by outside threats such as fires. Enhanced rock weathering sequesters carbon for hundreds or thousands of years which, in terms of humanity, is effectively permanent.

A carbon crediting platform specialising in carbon removal technology. Its accreditation programme, the Puro Standard, is the first standard for engineered carbon removal methods in the voluntary carbon market.

The process of repopulating an area of historically forest-covered land with trees following deforestation of the area.

An approach to agriculture that prioritises soil health and the general improvement of biodiversity through various sustainable farming practices. With its roots in indigenous cultures, regenerative farming contributes to climate change mitigation through strengthening carbon sequestration.

Systems of energy generation that do not rely on the extraction and burning of fossil fuels and can be sustainably renewed without causing a rise in carbon emissions. The most common forms of renewable energy are wind and solar power.

A company’s emissions can be categorised in three groups.

Scope 1 Emissions refers to the greenhouse gases emitted as a direct result of the company’s operations, for example from its boilers or vehicles.

Scope 2 Emissions are emissions generated indirectly, for example by paying an energy company to produce electricity on its behalf to be consumed by the company.

Scope 3 Emissions covers all other indirect emissions that result from a company’s operations, from the emissions generated by the use of their products once purchased by customers, to business travel and emissions caused by employee commutes.

If a company wishes to achieve net zero, they must reduce emissions across all three scopes.

The changing over time of the pH of soil to become more acidic, leading to stunted growth in plants and lower crop yield. Soil acidification occurs when acids, such as nitric and sulfuric acids, react with the soil; it can also be due to the leaching of key soil nutrients such as calcium, magnesium, sodium and potassium. Pollution from the burning of fossil fuels, as well as agricultural practices such as monocultures and increased use of synthetic fertilisers, are contributing factors to soil acidification.

The weathering of silicate rocks, such as basalt, supports deacidification. Enhanced rock weathering accelerates this process, replenishing key alkalising minerals and nutrients to increase the soil’s pH.

A term to describe carbon stored in Earth’s soil. Carbon present in the soil consists of both organic carbon and inorganic carbon.

Soil organic carbon is made up of organic matter such as decomposing plant and animal remains, charcoal and soil microbes.

Soil inorganic carbon consists of mineral carbon, namely carbonates, produced through natural or enhanced weathering processes. 

Both organic and inorganic soil matter constitute important carbon sinks. Proper health and management of soil is crucial in ensuring it does not release sequestered carbon. Intensive agricultural practices, such as cultivation and grazing, as well as fires and forest management, can disrupt soil health and cause soil carbon to be emitted.

An international treaty on climate change, negotiated and signed by 195 countries. The treaty’s main goal is to prevent global temperatures from rising above 2°C, with a preferred limit of 1.5°C. Although there’s no legal obligation to set specific targets, states which have signed the agreement must seek to mitigate the effects of climate change and report on their efforts.

A process through which a product, service or offering is assessed to ensure it meets and delivers certain standards and criteria. In the climate space, projects go through the validation and verification (V&V) process before being accredited and entering the carbon credits market.

Validation takes place first, at the project level. A project is evaluated on whether or not it meets the standards required to register for a particular accreditation programme or methodology, such as Verra.

Once a project has passed the validation stage, verification is conducted to ensure that its carbon credits deliver the outcomes outlined by the project, and can be measured and quantified in line with the accreditation programme’s requirements.

Validation and Verification is conducted by independent, third-party Validation/Verification Bodies (VVBs) as part of Measurement, Reporting and Verification (MRV).

Organisations that provide third-party analysis of data relating to climate change projects, as part of the Measurement, Reporting and Verification (MRV) process through which carbon credits are created.

A non-profit organisation that manages voluntary carbon markets and verifies carbon offsets to aid in governments’ and businesses’ carbon emissions reductions.

Wollastonite is a calcium-silicate mineral (CaSiO3) created when impure limestone, often in the presence of silica-bearing metamorphic rock, is subjected to high temperature and pressure. Though relatively rare, it can be found in large deposits across North America, China and India, and these places are its top producers. 

It is a bright white, relatively soft mineral with a Mohs hardness between 4.5 and 5. Wollastonite has a wide range of uses thanks to a unique chemical makeup, mineralogical structure and physical characteristics. The wollastonite we source at UNDO is mined and crushed specifically for spreading on agricultural land. It is so efficient at capturing carbon through the enhanced weathering process that UNDO can maintain a 90% carbon efficiency during the process. (IE. For every 100 tonnes of CO2 captured through spreading of wollastonite, we only use 10 tonnes of CO2 to mine, crush, haul and spread the rock.)