Climate change mitigation/ja: Difference between revisions

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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%.

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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]] (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 [[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]].

=== 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.

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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.

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.

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== 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.

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=== 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.

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=== 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.

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=== 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.

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=== 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.

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=== 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]].

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===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.

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=== 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 ==

| 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.

}}

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=== United States ===

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

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

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=== 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.