Climate change mitigation, also called decarbonisation, is an action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include conserving energy and replacing fossil fuels with clean energy sources. Secondary mitigation strategies include changes to land use and removing carbon dioxide (CO2) from the atmosphere. 2022 assessments emphasize that global greenhouse gas emissions must peak before 2025 and decline by about 43% by 2030 to limit warming to 1.5 °C, requiring rapid transitions in energy, transport, and land-use systems. The adopted climate change mitigation policies are insufficient, as they contribute to some changes but fail to accelerate transitions at the scale and speed required, and would still result in global warming of about 2.7 °C by 2100, significantly above the 2015 Paris Agreement's goal of limiting global warming to below 2 °C.Recent research shows that demand-side climate solutions—such as shifts in transportation behavior, dietary change, improved building energy efficiency, and reduced material consumption—could reduce global greenhouse gas emissions by 40% to 70% by 2050 while improving human well-being. Solar energy and wind power can replace fossil fuels at the lowest cost compared to other renewable energy options. The availability of sunshine and wind is variable and can require electrical grid upgrades, such as using long-distance electricity transmission to group a range of power sources. Energy storage can also be used to even out power output, and demand management can limit power use when power generation is low. Cleanly generated electricity can usually replace fossil fuels for powering transportation, heating buildings, and running industrial processes. Certain processes are more difficult to decarbonise, such as air travel and cement production. Carbon capture and storage (CCS) can be an option to reduce net emissions in these circumstances, although fossil fuel power plants with CCS technology is currently a high-cost climate change mitigation strategy. Human land use changes such as agriculture and deforestation cause about 1/4th of climate change. These changes impact how much CO2 is absorbed by plant matter and how much organic matter decays or burns to release CO2. These changes are part of the fast carbon cycle, whereas fossil fuels release CO2 that was buried underground as part of the slow carbon cycle. Methane is a short-lived greenhouse gas that is produced by decaying organic matter and livestock, as well as fossil fuel extraction. Land use changes can also impact precipitation patterns and the reflectivity of the surface of the Earth. It is possible to cut emissions from agriculture by reducing food waste, switching to a more plant-based diet (also referred to as low-carbon diet), and by improving farming processes. Various policies can encourage climate change mitigation. Carbon pricing systems have been set up that either tax CO2 emissions or cap total emissions and trade emission credits. Fossil fuel subsidies can be eliminated in favour of clean energy subsidies, and incentives offered for installing energy efficiency measures or switching to electric power sources. The first global carbon tax has been proposed by the United Nations IMO Net-Zero Framework. Another issue is overcoming environmental objections when constructing new clean energy sources and making grid modifications. Limiting climate change by reducing greenhouse gas emissions or removing greenhouse gases from the atmosphere could be supplemented by climate technologies such as solar radiation management (or solar geoengineering). Complementary climate change actions, including climate activism, have a focus on political and cultural aspects. While climate mitigation is often cast as a burden to be distributed in some or other way, it can also be seen as an opportunity for industrial development, exports, and status seeking for countries. The examples and precedents that countries set may influence other countries to follow suit.
Definitions and scope
Climate change mitigation aims to sustain ecosystems to maintain human civilisation. This requires drastic cuts in greenhouse gas emissions. The Intergovernmental Panel on Climate Change (IPCC) defines mitigation (of climate change) as "a human intervention to reduce emissions or enhance the sinks of greenhouse gases". It is possible to approach various mitigation measures in parallel. This is because there is no single pathway to limit global warming to 1.5 or 2 °C. There are four types of measures:
Sustainable energy and sustainable transport Energy conservation, including efficient energy use Sustainable agriculture and green industrial policy Enhancing carbon sinks and carbon dioxide removal (CDR), including carbon sequestration The IPCC defined carbon dioxide removal as "Anthropogenic activities removing carbon dioxide (CO2) from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical CO2 sinks and direct air carbon dioxide capture and storage (DACCS) but excludes natural CO2 uptake not directly caused by human activities."
Emission trends and pledges
Greenhouse gas emissions from human activities strengthen the greenhouse effect. This contributes to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. Human-caused emissions have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. Emissions in the 2010s averaged a record 56 billion tons (Gt) a year. In 2016, energy for electricity, heat and transport was responsible for 73.2% of GHG emissions. Direct industrial processes accounted for 5.2%, waste for 3.2% and agriculture, forestry and land use for 18.4%. Electricity generation and transport are major emitters. The largest single source is coal-fired power stations with 20% of greenhouse gas emissions. Deforestation and other changes in land use also emit carbon dioxide and methane. The largest sources of anthropogenic methane emissions are agriculture, and gas venting and fugitive emissions from the fossil-fuel industry. The largest agricultural methane source is livestock. Agricultural soils emit nitrous oxide, partly due to fertilizers. There is now a political solution to the problem of fluorinated gases from refrigerants. This is because many countries have ratified the Kigali Amendment. Carbon dioxide (CO2) is the dominant emitted greenhouse gas. Methane (CH4) emissions almost have the same short-term impact. Nitrous oxide (N2O) and fluorinated gases (F-Gases) play a minor role. Livestock and manure produce 5.8% of all greenhouse gas emissions. But this depends on the time frame used to calculate the global warming potential of the respective gas. Greenhouse gas (GHG) emissions are measured in CO2 equivalents. Scientists determine their CO2 equivalents from their global warming potential (GWP). This depends on their lifetime in the atmosphere. There are widely used greenhouse gas accounting methods that convert volumes of methane, nitrous oxide and other greenhouse gases to carbon dioxide equivalents. Estimates largely depend on the ability of oceans and land sinks to absorb these gases. Short-lived climate pollutants (SLCPs) persist in the atmosphere for a period ranging from days to 15 years. Carbon dioxide can remain in the atmosphere for millennia. Short-lived climate pollutants include methane, hydrofluorocarbons (HFCs), tropospheric ozone and black carbon. Scientists have increased the use satellites to locate and measure greenhouse gas emissions and deforestation. Earlier, scientists largely relied on or calculated estimates of greenhouse gas emissions and governments' self-reported data.
Needed emissions cuts
The annual "Emissions Gap Report" by UNEP stated in 2022 that it was necessary to almost halve emissions. "To get on track for limiting global warming to 1.5°C, global annual GHG emissions must be reduced by 45 per cent compared with emissions projections under policies currently in place in just eight years, and they must continue to decline rapidly after 2030, to avoid exhausting the limited remaining atmospheric carbon budget." The report commented that the world should focus on broad-based economy-wide transformations and not incremental change. In 2022, the Intergovernmental Panel on Climate Change (IPCC) released its Sixth Assessment Report on climate change. It warned that greenhouse gas emissions must peak before 2025 at the latest and decline 43% by 2030 to have a good chance of limiting global warming to 1.5 °C (2.7 °F). Or in the words of Secretary-General of the United Nations António Guterres: "Main emitters must drastically cut emissions starting this year". According to a joint press release published by the German Physical society and the German meteorological society in September 2025, if the current trends will continue, global temperature can rise to 3°C above pre-industrial level by the year 2050, and by 5°C by the year 2100. The scientists emphasised the need to urgently implement already existing solutions.
Pledges
Climate Action Tracker described the situation on 9 November 2021 as follows. The global temperature will rise by 2.7 °C by the end of the century with current policies and by 2.9 °C with nationally adopted policies. The temperature will rise by 2.4 °C if countries only implement the pledges for 2030. The rise would be 2.1 °C with the achievement of the long-term targets too. Full achievement of all announced targets would mean the rise in global temperature will peak at 1.9 °C and go down to 1.8 °C by the year 2100. Experts gather information about climate pledges in the Global Climate Action Portal - Nazca. The scientific community is checking their fulfilment. There has not been a definitive or detailed evaluation of most goals set for 2020. But it appears the world failed to meet most or all international goals set for that year. One update came during the 2021 United Nations Climate Change Conference in Glasgow. The group of researchers running the Climate Action Tracker looked at countries responsible for 85% of greenhouse gas emissions. It found that only four countries or political entities—the EU, UK, Chile and Costa Rica—have published a detailed official policy‑plan that describes the steps to realise 2030 mitigation targets. These four polities are responsible for 6% of global greenhouse gas emissions. In 2021 the US and EU launched the Global Methane Pledge to cut methane emissions by 30% by 2030. The UK, Argentina, Indonesia, Italy and Mexico joined the initiative. Ghana and Iraq signalled interest in joining. A White House summary of the meeting noted those countries represent six of the top 15 methane emitters globally. Israel also joined the initiative.
Low-carbon energy
The energy system includes the delivery and use of energy. It is the main emitter of carbon dioxide (CO2). Rapid and deep reductions in the carbon dioxide and other greenhouse gas emissions from the energy sector are necessary to limit global warming to well below 2 °C. IPCC recommendations include reducing fossil fuel consumption, increasing production from low- and zero carbon energy sources, and increasing use of electricity and alternative energy carriers. Nearly all scenarios and strategies involve a major increase in the use of renewable energy in combination with increased energy efficiency measures. It will be necessary to accelerate the deployment of renewable energy six-fold from 0.25% annual growth in 2015 to 1.5% to keep global warming under 2 °C.
The competitiveness of renewable energy is a key to a rapid deployment. In 2020, onshore wind and solar photovoltaics were the cheapest source for new bulk electricity generation in many regions. Renewables may have higher storage costs but non-renewables may have higher clean-up costs. A carbon price can increase the competitiveness of renewable energy.
Solar and wind energy
Wind and sun can provide large amounts of low-carbon energy at competitive production costs. The IPCC estimates that these two mitigation options have the largest potential to reduce emissions before 2030 at low cost. Solar photovoltaics (PV) has become the cheapest way to generate electricity in many regions of the world.
A 2024 review found that the global levelized cost of electricity for solar PV had fallen to between US$0.039 and 0.041 per kWh. The growth of photovoltaics has been close to exponential. It has about doubled every three years since the 1990s. A different technology is concentrated solar power (CSP). This uses mirrors or lenses to concentrate a large area of sunlight on to a receiver. With CSP, the energy can be stored for a few hours. This provides supply in the evening. Solar water heating doubled between 2010 and 2019. Regions in the higher northern and southern latitudes have the greatest potential for wind power. Offshore wind farms are more expensive. But offshore units deliver more energy per installed capacity with less fluctuations. In most regions, wind power generation is higher in the winter when PV output is low. For this reason, combinations of wind and solar power lead to better-balanced systems.
Other renewables Other well-established renewable energy forms include hydropower, bioenergy and geothermal energy. Hydroelectricity is electricity generated by hydropower and plays a leading role in countries like Brazil, Norway and China. but there are geographical limits and environmental issues. Tidal power can be used in coastal regions. Bioenergy can provide energy for electricity, heat and transport. Bioenergy, in particular biogas, can provide dispatchable electricity generation. While burning plant-derived biomass releases CO2, the plants withdraw CO2 from the atmosphere while they grow. The technologies for producing, transporting and processing a fuel have a significant impact on the lifecycle emissions of the fuel. For example, aviation is starting to use renewable biofuels. Geothermal power is electrical power generated from geothermal energy. Geothermal electricity generation is currently used in 26 countries. Geothermal heating is in use in 70 countries.
Integrating variable renewable energy
Wind and solar power production does not consistently match demand. To deliver reliable electricity from variable renewable energy sources such as wind and solar, electrical power systems must be flexible. Most electrical grids were constructed for non-intermittent energy sources such as coal-fired power plants. The integration of larger amounts of solar and wind energy into the grid requires a change of the energy system; this is necessary to ensure that the supply of electricity matches demand.
There are various ways to make the electricity system more flexible. In many places, wind and solar generation are complementary on a daily and a seasonal scale. There is more wind during the night and in winter when solar energy production is low. Linking different geographical regions through long-distance transmission lines also makes it possible to reduce variability. It is possible to shift energy demand in time. Energy demand management and the use of smart grids make it possible to match the times when variable energy production is highest. Sector coupling can provide further flexibility. This involves coupling the electricity sector to the heat and mobility sector via power-to-heat-systems and electric vehicles. Energy storage helps overcome barriers to intermittent renewable energy. The most commonly used and available storage method is pumped-storage hydroelectricity. This requires locations with large differences in height and access to water. Batteries are also in wide use. They typically store electricity for short periods. Batteries have low energy density. This and their cost makes them impractical for the large energy storage necessary to balance inter-seasonal variations in energy production. Some locations have implemented pumped hydro storage with capacity for multi-month usage.
Nuclear power
Nuclear power could complement renewables for electricity. On the other hand, environmental and security risks could outweigh the benefits. Examples of these environmental risks being the discharge of radioactive water to nearby ecosystems, and the routine release of radioactive gases as well. The construction of new nuclear reactors currently takes about 10 years. This is much longer than scaling up the deployment of wind and solar. And this timing gives rise to credit risks. However nuclear may be much cheaper in China. China is building a significant number of new power plants. As of 2019 the cost of extending nuclear power plant lifetimes is competitive with other electricity generation technologies if long term costs for nuclear waste disposal are excluded from the calculation. There is also no sufficient financial insurance for nuclear accidents.
Replacing coal with natural gas
Demand reduction
Reducing demand for products and services that cause greenhouse gas emissions can help in mitigating climate change. One is to reduce demand by behavioural and cultural changes, for example by making changes in diet, especially the decision to reduce meat consumption, an effective action individuals take to fight climate change. Another is by reducing the demand by improving infrastructure, by building a good public transport network, for example. Lastly, changes in end-use technology can reduce energy demand. For instance a well-insulated house emits less than a poorly-insulated house. Mitigation options that reduce demand for products or services help people make personal choices to reduce their carbon footprint. This could be in their choice of transport or food. So these mitigation options have many social aspects that focus on demand reduction; they are therefore demand-side mitigation actions. For example, people with high socio-economic status often cause more greenhouse gas emissions than those from a lower status. If they reduce their emissions and promote green policies, these people could become low-carbon lifestyle role models. However, there are many psychological variables that influence consumers. These include awareness and perceived risk. Government policies can support or hinder demand-side mitigation options. For example, public policy can promote circular economy concepts which would support climate change mitigation. Reducing greenhouse gas emissions is linked to the sharing economy. There is a debate regarding the correlation of economic growth and emissions. It seems economic growth no longer necessarily means higher emissions. A 2024 article in Nature Climate Change emphasised the importance of integrating behavioural science into climate change mitigation strategies. Six key recommendations aimed at improving individual and collective actions toward reducing greenhouse gas emissions include overcoming barriers to research, fostering cross-disciplinary collaborations, and promoting practical behaviour-oriented solutions. These insights suggest that behavioural science plays a crucial role alongside technological and policy measures in addressing climate change. A paper published in Environmental Research Letters in 2024 described the growing role of demand-side strategies in achieving climate change mitigation. It described how behavioural, social, and infrastructural interventions, such as shifting consumption patterns, improving urban design, and promoting shared mobility could collectively reduce global greenhouse gas emissions by up to 40–70% by mid-century—describing how changes in lifestyles and demand systems are essential complements to technological and policy solutions.
Energy conservation and efficiency
Global primary energy demand exceeded 161,000 terawatt hours (TWh) in 2018. This refers to electricity, transport and heating including all losses. In transport and electricity production, fossil fuel usage has a low efficiency of less than 50%. Large amounts of heat in power plants and in motors of vehicles go to waste. The actual amount of energy consumed is significantly lower at 116,000 TWh. Energy conservation is the effort made to reduce the consumption of energy by using less of an energy service. One way is to use energy more efficiently. This means using less energy than before to produce the same service. Another way is to reduce the amount of service used. An example of this would be to drive less. Energy conservation is at the top of the sustainable energy hierarchy. When consumers reduce wastage and losses they can conserve energy. The upgrading of technology as well as the improvements to operations and maintenance can result in overall efficiency improvements. Efficient energy use (or energy efficiency) is the process of reducing the amount of energy required to provide products and services. Improved energy efficiency in buildings ("green buildings"), industrial processes and transportation could reduce the world's energy needs in 2050 by one third. This would help reduce global emissions of greenhouse gases. For example, insulating a building allows it to use less heating and cooling energy to achieve and maintain thermal comfort. Improvements in energy efficiency are generally achieved by adopting a more efficient technology or production process. Another way is to use commonly accepted methods to reduce energy losses.
Lifestyle changes
Individual action on climate change can include personal choices in many areas. These include diet, travel, household energy use, consumption of goods and services, and family size. People who wish to reduce their carbon footprint can take high-impact actions such as avoiding frequent flying and petrol-fuelled cars, eating mainly a plant-based diet, having fewer children, using clothes and electrical products for longer, and electrifying homes. These approaches are more practical for people in high-income countries with high-consumption lifestyles. Naturally, it is more difficult for those with lower income statuses to make these changes. This is because choices like electric-powered cars may not be available. Excessive consumption is more to blame for climate change than population increase. High-consumption lifestyles have a greater environmental impact, with the richest 10% of people emitting about half the total lifestyle emissions.
Dietary change
Some scientists say that avoiding meat and dairy foods is the single biggest way an individual can reduce their environmental impact. The widespread adoption of a vegetarian diet could cut food-related greenhouse gas emissions by 63% by 2050. China introduced new dietary guidelines in 2016 which aim to cut meat consumption by 50% and thereby reduce greenhouse gas emissions by 1 Gt per year by 2030. Overall, food accounts for the largest share of consumption-based greenhouse gas emissions. It is responsible for nearly 20% of the global carbon footprint. Almost 15% of all anthropogenic greenhouse gas emissions have been attributed to the livestock sector. A shift towards plant-based diets would help to mitigate climate change. In particular, reducing meat consumption would help to reduce methane emissions. The Global Methane Pledge is an initiative launched by the United States and European Union to reduce global methane emissions by 30% by 2030 to keep the 1.5°C global warming limit in reach. If high-income nations switched to a plant-based diet, vast amounts of land used for animal agriculture could be allowed to return to their natural state. This in turn has the potential to sequester 100 billion tonnes of CO2 by the end of the century. A comprehensive analysis found that plant based diets reduce emissions, water pollution and land use significantly (by 75%), while reducing the destruction of wildlife and usage of water.
Family size Population growth has resulted in higher greenhouse gas emissions in most regions, particularly Africa. However, economic growth has a bigger effect than population growth. Rising incomes, changes in consumption and dietary patterns, as well as population growth, cause pressure on land and other natural resources. This leads to more greenhouse gas emissions and fewer carbon sinks. Some scholars have argued that humane policies to slow population growth should be part of a broad climate response together with policies that end fossil fuel use and encourage sustainable consumption. Advances in female education and reproductive health, especially voluntary family planning, can contribute to reducing population growth.
Preserving and enhancing carbon sinks
An important mitigation measure is "preserving and enhancing carbon sinks". This refers to the management of Earth's natural carbon sinks in a way that preserves or increases their capability to remove CO2 from the atmosphere and to store it durably. Scientists call this process also carbon sequestration. In the context of climate change mitigation, the IPCC defines a sink as "Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere". Globally, the two most important carbon sinks are vegetation and the ocean. To enhance the ability of ecosystems to sequester carbon, changes are necessary in agriculture and forestry. Examples are preventing deforestation and restoring natural ecosystems by reforestation. Scenarios that limit global warming to 1.5 °C typically project the large-scale use of carbon dioxide removal methods over the 21st century. There are concerns about over-reliance on these technologies, and their environmental impacts. But ecosystem restoration and reduced conversion are among the mitigation tools that can yield the most emissions reductions before 2030. Land-based mitigation options are referred to as "AFOLU mitigation options" in the 2022 IPCC report on mitigation. The abbreviation stands for "agriculture, forestry and other land use" The report described the economic mitigation potential from relevant activities around forests and ecosystems as follows: "the conservation, improved management, and restoration of forests and other ecosystems (coastal wetlands, peatlands, savannas and grasslands)". A high mitigation potential is found for reducing deforestation in tropical regions. The economic potential of these activities has been estimated to be 4.2 to 7.4 gigatonnes of carbon dioxide equivalent (GtCO2 -eq) per year.
Forests
Conservation
The Stern Review on the economics of climate change stated in 2007 that curbing deforestation was a highly cost-effective way of reducing greenhouse gas emissions. About 95% of deforestation occurs in the tropics, where clearing of land for agriculture is one of the main causes. One forest conservation strategy is to transfer rights over land from public ownership to its indigenous inhabitants. Land concessions often go to powerful extractive companies. Conservation strategies that exclude and even evict humans, called fortress conservation, often lead to more exploitation of the land. This is because the native inhabitants turn to work for extractive companies to survive. Proforestation is promoting forests to capture their full ecological potential. This is a mitigation strategy as secondary forests that have regrown in abandoned farmland are found to have less biodiversity than the original old-growth forests. Original forests store 60% more carbon than these new forests. Strategies include rewilding and establishing wildlife corridors.
Afforestation, reforestation and preventing desertification
Afforestation is the establishment of trees where there was previously no tree cover. Scenarios for new plantations covering up to 4000 million hectares (Mha) (6300 x 6300 km) suggest cumulative carbon storage of more than 900 GtC (2300 GtCO2) until 2100. But they are not a viable alternative to aggressive emissions reduction. This is because the plantations would need to be so large they would eliminate most natural ecosystems or reduce food production. One example is the Trillion Tree Campaign. However, preserving biodiversity is also important and for example not all grasslands are suitable for conversion into forests. Grasslands can even turn from carbon sinks to carbon sources. Reforestation is the restocking of existing depleted forests or in places where there were recently forests. Reforestation could save at least 1 GtCO2 per year, at an estimated cost of $5–15 per tonne of carbon dioxide (tCO2). Restoring all degraded forests all over the world could capture about 205 GtC (750 GtCO2). With increased intensive agriculture and urbanisation, there is an increase in the amount of abandoned farmland. By some estimates, for every acre of original old-growth forest cut down, more than 50 acres of new secondary forests are growing. In some countries, promoting regrowth on abandoned farmland could offset years of emissions. Planting new trees can be expensive and a risky investment. For example, about 80 per cent of planted trees in the Sahel die within two years. Reforestation has higher carbon storage potential than afforestation. Even long-deforested areas still contain an "underground forest" of living roots and tree stumps. Helping native species sprout naturally is cheaper than planting new trees and they are more likely to survive. This could include pruning and coppicing to accelerate growth. This also provides woodfuel, which is otherwise a major source of deforestation. Such practices, called farmer-managed natural regeneration, are centuries old but the biggest obstacle towards implementation is ownership of the trees by the state. The state often sells timber rights to businesses which leads to locals uprooting seedlings because they see them as a liability. Legal aid for locals and changes to property law such as in Mali and Niger have led to significant changes. Scientists describe them as the largest positive environmental transformation in Africa. It is possible to discern from space the border between Niger and the more barren land in Nigeria, where the law has not changed. Rangelands account for more half the world's land and could sequester 35% of terrestrial carbon. Pastoralists are those who move with their herds that feed and migrate over often unenclosed grazelands. Such land is usually unable to grow any other kind of food. Rangelands coevolved with large wild herds, many of which have decreased or gone extinct, and pastoralists' herds replace such wild herds and thus help maintain the ecosystem. However, the movement of herds grazing on large areas over vast distances is increasingly restricted by governments, who often grant exclusive title to lands for more profitable uses which restricts pastoralists to more enclose spaces. This has led to the overgrazing of the land and desertification, as well as conflict.
Soils
There are many measures to increase soil carbon. This makes it complex and hard to measure and account for. One advantage is that there are fewer trade-offs for these measures than for BECCS or afforestation, for example. Globally, protecting healthy soils and restoring the soil carbon sponge could remove 7.6 billion tonnes of carbon dioxide from the atmosphere annually. This is more than the annual emissions of the US. Trees capture CO2 while growing above ground and exuding larger amounts of carbon below ground. Trees contribute to the building of a soil carbon sponge. Carbon formed above ground is released as CO2 immediately when wood is burned. If dead wood remains untouched, only some of the carbon returns to the atmosphere as decomposition proceeds. Farming can deplete soil carbon and render soil incapable of supporting life. However, conservation farming can protect carbon in soils, and repair damage over time. The farming practice of cover crops is a form of carbon farming. Methods that enhance carbon sequestration in soil include no-till farming, residue mulching and crop rotation. Scientists have described the best management practices for European soils to increase soil organic carbon. These are conversion of arable land to grassland, straw incorporation, reduced tillage, straw incorporation combined with reduced tillage, ley cropping system and cover crops. Another mitigation option is the production of biochar and its storage in soils This is the solid material that remains after the pyrolysis of biomass. Biochar production releases half of the carbon from the biomass—either released into the atmosphere or captured with CCS—and retains the other half in the stable biochar. It can endure in soil for thousands of years. Biochar may increase the soil fertility of acidic soils and increase agricultural productivity. During production of biochar, heat is released which may be used as bioenergy.
Wetlands
Wetland restoration is an important mitigation measure. It has moderate to great mitigation potential on a limited land area with low trade-offs and costs. Wetlands perform two important functions in relation to climate change. They can sequester carbon, converting carbon dioxide to solid plant material through photosynthesis. They also store and regulate water. Wetlands store about 45 million tonnes of carbon per year globally. Some wetlands are a significant source of methane emissions. Some also emit nitrous oxide. Peatland globally covers just 3% of the land's surface. But it stores up to 550 gigatonnes (Gt) of carbon. This represents 42% of all soil carbon and exceeds the carbon stored in all other vegetation types, including the world's forests. The threat to peatlands includes draining the areas for agriculture. Another threat is cutting down trees for lumber, as the trees help hold and fix the peatland. Additionally, peat is often sold for compost. It is possible to restore degraded peatlands by blocking drainage channels in the peatland, and allowing natural vegetation to recover. Mangroves, salt marshes and seagrasses make up the majority of the ocean's vegetated habitats. They only equal 0.05% of the plant biomass on land. But they store carbon 40 times faster than tropical forests. Bottom trawling, dredging for coastal development and fertiliser runoff have damaged coastal habitats. Notably, 85% of oyster reefs globally have been removed in the last two centuries. Oyster reefs clean the water and help other species thrive. This increases biomass in that area. In addition, oyster reefs mitigate the effects of climate change by reducing the force of waves from hurricanes. They also reduce the erosion from rising sea levels. Restoration of coastal wetlands is thought to be more cost-effective than restoration of inland wetlands.
Deep ocean
These options focus on the carbon which ocean reservoirs can store. They include ocean fertilization, ocean alkalinity enhancement or enhanced weathering. The IPCC found in 2022 ocean-based mitigation options currently have only limited deployment potential. But it assessed that their future mitigation potential is large. It found that in total, ocean-based methods could remove 1–100 Gt of CO2 per year. Their costs are in the order of US$40–500 per tonne of CO2. Most of these options could also help to reduce ocean acidification. This is the drop in pH value caused by increased atmospheric CO2 concentrations. The recovery of whale populations can play a role in mitigation as whales play a significant part in nutrient recycling in the ocean. This occurs through what is referred to as the whale pump, where whales' liquid feces stay at the surface of the ocean. Phytoplankton live near the surface of the ocean in order use sunlight to photosynthesize and rely on much of the carbon, nitrogen and iron of the feces. As the phytoplankton form the base of the marine food chain this increases ocean biomass and thus the amount of carbon sequestrated in it. Blue carbon management is another type of ocean-based biological carbon dioxide removal (CDR). It can involve land-based as well as ocean-based measures. The term usually refers to the role that tidal marshes, mangroves and seagrasses can play in carbon sequestration. Some of these efforts can also take place in deep ocean waters. This is where the vast majority of ocean carbon is held. These ecosystems can contribute to climate change mitigation and also to ecosystem-based adaptation. Conversely, when blue carbon ecosystems are degraded or lost they release carbon back to the atmosphere. There is increasing interest in developing blue carbon potential. Scientists have found that in some cases these types of ecosystems remove far more carbon per area than terrestrial forests. However, the long-term effectiveness of blue carbon as a carbon dioxide removal solution remains under discussion.
Enhanced weathering
Enhanced weathering could remove 2–4 Gt of CO2 per year. This process aims to accelerate natural weathering by spreading finely ground silicate rock, such as basalt, onto surfaces. This speeds up chemical reactions between rocks, water, and air. It removes carbon dioxide from the atmosphere, permanently storing it in solid carbonate minerals or ocean alkalinity. Cost estimates are in the US$50–200 per tonne range of CO2.
Other methods to capture and store CO2
In addition to traditional land-based methods to remove carbon dioxide (CO2) from the air, other technologies are under development. These could reduce CO2 emissions and lower existing atmospheric CO2 levels. Carbon capture and storage (CCS) is a method to mitigate climate change by capturing CO2 from large point sources, such as cement factories or biomass power plants. It then stores it away safely instead of releasing it into the atmosphere. The IPCC estimates that the costs of halting global warming would double without CCS. Among the most viable carbon dioxide removal methods considered alongside solar radiation modification, biochar soil amendment is already being deployed commercially. Studies indicate that the carbon it contains remains stable in soils for centuries, giving it a durable potential of removing gigatonnes of CO2 per year. Expert assessments place the net cost of removing CO2 with biochar between US$30 and $120 per tonne. Market data show that biochar supplied 94% of all durable CDR credits delivered in 2023, demonstrating current scalability. Stratospheric aerosol injection (SAI), by comparison, could reduce global temperature quickly by dispersing sulfate aerosols in the stratosphere; however, deployment at climatically relevant scale would require the design and certification of a new fleet of high‑altitude aircraft, a process estimated to take a decade or more, and ongoing operating costs of about US$18 billion for each degree Celsius of cooling. While models confirm that SAI would lower global mean temperature, there are potential side effect including ozone depletion, altered regional precipitation patterns, and the risk of a sudden "termination shock" warming if the programme were interrupted. These systemic risks are absent from biochar deployment. Bioenergy with carbon capture and storage (BECCS) expands on the potential of CCS and aims to lower atmospheric CO2 levels. This process uses biomass grown for bioenergy. The biomass yields energy in useful forms such as electricity, heat, biofuels, etc. through consumption of the biomass via combustion, fermentation, or pyrolysis. The process captures the CO2 that was extracted from the atmosphere when it grew. It then stores it underground or via land application as biochar. This effectively removes it from the atmosphere. This makes BECCS a negative emissions technology (NET). Scientists estimated the potential range of negative emissions from BE