Whales play a critical role in the ocean carbon cycle, but commercial whaling in the 20th century drastically diminished their populations. Restoring the abundance of whales to pre-whaling levels has been proposed as a way to remove additional CO₂ from the atmosphere and store it in the ocean. Whales directly store carbon in their bodies, and when they die, some of this carbon sinks to the deep ocean. Whales also contribute to CO₂ removal by bringing critical nutrients (such as iron) from the deep ocean to the surface and stimulating phytoplankton growth. Although boosting whale populations could bring a wide range of ecological benefits, there is limited evidence that whales make a significant contribution to global CO₂ removal. We will “Keep Watching” this potential solution.
Restoring whales will have ecological benefits, but there is limited and uncertain evidence on its effectiveness. The limited evidence available suggests it would be a small contribution to climate change mitigation. Therefore, we will “Keep Watching” this as a climate solution.
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | Yes |
| Evidence | Are there data to evaluate it? | Limited |
| Effective | Does it consistently work? | ? |
| Impact | Is it big enough to matter? | No |
| Risk | Is it risky or harmful? | No |
| Cost | Is it cheap? | ? |
Large whales can remove and store carbon via two pathways. They remove carbon when, after they die, some of their biomass reaches the deep ocean, where it can remain for long periods. In addition, while alive, defecation adds nutrients, such as iron, to surface ocean waters, stimulating the growth of phytoplankton that absorb CO₂ via photosynthesis. As phytoplankton draw in seawater CO₂ and convert it into biomass, the ocean can absorb more CO₂ from the atmosphere. Some of this biomass carbon eventually sinks or is transported to the deep sea or seafloor, where it can be stored for decades or centuries. Current whale populations are low due to commercial whaling, climate change, and habitat disturbance. An estimated 3 million whales were killed for commercial purposes during the 20th century, leaving populations at only a fraction of what they once were (Stewart et al., 2025). Increasing the number of large whales through various restoration activities could increase carbon removal.
Restrictions on whaling have allowed for the humpback whale and other species to make a dramatic comeback over the past 40 years (Zerbini et al., 2019). However, climate benefits from whale restoration are still not clear (Ritchie, 2025). The amount of carbon that could be stored directly in whale tissue is better understood than the extent to which whales stimulate phytoplankton growth, although it’s difficult to directly measure either mechanism. Carcasses that sink to the deep seafloor can sequester carbon for hundreds to thousands of years (NAS, 2022). However, only a small fraction of whales die each year, and only a small fraction of their biomass sinks to the deep ocean. An analysis of the life cycle of great whales estimates that whale carcasses were responsible for storing about 0.0001 Gt CO₂ in the deep ocean in 2001 (Pershing et al., 2010). However, when whales were more numerous and larger during the pre-whaling era, it’s estimated that they could have stored 0.0007 Gt CO₂. (This assumes that none of the CO₂ removed returns to the atmosphere, which is not always the case [Hurd et al., 2024]). Whales’ role in enhancing phytoplankton growth is even trickier to estimate. Whales forage at different ocean depths, depending on the species, but much of the defecation occurs at the ocean surface (Lavery et al., 2010). If whale populations were restored to 10 times their current numbers, estimates suggest that about 0.01 Gt CO₂ could be sequestered (Pershing et al. 2010), which is less than .002% of annual global GHG emissions (59 Gt) in 2019.
Restoring whale populations to their pre-whaling numbers could have multiple ecological benefits, including enhanced growth of phytoplankton and other marine life. Whales play multiple roles in the biological carbon pump of the ocean, including by linking trophic levels (Boyd et al., 2024).
Great whales are vulnerable to entanglement in fishing gear, whaling, ship strikes, climate change, and ocean pollution (Pearson et al., 2023). Although commercial whaling became illegal in most countries in 1986, a handful of countries still allow it (WWF, 2026). Restricting whaling, establishing marine protected areas, and regulating fishing and shipping in known migratory routes could counter threats to whales and allow their populations to thrive (NAS, 2022).
The limited published research on whales’ contribution to carbon uptake from the atmosphere estimates that its potential carbon removal is likely quite small (<0.02 Gt CO₂). Overstating the role of great whales in carbon capture may hinder, rather than facilitate, effective climate mitigation efforts (Duvall et al., 2024).
Boyd, P. W., Gattuso, J.-P., Hurd, C. L., & Williamson, P. (2024). Limited understanding of basic ocean processes is hindering progress in marine carbon dioxide removal. Environmental Research Letters, 19(6), 061002. Link to source: https://doi.org/10.1088/1748-9326/ad502f
Duvall, E. S., le Roux, E., Pearson, H. C., Roman, J., Malhi, Y., & Abraham, A. J. (2024). Resisting the carbonization of animals as climate solutions. Nature Climate Change, 14(9), 892–895. Link to source: https://doi.org/10.1038/s41558-024-02106-y
Hurd, C. L., Gattuso, J.-P., & Boyd, P. W. (2024). Air-sea carbon dioxide equilibrium: Will it be possible to use seaweeds for carbon removal offsets? Journal of Phycology, 60(1), 4–14. Link to source: https://doi.org/10.1111/jpy.13405
Lavery, T. J., Roudnew, B., Gill, P., Seymour, J., Seuront, L., Johnson, G., Mitchell, J. G., & Smetacek, V. (2010). Iron defecation by sperm whales stimulates carbon export in the Southern Ocean. Proceedings of the Royal Society B: Biological Sciences, 277(1699), 3527–3531. Link to source: https://doi.org/10.1098/rspb.2010.0863
National Academies of Sciences, Engineering, and Medicine (NAS). (2022). A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. The National Academies Press. Link to source: https://doi.org/10.17226/26278
Pearson, H. C., Savoca, M. S., Costa, D. P., Lomas, M. W., Molina, R., Pershing, A. J., Smith, C. R., Villaseñor-Derbez, J. C., Wing, S. R., & Roman, J. (2023). Whales in the carbon cycle: Can recovery remove carbon dioxide? Trends in Ecology & Evolution, 38(3), 238–249. Link to source: https://doi.org/10.1016/j.tree.2022.10.012
Pershing, A. J., Christensen, L. B., Record, N. R., Sherwood, G. D., & Stetson, P. B. (2010). The Impact of Whaling on the Ocean Carbon Cycle: Why Bigger Was Better. PLOS ONE, 5(8), e12444. Link to source: https://doi.org/10.1371/journal.pone.0012444
Ritchie, H. (2025, March 24). Could whales be a solution to climate change? Probably only a very small one. [Substack newsletter]. By the Numbers. Link to source: https://hannahritchie.substack.com/p/whale-carbon-capture
Stewart, J. D., Tinker, M. T., Brownell, R. L., & Read, A. J. (2025). The future of baleen whales: Recoveries, environmental constraints, and climate change. Science Advances, 11(26), eadv8031. Link to source: https://doi.org/10.1126/sciadv.adv8031
World Wildlife Fund (WWF). (2026, March 11). Forty years after the whaling ban: Progress and challenges. World Wildlife Fund. Link to source: https://www.worldwildlife.org/news/stories/forty-years-after-the-commercial-whaling-ban-theres-both-progress-and-more-work-ahead/
Zerbini, A. N., Adams, G., Best, J., Clapham, P. J., Jackson, J. A., & Punt, A. E. (2019). Assessing the recovery of an Antarctic predator from historical exploitation. Royal Society Open Science, 6(10), 190368. Link to source: https://doi.org/10.1098/rsos.190368
Credits
Lead Fellow
Emily Cassidy
Internal Reviewers
Christina Richardson, 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.
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.
Lacking dissolved oxygen but containing other sources of oxygen bound within molecules that can be stripped and used by microorganisms.
aerated static piles
Hardware required to support PV modules and arrays, including racking and mounting structures, wires, and other physical components.
Building automation system
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.
Balance-of-system
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.
The stocking rate a pasture can sustain without degrading forage supply or vegetation condition.
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.
A factor that warms or cools the planet.
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.
A measure of how long removed carbon stays out of the atmosphere.
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.
A policy mechanism that incentivizes renewables through contracts that guarantee a set price for the electricity generated.
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.
Heavy-duty, low-permeability liners made mostly from synthetic plastics or rubber, used to block the movement of liquids or gases in engineered storage sites.
greenhouse gas
Global horizontal irradiance
gigajoule or billion joules
The glass layers or panes in a window.
The intensity of all solar radiant energy on a horizontal surface over a specific time frame, which limits PV power output. Measured as energy per area per year (kWh/m2/yr).
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.
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.
Intertidal coastal wetlands with salt-tolerant trees and shrubs found in tropical and subtropical regions.
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 lb), also known as tonne.
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.
Reduce adverse impact of
A reduction in adverse impact
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.
Transitional zone between urban and rural areas that combines features of both such as housing, farms, lower-density development, and mixed land uses.
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
High-efficiency solar cells with a traditional silicon base and a thin-film perovskite layer on top that allows the combined cell to capture more energy without significantly increasing its size.
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.
A chemical or material that initiates or accelerates a chemical reaction when exposed to light without being consumed.
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 Agreement.
Purchase Power Agreements
Parts per million
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
Petawatt-hour, equal to 1 billion MWh
research and development
An atom, molecule, or ion that contains at least one unpaired valence electron, making it highly reactive and often short-lived.
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.
The risk that removed or stored carbon can be released into the atmosphere. Lower reversibility means the carbon is more securely stored.
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).
Devices that control indoor temperature according to user-defined schedules or conditions.
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.
A measure of the intensity of solar radiant energy on a surface, measured in watts per square meter (W/m2) or power per unit area.
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.
How easily and reliably a carbon‑removal claim can be measured and independently confirmed as accurate; part of measurement, reporting and verification (MRV) for carbon removal.
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 how much free water is available for microbes to use. It ranges from 0 (completely dry) to 1 (pure water), and low values (<0.60) indicate conditions too dry for microbes to function.
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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