View source for Climate change mitigation/en

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{{Short description|Actions to reduce net greenhouse gas emissions to limit climate change}}
{{About|reducing greenhouse gas emissions or removing greenhouse gases from the atmosphere|other topics|Solar radiation modification|and|Climate movement|and|Climate change adaptation}}
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| image1            = Westmill Solar 2.jpg
| alt1              = Aerial view of a solar farm with part of a wind farm in the background
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| image3            = Haiti reforestation nursery.jpg
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| footer            = Various aspects of climate change mitigation: [[Renewable energy]] ([[solar power|solar]] and [[wind power]]) in England, electrified [[public transport in France]], a [[reforestation]] project in [[Haiti]] to [[carbon dioxide removal|remove carbon dioxide from the atmosphere]], and an example of a [[plant-based diet|plant-based meal]]
}}

'''Climate change mitigation''' (or '''decarbonisation''') is action to limit the [[greenhouse gases]] in the atmosphere that cause [[climate change]]. Climate change mitigation actions include [[energy conservation|conserving energy]] and [[Fossil fuel phase-out|replacing fossil fuels]] with [[sustainable energy|clean energy sources]]. Secondary mitigation strategies include changes to land use and [[carbon sequestration|removing carbon dioxide (CO<sub>2</sub>)]] from the atmosphere. Current climate change mitigation policies are insufficient as they would still result in global warming of about 2.7&nbsp;°C by 2100, significantly above the 2015 [[Paris Agreement]]'s goal of limiting global warming to below 2&nbsp;°C. 

[[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 [[super grid|long-distance electricity transmission]] to group a range of power sources. [[Energy storage]] can also be used to even out power output, and [[Energy demand management|demand management]] can limit power use when power generation is low. Cleanly generated [[Electrification|electricity can usually replace fossil fuels]] for powering transportation, heating buildings, and running industrial processes. Certain processes are more difficult to decarbonise, such as [[Environmental effects of aviation|air travel]] and [[Cement|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 [[Greenhouse gas emissions from agriculture|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 [[Albedo|reflectivity of the surface of the Earth]]. It is possible to cut emissions from agriculture by reducing [[Food loss and waste|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 price|Carbon pricing]] systems have been set up that either [[carbon tax|tax {{CO2}} emissions]] or [[carbon emission trading|cap total emissions and trade emission credits]]. [[Fossil fuel subsidies]] can be eliminated in favour of clean [[energy subsidy|energy subsidies]], and incentives offered for installing energy efficiency measures or switching to electric power sources. 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 action]]s, including [[climate activism]], have a focus on political and cultural aspects.

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== Definitions and scope ==
{{Climate change mitigation}}
Climate change mitigation aims to sustain [[ecosystem]]s 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 [[Greenhouse gas emissions|emissions]] or enhance the [[Carbon sink|sinks]] of [[greenhouse gas]]es".

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&nbsp;°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 sink]]s 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 capture and storage|direct air carbon dioxide capture and storage]] (DACCS) but excludes natural {{CO2}} uptake not directly caused by human activities."

== Emission trends and pledges ==
{{Main|Greenhouse gas emissions}}

{{Pie chart|thumb=right|caption=''GHG emissions 2020 by gas type''<br />without land-use change<br />using 100 year GWP<br />Total: 49.8 Gt{{CO2}}e|label1={{CO2}} mostly by fossil fuel|value1=72|color1=black|label2=CH<sub>4</sub> methane|color2=brown|value2=19|label3={{chem|N|2|O}} nitrous oxide|value3=6|color3=grey|label4=Fluorinated gases|value4=3|color4=blue}}

{{Pie chart|thumb=right|caption={{CO2}} emissions by fuel type|label1=coal|value1=39|color1=#602200|label2=oil|value2=34|color2=#333333|label3=gas|value3=21|color3=#888800|label4=cement|value4=4|color4=#888888|label5=others|value5=1.5|color5=#000050}}

Greenhouse gas emissions from human activities strengthen the [[greenhouse effect]]. This contributes to [[climate change]]. Most is [[carbon dioxide]] from burning [[fossil fuel]]s: 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 station]]s 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 [[Greenhouse gas emissions from agriculture|agriculture]], and [[gas venting]] and [[fugitive emissions]] from the fossil-fuel industry. The largest agricultural methane source is livestock. [[Agricultural soil science|Agricultural soils]] emit [[nitrous oxide]], partly due to fertilizers. There is now a political solution to the problem of fluorinated gases from [[refrigerant]]s. 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]] (N<sub>2</sub>O) 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 [[Global warming potential#Carbon dioxide equivalent|{{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 [[Carbon accounting|greenhouse gas accountin]]g methods that convert volumes of methane, nitrous oxide and other greenhouse gases to [[Global warming potential#Carbon dioxide equivalent|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]], [[Hydrofluorocarbon|hydrofluorocarbons (HFCs)]], [[tropospheric ozone]] and [[black carbon]].

Scientists increasingly 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 ===
[[File:Greenhouse gas emission scenarios 01.svg|thumb|upright=1.35|right|Global greenhouse gas emission scenarios, based on policies and pledges as of 11/21]]
The annual "Emissions Gap Report" by [[United Nations Environment Programme|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 [[IPCC Sixth Assessment Report|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&nbsp;°C (2.7&nbsp;°F). Or in the words of Secretary-General of the United Nations [[António Guterres]]: "Main emitters must drastically cut emissions starting this year".

A 2023 synthesis by leading climate scientists highlighted ten critical areas in climate science with significant policy implications. These include the near inevitability of temporarily exceeding the 1.5&nbsp;°C warming limit, the urgent need for a rapid and managed fossil fuel phase-out, challenges in scaling carbon dioxide removal technologies, uncertainties regarding the future contribution of natural carbon sinks, and the interconnected crises of biodiversity loss and climate change. These insights underscore the necessity for immediate and comprehensive mitigation strategies to address the multifaceted challenges of climate change.

=== Pledges ===
{{Further|Climate target}}
[[Climate Action Tracker]] described the situation on 9 November 2021 as follows. The global temperature will rise by 2.7&nbsp;°C by the end of the century with current policies and by 2.9&nbsp;°C with nationally adopted policies. The temperature will rise by 2.4&nbsp;°C if countries only implement the pledges for 2030. The rise would be 2.1&nbsp;°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&nbsp;°C and go down to 1.8&nbsp;°C by the year 2100.

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{{nbhyph}}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.

== Low-carbon energy ==
{{main|Sustainable energy|Energy transition||}}

[[File:Global Energy Consumption.svg|thumb|upright=1.35|right|Coal, oil, and [[natural gas]] remain the primary global energy sources even as [[Renewable energy|renewables]] have begun rapidly increasing.]]

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&nbsp;°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&nbsp;°C.

[[File:2010- Power capacity by technology - Dec 2022 International Energy Agency.svg|thumb| Renewable energy sources, especially [[Photovoltaic system|solar photovoltaic]] and [[Wind power|wind]] power, are providing an increasing share of power capacity.]]
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 ===
{{main|Solar energy|Wind power}}

[[File:Andasol Guadix 4.jpg|thumb|right|The 150 MW [[Andasol solar power station]] is a commercial [[parabolic trough]] [[solar thermal]] power plant, located in [[Renewable energy in Spain|Spain]]. The Andasol plant uses tanks of molten salt to store solar energy so that it can continue generating electricity for 7.5 hours after the sun has stopped shining.]]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. 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.[[File:Shepherds Flat Wind Farm 2011.jpg|thumb |The [[Shepherds Flat Wind Farm]] is an 845 [[megawatt]] (MW) [[nameplate capacity]], wind farm in the US state of [[Oregon]]. Each turbine is a nameplate 2 or 2.5 MW electricity generator.]]
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 ===
[[File:ThreeGorgesDam-China2009.jpg|thumb |The 22,500 [[megawatt|MW]] [[nameplate capacity]] [[Three Gorges Dam]] in the [[People's Republic of China]], the largest hydroelectric power station in the world]]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 generation|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 [[biofuel]]s.
* [[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 ===
{{Further|Variable renewable energy|energy storage}}

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 [[High-voltage direct current|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.
[[File:1 MW 4 MWh Turner Energy Storage Project in Pullman, WA.jpg|alt=Photo with a set of white containers|thumb|Battery storage facility]]
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. 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 ===
{{Further|Sustainable energy#Nuclear power|Nuclear power#Carbon emissions|Nuclear power#Comparison with renewable energy}}

[[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 ===
{{excerpt|sustainable energy#Fossil fuel switching and mitigation|paragraphs=1-2|file=no}}

== Demand reduction ==
{{Further|Individual action on climate change}}
Reducing demand for products and services that cause greenhouse gas emissions can help in mitigating climate change. One is to reduce demand by [[Individual action on climate change|behavioural and cultural changes]], for example by making changes in diet, especially the decision to reduce meat consumption, an effective [[Individual action on climate change|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 emphasises the importance of integrating behavioural science into climate change mitigation strategies. The article presents six key recommendations aimed at improving individual and collective actions toward reducing greenhouse gas emissions, including 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.

===Energy conservation and efficiency===
{{Main|2 = Energy conservation|3 = Efficient energy use}}
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 [[Energy consumption|consumption of energy]] by using less of an energy service. One way is to [[Efficient energy use|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-efficient buildings|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 ===
[[File:2019 Carbon dioxide emissions by income group - Oxfam data.svg|thumb|upright=1.2|This pie chart illustrates both total emissions for each income group, and emissions ''per person'' within each income group. For example, the 10% with the highest incomes are responsible for half of carbon emissions, and its members emit an average of more than five times as much ''per person'' as members of the lowest half of the income scale.]]

[[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, 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 ===
{{main|Low-carbon diet|Plant-based diet}}

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{{nbsp}}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. If high-income nations switched to a plant-based diet, vast amounts of land used for animal agriculture could be allowed to [[Restoration ecology|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.
[[File:GHG by diet groups.svg|thumb|right|Environmental footprint of 55,504 UK citizens by diet group (''Nat Food'' 4, 565–574, 2023).]]

=== Family size ===
{{Further|Individual action on climate change#Family size}}[[File:World population (UN).svg|thumb|right|upright=1.35|Since 1950, world population has tripled.]]<nowiki> </nowiki>[[Projections of population growth|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 [[Sexual and reproductive health|reproductive health]], especially voluntary [[family planning]], can contribute to reducing population growth.

== Preserving and enhancing carbon sinks ==
[[File:Carbon Dioxide Partitioning.svg|thumb|upright=1.35|right|About 58% of {{CO2}} emissions have been absorbed by [[carbon sinks]], including plant growth, soil uptake, and ocean uptake ([[Global Carbon Project#Global Carbon Budget|2020 Global Carbon Budget]]).]]
{{Main|Carbon dioxide removal|Carbon sequestration|Carbon sink}}

An important mitigation measure is "preserving and enhancing [[carbon sink]]s". This refers to the management of Earth's natural [[carbon sink]]s in a way that preserves or increases their capability to remove CO<sub>2</sub> 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 [[ecosystem]]s 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&nbsp;°C typically project the large-scale use of [[Carbon dioxide removal|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 (GtCO<sub>2</sub> -eq) per year.

=== Forests ===
{{Further|Carbon sequestration#Forestry|Deforestation and climate change|Reducing emissions from deforestation and forest degradation}}

====Conservation====
{{Main|Deforestation#Control|Proforestation|Wildfire#Prevention}}

[[File:Shennongjia virgin forest.jpg|thumb|Transferring [[land rights]] to indigenous inhabitants is argued to efficiently conserve forests.]]
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 forest]]s that have regrown in abandoned farmland are found to have less biodiversity than the original [[old-growth forest]]s. Original forests store 60% more carbon than these new forests. Strategies include [[Rewilding (conservation biology)|rewilding]] and establishing [[wildlife corridor]]s.

====Afforestation, reforestation and preventing desertification====
{{Seealso|Desertification#Countermeasures}}

[[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&nbsp;km) suggest cumulative carbon storage of more than 900&nbsp;GtC (2300&nbsp;Gt{{CO2}}) 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 [[grassland]]s are suitable for conversion into forests. Grasslands can even turn from [[carbon sink]]s to [[carbon source]]s. [[File:Coppice stool.jpg|thumb|right|Helping existing roots and tree stumps regrow even in long deforested areas is argued to be more efficient than planting trees. Lack of legal ownership to trees by locals is the biggest obstacle preventing regrowth.]]

[[Reforestation]] is the restocking of existing depleted forests or in places where there were recently forests. Reforestation could save at least 1{{nbsp}}GtCO<sub>2</sub> per year, at an estimated cost of $5–15 per tonne of carbon dioxide (tCO<sub>2</sub>). Restoring all degraded forests all over the world could capture about 205&nbsp;GtC (750&nbsp;Gt{{CO2}}). 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 forest]]s 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.

[[Rangeland]]s account for more half the world’s land and could sequester 35% of terrestrial carbon. [[Pastoralism|Pastoralist]]s are those who move with their herds that feed and migrate over often [[extensive farming|unenclosed grazeland]]s. 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 [[nomadic pastoralism|pastoralist]]s’ 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 [[nomadic conflict|conflict]].

===Soils===
{{Further|Carbon sequestration#Agriculture|Carbon farming|}}

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 [[Bioenergy with carbon capture and storage|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 [[Plant root exudates|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 crop]]s 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 farming|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 soil]]s and increase [[agricultural productivity]]. During production of biochar, heat is released which may be used as [[bioenergy]].

=== Wetlands ===
{{Further|Carbon sequestration#Wetlands|Wetland#Climate change mitigation}}

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 [[Carbon sink|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 [[Wetland methane emissions|wetlands are a significant source of methane emissions]]. Some also emit [[nitrous oxide]]. [[Peat]]land 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.

[[Mangrove]]s, [[salt marsh]]es and [[seagrass]]es 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 reef]]s 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 ===
{{Further|Carbon sequestration#Sequestration techniques in oceans|Ocean acidification#Technologies to remove carbon dioxide from the ocean|Blue carbon}}

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&nbsp;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 CO<sub>2</sub> concentrations.

The recovery of whale populations can play a role in mitigation as [[whale]]s 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 [[Primary production|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 marsh]]es, [[mangrove]]s and [[seagrass]]es 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===
{{Main|Enhanced weathering}}

Enhanced weathering could remove 2–4&nbsp;Gt of {{CO2}} per year. This process aims to accelerate natural [[weathering]] by spreading finely ground [[Silicate mineral|silicate]] rock, such as [[basalt]], onto surfaces. This speeds up chemical reactions between rocks, water, and air. It [[Carbon dioxide removal|removes carbon dioxide]] from the atmosphere, permanently storing it in solid [[carbonate mineral]]s or ocean [[alkalinity]].

== Other methods to capture and store CO<sub>2</sub> ==
{{Main|Direct air capture|Carbon capture and storage|Bioenergy with carbon capture and storage}}

[[File:Carbon sequestration-2009-10-07.svg|thumb|upright=1.35|Schematic showing both terrestrial and geological sequestration of carbon dioxide emissions from a large point source, for example burning natural gas]]

In addition to traditional land-based methods to remove carbon dioxide (CO<sub>2</sub>) from the air, other technologies are under development. These could reduce CO<sub>2</sub> emissions and lower existing atmospheric CO<sub>2</sub> levels. [[Carbon capture and storage]] (CCS) is a method to mitigate climate change by capturing CO<sub>2</sub> from large [[Point source pollution|point sources]], such as cement factories or [[Bioenergy with carbon capture and storage|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 CO<sub>2</sub> 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 CO<sub>2</sub> that was extracted from the atmosphere when it grew. It then stores it underground or via land application as [[biochar]]. This effectively [[Carbon dioxide removal|removes it from the atmosphere]]. This makes BECCS a negative emissions technology (NET).

Scientists estimated the potential range of negative emissions from BECCS in 2018 as 0–22&nbsp;Gt per year. {{As of|2022}}, BECCS was capturing approximately 2 million tonnes per year of CO<sub>2</sub> annually. The cost and availability of biomass limits wide deployment of BECCS.{{rp|10}} BECCS currently forms a big part of achieving climate targets beyond 2050 in modelling, such as by the [[Integrated assessment modelling|Integrated Assessment Models]] (IAMs) associated with the IPCC process. But many scientists are sceptical due to the risk of loss of biodiversity.

[[Direct air capture]] is a process of capturing {{co2}} directly from the ambient air. This is in contrast to CCS which captures carbon from point sources. It generates a concentrated stream of {{CO2}} for [[Carbon sequestration|sequestration]], [[Carbon capture and utilization|utilisation]] or production of [[carbon-neutral fuel]] and [[windgas]].

== Mitigation by sector ==
{{See also|Greenhouse gas emissions#Emissions by sector}}
{{multiple image
| total_width       = 500
| image1            = Greenhouse Gas Emissions by Economic Sector.svg
| caption1          = Taking into account direct and indirect emissions, industry is the sector with the highest share of global emissions.
| image2            = Global GHG Emissions by Sector 2016.png
| caption2          = 2016 global greenhouse gas emissions by sector.Percentages are calculated from estimated global emissions of all Kyoto Greenhouse Gases, converted to {{CO2}} equivalent quantities (Gt{{CO2}}e).
}}

=== Buildings ===
{{Further|Energy-efficient buildings|Sustainable architecture|Green building|Low-energy house|Air conditioning paradox}}

The building sector accounts for 23% of global energy-related {{CO2}} emissions. About half of the energy is used for space and [[water heating]]. Building insulation can reduce the primary energy demand significantly. [[Heat pump]] loads may also provide a flexible resource that can participate in [[demand response]] to integrate variable renewable resources into the grid. [[Solar water heating]] uses thermal energy directly. Sufficiency measures include moving to smaller houses when the needs of households change, mixed use of spaces and the collective use of devices. Planners and civil engineers can construct new buildings using [[passive solar building design]], [[low-energy building]], or [[zero-energy building]] techniques. In addition, it is possible to design buildings that are more energy-efficient to cool by using lighter-coloured, more reflective materials in the development of urban areas.

Heat pumps efficiently heat buildings, and cool them by [[air conditioning]]. A modern heat pump typically transports around three to five times more thermal energy than electrical energy consumed. The amount depends on the [[coefficient of performance]] and the outside temperature.

Refrigeration and air conditioning account for about 10% of global {{CO2}} emissions caused by fossil fuel-based energy production and the use of fluorinated gases. Alternative cooling systems, such as [[passive cooling]] building design and [[passive daytime radiative cooling]] surfaces, can reduce air conditioning use. Suburbs and cities in hot and arid climates can significantly reduce energy consumption from cooling with daytime radiative cooling.

Energy consumption for cooling is likely to rise significantly due to increasing heat and availability of devices in poorer countries. Of the 2.8 billion people living in the hottest parts of the world, only 8% currently have air conditioners, compared with 90% of people in the US and Japan. By combining energy efficiency improvements and decarbonising electricity for air conditioning with the transition away from super-polluting refrigerants, the world could avoid cumulative greenhouse gas emissions of up to 210–460 Gt{{CO2}}-eq over the next four decades. A shift to renewable energy in the cooling sector comes with two advantages: Solar energy production with mid-day peaks corresponds with the load required for cooling and additionally, cooling has a large potential for load management in the electric grid.

=== Urban planning ===
{{Main|Climate change and cities}}

[[File:BikesInAmsterdam 2004 SeanMcClean.jpg|right|thumb|[[Bicycle]]s have almost no [[carbon footprint]].]]

Cities emitted 28&nbsp;GtCO<sub>2</sub>-eq in 2020 of combined CO<sub>2</sub> and {{CH4}} emissions. This was from producing and consuming goods and services. Climate-smart [[urban planning]] aims to reduce [[urban sprawl|sprawl]] to reduce the distance travelled. This lowers emissions from transportation. Switching from cars by improving [[walkability]] and [[cycling infrastructure]] is beneficial to a country's economy as a whole.

[[Urban forestry]], lakes and other blue and green infrastructure can reduce emissions directly and indirectly by reducing energy demand for cooling. Methane emissions from [[municipal solid waste]] can be reduced by segregation, [[compost]]ing, and recycling.

=== Transport ===
{{Main|Sustainable transport|Phase-out of fossil fuel vehicles}}

[[File:2015- Passenger electric vehicle (EV) annual sales - BloombergNEF.svg|thumb|Sales of electric vehicles (EVs) indicate a trend away from gas-powered vehicles that generate greenhouse gases.]]
Transportation accounts for 15% of emissions worldwide. Increasing the use of public transport, low-carbon freight transport and [[cycling]] are important components of transport decarbonisation.

[[Electric vehicle]]s and environmentally friendly rail help to reduce the consumption of fossil fuels. In most cases, electric trains are more efficient than air transport and truck transport. Other efficiency means include improved public transport, [[smart mobility]], carsharing and [[hybrid vehicle|electric hybrids]]. Fossil-fuel for passenger cars can be included in emissions trading. Furthermore, moving away from a [[car]]-dominated transport system towards low-carbon advanced public transport system is important.

Heavyweight, large personal vehicles (such as cars) require a lot of energy to move and take up much urban space. Several alternatives modes of transport are available to replace these. The European Union has made smart mobility part of its [[European Green Deal]]. In [[Smart city|smart cities]], smart mobility is also important.[[File:Societe de transport de Montreal bus 36-902 - 08.jpg|thumb|[[Battery electric bus]] in [[Montreal]]]]
The World Bank is helping lower income countries buy electric buses. Their purchase price is higher than diesel buses. But lower running costs and health improvements due to cleaner air can offset this higher price.

Between one quarter and three quarters of cars on the road by 2050 are forecast to be electric vehicles. [[Hydrogen]] may be a solution for long-distance heavy freight trucks, if batteries alone are too heavy.

==== Shipping ====
{{Further|Environmental effects of shipping#Greenhouse gas emissions}}

In the shipping industry, the use of [[liquefied natural gas]] (LNG) as a marine bunker fuel is driven by emissions regulations. Ship operators must switch from [[heavy fuel oil]] to more expensive oil-based fuels, implement costly flue gas treatment technologies or switch to [[Marine LNG Engine|LNG engines]]. Methane slip, when gas leaks unburned through the engine, lowers the advantages of LNG. [[Maersk]], the world's biggest container shipping line and vessel operator, warns of [[stranded asset]]s when investing in transitional fuels like LNG. The company lists green [[ammonia]] as one of the preferred fuel types of the future. It has announced the first carbon-neutral vessel on the water by 2023, running on carbon-neutral [[methanol]]. Cruise operators are trialling partially [[hydrogen-powered ship]]s.

Hybrid and all electric ferries are suitable for short distances. Norway's goal is an all electric fleet by 2025.

==== Air transport ====
{{Further|environmental impact of aviation}}
[[File:CO2 emissions fraction of Aviation (%25).png|thumb|Between 1940 and 2018, aviation [[CO2 emissions|CO<sub>2</sub> emissions]] grew from 0.7% to 2.65% of all {{CO2}} emissions.]]

Jet airliners contribute to climate change by emitting carbon dioxide, [[nitrogen oxides]], [[Condensation trails|contrails]] and particulates. Their [[radiative forcing]] is estimated at 1.3–1.4 that of {{CO2}} alone, excluding induced [[cirrus cloud]]. In 2018, global commercial operations generated 2.4% of all {{CO2}} emissions.

The aviation industry has become more fuel efficient. But overall emissions have risen as the volume of air travel has increased.By 2020, aviation emissions were 70% higher than in 2005 and they could grow by 300% by 2050.

It is possible to reduce aviation's environmental footprint by better [[fuel economy in aircraft]]. Optimising flight routes to lower non-{{CO2}} effects on climate from nitrogen oxides, particulates or contrails can also help. [[Aviation biofuel]], [[carbon emission trading]] and [[carbon offsetting]], part of the 191 nation ICAO's [[Carbon Offsetting and Reduction Scheme for International Aviation]] (CORSIA), can lower {{CO2}} emissions. [[Short-haul flight ban]]s, train connections, personal choices and [[aviation taxation and subsidies|taxation on flights]] can lead to fewer flights. [[Hybrid electric aircraft]] and [[electric aircraft]] or [[hydrogen-powered aircraft]] may replace fossil fuel-powered aircraft.

Experts expect emissions from aviation to rise in most projections, at least until 2040. They currently amount to 180&nbsp;Mt of {{CO2}} or 11% of transport emissions. [[Aviation biofuel]] and hydrogen can only cover a small proportion of flights in the coming years. Experts expect hybrid-driven aircraft to start commercial regional scheduled flights after 2030. Battery-powered aircraft are likely to enter the market after 2035. Under CORSIA, flight operators can purchase [[carbon offset]]s to cover their emissions above 2019 levels. CORSIA will be compulsory from 2027.

=== Agriculture, forestry and land use ===
[[File:Environmental-impact-of-food-by-life-cycle-stage.png|thumb|upright=1.35|[[Greenhouse gas emissions]] across the [[supply chain]] for different foods, showing which type of food should be encouraged and which discouraged from a mitigation perspective]]
{{See also|Greenhouse gas emissions from agriculture|Environmental impact of meat production|4=Sustainable agriculture}}

Almost 20% of greenhouse gas emissions come from the agriculture and forestry sector. To significantly reduce these emissions, annual investments in the agriculture sector need to increase to $260 billion by 2030. The potential benefits from these investments are estimated at $4.3 trillion by 2030, offering a substantial economic return of 16-to-1.

Mitigation measures in the food system can be divided into four categories. These are demand-side changes, ecosystem protections, mitigation on farms, and mitigation in [[supply chains]]. On the demand side, limiting [[food waste]] is an effective way to reduce food emissions. Changes to a diet less reliant on animal products such as [[plant-based diets]] are also effective.

With 21% of global methane emissions, cattle are a major driver of global warming. When rainforests are cut and the land is converted for grazing, the impact is even higher. In Brazil, producing 1&nbsp;kg of beef can result in the emission of up to 335&nbsp;kg CO<sub>2</sub>-eq.
Other livestock, manure management and rice cultivation also emit greenhouse gases, in addition to fossil fuel combustion in agriculture.

Important mitigation options for reducing the greenhouse gas emissions from livestock include genetic selection, introduction of [[Methanotroph|methanotrophic bacteria]] into the rumen, diet modification and grazing management. Other options are diet changes towards [[ruminant]]-free alternatives, such as [[milk substitute]]s and [[meat analogue]]s. Non-ruminant livestock, such as poultry, emit far fewer GHGs.

It is possible to cut methane emissions in rice cultivation by improved water management, combining dry seeding and one drawdown, or executing a [[alternate wetting and drying|sequence of wetting and drying]]. This results in emission reductions of up to 90% compared to full flooding and even increased yields.

Reducing the usage of [[Fertilizer#Nitrogen_fertilizers|nitrogen fertilizers]] through [[nutrient management]] could avoid nitrous oxide emissions equal to 2.77 - 11.48 gigatons of carbon dioxide from 2020 to 2050.

=== Industry ===
{{Pie chart
 | caption= Global [[List of countries by carbon dioxide emissions|carbon dioxide emissions]] by country in 2023:
 | other = yes
 | label1 = China
 | value1 = 31.8 | color1=#E33
 | label2 = United States
 | value2 = 14.4 | color2=#1A9
 | label3 = European Union
 | value3 = 4.9  | color3=#36A
 | label4 = India
 | value4 = 9.5  | color4=#CC5
 | label5 = Russia
 | value5 = 5.8  | color5=#E72
 | label6 = Japan
 | value6 = 3.5  | color6=#928
 }}
Industry is the largest emitter of greenhouse gases when direct and indirect emissions are included. [[Electrification]] can reduce emissions from industry. [[Green hydrogen]] can play a major role in [[energy-intensive industries]] for which electricity is not an option. Further mitigation options involve the steel and cement industry, which can switch to a less polluting production process. Products can be made with less material to reduce emission-intensity and industrial processes can be made more efficient. Finally, [[circular economy]] measures reduce the need for new materials. This also saves on emissions that would have been released from the mining of collecting of those materials.

The decarbonisation of cement production requires new technologies, and therefore investment in innovation. But no technology for mitigation is yet mature. So CCS will be necessary at least in the short-term.

Another sector with a significant carbon footprint is the steel sector, which is responsible for about 7% of global emissions. Emissions can be reduced by using [[electric arc furnaces]] to melt and recycle scrap steel. To produce virgin steel without emissions, [[blast furnace]]s could be replaced by hydrogen [[direct reduced iron]] and [[electric arc furnace]]s. Alternatively, carbon capture and storage solutions can be used.

Coal, gas and oil production often come with significant methane leakage. In the early 2020s some governments recognised the scale of the problem and introduced regulations. [[Methane leaks]] at oil and gas wells and processing plants are cost-effective to fix in countries which can easily trade gas internationally. There are leaks in countries where gas is cheap; such as Iran, and Turkmenistan. Nearly all this can be stopped by replacing old components and preventing routine flaring. [[Coalbed methane]] may continue leaking even after the mine has been closed. But it can be captured by drainage and/or ventilation systems. Fossil fuel firms do not always have financial incentives to tackle methane leakage.

== Co-benefits ==
Co-benefits of climate change mitigation, also often referred to as ''ancillary benefits'', were firstly dominated in the scientific literature by studies that describe how lower GHG emissions lead to better air quality and consequently impact human health positively. The scope of co-benefits research expanded to its economic, social, ecological and political implications.

Positive secondary effects that occur from climate mitigation and [[climate change adaptation|adaptation]] measures have been mentioned in research since the 1990s. The IPCC first mentioned the role of co-benefits in 2001, followed by its fourth and fifth assessment cycle stressing improved working environment, reduced waste, health benefits and reduced capital expenditures.

The IPCC pointed out in 2007: "Co-benefits of GHG mitigation can be an important decision criteria in analyses carried out by policy-makers, but they are often neglected" and added that the co-benefits are "not quantified, monetised or even identified by businesses and decision-makers". Appropriate consideration of co-benefits can greatly "influence policy decisions concerning the timing and level of mitigation action", and there can be "significant advantages to the national economy and technical innovation".

An analysis of climate action in the UK found that public health benefits are a major component of the total benefits derived from climate action.

=== Employment and economic development ===
{{See also|Renewable energy#Market and industry trends}}
Co-benefits can positively impact employment, industrial development, states' energy independence and energy self-consumption. The deployment of renewable energies can foster job opportunities. Depending on the country and deployment scenario, replacing coal power plants with renewable energy can more than double the number of jobs per average MW capacity. Investments in renewable energies, especially in solar- and wind energy, can boost the value of production. Countries which rely on energy imports can enhance their energy independence and ensure supply security by deploying renewables. National energy generation from renewables lowers the demand for fossil fuel imports which scales up annual economic saving.

The European Commission forecasts a shortage of 180,000 skilled workers in hydrogen production and 66,000 in solar photovoltaic power by 2030.

=== Energy security ===
A higher share of renewables can additionally lead to more [[energy security]].Socioeconomic co-benefits have been analysed such as energy access in rural areas and improved rural livelihoods. Rural areas which are not fully electrified can benefit from the deployment of [[Renewable energy|renewable energies]]. Solar-powered mini-grids can remain economically viable, cost-competitive and reduce the number of power cuts. Energy reliability has additional social implications: stable electricity improves the quality of education.

The International Energy Agency ([[International Energy Agency|IEA]]) spelled out the "multiple benefits approach" of [[Efficient energy use|energy efficiency]] while the International Renewable Energy Agency ([[International Renewable Energy Agency|IRENA]]) operationalised the list of co-benefits of the renewable energy sector.

===Health and well-being===
{{Further|Effects of climate change on human health#Benefits from climate change mitigation and adaptation}}
{{See also|Health and environmental impact of the coal industry|Health and environmental impact of the petroleum industry}}

The health benefits from climate change mitigation are significant. Potential measures can not only mitigate future health impacts from climate change but also improve health directly. Climate change mitigation is interconnected with various health co-benefits, such as those from reduced [[air pollution]]. Air pollution generated by fossil fuel combustion is both a major driver of global warming and the cause of a large number of annual deaths. Some estimates are as high as {{tooltip|2=A review of this and a more nuanced assessment of mortality impacts in terms of contribution to death, rather than number of deceased, may be needed|8.7 million}} excess deaths during 2018. A 2023 study estimated that fossil fuels kill over 5 million people each year, as of 2019, by causing diseases such as [[heart attack]], [[stroke]] and [[chronic obstructive pulmonary disease]]. [[Particulate pollution|Particulate air pollution]] kills by far the most, followed by [[ground-level ozone]].

Mitigation policies can also promote healthier diets such as less red meat, more active lifestyles, and increased exposure to green urban spaces. Access to urban green spaces provides benefits to mental health as well. The increased use of [[Green infrastructure|green]] and [[Blue space|blue infrastructure]] can reduce the [[urban heat island]] effect. This reduces [[Hyperthermia|heat stress]] on people.

===Climate change adaptation===
{{Further|Climate change adaptation#Co-benefits with mitigation}}
Some mitigation measures have co-benefits in the area of [[climate change adaptation]]. This is for example the case for many [[nature-based solutions]]. Examples in the urban context include urban green and blue infrastructure which provide mitigation as well as adaptation benefits. This can be in the form of [[Urban forestry|urban forests]] and street trees, [[green roof]]s and [[Green wall|walls]], [[urban agriculture]] and so forth. The mitigation is achieved through the conservation and expansion of carbon sinks and reduced energy use of buildings. Adaptation benefits come for example through reduced heat stress and flooding risk.

[[File:Carbon taxes and emission trading worldwide.svg|alt=Carbon taxes and emission trading worldwide|thumb|upright=1.35|Emission trading and carbon taxes around the world (2019)
{{Legend|#009a3e|[[Carbon emission trading]] implemented or scheduled}}
{{Legend|#323b90|[[Carbon tax]] implemented or scheduled}}
{{Legend|#fbba00|[[Carbon emission trading]] or [[carbon tax]] under consideration}}]]

== Negative side effects ==
Mitigation measures can also have negative side effects and risks. In agriculture and forestry, mitigation measures can affect biodiversity and ecosystem functioning. In renewable energy, mining for metals and minerals can increase threats to conservation areas. There is some research into ways to recycle solar panels and electronic waste. This would create a source for materials so there is no need to mine them.

Scholars have found that discussions about risks and negative side effects of mitigation measures can lead to deadlock or the feeling that there are insuperable barriers to taking action.

== Costs and funding ==
{{Main|Economics of climate change mitigation#Assessing costs and benefits|Economic analysis of climate change}}

Several factors affect mitigation cost estimates. One is the baseline. This is a reference scenario that the alternative mitigation scenario is compared with. Others are the way costs are modelled, and assumptions about future government policy. Cost estimates for mitigation for specific regions depend on the quantity of emissions allowed for that region in future, as well as the timing of interventions.

Mitigation costs will vary according to how and when emissions are cut. Early, well-planned action will minimise the costs. Globally, the benefits of keeping warming under 2&nbsp;°C exceed the costs, which according to [[The Economist]] are affordable.

Economists estimate the cost of climate change mitigation at between 1% and 2% of [[Gross domestic product|GDP]]. While this is a large sum, it is still far less than the subsidies governments provide to the ailing fossil fuel industry. The [[International Monetary Fund]] estimated this at more than $5 trillion per year.

Another estimate says that financial flows for climate mitigation and adaptation are going to be over $800 billion per year. These financial requirements are predicted to exceed $4 trillion per year by 2030.

Globally, limiting warming to 2&nbsp;°C may result in higher economic benefits than economic costs. The economic repercussions of mitigation vary widely across regions and households, depending on policy design and level of [[international cooperation]]. Delayed global cooperation increases policy costs across regions, especially in those that are relatively carbon intensive at present. Pathways with uniform carbon values show higher mitigation costs in more carbon-intensive regions, in fossil-fuels exporting regions and in poorer regions. Aggregate quantifications expressed in GDP or monetary terms undervalue the economic effects on households in poorer countries. The actual effects on welfare and well-being are comparatively larger.

[[Cost–benefit analysis]] may be unsuitable for analysing climate change mitigation as a whole. But it is still useful for analysing the difference between a 1.5&nbsp;°C target and 2&nbsp;°C. One way of estimating the cost of reducing emissions is by considering the likely costs of potential technological and output changes. Policymakers can compare the [[marginal abatement costs]] of different methods to assess the cost and amount of possible abatement over time. The marginal abatement costs of the various measures will differ by country, by sector, and over time.

[[Eco-tariff]]s on only imports contribute to reduced global export [[Competition (economics)|competitiveness]] and to [[deindustrialisation]].

=== Avoided costs of climate change effects ===
{{See also|Economic impacts of climate change}}

It is possible to avoid some of the costs of the [[effects of climate change]] by limiting climate change. According to the [[Stern Review]], inaction can be as high as the equivalent of losing at least 5% of global gross domestic product (GDP) each year, now and forever. This can be up to 20% of GDP or more when including a wider range of risks and impacts. But mitigating climate change will only cost about 2% of GDP. Also it may not be a good idea from a financial perspective to delay significant reductions in greenhouse gas emissions.

Mitigation solutions are often evaluated in terms of costs and greenhouse gas reduction potentials. This fails to take into account the direct effects on human well-being.

=== Distributing emissions abatement costs ===
Mitigation at the speed and scale required to limit warming to 2&nbsp;°C or below implies deep economic and structural changes. These raise multiple types of distributional concerns across regions, income classes and sectors.

There have been different proposals on how to allocate responsibility for cutting emissions. These include [[egalitarianism]], [[basic needs]] according to a minimum level of consumption, proportionality and the [[Polluter pays principle|polluter-pays principle]]. A specific proposal is "equal per capita entitlements". This approach has two categories. In the first category, emissions are allocated according to national population. In the second category, emissions are allocated in a way that attempts to account for historical or cumulative emissions.

===Funding===
{{main|Climate finance|Economics of climate change mitigation#Finance}}

In order to reconcile economic development with mitigating carbon emissions, developing countries need particular support. This would be both financial and technical. The IPCC found that accelerated support would also tackle inequities in financial and economic vulnerability to climate change. One way to achieve this is the Kyoto Protocol's [[Clean Development Mechanism]] (CDM).

== Policies ==

=== National policies ===
[[File:Total CO2 emissions by country in 2017 vs per capita emissions (top 40 countries).svg|thumb|Although China is the leading producer of {{CO2}} emissions in the world with the U.S. second, per capita the U.S. leads China by a fair margin (data from 2017).]]Climate change mitigation policies can have a large and complex impact on the socio-economic status of individuals and countries This can be both positive and negative. It is important to design policies well and make them inclusive. Otherwise climate change mitigation measures can impose higher financial costs on poor households.

An evaluation was conducted on 1,500 climate policy interventions made between 1998 and 2022. The interventions took place in 41 countries and across 6 continents, which together contributed 81% of the world's total emissions as of 2019. The evaluation found 63 successful interventions that resulted in significant emission reductions; the total {{CO2}} release averted by these interventions was between 0.6 and 1.8 billion metric tonnes. The study focused on interventions with at least 4.5% emission reductions, but the researchers noted that meeting the reductions required by the Paris Agreement would require 23 billion metric tonnes per year. Generally, carbon pricing was found to be most effective in [[Developed country|developed countries]], while regulation was most effective in the [[Developing country|developing countries]]. Complementary policy mixes benefited from synergies, and were mostly found to be more effective interventions than the implementation of isolated policies.

The [[OECD]] recognise 48 distinct climate mitigation policies suitable for implementation at national level. Broadly, these can be categorised into three types: ''market based'' instruments, ''non market based'' instruments and ''other'' policies.
* '''Other''' policies include the ''Establishing an Independent climate advisory body''.
* '''Non market based''' policies include the Implementing or tighening of ''Regulatory standards''. These set technology or performance standards. They can be effective in addressing the [[market failure]] of informational barriers.
*Among '''market based''' policies, the ''carbon price'' has been found to be the most effective (at least for developed economies), and has its own section below. Additional ''market based'' policy instruments for climate change mitigation include:
''Emissions taxes'' These often require domestic emitters to pay a fixed fee or tax for every tonne of CO<sub>2</sub> emissions they release into the atmosphere. [[Methane emissions]] from fossil fuel extraction are also occasionally taxed. But methane and nitrous oxide from agriculture are typically not subject to tax.
<br />''Removing unhelpful subsidies:'' Many countries provide subsidies for activities that affect emissions. For example, significant [[fossil fuel subsidies]] are present in many countries. [[Fossil fuel phase-out#Phase-out of fossil fuel subsidies|Phasing-out fossil fuel subsidies]] is crucial to address the climate crisis. It must however be done carefully to avoid protests and making poor people poorer.
<br />''Creating helpful subsidies'': Creating subsidies and financial incentives. One example is [[Energy subsidy|energy subsidies]] to support clean generation which is not yet commercially viable such as tidal power.
<br />''Tradable permits'': A [[carbon emission trading|permit system]] can limit emissions.

==== Carbon pricing ====
{{Main|Carbon price}}

[[File:ETS-allowance-prices.svg|thumb|upright=1.35|Carbon emission trade – allowance prices from 2008]]
Imposing additional costs on greenhouse gas emissions can make fossil fuels less competitive and accelerate investments into low-carbon sources of energy. A growing number of countries raise a fixed [[carbon tax]] or participate in dynamic [[carbon emission trading]] (ETS) systems. In 2021, more than 21% of global greenhouse gas emissions were covered by a carbon price. This was a big increase from earlier due to the introduction of the [[Chinese national carbon trading scheme]].

Trading schemes offer the possibility to limit emission allowances to certain reduction targets. However, an oversupply of allowances keeps most ETS at low price levels around $10 with a low impact. This includes the Chinese ETS which started with $7/t{{CO2}} in 2021. One exception is the [[European Union Emission Trading Scheme]] where prices began to rise in 2018. They reached about €80/t{{CO2}} in 2022. This results in additional costs of about €0.04/KWh for coal and €0.02/KWh for gas combustion for electricity, depending on the [[emission intensity]]. Industries which have high energy requirements and high emissions often pay only very low energy taxes, or even none at all.

While this is often part of national schemes, [[carbon offsets and credits]] can be part of a voluntary market as well such as on the international market. Notably, the company [[Blue Carbon (company)|Blue Carbon]] of the [[UAE]] has bought ownership over an area equivalent to the United Kingdom to be preserved in return for carbon credits.

=== International agreements ===
{{Main|Politics of climate change}}

{{See also|Climate change#Policies and politics|Climate change mitigation framework}}

[[International cooperation]] is considered a ''critical enabler'' for climate action Almost all countries are parties to the [[United Nations Framework Convention on Climate Change]] (UNFCCC). The ultimate objective of the UNFCCC is to stabilise atmospheric concentrations of greenhouse gases at a level that would prevent dangerous human interference with the climate system.

Although not designed for this purpose, the [[Montreal Protocol]] has benefited climate change mitigation efforts. The Montreal Protocol is an international treaty that has successfully reduced emissions of [[ozone-depleting substance]]s such as [[Chlorofluorocarbon|CFCs]]. These are also greenhouse gases.

==== Paris Agreement ====
[[File:ParisAgreement.svg|thumb|[[Paris Agreement#Parties and signatories|Signatories (yellow) and parties (blue)]] to the [[Paris Agreement]]]]
{{excerpt|Paris Agreement|paragraphs=1|file=no}}

== History ==
{{See also|Climate change mitigation framework|History of climate change policy and politics|Kyoto Protocol#Chronology|Paris Agreement#Development}}
Historically efforts to deal with climate change have taken place at a multinational level. They involve attempts to reach a consensus decision at the United Nations, under the [[United Nations Framework Convention on Climate Change]] (UNFCCC). This is the dominant approach historically of engaging as many international governments as possible in taking action on a worldwide public issue. The [[Montreal Protocol]] in 1987 is a precedent that this approach can work. But some critics say the top-down framework of only utilising the UNFCCC consensus approach is ineffective. They put forward counter-proposals of bottom-up governance. At this same time this would lessen the emphasis on the UNFCCC.

The [[Kyoto Protocol]] to the UNFCCC adopted in 1997 set out legally binding emission reduction commitments for the "Annex 1" countries. The Protocol defined three international policy instruments ("[[Flexibility mechanisms|Flexibility Mechanisms]]") which could be used by the Annex 1 countries to meet their emission reduction commitments. According to Bashmakov, use of these instruments could significantly reduce the costs for Annex 1 countries in meeting their emission reduction commitments.

The Paris Agreement reached in 2015 succeeded the [[Kyoto Protocol]] which expired in 2020. [[List of Kyoto Protocol signatories|Countries that ratified the Kyoto protocol]] committed to reduce their emissions of carbon dioxide and five other greenhouse gases, or engage in [[carbon emissions trading]] if they maintain or increase emissions of these gases.

In 2015, the UNFCCC's "structured expert dialogue" came to the conclusion that, "in some regions and vulnerable ecosystems, high risks are projected even for warming above 1.5&nbsp;°C". Together with the strong diplomatic voice of the poorest countries and the island nations in the Pacific, this expert finding was the driving force leading to the decision of the 2015 [[2015 United Nations Climate Change Conference|Paris Climate Conference]] to lay down this 1.5&nbsp;°C long-term target on top of the existing 2&nbsp;°C goal.

== Barriers ==
{{See also|Economic analysis of climate change#Economic barriers to addressing climate change mitigation|Climate change denial|Public opinion on climate change|Sustainability#Barriers}}
[[File:A typology of climate delay discourses.png|thumb|A typology of discourses aimed at delaying climate change mitigation]]
[[File:Distribution of committed CO2 emissions from developed fossil fuel reserves.jpg|thumb|upright=1.35|Distribution of committed {{CO2}} emissions from developed fossil fuel reserves]]

There are individual, institutional and market barriers to achieving climate change mitigation. They differ for all the different mitigation options, regions and societies.

Difficulties with [[Carbon accounting|accounting for carbon dioxide removal]] can act as economic barriers. This would apply to BECCS ([[bioenergy with carbon capture and storage]]). The strategies that companies follow can act as a barrier. But they can also accelerate decarbonisation.

In order to decarbonise societies the state needs to play a predominant role. This is because it requires a massive coordination effort. This strong government role can only work well if there is social cohesion, political stability and trust.

For land-based mitigation options, finance is a major barrier. Other barriers are cultural values, governance, accountability and institutional capacity.

Developing countries face further barriers to mitigation.
* The cost of capital increased in the early 2020s. A lack of available capital and finance is common in developing countries. Together with the absence of regulatory standards, this barrier supports the proliferation of inefficient equipment.
* There are also financial and [[Capacity building|capacity]] barrier in many of these countries.

One study estimates that only 0.12% of all funding for climate-related research goes on the social science of climate change mitigation. Vastly more funding goes on natural science studies of climate change. Considerable sums also go on studies of the impact of climate change and adaptation to it.

== Society and culture ==

=== Commitments to divest ===
[[File:Climate investment is stalling, but more firms plan to invest, with firms in low-carbon sectors taking the lead.jpg|thumb|upright=1.35|More firms plan to invest in climate change mitigation, specifically focusing on low-carbon sectors.]]More than 1000 organisations with investments worth US$8 trillion have made commitments to [[fossil fuel divestment]]. Socially responsible investing funds allow investors to invest in funds that meet high [[environmental, social and corporate governance]] (ESG) standards.

=== Impacts of the COVID-19 pandemic ===
{{Main|Impact of the COVID-19 pandemic on the environment#Climate change}}

The [[COVID-19 pandemic]] led some governments to shift their focus away from climate action, at least temporarily. This obstacle to environmental policy efforts may have contributed to slowed investment in green energy technologies. The economic slowdown resulting from COVID-19 added to this effect.

In 2020, carbon dioxide emissions fell by 6.4% or 2.3 billion tonnes globally. Greenhouse gas emissions rebounded later in the pandemic as many countries began lifting restrictions. The direct impact of pandemic policies had a negligible long-term impact on climate change.

== Examples by country ==
{{multiple image
| total_width       = 450
| image1            = 20210626 Variwide chart of greenhouse gas emissions per capita by country.svg
| caption1          = Greenhouse gas emissions ''per person'' in the highest-emitting countries. Though China has the greatest total annual carbon dioxide emissions, the U.S. and a few other high-emitting countries exceed China in ''per capita'' emissions.
| image2            = 2021 Carbon dioxide (CO2) emissions per person versus GDP per person - scatter plot.svg
| caption2          = Richer [[Developed country|(developed)]] countries emit more {{CO2}} per person than poorer [[Developing country|(developing)]] countries. Emissions are roughly proportional to [[Gross domestic product|GDP]] per person, though the rate of increase diminishes with average GDP/pp of about $10,000.
}}

=== United States ===
{{Main|Climate change in the United States}}

{{excerpt|Greenhouse gas emissions by the United States#Federal Policies}}

=== China ===
{{main|Greenhouse gas emissions by China|Climate change in China|Debate over China's economic responsibilities for climate change mitigation}}

China has committed to peak emissions by 2030 and reach [[net zero]] by 2060. Warming cannot be limited to 1.5&nbsp;°C if any [[Electricity sector in China#Coal power|coal plants in China]] (without carbon capture) operate after 2045. The [[Chinese national carbon trading scheme]] started in 2021.

=== European Union ===
The [[European Commission]] estimates that an additional €477 million in annual investment is needed for the European Union to meet its [[Fit for 55|Fit-for-55]] decarbonisation goals.

In the European Union, government-driven policies and the [[European Green Deal]] have helped position greentech (as an example) as a vital area for venture capital investment. By 2023, venture capital in the EU's greentech sector equalled that of the United States, reflecting a concerted effort to drive innovation and mitigate climate change through targeted financial support. The European Green Deal has fostered policies that contributed to a 30% rise in venture capital for greentech companies in the EU from 2021 to 2023, despite a downturn in other sectors during the same period.

While overall venture capital investment in the EU remains about six times lower than in the United States, the greentech sector has closed this gap significantly, attracting substantial funding. Key areas benefitting from increased investments are energy storage, circular economy initiatives, and agricultural technology. This is supported by the EU's ambitious goal to reduce greenhouse gas emissions by at least 55% by 2030.

== Related approaches ==

=== Relationship with solar radiation modification (SRM) ===
While [[solar geoengineering|solar radiation modification]] (SRM) could reduce surface temperatures, it temporarily masks climate change rather than addressing the root cause, which is greenhouse gases. SRM would work by altering how much solar radiation the Earth absorbs. Examples include reducing the amount of sunlight reaching the surface, reducing the optical thickness and lifetime of clouds, and changing the ability of the surface to reflect radiation. The [[Intergovernmental Panel on Climate Change|IPCC]] describes SRM as a climate risk reduction strategy or supplementary option rather than a climate mitigation option.

The terminology in this area is still evolving. Experts sometimes use the term ''geoengineering'' or [[climate engineering]] in the scientific literature for both CDR or SRM, if the techniques are used at a global scale. IPCC reports no longer use the terms ''geoengineering'' or ''climate engineering''.

== See also ==
* [[Carbon budget]]
* [[Carbon offsets and credits]]
* [[Carbon price]]
* [[Climate movement]]
* [[Climate change denial]]
* [[Tipping points in the climate system]]
{{subject bar|auto=y|d=y|Climate change|Plants|Trees}}

==Further reading==
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[[Category:Climate change mitigation| ]]
[[Category:Biogeochemical cycle]]
[[Category:Biogeography]]
[[Category:Carbon|Cycle]]
[[Category:Chemical oceanography]]
[[Category:Climate change policy]]
[[Category:Geochemistry]]
[[Category:Numerical climate and weather models]]
[[Category:Soil]]
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