Cool roofs cut GHG emissions from electricity generation by lowering the amount of cooling required to condition indoor spaces, thereby decreasing the use of air conditioners. Using cool roofs in building design lowers electricity use, improves thermal comfort for building occupants, and is relatively cheap to deploy. However, its potential climate impact is relatively small, and its relevance is largely limited to hot climates where buildings need more cooling than heating to be thermally comfortable. Its application has mostly been in pilot projects, but we conclude that this solution is “Worthwhile” with potential for large-scale deployment.
Our analysis concludes that the projected climate impact of using cool roofs on buildings is not large enough to be globally significant (>0.1 Gt CO₂‑eq/yr ). However, we consider it “Worthwhile” because it helps reduce electricity consumption in buildings, makes indoor spaces more thermally comfortable, and lessens the urban heat island effect.
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | Yes |
| Evidence | Are there data to evaluate it? | Limited |
| Effective | Does it consistently work? | Yes |
| Impact | Is it big enough to matter? | No |
| Risk | Is it risky or harmful? | No |
| Cost | Is it cheap? | Yes |
Using cool roofs reduces the amount of electricity needed to cool indoor spaces, thereby cutting GHG emissions from electricity generation. Cool roofs are generally defined as light-colored roofs designed to reflect more sunlight and transfer less solar energy into the interior compared to traditional roofs, thereby reducing cooling loads. Cool roofs can be achieved by applying coatings or using roofing materials with a high solar reflectance index (SRI), which results from high solar reflectance and thermal emittance. These properties ensure that surface temperatures on cool roofs remain substantially cooler than conventional roofs.
Using cool roofs can effectively reduce the amount of air conditioning needed to cool indoor spaces, though their potential to cut annual electricity use in buildings and resulting GHG emissions is minimal. Nonetheless, evidence from real-world applications demonstrates that the surface temperatures of cool roofs can be as much as 28–30°C cooler than conventional roofs on extremely hot afternoons. Other studies have shown that cool roofs can decrease indoor air temperatures by 2–3°C while simultaneously reducing surrounding outdoor air temperatures by about 10°C, thereby minimizing the urban heat island effect.
Several organizations are deploying initiatives to drive cool roof adoption as a passive cooling strategy in the building sector. For example, C40 Cities previously launched a cool roofs program across New York City. Over a six-year period (2009–2015), the initiative resulted in nearly 530,000 m2 of building roof tops being retrofitted as cool roofs. As of 2023, the United States is estimated to have over 232 million m2 of installed cool roofs. Recently, the Million Cool Roofs Challenge organized by the Global Cool Cities Alliance resulted in 1.1 million m2 of additional cool roofs in 2022 across 10 countries, including Indonesia, Mexico, and Rwanda.
Some studies estimate that about 229 billion m2 of roof space existed as of 2022. Given the existing building stock – and the fact that the bulk of projected new construction by 2050 is expected in regions with hot climates – the impact of this potential solution could grow.
There are several advantages to using cool roofs in buildings. First, it is cheap to implement, and the incremental cost of applying new coatings or selecting light-colored roofing materials during construction is often minimal compared to conventional roofs. Second, it is expedient as a cooling strategy when buildings are not mechanically air-conditioned or designed to be naturally ventilated. This is important because many countries in hot climates (where cooling is generally required for indoor thermal comfort more than heating) also lack access to reliable electricity, thereby necessitating the use of passive measures in building design.
In addition, a recent analysis of 77 low- and middle-income countries determined that cooling systems are not readily available, sustainable, or affordable, especially for building applications, placing nearly 4 billion people at risk. Deploying scalable strategies such as cool roofs in buildings helps reduce exposure to these risks, which could lead to greater adoption and climate impact. Several studies have also shown that using cool roofs can help reduce indoor heat stress, especially in hot and humid environments. Others are exploring the concept of cool-colored roofs, where non-white roof materials can provide similar cooling effects while preserving aesthetic choice for building owners and developers.
Despite the advantages of using cool roofs as a potential climate solution, a few challenges exist. Some studies have shown that cool roofs can slightly increase heating loads during winter, especially in cold climates. However, other studies conclude that the increase is marginal and often inconsequential. Another concern is that cool roofs can produce glare as the incident sunlight is reflected. This could adversely impact building users if the buildings with cool roofs are surrounded by taller structures with daytime occupancy, such as offices, which is an increasing reality in urban spaces. Lastly, we found examples of pilot projects and resources for cool roofs, but could not find reliable datasets for a comprehensive assessment of their current impact. Addressing such data gaps could help drive cool roofs research, integration into industry practices and building codes, and, ultimately, greater adoption.
Bamdad, K. (2023). Cool roofs: A climate change mitigation and adaptation strategy for residential buildings. Building and Environment, 236, Article 110271. Link to source: https://doi.org/10.1016/j.buildenv.2023.110271
C40 Cities. (2015, January). NYC CoolRoofs. C40 Cities Leadership Group, Inc. Link to source: https://www.c40.org/case-studies/nyc-coolroofs/#:~:text=The%20NYC%20%C2%B0CoolRoofs%20program%2C%20launched%20in%202009%2C,(GHG)%20and%20also%20directly%20cooling%20the%20city.
Challenge Works. (n.d.). Million cool roofs challenge. Retrieved January 16, 2026, from Link to source: https://challengeworks.org/challenge-prizes/million-cool-roofs-challenge/
Cool Roof Paint. (2025, November). Cool roof vs conventional roof. Link to source: https://www.coolroofpaint.com/cool-roof-vs-conventional-roof/
Cool Roof Rating Council. (n.d.). Resources: What is a cool roof? Retrieved December 22, 2025, from Link to source: https://coolroofs.org/resources/what-is-a-cool-roof
Energy Star. (n.d.). Cool roofs. U.S. Environmental Protection Agency. Retrieved January 05, 2026, from Link to source: https://www.energystar.gov/products/cool-roofs
Heat Island Group. (n.d.). Cool science. Energy Technologies Area, Berkeley Lab. Retrieved December 23, 2025, from Link to source: https://heatisland.lbl.gov/coolscience/cool-roofs
Hosseini, M., Lee, B., & Vakilinia, S. (2017). Energy performance of cool roofs under the impact of actual weather data. Energy and Buildings, 145, 284–292. Link to source: https://doi.org/10.1016/j.enbuild.2017.04.006
Market Reports World. (2025, December 29). Cool Roofs Market Size, Share, Growth, and Industry Analysis, By Type (PVC(Polyvinyl Chloride), EPDM(Rubber), TPO(Thermoplastic)), By Application (Residential Buildings, Non-Residential Buildings), Regional Insights and Forecast to 2033. Link to source: https://www.marketreportsworld.com/market-reports/cool-roofs-market-14716807
Nutkiewicz, A., Mastrucci, A., Rao, N. D., & Jain, R. K. (2022). Cool roofs can mitigate cooling energy demand for informal settlement dwellers. Renewable and Sustainable Energy Reviews, 159, Article 112183. Link to source: https://doi.org/10.1016/j.rser.2022.112183
Sustainable Energy For All. (2022). Chilling prospects 2022: The million cool roofs challenge. Link to source: https://www.seforall.org/data-stories/million-cool-roofs-challenge
Sustainable Energy For All. (2025, July). Chilling prospects: Tracking sustainable cooling for all 2025. Link to source: https://www.seforall.org/data-stories/chilling-prospects-2025
U.S. Department of Energy. (n.d.). Cool roofs. Retrieved December 22, 2025, from Link to source: https://www.energy.gov/energysaver/cool-roofs
U.S. Environmental Protection Agency. (2025, May 30). Using cool roofs to reduce heat islands. Link to source: https://www.epa.gov/heatislands/using-cool-roofs-reduce-heat-islands
Ürge-Vorsatz, D., Chatterjee, S., Cabeza, L. F., & Molnár, G. (2025). Global and regional estimation and evaluation of suitable roof area for solar and green roof applications. Developments in the Built Environment, 21, Article 100607. Link to source: https://doi.org/10.1016/j.dibe.2025.100607
Henry Igugu, Ph.D.
Christina Swanson, Ph.D.
Greenhouse gas quantity expressed relative to CO₂ with the same warming impact over 100 years, calculated by multiplying emissions by the 100-yr GWP for the emitted gases.
Greenhouse gas quantity expressed relative to CO₂ with the same warming impact over 20 years, calculated by multiplying emissions by the 20-yr GWP for the emitted gases.
8th World Congress on Conservation Agriculture
Reducing greenhouse gas concentrations in the atmosphere by preventing or reducing emissions.
Air conditioning
A liquid with a low pH (below 7).
The process of increasing acidity.
The extent to which emissions reduction or carbon removal is above and beyond what would have occurred without implementing a particular action or solution.
An upper limit on solution adoption based on physical or technical constraints, not including economic or policy barriers. This level is unlikely to be reached and will not be exceeded.
The quantity and metric to measure implementation for a particular solution that is used as the reference unit for calculations within that solution.
A composting method in which organic waste is processed in freestanding piles that can be aerated actively with forced air or passively by internal convection.
The interactions of aerodynamic forces and flexible structures, often including the stucture's control system.
A process in which microbes break down organic materials in the presence of oxygen. This process converts food and green waste into nutrient-rich compost.
Establishment of new forests in areas that did not historically support forests.
Farming practices that work to create socially and ecologically sustainable food production.
Addition of trees and shrubs to crop or animal farming systems.
Artificial intelligence
Spread out the cost of an asset over its useful lifetime.
A process in which microorganisms break down organic material in the absence of oxygen. Methane and CO₂ are the main byproducts.
A crop that live one year or less from planting to harvest; also called annual.
aerated static piles
Electric power delivered at a steady, around-the-clock rate, to cover power demand that exists at all times. Baseload power is typically supplied by high availability, low operating-cost plants, such as nuclear or geothermal.
A liquid with a high pH (above 7).
black carbon
Solar panels that generate electricity from sunlight captured on both sides, increasing energy output by reflecting light from the ground and surroundings.
Made from material of biological origin, such as plants, animals, or other organisms.
A renewable energy source generated from organic matter from plants and/or algae.
An energy source composed primarily of methane and CO₂ that is produced by microorganisms when organic matter decomposes in the absence of oxygen.
Carbon stored in biological matter, including soil, plants, fungi, and plant products (e.g., wood, paper, biofuels). This carbon is sequestered from the atmosphere but can be released through decomposition or burning.
Living or dead renewable matter from plants or animals, not including organic material transformed into fossil fuels. Peat, in early decay stages, is partially renewable biomass.
Biogas refined to the same quality as natural gas. CO₂
and impurities are removed, and the biomethane can be distributed and used in existing natural gas technologies.
A type of carbon sequestration that captures carbon from CO₂ via photosynthesis and stores it in soils, sediments, and biomass, distinct from sequestration through chemical or industrial pathways.
A synthetic organic compound used to make a type of hard, clear plastic for food and drink packaging and many consumer goods.
A climate pollutant, also called soot, produced from incomplete combustion of organic matter, either naturally (wildfires) or from human activities (biomass or fossil fuel burning).
A secure, decentralized way of digitally tracking transactions that could be used to improve the transparency and efficiency of carbon markets.
Fixed income debt instruments focused on sustainable ocean projects. Blue bonds work in the same manner as traditional bonds and may be issued by corporations, financial institutions, and governments.
A global initiative launched by Germany and the IUCN in 2011 to restore 150 Mha of land by 2020 and 350 Mha by 2030.
High-latitude (>50°N or >50°S) climate regions characterized by short growing seasons and cold temperatures.
bisphenol A
Revenue from carbon credits reserved for payout to land- and rights-holders in the event of a disturbance such as a fire; similar to insurance scheme.
The components of a building that physically separate the indoors from the outdoor environment.
Businesses involved in the sale and/or distribution of solution-related equipment and technology, and businesses that want to support adoption of the solution.
Compound annual growth rate
A chemical reaction involving heating a solid to a high temperature; to make cement clinker, limestone is calcined into lime in a process that requires high heat and produces CO₂.
The ratio of the actual electricity an energy technology generates over a period of time to the maximum it could have produced if it operated continuously at full capacity.
A four-wheeled passenger vehicle.
Average number of people traveling in a car per trip.
Technologies that collect CO₂ before it enters the atmosphere, preventing emissions at their source. Collected CO₂ can be used onsite or in new products, or stored long term to prevent release.
A greenhouse gas that is naturally found in the atmosphere. Its atmospheric concentration has been increasing due to human activities, leading to warming and climate impacts.
Total GHG emissions resulting from a particular action, material, technology, or sector.
Amount of GHG emissions released per activity or unit of production.
A marketplace where carbon credits are purchased and sold. One carbon credit represents activities that avoid, reduce, or remove one metric ton of GHG emissions.
A colorless, odorless gas released during the incomplete combustion of fuels containing carbon. Carbon monoxide can harm health and be fatal at high concentrations.
The time it takes for the emissions reduction from a measure to equal the emissions invested in implementing the measure.
Activities or technologies that pull CO₂ out of the atmosphere, including enhancing natural carbon sinks and deploying engineered sinks.
Long-term storage of carbon in soils, sediment, biomass, oceans, and geologic formations after removal of CO₂ from the atmosphere or CO₂ capture from industrial and power generation processes.
The interconnected pool of dissolved inorganic carbon forms in water. Composed of dissolved CO₂, carbonic acid, bicarbonate ions, and carbonate ions.
carbon capture and storage
carbon capture, utilization, and storage
Cooling degree days
A binding ingredient in concrete responsible for most of concrete’s life-cycle emissions. Cement is made primarily of clinker mixed with other mineral components.
chlorofluorocarbon
Processes that use chemical reactions or heat to break down plastic waste into basic molecular components or feedstocks that can then be used to make new plastic products.
Process that uses chemical reactions or heat to break down plastic waste into basic molecular components that can be used to make new plastic products.
methane
A system in which resources, materials, and products are used for as long as possible through reuse, repair, refurbishment, and recycling.
Energy sources that have little to no negative environmental or climate impacts during operation relative to fossil fuel–based energy sources.
Gases or particles that have a planet-warming effect when released to the atmosphere. Some climate pollutants also cause other forms of environmental damage.
Areas that have natural buffers from local climate change impacts, offering safe havens for species and ecosystems.
A binding ingredient in cement responsible for most of the life-cycle emissions from cement and concrete production.
A waste management process where waste is made into the same original product, preserving quality and value so materials can be reused multiple times while keeping resources in continuous use.
A system that encompasses both forward supply chains (from producer to consumer) and reverse logistics for reuse, recycling, or proper disposal.
Neighbors, volunteer organizations, hobbyists and interest groups, online communities, early adopters, individuals sharing a home, and private citizens seeking to support the solution.
A solution that potentially lowers the benefit of another solution through reduced effectiveness, higher costs, reduced or delayed adoption, or diminished global climate impact.
The average annual rate at which a value grows over a specified period, assuming profits are reinvested and growth occurs steadily each year.
Funding with substantially more generous terms than market loans (typically due to lower interest rates, longer repayment periods, or partial grants) used to support projects with public or development benefits.
A farming system that combines reduced tillage, cover crops, and crop rotations.
The proportion of water used or applied that is evaporated, transpired, or incorporated into a product and therefore is not returned to the local hydrological system through runoff or leaching.
Risk-sharing financial agreements in which two parties (e.g., renewable generator, government) guarantee a fixed price (e.g., electricity price). If market prices fluctuate, one party pays the other the difference.
Persistent long, thin clouds that form behind aircraft when water vapor in the exhaust condenses, then freezes into ice crystals at high altitudes.
A measure of the total space cooling demand to maintain an indoor temperature below 24 °C
carbon dioxide
A measure standardizing the warming effects of greenhouse gases relative to CO₂. CO₂-eq is calculated as quantity (metric tons) of a particular gas multiplied by its GWP.
carbon dioxide equivalent
Plant materials left over after a harvest, such as stalks, leaves, and seed husks.
A granular material made by crushing broken or waste glass.
direct air capture
Financial agreements in which government creditors forgive a portion of debt in exchange for specific conservation commitments.
The process of cutting greenhouse gas emissions (primarily CO₂) from a particular sector or activity.
An industrial process that removes printing ink from used or waste paper fibers, creating clean pulp that can be turned into new paper products.
A solution that works slower than gradual solutions and is expected to take longer to reach its full potential.
Microbial conversion of nitrate into inert nitrogen gas under low-oxygen conditions, which produces the greenhouse gas nitrous oxide as an intermediate compound.
Electronic document that verifies whether a product has been manufactured according to environmental and social standards and/or material origins, environmental impact, and disposal recommendations.
Electronic documents that verify whether or not a product has been manufactured according to environmental and social standards and/or material origins, environmental impact, and disposal recommendations.
Greenhouse gas emissions produced as a direct result of the use of a technology or practice.
Electric power that can be increased, decreased, or turned on/off to match real-time fluctuations in grid conditions. Typically supplied by fast-responding plants such as natural gas, hydroelectric, or battery storage.
The inorganic forms of carbon dissolved in seawater. Composed of dissolved CO₂, carbonic acid, bicarbonate ions, and carbonate ions.
A system of underground distribution pipes that supply heat from centralized sources to a large number of buildings for space and water heating or industrial use.
A window consisting of two glass panes separated by a sealed gap and typically filled with air or an inert gas to improve the heat flow resistance.
A waste management system that transforms waste into different products of lower quality and value, making materials harder to recycle again and limiting reuse.
Flexible benchmarks derived from independent, publicly available, frequently updated data sets.
European Energy Agency
Ability of a solution to reduce emissions or remove carbon, expressed in CO₂-eq per installed adoption unit. Effectiveness is quantified per year when the adoption unit is cumulative over time.
Enhanced geothermal system
Exajoule (one quintillion joules)
A process that uses electric current to drive a reaction, such as using electricity to split water molecules into hydrogen and oxygen.
Produced by electrolysis.
Greenhouse gas emissions accrued over the lifetime of a material or product, including as it is produced, transported, used, and disposed of.
Solutions that work faster than gradual solutions, front-loading their impact in the near term.
Methane produced by microbes in the digestive tracts of ruminant livestock, such as cattle, sheep and goats.
The unintended capture of organisms in intake flows.
Environmental Protection Agency
Extended Producer Responsibility
expanded polystyrene
Environmental Research & Education Foundation
environmental, social, and governance
exchange-traded fund
A process triggered by an overabundance of nutrients in water, particularly nitrogen and phosphorus, that stimulates excessive plant and algae growth and can harm aquatic organisms.
Electric vehicle
The movement of water from the earth’s surface to the atmosphere directly from land or water surfaces (evaporation) and through plant tissues (transpiration).
The scientific literature that supports our assessment of a solution's effectiveness.
A policy framework that assigns responsibility to producers for the end-of-life servicing of their products.
A group of human-made molecules that contain fluorine atoms. They are potent greenhouse gases with GWPs that can be hundreds to thousands times higher than CO₂.
Food, agriculture, land, and ocean
Food and Agriculture Organization of the United Nations
feed conversion ratio
The efficiency with which an animal converts feed into increased body mass, measured as the ratio of the weight of the feed given to weight gain. Lower FCR means less feed for the same growth.
Raw material inputs for manufacturing, processing, and managing waste.
Containing or consisting of iron.
A measure of fishing activity over time and area, commonly measured by number of trips, vessel time, or gear deployed.
A solar PV system with panels mounted at a constant angle.
Glass is manufactured by floating molten glass on a molten tin bath, producing a smooth, flat product with high optical clarity, often used for window applications.
food loss and waste
Food discarded during pre-consumer supply chain stages, including production, harvest, and processing.
Food discarded during pre-consumer supply chain stages, including production, harvest, and processing, along with food discarded wt the retail and consumer stages of the supply chain.
Food discarded at the retail and consumer stages of the supply chain.
Combustible materials found in Earth's crust that can be burned for energy, including oil, natural gas, and coal. They are formed from decayed organisms through prehistoric geological processes.
Free, prior, and informed consent
A principled process of working with Indigenous communities that requires consent from Indigenous peoples for any decision, action, or activity that impacts their community and/or lands.
Unintentional leaks of gases or vapor into the atmosphere.
A group of countries representing the majority of the world's population, trade, and GDP. There are 19 member countries plus the European Union and the African Union
Gas collection and control system
A design or approach to policy, programs, or activities that addresses the different situations, roles, needs, and interests of women, men, girls, and boys.
Manipulating the environment to influence the quantities or impact of climate pollutants in the atmosphere.
greenhouse gas
Global Horizontal Irradiance
gigajoule or billion joules
The glass layers or panes in a window.
A measure of how effectively a gas traps heat in the atmosphere relative to CO₂. GWP converts greenhouse gases into CO₂-eq emissions based on their 20- or 100-year impacts.
A solution that has a steady impact on the atmosphere. Effectiveness is expected to be constant over time rather than having a higher impact in the near or long term.
A system that uses the slope of a field and furrows, borders, or flooding to apply water without pumping.
Hydrogen produced from natural gas, most commonly by combining heated steam with methane. Producing grey hydrogen emits CO₂ and leaks methane. Most hydrogen made today is grey.
A fixed income debt instrument focused on sustainable projects. Green bonds work in the same manner as traditional bonds and may be issued by corporations, financial institutions, and governments.
A fixed income debt instrument focused on sustainable projects. They work in the same manner as traditional bonds and may be issued by corporations, financial institutions, and governments.
Hydrogen gas made through electrolysis using electricity produced onsite using renewable energy sources.
The practice of charging more for renewable energy than for conventional energy to cover added costs .
Roofs that are designed to be partially or completely covered in vegetation.
Biomass discarded during landscaping and gardening.
A gas that traps heat in the atmosphere, contributing to climate change.
The makeup of electricity generation on a power grid, showing the share contributed by various energy sources (e.g., coal, natural gas, nuclear, wind, solar, hydro) relative to total electricity production.
A process by which GHGs dissolved in groundwater are released to the atmosphere when the groundwater is extracted from the aquifer.
metric gigatons or billion metric tons
global warming potential
A low-carbon steel-making technology that uses hydrogen from water, direct reduction of iron, and electric arc furnaces.
hectare
household air pollution
A sector or process that is exceptionally challenging to decarbonize, often because of a lack of mature technology options.
hydrochlorofluorocarbon
Number of years a person is expected to live without disability or other limitations that restrict basic functioning and activity.
A measure of the total space heating demand to maintain an indoor temperature above 18 °C
A unit of land area comprising 10,000 square meters, roughly equal to 2.5 acres.
Hybrid electric car
hydrofluorocarbon
hydrofluoroolefin
hydrofluoroolefin
high-income countries
Metal waste that is produced at a mill or foundry during the metal production process and recycled internally.
Particles and gases released from use of polluting fuels and technologies such as biomass cookstoves that cause poor air quality in and around the home.
heating, ventilation, air conditioning, and refrigeration
Organic compounds that contain hydrogen and carbon.
Human-made F-gases that contain hydrogen, fluorine, and carbon. They typically have short atmospheric lifetimes and GWPs hundreds or thousands times higher than CO₂.
Human-made F-gases that contain hydrogen, fluorine, and carbon, with at least one double bond. They have low GWPs and can be climate-friendly alternatives to HFC refrigerants.
Hydrogen is a gas that can be a fuel, feedstock, or means of storing energy. It generates water instead of GHG when burned, but the process of producing it can emit high levels of GHGs.
A recycling process that separates fibers from contaminants for reuse. Paper or cardboard is mixed with water to break down fibrous materials into pulp.
internal combustion engine
International Energy Agency
Aerobic decomposition of organic waste in a sealed container or bin/bay system.
Greenhouse gas emissions produced as a result of a technology or practice but not directly from its use.
A solid block of purified silicon formed by melting and crystallizing raw silicon; it serves as the base material for slicing into wafers used in solar cells.
Device used to power vehicles by the intake, compression, combustion, and exhaust of fuel that drives moving parts.
The annual discount rate that balances net cash flows for a project over time. Also called IRR, internal rate of return is used to estimate profitability of potential investments.
Individuals or institutions willing to lend money in search of a return on their investment.
Intergovernmental Panel on Climate Change
Indigenous peoples’ land
Integrated pest management.
internal rate of return
The timing and amount of irrigation water applied.
International Union for Conservation of Nature
The most comprehensive global list of species threatened with extinction, maintained by the International Union for Conservation of Nature.
International agreement adopted in 2016 to phase down the use of high-GWP HFC F-gases over the time frame 2019–2047.
A measure of energy equivalent to the energy delivered by 1,000 watts of power over one hour.
kiloton or one thousand metric tons
kilowatt-hour
The intentional or unintentional act of property use crossing ownership boundaries without permission.
A land-holding system, e.g. ownership, leasing, or renting. Secure land tenure means farmers or other land users will maintain access to and use of the land in future years.
Gases, mainly methane and CO₂, created by the decomposition of organic matter in the absence of oxygen.
levelized cost of electricity
leak detection and repair
Regular monitoring for fugitive methane leaks throughout oil and gas, coal, and landfill sector infrastructure and the modification or replacement of leaking equipment.
Relocation of emissions-causing activities outside of a mitigation project area rather than a true reduction in emissions.
The rate at which solution costs decrease as adoption increases, based on production efficiencies, technological improvements, or other factors.
Percent decrease in costs per doubling of adoption.
A metric describing the expected break-even cost of generating electricity per megawatt-hour ($/MWh), combining costs related to capital, operation, and fuel (if used) and dividing by total output over the generator's lifetime.
landfill gas
Greenhouse gas emissions from the sourcing, production, use, and disposal of a technology or practice.
A process that converts biomass, plastics, or other solid wastes into liquid fuel or chemicals.
The total weight of an organism before any meat processing.
low- and middle-income countries
liquefied petroleum gas
land use change
A measure of the amount of light produced by a light source per energy input.
live weight
Mobility as a Service
marginal abatement cost curve
Livestock grazing practices that strategically manage livestock density, grazing intensity, and timing. Also called improved grazing, these practices have environmental, soil health, and climate benefits, including enhanced soil carbon sequestration.
A tool to measure and compare the financial cost and abatement benefit of individual actions based on the initial and operating costs, revenue, and emission reduction potential.
Periods of unusually warm ocean temperatures that typically last from days to months and can affect large areas of the ocean.
Defined by the International Union for Conservation of Nature as: "A clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values." References to PAs here also include other effective area-based conservation measures defined by the IUCN.
The transfer of economic activity or environmental impact from one area to another as a result of conservation activities, often having the effect of reducing or offsetting intended benefits.
The transfer of economic activity or environmental impact from one location to another as a result of conservation activities, often having the effect of reducing or offsetting intended benefits.
A facility that receives recyclable waste from residential, commercial, and industrial sources; separates, processes, and prepares them; and then sells them to manufacturers for reuse in new products.
A measure of energy equivalent to the energy delivered by one million watts of power over one hour.
A greenhouse gas with a short lifetime and high GWP that can be produced through a variety of mechanisms including the breakdown of organic matter.
A measure of mass equivalent to 1,000 kilograms (~2,200 lbs).
million hectares
The natural process by which microbes convert matter to energy, often producing CO₂ or other GHGs as a byproduct.
Soils mostly composed of inorganic materials formed through the breakdown of rocks. Most soils are mineral soils, and they generally have less than 20% organic matter by weight.
A localized electricity system that independently generates and distributes power. Typically serving limited geographic areas, mini-grids can operate in isolation or interconnected with the main grid.
Reducing the concentration of greenhouse gases in the atmosphere by cutting emissions or removing CO₂.
megajoule or one million joules
Digital platform that integrates transport modes such as public transit, carpooling, and bike sharing into a single service, allowing users to plan, book, and pay for multimodal trips through one application.
Percent of trips made by different passenger and freight transportation modes.
A condition of being diseased, unhealthy, or injured.
Marine Protected Area
materials recovery facility
Municipal solid waste
megaton or million metric tons
Materials discarded from residential and commercial sectors, including organic waste, glass, metals, plastics, paper, and cardboard.
megawatt
Megawatt-hour
micro wind turbine
square meter kelvins per watt (a measure of thermal resistance, also called R-value)
nitrous oxide
The enclosed housing at the top of a wind turbine tower that contains the main mechanical and electrical components of the turbine.
A commitment from a country to reduce national emissions and/or sequester carbon in alignment with global climate goals under the Paris Agreement, including plans for adapting to climate impacts.
A gaseous form of hydrocarbons consisting mainly of methane.
Chemicals found in nature that are used for cooling and heating, such as CO₂, ammonia, and some hydrocarbons. They have low GWPs and are ozone friendly, making them climate-friendly refrigerants.
The rate of primary production for photosynthetic organisms, excluding the carbon they respire for their own metabolic processes.
The rate at which photosynthetic organisms convert carbon dioxide into organic matter, minus the carbon they respire for their own metabolic processes.
Microbial conversion of ammonia or ammonium to nitrite and then to nitrate under aerobic conditions.
A group of air pollutant molecules composed of nitrogen and oxygen, including NO and NO₂.
A greenhouse gas produced during fossil fuel combustion and agricultural and industrial processes. N₂O is hundreds of times more potent than CO₂ at trapping atmospheric heat, and it depletes stratospheric ozone.
Metals or alloys that do not contain significant amounts of iron.
Social welfare organizations, civic leagues, social clubs, labor organizations, business associations, and other not-for-profit organizations.
A material or energy source that relies on resources that are finite or not naturally replenished at the rate of consumption, including fossil fuels like coal, oil, and natural gas.
nitrogen oxides
Net primary production
nitrous oxide
The process of increasing the acidity of seawater, primarily caused by absorption of CO₂ from the atmosphere.
Organisation for Economic Co-operation and Development
An agreement between a seller who will produce future goods and a purchaser who commits to buying them, often used as project financing for producers prior to manufacturing.
Waste made of plant or animal matter, including food waste and green waste.
Systems to connect buyers with a network of smallholder farmers to stabilize supply and demand (sometimes called "contract farming.”
organic waste
Protected area
Protected Area
A certification that verifies a metric ton of packaging waste has been recovered and is being exported for reprocessing.
A certification that verifies a metric ton of packaging waste has been recovered and reprocessed.
Productive use of wet or rewetted peatlands that does not disturb the peat layer, such as for hunting, gathering, and growing wetland-adapted crops for food, fiber, and energy.
A legally protected area that lacks effective enforcement or management, resulting in minimal to no conservation benefit.
Airborne particles composed of solids and liquids.
A measure of transporting one passenger over a distance of one kilometer.
Incentive payments to landowners or managers to conserve natural resources and promote healthy ecological functions or ecosystem services.
Small, hardened pieces of plastic made from cooled resin that can be melted to make new plastic products.
The longevity of any greenhouse gas emission reductions or removals. Solution impacts are considered permanent if the risk of reversing the positive climate impacts is low within 100 years.
Packaging waste export recovery note
Advanced solar cells combining perovskite and silicon layers to capture more of the solar spectrum, achieving higher efficiency than conventional silicon cells.
Payments for ecosystem services
A mixture of hydrocarbons, small amounts of other organic compounds, and trace amounts of metals used to produce products such as fuels or plastics.
Per- and polyfluoroalkyl substances, a class of synthetic chemicals that do not degrade easily in the environment. They can pollute the environment and can have negative impacts on human health.
A measure of the acidity (pH<7) or alkalinity (pH>7) of a solution.
Reduce the use of a material or practice over time.
Eliminate the use of a material or practice over time.
Plug-in hybrid electric car
Private, national, or multilateral organizations dedicated to providing aid through in-kind or financial donations.
An atmospheric reaction among sunlight, VOCs, and nitrogen oxide that leads to ground-level ozone formation. Ground-level ozone, a component of smog, harms human health and the environment.
The process by which certain materials, such as those in solar cells, convert sunlight into electricity by releasing electrons.
The process by which sunlight is converted into electricity. When light hits certain materials, such as those in solar panels, it mobilizes electrons, creating an electric current.
A family of synthetic organic compounds used to make plastics softer, more flexible, and durable. They are added to a wide range of plastics for consumer and industrial uses.
polyisocyanurate
The adjustment of turbine blade angles around their long axis in which a control system rotates blades slightly forward or backward to regulate wind capture and optimize electricity generation.
passenger kilometer
particulate matter
Particulate matter 2.5 micrometers or less in diameter that can harm human health when inhaled.
Elected officials and their staff, bureaucrats, civil servants, regulators, attorneys, and government affairs professionals.
System in a vehicle that generates power and delivers it to the wheels. It typically includes an engine and/or motor, transmission, driveshaft, and differential.
Purchase Power Agreements
Purchase Power Agreement.
People who most directly interface with a solution and/or determine whether the solution is used and/or available.
A chemical reaction that creates a solid from a solution.
A substance that is the starting material for a chemical reaction that forms a different substance.
Extraction of naturally occurring resources from the Earth, including mining, logging, and oil and gas refining. These resources can be used in raw or minimally processed forms to produce materials.
The process of converting inorganic matter, including carbon dioxide, into organic matter (biomass), primarily by photosynthetic organisms such as plants and algae.
Packaging waste recovery note
Defined by the International Union for the Conservation of Nature as "A clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values". References to PAs here also include other effective area-based conservation measures defined by the IUCN.
A process that separates and breaks down wood and other raw materials into fibers that form pulp, the base ingredient for making paper products.
polyurethane
Long-term contract between a company (the buyer) and a renewable energy producer (the seller).
Long-term contracts between a company (the buyer) and a renewable energy producer (the seller).
photovoltaic
research and development
A situation in which improvements in efficiency or savings lead to consumers increasing consumption, partially or fully offsetting or exceeding the emissions or cost benefits.
renewable energy certificate
Chemical or mixture used for cooling and heating in refrigeration, air conditioning, and heat pump equipment. Refrigerants absorb and release heat as they move between states under changing pressure.
The amount of refrigerant needed for a particular refrigeration, air conditioning, or heat pump system.
A group of approaches to farming and ranching that emphasizes enhancing the health of soil by restoring its carbon content and providing other benefits to the farm and surrounding ecosystem.
A solution that can increase the beneficial impact of another solution through increased effectiveness, lower costs, improved adoption, enhanced global climate impact, and/or other benefits to people and nature.
A material or energy source that relies on naturally occuring and replenishing resources such as plant matter, wind, or sunlight.
A market-based instrument that tracks ownership of renewable energy generation.
The moldable form of raw plastic material, created by melting down waste or virgin plastics and serving as the building block for creating new plastic goods.
The process of moving items from end users (e.g., consumers) back to the sellers or manufacturers to reuse, recycle, or dispose of. This can include transportation, cleaning, sorting, and more.
Hiring a vehicle to take a passenger or passengers to a particular destination.
U.N. treaties to combat climate change, biodiversity loss, and desertification. They include the U.N. Framework Convention on Climate Change (UNFCCC), the Convention on Biological Diversity (CBD), and the U.N. Convention to Combat Desertification (UNCCD).
A class of animals with complex stomachs that can digest grass. Most grazing livestock are ruminants including cows, sheep, and goats along with several other species.
sustainable aviation fuel
A wetland ecosystem regularly flooded by tides and containing salt-tolerant plants, such as grasses and herbs.
Intertidal coastal wetlands with salt-tolerant plants.
An ecosystem characterized by low-density tree cover that allows for a grass subcanopy.
Very large or small numbers are formatted in scientific notation. A positive exponent multiplies the number by powers of ten; a negative exponent divides the number by powers of ten.
Seasonal coefficient of performance
Sustainable Development Goals
Average units of heat energy released for every unit of electrical energy consumed, used to measure heat pump efficiency.
A single pane window (glass and frame) added to an existing single-glazed window, converting the unit into double glazing, with each pane independently operable.
A practice in which multiple utility companies own and operate high-voltage power lines, sharing both costs and benefits.
A window consisting of one glass pane without any additional insulating layers.
Small-scale family farmers and other food producers, often with limited resources, usually in the tropics. The average size of a smallholder farm is two hectares (about five acres).
soil organic carbon
The process of using direct, real-world observations to verify, validate, and/or improve data and models about social systems, often using in-person observations in the field.
Carbon stored in soils, including both organic (from decomposing plants and microbes) and inorganic (from carbonate-containing minerals).
Carbon stored in soils in organic forms (from decomposing plants and microbes). Soil organic carbon makes up roughly half of soil organic matter by weight.
Biologically derived matter in soils, including living, dead, and decayed plant and microbial tissues. Soil organic matter is roughly half carbon on a dry-weight basis.
Reducing global warming by increasing how much of the sun's radiation is reflected back to space and/or decreasing how much of the Earth's radiative heat is trapped in the atmosphere.
A material's ability to reflect solar radiation incident on its surface, often reported as a fraction or percentage.
soil organic matter
A substance that takes up another liquid or gas substance, either by absorbtion or adsorption.
sulfur oxides
sulfur dioxide
The rate at which a climate solution physically affects the atmosphere after being deployed. At Project Drawdown, we use three categories: emergency brake (fastest impact), gradual, or delayed (slowest impact).
Climate regions between latitudes 23.4° to 35° above and below the equator characterized by warm summers and mild winters.
A polluting gas produced primarily from burning fossil fuels and industrial processes that directly harms the environment and human health.
A group of gases containing sulfur and oxygen that predominantly come from burning fossil fuels. They contribute to air pollution, acid rain, and respiratory health issues.
Processes, people, and resources involved in producing and delivering a product from supplier to end customer, including material acquisition.
Sport utility vehicle
A mixture of hydrogen, carbon monoxide, and other gases, used to produce chemicals like ammonia and methanol, or as a synthetic fuel made from non-fossil feedstocks, including biomass and waste.
metric ton
metric tons
Technology developers, including founders, designers, inventors, R&D staff, and creators seeking to overcome technical or practical challenges.
Climate regions between 35° to 50° above and below the equator characterized by moderate mean annual temperatures and distinct seasons, with warm summers and cold winters.
A measure of energy equivalent to the energy delivered by one trillion watts of power over one hour.
trifluoroacetic acid
trifluoroacetic acid
A measurement indicating the ability of a material to release heat after it has been absorbed.
A measure of how well a material prevents heat flow, often called R-value or RSI-value for insulation. A higher R-value means better thermal performance.
A measure of the rate of heat flow or heat transfer through a material or building component. A lower U-value means better thermal performance.
Individuals with an established audience for their work, including public figures, experts, journalists, and educators.
Charges for disposal of materials paid to facility operators. Fees can be charged per ton of waste disposed or based on economic indicators such as the Consumer Price Index.
A solar PV systems with panels that move automatically to follow the sun’s path, maximizing energy capture and improving efficiency over fixed systems.
A window consisting of three panes of glass separated by two insulating inert gas-filled layers, providing more heat flow resistance than single or double glazing.
Low-latitude (23.4°S to 23.4°N) climate regions near the Equator characterized by year-round high temperatures and distinct wet and dry seasons.
Terawatt, equal to 1,000 gigawatts
terawatt-hour
United Nations
United Nations Environment Programme
U.S. Composting Council
Self-propelled machine for transporting passengers or freight on roads.
A measure of one vehicle traveling a distance of one kilometer.
Aerobic decomposition of organic waste by earthworms and microorganisms.
vehicle kilometer
volatile organic compound
Gases made of organic, carbon-based molecules that are readily released into the air from other solid or liquid materials. Some VOCs are greenhouse gases or can harm human health.
watt (a measure of power or energy transfer.)
Watts per square meter Kelvin
A thin, flat slice of silicon cut from an ingot and processed to create individual solar cells that convert sunlight into electricity.
Landscape waste, storm debris, wood processing residues, and recovered post-consumer wood.
A framework for waste management that ranks options by their sustainability: 1) prevent (do not purchase unnecessary waste), 2) reduce, 3) reuse, 4) recycle, 5) recover, 6) dispose.
A measure of power equal to one joule per second.
World Conservation Monitoring Centre
Using strategies such as insulation, air sealing, ventilation, and moisture control to upgrade a building’s exterior structure, making indoors more comfortable and energy efficient.
Aerobic decomposition of organic waste in long, narrow rows called windrows. Windrows are generally twice as long as they are wide.
A subset of forest ecosystems that may have sparser canopy cover, smaller-stature trees, and/or trees characterized by basal branching rather than a single main stem.
extruded polystyrene
The rotation of the nacelle (the enclosed housing at the top of a wind turbine tower that contains the main mechanical and electrical components of the turbine) so that the rotor blades are always facing directly into the wind.
year-over-year
year
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