02 Jan 2024

Climate and environment glossary

This glossary was written by the CIEP’s Environmental Policy Working Group (EPWG) as part of their ongoing work, which has included preparing the CIEP’s Environmental and Energy Policy.

Would you like us to add any terms to this glossary? Contact our office.


1.5 degrees: the lower of the two targets to limit global average temperature increase set under the Paris Agreement. Climate scientists use ‘average global temperature rise’ as a way to measure how the climate has changed since the Industrial Revolution. They use computer models to test scenarios under different future climate conditions (see IPCC) so that the global community can set targets for global action to combat climate change.

In 1997, when the first global treaty on reducing greenhouse gas emissions was agreed, the aim was to limit ‘global warming’ to no more than 2 degrees (2°C) above the pre-industrial level. By 2015, with a great deal more evidence available of climate change and its impacts the goal was to strengthen this to ‘avoid dangerous climate change by limiting global warming to well below 2°C and pursuing efforts to limit it to 1.5°C’.



adaptation: communities, businesses, organisations, countries or regions making changes to ecological, social or economic systems in response to the actual or expected effects and impacts of climate change. Adaptations can range from building flood defences, setting up early warning systems for cyclones and switching to drought-resistant crops, to redesigning communication systems, business operations and government policies.

Source: https://unfccc.int/topics/resilience/resources/adaptation-committee-adaptation-forum-video-documentary-adapting-to-a-changing-climate
afforestation: creating new areas of forest on land that was not previously tree-covered. This is often promoted as universally positive (especially as a ‘carbon offsetting scheme’), but it is crucial to plant the right trees in the right places. For instance, a rush to plant fast-growing conifers on well-established peatland and heathland in the UK during the second half of the 20th century was ultimately halted once the true impact of damaging the existing peat bog carbon storage, or destroying rare or endangered habitats, was understood.
Anthropocene: an unofficial unit of geologic time, during which human activity is having a profound influence on climate and the environment. Many geologists and other scientists have suggested the Anthropocene began in 1950, when radioactive dust was widely scattered from nuclear bomb tests.
anthropogenic climate change: human-induced changes to the global atmosphere and therefore to global weather patterns via ‘global warming’, caused by burning fossil fuels and other practices that emit greenhouse gases (eg large-scale livestock farming, deforestation).

biodiversity: the biological variety and variability of life on Earth. Biodiversity tends to be measured by counting the number of species at the local level (eg by geographical region), but it can also be measured by assessing the number of genes in a given population. In 2017 scientists estimated that there are about 8.7 million species, but only around 1.2 million have been formally described.

Source: https://www.nature.com/articles/news.2011.498

bioeconomy: economic activity centred on harvesting renewable resources (in a sustainable manner) from land, fisheries and aquaculture environments and converting them into food and animal feed, or using them as raw materials for the pulp and paper industries and parts of the chemical, biotechnological and energy industries.

biomass/biofuel: organic material (biomass) such as certain crops, wood chips and animal waste, collected or grown specifically to be used as biofuels, either directly (eg woodchip-based heating systems) or indirectly (eg converted into ethanol or biodiesel). Biofuels are regarded as ‘renewable’ because they are quick to grow and they displace the use of fossil fuels that have been stored underground for millennia. They are sometimes also classed as ‘carbon neutral’ (taking in carbon dioxide from the atmosphere as they grow, then releasing the same amount when they are burned). However, this is controversial because some are grown on land suitable for growing food, and the vast quantities needed mean habitats are destroyed in favour of monoculture crops (eg miscanthus). There are also significant implications for water resources.

Further reading: http://www.fao.org/3/i0100e/i0100e05.pdf

bioregion: a region defined by characteristics of the natural environment, such as mountains and bodies of water, rather than by human divisions such as political boundaries.
biosphere: the ‘zone of life on Earth’, also known as the ecosphere (ie the sum of all ecosystems of the world).
birthstrikers: a movement of women who have chosen not to have children as a protest in response to the climate crisis and perceived collapse of civilisation. Further reading: https://www.theguardian.com/lifeandstyle/2019/mar/12/birthstrikers-meet-the-women-who-refuse-to-have-children-until-climate-change-ends


carbon calculator: a program or app that calculates the approximate amount of carbon dioxide produced by a person, household, business or organisation, etc.
carbon dioxide capture and storage (CCS): also known as ‘carbon capture and storage’, this refers to extracting the greenhouse gas carbon dioxide (CO2) emitted during the process of generating power from fossil fuels, then storing it deep underground under compression. The aim is to reduce the amount of GHG emissions in the atmosphere. See also sequestration.
carbon footprint: a calculation of the quantity of greenhouse gases (measured as carbon dioxide (CO2) equivalent) released into the atmosphere as a result of human activity. It is theoretically possible to calculate the carbon footprint of the world, a country, a community, a business, an individual, an event, a product, etc. Such calculations are also used as the basis for carbon offsetting. However, it can be very challenging to capture all the necessary information for such calculations. See embodied energy.
carbonisation/decarbonisation: the conversion of an organic substance into carbon or a carbon-containing residue through pyrolysis or destructive distillation. Carbonisation produces substances that can prove harmful if emitted and have a high carbon monoxide content. Decarbonisation means the reduction of the amount of carbon in the economy with the ultimate aim of eliminating it in modern life.
carbon neutral: a closed-cycle process that emits and absorbs equal amounts of greenhouse gas (measured in carbon dioxide equivalent). See also net zero emissions.
carbon tax: a fee imposed on businesses and organisations that burn carbon-based fuels (coal, gas, oil). Carbon taxes are seen as a way of reducing emissions by making it more expensive for businesses to use carbon-based fuels, with the aim of encouraging them to be more energy efficient.
circular economy: a system based on the principles of designing out waste and pollution by keeping materials and products in use and regenerating natural systems. A circular economy is one that exchanges the typical cycle of make, use, dispose in favour of as much reuse and recycling as possible.
climate crisis/climate emergency: terms commonly used to emphasise the urgent need to reduce the amount of human-induced (anthropogenic) climate change, which was identified by scientists in the second half of the 1800s. It was pinpointed as a matter for international concern in the mid 1960s, and acknowledged by global governments at the first United Nations environment conference in 1972. By 1990 global temperatures had risen by 0.3°–0.6°C since the 1890s and they have continued to rise. Although national and international efforts to curb global warming have increased, scientists and governments warn that the pace of change has not been sufficient, and must be quickly increased to prevent devastating global impacts (eg droughts, famine, storms, floods, melting icecaps).
climate denier/climate science denier: someone who entirely dismisses the existence of the climate crisis. See also climate sceptic.

climate disinformation: false online information that companies or entities spread about the climate crisis in order to target the climate policy agenda and confuse or mislead the public.

Further reading: https://www.isdglobal.org/disinformation/climate-disinformation/

climate justice: a term used to acknowledge the political, ethical and social aspects of the climate crisis. It connects the dots between the environmental crisis and inequality, human rights and gender rights issues, and the concept of economic social justice. It emphasises that those most affected by climatic extremes are often those least responsible for them and spotlights the historical responsibility of wealthy nations for the bulk of carbon emissions.
climate sceptic/climate science sceptic: someone who does not believe or accept the scientific evidence on climate change, often not wishing to engage in debate or have their views challenged. Most recently, individuals or online entities have been associating the climate crisis with conspiracy theories and actively spreading disinformation/misinformation on the issues. Most broadsheet newspapers now use the term climate denier for someone who entirely dismisses the existence of the climate crisis.
COP: acronym used to refer to the Conference of the Parties to the United Nations Framework Convention on Climate Change, sometimes known as the ‘Conference of the Parties’. This is the periodic meeting of all the countries that are Parties (ie signatories) to the Convention (also known as the UNFCCC). This COP is the ultimate governing body for coordinated global action on climate change. Its first meeting was in Berlin in 1995; COP 26 was held in Glasgow in 2021. Other UN organisations also have COPs, also related to the environment, such as the United Nations Convention to Combat Desertification (UNCCD).
coral bleaching: this occurs when coral loses its vibrant colour and turns white. Coral is bright and colourful because of microscopic algae that live in the coral. However, when the ocean environment changes (eg if it gets too hot) the coral becomes stressed and expels the algae living in its tissues, causing it to turn white. When a coral bleaches it is not dead, but if the stress is prolonged, bleached corals begin to starve and will eventually die if the stress is not relieved.
deforestation: the decrease in forest areas caused by humans converting the land to other purposes, such as agricultural croplands, urbanisation or mining activities. Eighty per cent of world deforestation is the result of agricultural practices such as the production of beef, soy, palm oil and rubber. As well as loss of trees, deforestation leads to biodiversity loss and the decline of wildlife populations, freshwater depletion and greenhouse gas emissions. Together agriculture and forestry account for 24 per cent of all global greenhouse gas emissions. Source: https://www.unep.org/resources/publication/financing-sustainable-land-use-people-and-planet
desertification: the process by which land becomes drier and degraded over time due to climate change and/or human activities.
downcycling: converting materials into something that has less economic value than the original materials. For example, old clothes can be downcycled into the materials needed for industrial carpeting. Source: BBC https://www.bbc.com/future/article/20200710-why-clothes-are-so-hard-to-recycle


Earth Overshoot Day: marks the date when humanity’s demand for ecological resources and services in a given year exceeds what Earth can regenerate in that year. Further reading: https://www.overshootday.org/
ecocide: crimes against nature, the definition of which is now recognised by the International Criminal Court.
ecoforestry (eco-forestry): a way to manage forests that prioritises sustainability rather than any financial returns. Some of the principles include looking at the entire ecosystem, protecting rare species, respecting the structure and natural make-up of the forest, encouraging regeneration, avoiding negative impacts on soil quality and limiting pesticide use.
ecofriendly (eco-friendly): an adjective used to describe something that does no harm to the environment or which may even bring a benefit to nature. It can be something produced or created, or a lifestyle choice. Other similar terms include ‘green’ or ‘environmentally friendly’. There is no international standard for measuring ecofriendliness, so decision-makers should check details when comparing products or services that use this term.
ecolinguistics: defined by the International Ecolinguistics Association as a discipline that explores the role of language in the life-sustaining interactions of humans, other species and the physical environment.
ecological anxiety/eco-anxiety: ‘a chronic fear of environmental doom’ as described by the American Psychiatric Association in 2017. Medical and psychiatric experts have started to gather research that suggests there is increasing public anxiety about the climate emergency and that people are feeling overwhelmed by the existential threat posed by the crisis. Further reading: https://www.apa.org/news/press/releases/2017/03/mental-health-climate.pdf
ecological footprint: how much land and water is needed to produce the resources used, and to absorb the waste produced, by an individual or a group (eg a business). See also carbon footprint.
ecological grief/ecogrief: a painful psychological response to the scale and speed of loss of biodiversity and other aspects of natural and human-made environmental breakdown. See also ecological anxiety/eco-anxiety.
ecopsychology (eco-psychology): a term coined in the 1960s that describes the psychology of humans and animals in relation to their natural environment. It was later used to study and expand the emotional connection between humans, the Earth and all sentient beings, with policymakers, healthcare providers and employers becoming increasingly aware of the great benefits of nature to human health.
ecosystems: a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit. Source: https://www.cbd.int/
ecosystem services: the various benefits that humans gain from a certain ecosystem. The term is often used in relation to land management and forestry. Ecosystem services include products such as food and water; regulation of floods, soil erosion and disease outbreaks; and non-material benefits such as the recreational and health benefits of natural areas.
ecotax: a tax levied on activities considered harmful to the environment, to prevent environmental harm and promote environmental benefit via economic incentives.
ecotherapy: therapeutic care that centres on the idea that nature has healing powers and can strengthen people’s mental resilience and wellbeing. It takes inspiration from the medical practices and traditions of indigenous populations. Practitioners may also use mindfulness techniques, alternative therapies or other activities such as yoga and tai chi.
effect: the outcomes for humans and biodiversity resulting from an environmental impact, such as loss of habitat and species from deforestation, higher global temperatures resulting from GHG emissions, or instances of asthma in humans due to pollution. Often incorrectly used interchangeably with impact. See impact.
electric vehicle (EV): a vehicle that runs on electricity rather than petrol or diesel fuel. It uses as a fuel source batteries that can be recharged at charging points.
electrification: the transition of power supplies away from direct burning of fossil fuels, including changes to systems and equipment that are currently powered directly by fossil fuels. The term is mainly in relation to transport, such as the electrification of buses, cars and delivery vehicles, but could also refer to the transition of gas-powered equipment to use electricity.
embodied energy: the total amount of energy used – directly and indirectly – in creating any item (from a paperclip to a passenger aircraft). Embodied energy (sometimes called embodied carbon) includes the energy used to transport the components (including packaging) and materials as well as the items themselves, from source to user. This measurement can be used to enable people to compare a wide range of products and choose those with lower embodied energy, such as building materials (concrete vs timber) or food products (eg tomatoes from England or Spain). See also carbon footprint.
emissions trading: a system whereby limits are set on the maximum amount of greenhouse gases that can be emitted by specific industry sectors in participating countries. Organisations that operate installations (eg gas-fired power stations) can trade permits, acquiring more if they exceed their allocation or selling surplus ones where their emissions are below that allocation. The limit on available permits creates a market for emissions permits.
environmental/climate refugee: someone forced from their home due to environmental conditions such as sea-level rise, usually as part of a group of people. The term applies to refugees fleeing sudden climatic extremes by moving across geographical borders, as well as to those moving within their own country/region. Disasters in 2020 triggered more than three-quarters (30.7 million) of the new internal displacements recorded worldwide (source: https://www.internal-displacement.org/global-report/grid2021/). Terms such as ‘climate change refugee’ or ‘environmental refugee’ have no legal basis in international refugee law, and there is also a growing consensus among concerned agencies, including the International Organization for Migration (IOM) and United Nations High Commissioner for Refugees (UNHCR) that their use is to be avoided.
environmentally sustainable: something designed to continue at the same rate or level of activity without any problems. However, the term ‘sustainable’ can be applied to a wide range of systems or activities, such as an organisation or a business/industry (ie it simply has the capacity to keep trading/operating) or the national economy (where it means non-inflationary). Therefore it is important to include the adverb ‘environmentally’ to emphasise the nature-related dimension over the purely economic. See sustainable development.
environmental management system (EMS): a well-established method for an organisation to first gain and then maintain control over its numerous environmental impacts.
environmental migrant: someone who is obliged to move from their home, land or local area – either temporarily or permanently – as a result of a sudden or longer-term climatic change, extreme weather events, lack of food, or conflict caused by food or water shortages, in search of a safer place to live and work. The UN Environmental Migration Portal notes that the term does not have an accepted legal definition, and that it is necessarily broad so that it encompasses a wide range of reasons for the movement of people. 
environmental stewardship: an organisation, business or individual taking responsibility for its impacts on the local and global environment. This can include responsible use and protection of the natural environment through conservation and sustainable practices to enhance ecosystem resilience and human wellbeing.


fast fashion: the relentless and quick production of poorly made clothing by high street mass retailers in order to offer ‘catwalk’-style clothes cheaply to consumers. It is often associated with slave labour or poor treatment of workers, pollution, waste and a throwaway mentality. See slow fashion.
feedback loops: processes that can either amplify or reduce the speed of change, such as climate change. An example of a positive (amplifying) climate feedback loop is the release of methane, which contributes to warming, from Arctic ice as it melts.
fish populations vs fish stocks: ‘fish populations’ refers to the number of fish in our oceans, whereas ‘fish stocks’ refers to fish as a source of food for human consumption. The latter term is being phased out by most organisations, with fish populations considered the more accurate term to describe the status of fisheries.

forest bathing: the act of spending time in nature to increase our wellbeing, find more peace and calm, and be reminded of our inherent connection to the environment. According to the National Trust, the term is the English translation of the Japanese phrase shinrin-yoku.

Source: https://www.nationaltrust.org.uk/discover/nature/trees-plants/a-beginners-guide-to-forest-bathing

fossil fuel: a source of combustible fuel associated with oil and its derivatives, such as natural gas, petrol/diesel, coal and coal products. Fossil fuels form through the decomposition of organic materials in the ground under pressure and heat, taking place over millennia.

fracking: a common abbreviation of ‘hydraulic fracturing’, which is the process of extracting difficult-to-reach resources of oil and gas (shale gas) from rock formations. This is achieved by drilling into the earth and injecting a mixture of water, sand and chemicals into the rock at high pressure, forcing the gas out of the rocks. Fracking is associated with pollution of underground aquifers, through the release of chemicals, and pollution of above-ground soils and watercourses, as well as noise associated with the vehicles travelling to/from fracking sites.

Source: https://www.bbc.co.uk/news/uk-14432401

geoengineering (geo-engineering): also known as climate engineering, this refers to human intervention in the Earth’s climate systems to reduce and reverse environmental harm. Examples include efforts to remove carbon dioxide from the atmosphere through carbon sequestration and carbon dioxide capture and storage.
global dimming: the reduction in the amount of light from the sun received at the Earth’s surface due to increased particulates in the atmosphere, such as pollution and dust resulting from human activity as well as from volcanic ash. These particulates absorb and reflect back light from the sun. They also become nuclei for water droplets to form around, leading to increased cloud cover, which in turn reflects light back into space before it can reach the Earth’s surface.
global heating vs global warming: some editorial house styles now prefer the term ‘global heating’ over ‘global warming’ to emphasise the urgency of the climate crisis. See 1.5 degrees.
global warming potential (GWP): a measure of the amount of heat absorbed by the various greenhouse gases (GHGs) in the atmosphere. Carbon dioxide (CO2) is the most prevalent GHG in the atmosphere and is given the GWP value of 1. When measuring global warming, the other greenhouse gases are measured in terms of carbon dioxide (CO2) equivalent, making it a useful way to understand the relative impact of different GHGs. For instance, the next most abundant GHG is methane (CH4), which has a GWP value of 25, making it 25 times more potent in terms of global warming potential than CO2.
greenhouse effect: the natural phenomenon whereby the sun’s energy warms the Earth and the Earth radiates the heat back out into the atmosphere, where some of that radiated energy is absorbed in the stratosphere (see ozone and ozone layer) such that not all of the heat is lost. This ‘greenhouse effect’ has enabled the Earth to support biodiversity, but if the greenhouse effect becomes too strong (i.e. the Earth and its atmosphere become too warm) weather patterns change, with potentially devastating consequences. The increase in greenhouse gas emissions is tipping the balance of the greenhouse effect, creating more warming of the Earth and disrupting its natural systems.
greenhouse gas emissions: greenhouse gases (GHGs) are constantly released (emitted) into the atmosphere as a result of natural processes (eg respiration, growth and excretion by plants and animals, rotting vegetation, earthquakes). Many are also absorbed/taken up from the atmosphere. In the context of climate change, GHG emissions refers to those emissions that are a direct result of human activities (farming, forestry, industrial activities and so on).
greenhouse gases (GHGs): gases in the atmosphere that contribute to the greenhouse effect. The main GHGs are carbon dioxide (CO2), methane (CH4) (see methane), nitrous oxide (N2O) and the fluorinated gases (hydrofluorocarbons, HFCs; perfluorocarbons, PFCs; sulfur hexafluoride, SF6; nitrogen trifluoride, NF3). See also sulfur.
greenwashing: making a statement about the environmental benefits of a product, process or business/organisation that does not stand up to rigorous (scientific) scrutiny.


impact: the processes and actions that have an effect on biodiversity and human health, either positive or negative. See also effect.

impact investing: investments in companies, organisations and funds that intend to generate a measurable, beneficial social or environmental impact alongside a financial return.

Source: thegiin.org

Industrial Revolution: the process of economic change from predominantly manual work to machine-based manufacture (in factories) and agriculture, to one dominated by industry and machine manufacturing, beginning in Britain in the late 18th century, and soon spreading to other parts of Europe and the USA.
Intergovernmental Panel on Climate Change (IPCC): compiles the scientific evidence for climate change and publishes a periodic Assessment Report (AR) on the three core aspects of climate change: the physical science basis; impacts, adaptation and vulnerability; and mitigation of climate change. The most recently published full report is AR5 (2014); sections of AR6 have been published, with the final report due in 2022.
ISO 14001: the International Standard for writing and implementing an environmental policy.
landfill: the practice of burying waste in the ground as a means of disposal. Where engineering practices are not applied (eg geotextile lining), this can result in leachate (the smelly liquid that forms as waste decomposes) getting into the soil and into groundwater and aquifers, causing pollution. Landfilling waste also leads to a build-up of methane gas as waste decomposes. This can be captured and used as a form of renewable power, but more often than not is flared – lit and burned to avoid potential explosions.
mangrove: a tree or shrub which grows in tidal, chiefly tropical, coastal swamps. Their tangled roots grow both above and below the water, forming a crucial part of the oceanic ecosystem by providing a habitat for many marine species. The tangled roots also help to filter dirty water as it flows into the sea. Mangroves are key in the fight against climate change because of their ability to store carbon – typically more than terrestrial forests.
methane: a gas with more than 80 times the warming power of carbon dioxide over the first 20 years after it reaches the atmosphere. Around 60 per cent of the world’s methane emissions are produced by human activities, mostly from agriculture, waste disposal and fossil fuel production. Methane is also present in large quantities in Arctic permafrost and will be released into the atmosphere as the permafrost melts, further intensifying warming. See also GWP; tipping point.

mitigation: efforts to reduce or prevent greenhouse gas emissions and other negative impacts. These efforts often involve using new technologies and renewable energies, making older equipment more energy efficient, or changing management practices or consumer behaviour. Mitigation can be as complex as a plan for a new city, or as simple as improvements to a cooking stove design. See also adaptation.


neoliberalism: a policy approach or philosophy that is commonly defined as characterised by a belief in sustained economic growth as the means to achieve human progress, confidence in free markets as the most efficient way of allocating resources, an emphasis on minimal state intervention in economic and social affairs, and commitment to the freedom of trade and capital.

net zero emissions: referring to the world as a whole, the IPCC defines net zero emissions as follows: ‘When anthropogenic emissions of greenhouse gases (GHGs) to the atmosphere are balanced by anthropogenic removals over a specified period.’

There are different ways to measure ‘net zero’ depending on which GHGs are involved (eg global warming potential, global temperature change potential) or factors such as time horizon. Achieving net zero emissions involves reducing the GHGs of an organisation, business, product or individual as far as possible, then using offsetting techniques – such as tree planting, selling surplus renewable energy to the electricity grid or buying carbon credits – so that a net zero (balance of emissions and removals of GHGs) is achieved. See also carbon neutral.

Note: ‘net zero’ may be used by some as a form of greenwashing, if the claim is not substantiated by quantifiable removal over a specified period.

ocean warming: higher ocean water temperatures, resulting from increasing atmospheric temperatures and thus increased amounts of heat being absorbed by oceans. Warmer water leads to lower levels of oxygen in oceans, affecting marine plants and animals. The phenomenon of coral bleaching is attributed to ocean warming.
ozone and the ozone layer: a form of oxygen created by ultraviolet light from the sun which converts oxygen molecules (O2) into ozone molecules (O3). This conversion generally happens in the Earth’s stratosphere, where the gas forms the ozone layer (‘ozone shield’), which protects the Earth from the full force of the sun’s ultraviolet radiation. Ozone is also present in the lower atmosphere (troposphere), where it is created from the interaction of pollutants such as nitrogen oxides and volatile organic compounds (VOCs), resulting in smog and poor air quality that can contribute to human health problems (eg asthma).
Paris Agreement: a legally binding international treaty on climate change. It was adopted by 196 Parties (states that have signed up to the agreement) at COP 21 in Paris on 12 December 2015 and came into force on 4 November 2016. Its goal is to limit global warming to well below 2°C, and preferably to 1.5°C (see 1.5 degrees), compared to pre-industrial levels. To achieve this long-term temperature goal, countries aim to reach global peaking of greenhouse gas emissions as soon as possible to achieve a climate-neutral world by mid-century.


reduce, reuse, recycle, replenish: an example of a variation of the ‘3 Rs – reduce, reuse, recycle’, used in relation to shopping or consumerism. As a customer/consumer, we’re encouraged to ‘reduce’ our consumption, ‘reuse’ the item for other purposes once its original function has ended (see downcycling), ‘recycle’ the item or product in order to divert what goes to landfill, and ‘replenish’ or ‘restore’ – to think about our own relationship with the environment, spending time with nature in order to refocus on what’s important. See waste hierarchy.

reforestation: the planting of trees on land that was previously forested. See also afforestation.

regenerative agriculture: farming and grazing practices that rebuild soil organic matter and restore degraded soil biodiversity, thus sequestering carbon and improving the water cycle.
renewable energy sources: useful energy from a source that is not depleted when used, such as solar energy (photovoltaics), solar thermal (water heated by the sun), geothermal (natural underground heat); onshore and offshore wind power, hydropower (water-driven power stations), heat pumps (ground-, air- or water-sourced), wave power and tidal power. In addition, biomass, biogas and energy-from-waste are classed as ‘renewable’ in some cases.
rewilding: allowing nature to recover, often after a period of exploitation. Areas of land are left to go ‘wild’ so that ecosystems can regenerate.
sequestration: the long-term extraction of carbon dioxide (CO2) from the atmosphere, which is then stored in solid or liquid form (eg using plants – specifically trees and grasses, soils, rock formations and the oceans).
sixth mass extinction event: the current rapid rate of species and habitat loss, considered by some scientists to indicate that we are undergoing a mass extinction event. Mass extinctions occur when the Earth loses around three-quarters of its species in a geologically short time interval.
slow fashion: the opposite of fast, cheap and poor-quality clothing. Slow fashion is a term that has gained ground as the fashion industry comes under scrutiny for its polluting manufacturing processes (accounting for 10 per cent of global carbon emissions and 20 per cent of wastewater. Source: https://www.bbc.com/future/article/20200310-sustainable-fashion-how-to-buy-clothes-good-for-the-climate). There is a call for brands to show more respect and fairness to the environment and the people behind the labels. Slow fashion focuses on sustainability, rejects excessive consumption, and involves producing better-quality garments that last longer. ‘Around 300,000 tonnes of unused clothes are burned or buried in landfill each year’ (source: Greenpeace). See also fast fashion.
sulfur: a chemical element significant for its presence in the greenhouse gas sulfur hexafluoride and in the gas sulfur dioxide, the precursor to acid rain. The International Union of Pure and Applied Chemistry (IUPAC) and the Royal Society of Chemistry use the f spelling variant, as do exam boards (eg AQA). However, the ph spelling variant persists in non-scientific contexts in British English.
sustainable development: development that meets the needs of the present without compromising the ability of future generations to meet their own needs. The term was coined in 1987 by Gro Harlem Brundtland, former Prime Minister of Norway and Chair of the Brundtland Commission. See also environmentally sustainable.


thermal comfort: the level of temperature and humidity that people, on average, find comfortable. This changes depending on numerous factors (eg age, health, activity, clothing). Maintaining thermal comfort is essential for people to live and work effectively, and may involve heating, cooling and (de)humidifying the indoor environment – which often involves the use of energy (and therefore greenhouse gas emissions).
tipping point: the point at which an irreversible chain of events is set in motion. For example, when global temperature rises to a certain level this will trigger a series of catastrophic events, such as the melting of polar ice leading to sea-level rise.
tree hugger: a derogatory term for someone who is concerned about protecting the natural world. The first ‘tree huggers’ were the 363 members of the Bishnoi branch of Hinduism who were killed in 1730 while trying to protect local trees from logging.
UNFCCC: United Nations Framework Convention on Climate Change. See COP.
upcycling: the process of transforming an item instead of throwing it away, changing it into something of greater creative and environmental value. ‘Upcycling’ is relatively recent term for a practice that has existed throughout history, particularly in the developing world. See also downcycling.
waste hierarchy: a tool for controlling and minimising the negative impact of waste, used by businesses and other organisations. It is often represented as a pyramid, from Prevention (Reduce) > Reuse > Recycle > Recovery > Disposal. See also reduce, reuse, recycle, replenish. Further reading: Waste-hierarchy-guidance.pdf
wet-bulb temperature (Tw): measured by covering a thermometer bulb with a damp cloth; as the water evaporates from the cloth it cools the thermometer, mimicking the effect of placing a damp cloth on a body to cool it down. A low wet-bulb temperature means that the air is drier (low humidity), so sweating will do its job of lowering body temperature. When the weather is hot and humidity is high, body temperature cannot be lowered by evaporation of sweat. Severe illness or even death can result from heat stress, and it can trigger other problems with breathing, heart attacks or strokes. At a wet-bulb temperature of over 35°C humans may not survive, even if there is unlimited water and shade, but that can also be true at lower levels (eg in the 2003 European heatwave thousands died although Tw was around 28°C). See thermal comfort.
zero carbon: causing or resulting in no net release of carbon emissions into the atmosphere. See also net zero emissions.

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