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Friday, February 16, 2024

Stratospheric aerosol injection

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Stratospheric_aerosol_injection

Stratospheric aerosol injection is a proposed method of solar geoengineering (or solar radiation modification) to reduce global warming. This would introduce aerosols into the stratosphere to create a cooling effect via global dimming and increased albedo, which occurs naturally from volcanic winter. It appears that stratospheric aerosol injection, at a moderate intensity, could counter most changes to temperature and precipitation, take effect rapidly, have low direct implementation costs, and be reversible in its direct climatic effects. The Intergovernmental Panel on Climate Change concludes that it "is the most-researched [solar geoengineering] method, with high agreement that it could limit warming to below 1.5 °C (2.7 °F)." However, like other solar geoengineering approaches, stratospheric aerosol injection would do so imperfectly and other effects are possible, particularly if used in a suboptimal manner.

Various forms of sulfur have been shown to cool the planet after large volcanic eruptions. However, as of 2021, there has been little research and existing natural aerosols in the stratosphere are not well understood. So there is no leading candidate material. Alumina, calcite and salt are also under consideration. The leading proposed method of delivery is custom aircraft.

Scientific basis

Natural and anthropogenic sulfates

There is a wide range of particulate matter suspended in the atmosphere at various height and in various sizes. By far the best-studied are the various sulfur compounds collectively referred to sulfate aerosols. This group includes inorganic sulfates (SO₄^2-),HSO₄^- and H₂SO₄^-: organic sulfur compounds are sometimes included as well, but are of lower importance. Sulfate aerosols can be anthropogenic (through the combustion of fossil fuels with a high sulfur content, primarily coal and certain less-refined fuels, like aviation and bunker fuel),biogenic from hydrosphere and biosphere, geological via volcanoes or weather-driven from wildfires and other natural combustion events.

Inorganic aerosols are mainly produced when sulfur dioxide reacts with water vapor to form gaseous sulfuric acid and various salts (often through an oxidation reaction in the clouds), which are then thought to experience hygroscopic growth and coagulation and then shrink through evaporation.as microscopic liquid droplets or fine (diameter of about 0.1 to 1.0 micrometre) sulfate solid particles in a colloidal suspension,with smaller particles at times coagulating into larger ones.The other major source are chemical reactions with dimethyl sulfide (DMS), predominantly sourced from marine plankton, with a smaller contribution from swamps and other such wetlands. And sometimes, aerosols are produced from photochemical decomposition of COS (carbonyl sulfide), or when solid sulfates in the sea salt spray can react with gypsum dust particles).

Major volcanic eruptions have an overwhelming effect on sulfate aerosol concentrations in the years when they occur: eruptions ranking 4 or greater on the Volcanic Explosivity Index inject SO₂ and water vapor directly into the stratosphere, where they react to create sulfate aerosol plumes. Volcanic emissions vary significantly in composition, and have complex chemistry due to the presence of ash particulates and a wide variety of other elements in the plume. Only stratovolcanoes containing primarily felsic magmas are responsible for these fluxes, as mafic magma erupted in shield volcanoes doesn't result in plumes which reach the stratosphere. However, before the Industrial Revolution, dimethyl sulfide pathway was the largest contributor to sulfate aerosol concentrations in a more average year with no major volcanic activity. According to the IPCC First Assessment Report, published in 1990, volcanic emissions usually amounted to around 10 million tons in 1980s, while dimethyl sulfide amounted to 40 million tons. Yet, by that point, the global human-caused emissions of sulfur into the atmosphere became "at least as large" as all natural emissions of sulfur-containing compounds combined: they were at less than 3 million tons per year in 1860, and then they increased to 15 million tons in 1900, 40 million tons in 1940 and about 80 millions in 1980. The same report noted that "in the industrialized regions of Europe and North America, anthropogenic emissions dominate over natural emissions by about a factor of ten or even more". In the eastern United States, sulfate particles were estimated to account for 25% or more of all air pollution. Meanwhile, the Southern Hemisphere had much lower concentrations due to being much less densely populated, with an estimated 90% of the human population in the north. In the early 1990s, anthropogenic sulfur dominated in the Northern Hemisphere, where only 16% of annual sulfur emissions were natural, yet amounted for less than half of the emissions in the Southern Hemisphere.

Such an increase in sulfate aerosol emissions had a variety of effects. At the time, the most visible one was acid rain, caused by precipitation from clouds carrying high concentrations of sulfate aerosols in the troposphere.

At its peak, acid rain has eliminated brook trout and some other fish species and insect life from lakes and streams in geographically sensitive areas, such as Adirondack Mountains in the United States. Acid rain worsens soil function as some of its microbiota is lost and heavy metals like aluminium are mobilized (spread more easily) while essential nutrients and minerals such as magnesium can leach away because of the same. Ultimately, plants unable to tolerate lowered pH are killed, with montane forests being some of the worst-affected ecosystems due to their regular exposure to sulfate-carrying fog at high altitudes. While acid rain was too dilute to affect human health directly, breathing smog or even any air with elevated sulfate concentrations is known to contribute to heart and lung conditions, including asthma and bronchitis. Further, this form of pollution is linked to preterm birth and low birth weight, with a study of 74,671 pregnant women in Beijing finding that every additional 100 µg/m³ of SO₂ in the air reduced infants' weight by 7.3 g, making it and other forms of air pollution the largest attributable risk factor for low birth weight ever observed.

Pollution controls and the discovery of radiative effects

The discovery of these negative effects spurred the rush to reduce atmospheric sulfate pollution, typically through flue-gas desulfurization installations at power plants, such as wet scrubbers or fluidized bed combustion. In the United States, this began with the passage of the Clean Air Act in 1970, which was strengthened in 1977 and 1990. According to the EPA, from 1970 to 2005, total emissions of the six principal air pollutants, including sulfates, dropped by 53% in the US. By 2010, it valued the healthcare savings from these reductions at $50 billion annually.In Europe, it was estimated in 2021 that the 18 coal-fired power plants in the western Balkans which lack controls on sulfur dioxide pollution have emitted two-and-half times more of it than all 221 coal plants in the European Union which are fitted with these technologies. Globally, the uptake of treaties such as the 1985 Helsinki Protocol on the Reduction of Sulfur Emissions and its successors had gradually spread from the developed to the developing countries. While China and India have seen decades in rapid growth of sulfur emissions while they declined in the U.S. and Europe, they have also peaked in the recent years. In 2005, China was the largest polluter, with its estimated 25,490,000 short tons (23.1 Mt) emissions increasing by 27% since 2000 alone and roughly matching the U.S. emissions in 1980. That year was also the peak, and a consistent decline was recorded since then. Similarly, India's sulfur dioxide emissions appear to have been largely flat in the 2010s, as more coal-fired power plants were fitted with pollution controls even as the newer ones were still coming online.

Sulfur dioxide in the world on April 15, 2017. Note that sulfur dioxide moves through the atmosphere with prevailing winds and thus local sulfur dioxide distributions vary day to day with weather patterns and seasonality.

Yet, around the time these treaties and technology improvements were taking place, evidence was coming in that sulfate aerosols were affecting both the visible light received by the Earth and its surface temperature. On one hand, the study of volcanic eruptions, notably 1991 eruption of Mount Pinatubo in the Philippines, had shown that the mass formation of sulfate aerosols by these eruptions formed a subtle whitish haze in the sky, reducing the amount of Sun's radiation reaching the Earth's surface and rapidly losing the heat they absorb back to space, as well increasing clouds' albedo (i.e. making them more reflective) by changing their consistency to a larger amount of smaller droplets, which was the principal reason for a clear drop in global temperatures for several years in their wake. On the other hand, multiple studies have shown that between 1950s and 1980s, the amount of sunlight reaching the surface declined by around 4–5% per decade, even though the changes in solar radiation at the top of the atmosphere were never more than 0.1-0.3%. Yet, this trend (commonly described as global dimming) began to reverse in the 1990s, consistent with the reductions in anthropogenic sulfate pollution, while at the same time, climate change accelerated. Areas like eastern United States went from seeing cooling in contrast to the global trend to becoming global warming hotspots as their enormous levels of air pollution were reduced, even as sulfate particles still accounted for around 25% of all particulates.

As the real world had shown the importance of sulfate aerosol concentrations to the global climate, research into the subject accelerated. Formation of the aerosols and their effects on the atmosphere can be studied in the lab, with methods like ion-chromatography and mass spectrometry Samples of actual particles can be recovered from the stratosphere using balloons or aircraft, and remote satellites were also used for observation. This data is fed into the climate models, as the necessity of accounting for aerosol cooling to truly understand the rate and evolution of warming had long been apparent, with the IPCC Second Assessment Report being the first to include an estimate of their impact on climate, and every major model able to simulate them by the time IPCC Fourth Assessment Report was published in 2007. Many scientists also see the other side of this research, which is learning how to cause the same effect artificially. While discussed around the 1990s, if not earlier, stratospheric aerosol injection as a solar geoengineering method is best associated with Paul Crutzen's detailed 2006 proposal. Deploying in the stratosphere ensures that the aerosols are at their most effective, and that the progress of clean air measures would not be reversed: more recent research estimated that even under the highest-emission scenario RCP 8.5, the addition of stratospheric sulfur required to avoid 4 °C (7.2 °F) relative to now (and 5 °C (9.0 °F) relative to the preindustrial) would be effectively offset by the future controls on tropospheric sulfate pollution, and the amount required would be even less for less drastic warming scenarios. This spurred a detailed look at its costs and benefits, but even with hundreds of studies into the subject completed by the early 2020s, some notable uncertainties remain.

Methods

Materials

Pinatubo eruption cloud. This volcano released huge quantities of stratospheric sulfur aerosols and contributed greatly to understanding of the subject.

Various forms of sulfur were proposed as the injected substance, as this is in part how volcanic eruptions cool the planet. Precursor gases such as sulfur dioxide and hydrogen sulfide have been considered. According to estimates, "one kilogram of well placed sulfur in the stratosphere would roughly offset the warming effect of several hundred thousand kilograms of carbon dioxide." One study calculated the impact of injecting sulfate particles, or aerosols, every one to four years into the stratosphere in amounts equal to those lofted by the volcanic eruption of Mount Pinatubo in 1991, but did not address the many technical and political challenges involved in potential solar geoengineering efforts. Use of gaseous sulfuric acid appears to reduce the problem of aerosol growth. Materials such as photophoretic particles, metal oxides (as in Welsbach seeding, and titanium dioxide), and diamond are also under consideration.

Delivery

Various techniques have been proposed for delivering the aerosol or precursor gases. The required altitude to enter the stratosphere is the height of the tropopause, which varies from 11 kilometres (6.8 mi/36,000 ft) at the poles to 17 kilometers (11 mi/58,000 ft) at the equator.

Civilian aircraft including the Boeing 747–400 and Gulfstream G550/650, C-37A could be modified at relatively low cost to deliver sufficient amounts of required material according to one study, but a later metastudy suggests a new aircraft would be needed but easy to develop.
Military aircraft such as the F15-C variant of the F-15 Eagle have the necessary flight ceiling, but limited payload. Military tanker aircraft such as the KC-135 Stratotanker and KC-10 Extender also have the necessary ceiling at latitudes closer to the poles and have greater payload capacity.
Modified artillery might have the necessary capability, but requires a polluting and expensive propellant charge to loft the payload. Railgun artillery could be a non-polluting alternative.
High-altitude balloons can be used to lift precursor gases, in tanks, bladders or in the balloons' envelope.

Injection system

The latitude and distribution of injection locations has been discussed by various authors. Whilst a near-equatorial injection regime will allow particles to enter the rising leg of the Brewer-Dobson circulation, several studies have concluded that a broader, and higher-latitude, injection regime will reduce injection mass flow rates and/or yield climatic benefits. Concentration of precursor injection in a single longitude appears to be beneficial, with condensation onto existing particles reduced, giving better control of the size distribution of aerosols resulting. The long residence time of carbon dioxide in the atmosphere may require a millennium-timescale commitment to aerosol injection if aggressive emissions abatement is not pursued simultaneously.

Advantages of the technique

The advantages of this approach in comparison to other possible means of solar geoengineering are:

Mimics a natural process: Stratospheric sulfur aerosols are created by existing natural processes (especially volcanoes), whose impacts have been studied via observations. This contrasts with other, more speculative solar geoengineering techniques which do not have natural analogs (e.g., space sunshade).
Technological feasibility: In contrast to other proposed solar geoengineering techniques, such as marine cloud brightening, much of the required technology is pre-existing: chemical manufacturing, artillery shells, high-altitude aircraft, weather balloons, etc. Unsolved technical challenges include methods to deliver the material in controlled diameter with good scattering properties.
Scalability: Some solar geoengineering techniques, such as cool roofs and ice protection, can only provide a limited intervention in the climate due to insufficient scale—one cannot reduce the temperature by more than a certain amount with each technique. Research has suggested that this technique may have a high radiative 'forcing potential'., yet can be finely tuned according to how much cooling is needed.
Speed: A common argument is that stratospheric aerosol injection can take place quickly, and would be able to buy time for carbon sequestration projects such as carbon dioxide air capture to be implemented and start acting over decades and centuries.

Uncertainties

It is uncertain how effective any solar geoengineering technique would be, due to the difficulties modeling their impacts and the complex nature of the global climate system. Certain efficacy issues are specific to stratospheric aerosols.

Lifespan of aerosols: Tropospheric sulfur aerosols are short-lived. Delivery of particles into the lower stratosphere in the arctic will typically ensure that they remain aloft only for a few weeks or months, as air in this region is predominantly descending. To ensure endurance, higher-altitude delivery is needed, ensuring a typical endurance of several years by enabling injection into the rising leg of the Brewer-Dobson circulation above the tropical tropopause. Further, sizing of particles is crucial to their endurance.
Aerosol delivery: There are two proposals for how to create a stratospheric sulfate aerosol cloud, either through the release of a precursor gas (SO
₂) or the direct release of sulfuric acid (H
₂SO
₄) and these face different challenges. If SO
₂ gas is released it will oxidize to form H
₂SO
₄ and then condense to form droplets far from the injection site. Releasing SO
₂ would not allow control over the size of the particles that are formed but would not require a sophisticated release mechanism. Simulations suggest that as the SO
₂ release rate is increased there would be diminishing returns on the cooling effect, as larger particles would be formed which have a shorter lifetime and are less effective scatterers of light. If H
₂SO
₄ is released directly then the aerosol particles would form very quickly and in principle the particle size could be controlled although the engineering requirements for this are uncertain. Assuming a technology for direct H
₂SO
₄ release could be conceived and developed, it would allow control over the particle size to possibly alleviate some of the inefficiencies associated with SO
₂ release.
Strength of cooling: The magnitude of the effect of forcing from aerosols by decreasing insolation received at the surface is not completely certain, as its scientific modelling involves complex calculations due to different confounding factors and parameters such as optical properties, spatial and temporal distribution of emission or injection, albedo, geography, loading, rate of transport of sulfate, global burden, atmospheric chemistry, mixing and reactions with other compounds and aerosols, particle size, relative humidity, and clouds. Along with others, aerosol size distribution and hygroscopicity have particularly high uncertainty due to being closely related to sulfate aerosol interactions with other aerosols which affects the amount of radiation reflected. As of 2021, state-of-the-art CMIP6 models estimate that total cooling from the currently present aerosols is between 0.1 °C (0.18 °F) to 0.7 °C (1.3 °F); the IPCC Sixth Assessment Report uses the best estimate of 0.5 °C (0.90 °F), but there's still a lot of contradictory research on the impacts of aerosols of clouds which can alter this estimate of aerosol cooling, and consequently, our knowledge of how many millions of tons must be deployed annually to achieve the desired effect.

Hydrological cycle: Since the historical global dimming from tropospheric sulfate pollution is already well-known to have reduced rainfall in certain areas, and is likely to have weakened Monsoon of South Asia and contributed to or even outright caused the 1984 Ethiopian famine, the impact on the hydrological cycle and patterns is one of the most-discussed uncertainties of the different stratospheric aerosol injection proposals. It has been suggested that while changes in precipitation from stratospheric aerosol injection are likely to be more manageable than the changes expected under future warming, one of the main impacts it would have on mortality is by shifting the habitat of mosquitoes and thus substantially affecting the distribution and spread of vector-borne diseases. Considering the already-extensive present-day mosquito habitat, it is currently unclear whether those changes are likely to be positive or negative.

Cost

Early studies suggest that stratospheric aerosol injection might have a relatively low direct cost. The annual cost of delivering 5 million tons of an albedo enhancing aerosol (sufficient to offset the expected warming over the next century) to an altitude of 20 to 30 km is estimated at US$2 billion to 8 billion. In comparison, the annual cost estimates for climate damage or emission mitigation range from US$200 billion to 2 trillion.

A 2016 study finds the cost per 1 W/m² of cooling to be between 5–50 billion USD/yr. Because larger particles are less efficient at cooling and drop out of the sky faster, the unit-cooling cost is expected to increase over time as increased dose leads to larger, but less efficient, particles by mechanism such as coalescence and Ostwald ripening. Assume RCP8.5, -5.5 W/m² of cooling would be required by 2100 to maintain 2020 climate. At the dose level required to provide this cooling, the net efficiency per mass of injected aerosols would reduce to below 50% compared to low-level deployment (below 1W/m²). At a total dose of -5.5 W/m², the cost would be between 55-550 billion USD/yr when efficiency reduction is also taken into account, bringing annual expenditure to levels comparable to other mitigation alternatives.

Other possible side effects

Solar geoengineering in general poses various problems and risks. However, certain problems are specific to or more pronounced with stratospheric sulfide injection.

Ozone depletion: a potential side effect of sulfur aerosols; and these concerns have been supported by modelling. However, this may only occur if high enough quantities of aerosols drift to, or are deposited in, polar stratospheric clouds before the levels of CFCs and other ozone destroying gases fall naturally to safe levels because stratospheric aerosols, together with the ozone destroying gases, are responsible for ozone depletion. The injection of other aerosols that may be safer such as calcite has therefore been proposed. The injection of non-sulfide aerosols like calcite (limestone) would also have a cooling effect while counteracting ozone depletion and would be expected to reduce other side effects.
Whitening of the sky: Volcanic eruptions are known to affect the appearance of sunsets significantly, and a change in sky appearance after the eruption of Mount Tambora in 1816 "The Year Without A Summer" was the inspiration for the paintings of J. M. W. Turner. Since stratospheric aerosol injection would involve smaller quantities of aerosols, it is expected to cause a subtler change to sunsets and a slight hazing of blue skies. How stratospheric aerosol injection may affect clouds remains uncertain.
Stratospheric temperature change: Aerosols can also absorb some radiation from the Sun, the Earth, and the surrounding atmosphere. This changes the surrounding air temperature and could potentially impact the stratospheric circulation, which in turn may impact the surface circulation.
Deposition and acid rain: The surface deposition of sulfate injected into the stratosphere may also have an impact on ecosystems. However, the amount and wide dispersal of injected aerosols means that their impact on particulate concentrations and acidity of precipitation would be very small.
Ecological consequences: The consequences of stratospheric aerosol injection on ecological systems are unknown and potentially vary by ecosystem with differing impacts on marine versus terrestrial biomes.
Mixed effects on agriculture: A historical study in 2018 found that stratospheric sulfate aerosols injected by the volcanic eruptions of Chicón (1982) and Mount Pinatubo (1991) had mixed effects on global crop yields of certain major crops. Based on several studies, the IPCC Sixth Assessment Report suggests that crop yields and carbon sinks would be largely unaffected or may even increase slightly, because reduced photosynthesis due to lower sunlight would be offset by CO2 fertilization effect and the reduction in thermal stress, but there's less confidence about how the specific ecosystems may be affected.
Inhibition of Solar Energy Technologies: Uniformly reduced net shortwave radiation would hurt solar photovoltaics by the same 2-5% as for plants. the increased scattering of collimated incoming sunlight would more drastically reduce the efficiencies (by 11% for RCP8.5) of concentrating solar thermal power for both electricity production and chemical reactions, such as solar cement production.

Outdoors research

Almost all work to date on stratospheric sulfate injection has been limited to modeling and laboratory work. In 2009, a Russian team tested aerosol formation in the lower troposphere using helicopters. In 2015, David Keith and Gernot Wagner described a potential field experiment, the Stratospheric Controlled Perturbation Experiment (SCoPEx), using stratospheric calcium carbonate injection, but as of October 2020 the time and place had not yet been determined.SCoPEx is in part funded by Bill Gates. Sir David King, a former chief scientific adviser to the government of the United Kingdom, stated that SCoPEX and Gates' plans to dim the sun with calcium carbonate could have disastrous effects.

In 2012, the Bristol University-led Stratospheric Particle Injection for Climate Engineering (SPICE) project planned on a limited field test in order to evaluate a potential delivery system. The group received support from the EPSRC, NERC and STFC to the tune of £2.1 million and was one of the first UK projects aimed at providing evidence-based knowledge about solar radiation management. Although the field testing was cancelled, the project panel decided to continue the lab-based elements of the project.^[140] Furthermore, a consultation exercise was undertaken with members of the public in a parallel project by Cardiff University, with specific exploration of attitudes to the SPICE test. This research found that almost all of the participants in the poll were willing to allow the field trial to proceed, but very few were comfortable with the actual use of stratospheric aerosols. A campaign opposing geoengineering led by the ETC Group drafted an open letter calling for the project to be suspended until international agreement is reached, specifically pointing to the upcoming convention of parties to the Convention on Biological Diversity in 2012.^[143]

Governance

Most of the existing governance of stratospheric sulfate aerosols is from that which is applicable to solar radiation management more broadly. However, some existing legal instruments would be relevant to stratospheric sulfate aerosols specifically. At the international level, the Convention on Long-Range Transboundary Air Pollution (CLRTAP Convention) obligates those countries which have ratified it to reduce their emissions of particular transboundary air pollutants. Notably, both solar radiation management and climate change (as well as greenhouse gases) could satisfy the definition of "air pollution" which the signatories commit to reduce, depending on their actual negative effects. Commitments to specific values of the pollutants, including sulfates, are made through protocols to the CLRTAP Convention. Full implementation or large scale climate response field tests of stratospheric sulfate aerosols could cause countries to exceed their limits. However, because stratospheric injections would be spread across the globe instead of concentrated in a few nearby countries, and could lead to net reductions in the "air pollution" which the CLRTAP Convention is to reduce.

The stratospheric injection of sulfate aerosols would cause the Vienna Convention for the Protection of the Ozone Layer to be applicable due to their possible deleterious effects on stratospheric ozone. That treaty generally obligates its Parties to enact policies to control activities which "have or are likely to have adverse effects resulting from modification or likely modification of the ozone layer." The Montreal Protocol to the Vienna Convention prohibits the production of certain ozone depleting substances, via phase outs. Sulfates are presently not among the prohibited substances.

In the United States, the Clean Air Act might give the United States Environmental Protection Agency authority to regulate stratospheric sulfate aerosols.

Welsbach seeding

Welsbach seeding is a patented climate engineering method, involving seeding the stratosphere with small (10 to 100 micron) metal oxide particles (thorium dioxide, aluminium oxide). The purpose of the Welsbach seeding would be to "(reduce) atmospheric warming due to the greenhouse effect resulting from a greenhouse gases layer," by converting radiative energy at near-infrared wavelengths into radiation at far-infrared wavelengths, permitting some of the converted radiation to escape into space, thus cooling the atmosphere. The seeding as described would be performed by airplanes at altitudes between 7 and 13 kilometres.

Patent

The method was patented by Hughes Aircraft Company in 1991, US patent 5003186. Quote from the patent:

"Global warming has been a great concern of many environmental scientists. Scientists believe that the greenhouse effect is responsible for global warming. Greatly increased amounts of heat-trapping gases have been generated since the Industrial Revolution. These gases, such as CO₂, CFC, and methane, accumulate in the atmosphere and allow sunlight to stream in freely but block heat from escaping (greenhouse effect). These gases are relatively transparent to sunshine but absorb strongly the long-wavelength infrared radiation released by the earth."
"This invention relates to a method for the reduction of global warming resulting from the greenhouse effect, and in particular to a method which involves the seeding of the earth's stratosphere with Welsbach-like materials."

Feasibility

The method has never been implemented, and is not considered to be a viable option by current geoengineering experts; in fact the proposed mechanism is considered to violate the second law of thermodynamics. Currently proposed atmospheric geoengineering methods would instead use other aerosols, at considerably higher altitudes.

History

Mikhail Budyko is believed to have been the first, in 1974, to put forth the concept of artificial solar radiation management with stratospheric sulfate aerosols if global warming ever became a pressing issue. Such controversial climate engineering proposals for global dimming have sometimes been called a "Budyko Blanket".

In popular-culture

In the film Snowpiercer, as well as in the television spin-off, an apocalyptic global ice-age is caused by the introduction of a fictional substance, dubbed, CW-7 into the atmosphere, with the intention of preventing global-warming by blocking out the light of the sun.

In the novel The Ministry for the Future by Kim Stanley Robinson, stratospheric aerosol injection is used by the Indian Government as a climate mitigation measure following a catastrophic and deadly heatwave.

The bestselling novel Termination Shock by Neal Stephenson revolves around a private initiative by a billionaire, with covert support or opposition from some national governments, to inject sulfur into the stratosphere using recoverable gliders launched with a railgun.

Stratospheric aerosol injection is a proposed method of solar geoengineering (or solar radiation modification) to reduce global warming. This would introduce aerosols into the stratosphere to create a cooling effect via global dimming and increased albedo, which occurs naturally from volcanic winter.^[1] It appears that stratospheric aerosol injection, at a moderate intensity, could counter most changes to temperature and precipitation, take effect rapidly, have low direct implementation costs, and be reversible in its direct climatic effects. The Intergovernmental Panel on Climate Change concludes that it "is the most-researched [solar geoengineering] method, with high agreement that it could limit warming to below 1.5 °C (2.7 °F)." However, like other solar geoengineering approaches, stratospheric aerosol injection would do so imperfectly and other effects are possible, particularly if used in a suboptimal manner.

Various forms of sulfur have been shown to cool the planet after large volcanic eruptions. However, as of 2021, there has been little research and existing natural aerosols in the stratosphere are not well understood. So there is no leading candidate material. Alumina, calcite and salt are also under consideration.The leading proposed method of delivery is custom aircraft.

Scientific basis

Natural and anthropogenic sulfates

There is a wide range of particulate matter suspended in the atmosphere at various height and in various sizes. By far the best-studied are the various sulfur compounds collectively referred to sulfate aerosols. This group includes inorganic sulfates (SO₄^2-),HSO₄^- and H₂SO₄^-: organic sulfur compounds are sometimes included as well, but are of lower importance. Sulfate aerosols can be anthropogenic (through the combustion of fossil fuels with a high sulfur content, primarily coal and certain less-refined fuels, like aviation and bunker fuel), biogenic from hydrosphere and biosphere, geological via volcanoes or weather-driven from wildfires and other natural combustion events.

Inorganic aerosols are mainly produced when sulfur dioxide reacts with water vapor to form gaseous sulfuric acid and various salts (often through an oxidation reaction in the clouds), which are then thought to experience hygroscopic growth and coagulation and then shrink through evaporation.as microscopic liquid droplets or fine (diameter of about 0.1 to 1.0 micrometre) sulfate solid particles in a colloidal suspension, with smaller particles at times coagulating into larger ones.The other major source are chemical reactions with dimethyl sulfide (DMS), predominantly sourced from marine plankton, with a smaller contribution from swamps and other such wetlands. And sometimes, aerosols are produced from photochemical decomposition of COS (carbonyl sulfide), or when solid sulfates in the sea salt spray can react with gypsum dust particles).

Pollution controls and the discovery of radiative effects

The discovery of these negative effects spurred the rush to reduce atmospheric sulfate pollution, typically through flue-gas desulfurization installations at power plants, such as wet scrubbers or fluidized bed combustion. In the United States, this began with the passage of the Clean Air Act in 1970, which was strengthened in 1977 and 1990. According to the EPA, from 1970 to 2005, total emissions of the six principal air pollutants, including sulfates, dropped by 53% in the US. By 2010, it valued the healthcare savings from these reductions at $50 billion annually. In Europe, it was estimated in 2021 that the 18 coal-fired power plants in the western Balkans which lack controls on sulfur dioxide pollution have emitted two-and-half times more of it than all 221 coal plants in the European Union which are fitted with these technologies. Globally, the uptake of treaties such as the 1985 Helsinki Protocol on the Reduction of Sulfur Emissions and its successors had gradually spread from the developed to the developing countries. While China and India have seen decades in rapid growth of sulfur emissions while they declined in the U.S. and Europe, they have also peaked in the recent years. In 2005, China was the largest polluter, with its estimated 25,490,000 short tons (23.1 Mt) emissions increasing by 27% since 2000 alone and roughly matching the U.S. emissions in 1980. That year was also the peak, and a consistent decline was recorded since then.

Similarly, India's sulfur dioxide emissions appear to have been largely flat in the 2010s, as more coal-fired power plants were fitted with pollution controls even as the newer ones were still coming online.

Yet, around the time these treaties and technology improvements were taking place, evidence was coming in that sulfate aerosols were affecting both the visible light received by the Earth and its surface temperature. On one hand, the study of volcanic eruptions, notably 1991 eruption of Mount Pinatubo in the Philippines,had shown that the mass formation of sulfate aerosols by these eruptions formed a subtle whitish haze in the sky, reducing the amount of Sun's radiation reaching the Earth's surface and rapidly losing the heat they absorb back to space, as well increasing clouds' albedo (i.e. making them more reflective) by changing their consistency to a larger amount of smaller droplets, which was the principal reason for a clear drop in global temperatures for several years in their wake. On the other hand, multiple studies have shown that between 1950s and 1980s, the amount of sunlight reaching the surface declined by around 4–5% per decade, even though the changes in solar radiation at the top of the atmosphere were never more than 0.1-0.3%. Yet, this trend (commonly described as global dimming) began to reverse in the 1990s, consistent with the reductions in anthropogenic sulfate pollution,while at the same time, climate change accelerated. Areas like eastern United States went from seeing cooling in contrast to the global trend to becoming global warming hotspots as their enormous levels of air pollution were reduced, even as sulfate particles still accounted for around 25% of all particulates.

As the real world had shown the importance of sulfate aerosol concentrations to the global climate, research into the subject accelerated. Formation of the aerosols and their effects on the atmosphere can be studied in the lab, with methods like ion-chromatography and mass spectrometry^[59] Samples of actual particles can be recovered from the stratosphere using balloons or aircraft, and remote satellites were also used for observation. This data is fed into the climate models, as the necessity of accounting for aerosol cooling to truly understand the rate and evolution of warming had long been apparent, with the IPCC Second Assessment Report being the first to include an estimate of their impact on climate, and every major model able to simulate them by the time IPCC Fourth Assessment Report was published in 2007. Many scientists also see the other side of this research, which is learning how to cause the same effect artificially. While discussed around the 1990s, if not earlier, stratospheric aerosol injection as a solar geoengineering method is best associated with Paul Crutzen's detailed 2006 proposal. Deploying in the stratosphere ensures that the aerosols are at their most effective, and that the progress of clean air measures would not be reversed: more recent research estimated that even under the highest-emission scenario RCP 8.5, the addition of stratospheric sulfur required to avoid 4 °C (7.2 °F) relative to now (and 5 °C (9.0 °F) relative to the preindustrial) would be effectively offset by the future controls on tropospheric sulfate pollution, and the amount required would be even less for less drastic warming scenarios. This spurred a detailed look at its costs and benefits, but even with hundreds of studies into the subject completed by the early 2020s, some notable uncertainties remain.

Methods

Materials

Delivery

Civilian aircraft including the Boeing 747–400 and Gulfstream G550/650, C-37A^[clarify] could be modified at relatively low cost to deliver sufficient amounts of required material according to one study, but a later metastudy suggests a new aircraft would be needed but easy to develop.
Military aircraft such as the F15-C variant of the F-15 Eagle have the necessary flight ceiling, but limited payload. Military tanker aircraft such as the KC-135 Stratotanker and KC-10 Extender also have the necessary ceiling at latitudes closer to the poles and have greater payload capacity.
Modified artillery might have the necessary capability, but requires a polluting and expensive propellant charge to loft the payload. Railgun artillery could be a non-polluting alternative.
High-altitude balloons can be used to lift precursor gases, in tanks, bladders or in the balloons' envelope.

Injection system

Advantages of the technique

The advantages of this approach in comparison to other possible means of solar geoengineering are:

Mimics a natural process: Stratospheric sulfur aerosols are created by existing natural processes (especially volcanoes), whose impacts have been studied via observations. This contrasts with other, more speculative solar geoengineering techniques which do not have natural analogs (e.g., space sunshade).
Technological feasibility: In contrast to other proposed solar geoengineering techniques, such as marine cloud brightening, much of the required technology is pre-existing: chemical manufacturing, artillery shells, high-altitude aircraft, weather balloons, etc. Unsolved technical challenges include methods to deliver the material in controlled diameter with good scattering properties.
Scalability: Some solar geoengineering techniques, such as cool roofs and ice protection, can only provide a limited intervention in the climate due to insufficient scale—one cannot reduce the temperature by more than a certain amount with each technique. Research has suggested that this technique may have a high radiative 'forcing potential', yet can be finely tuned according to how much cooling is needed.
Speed: A common argument is that stratospheric aerosol injection can take place quickly, and would be able to buy time for carbon sequestration projects such as carbon dioxide air capture to be implemented and start acting over decades and centuries.

Uncertainties

Lifespan of aerosols: Tropospheric sulfur aerosols are short-lived.^[87] Delivery of particles into the lower stratosphere in the arctic will typically ensure that they remain aloft only for a few weeks or months, as air in this region is predominantly descending. To ensure endurance, higher-altitude delivery is needed, ensuring a typical endurance of several years by enabling injection into the rising leg of the Brewer-Dobson circulation above the tropical tropopause. Further, sizing of particles is crucial to their endurance.
Aerosol delivery: There are two proposals for how to create a stratospheric sulfate aerosol cloud, either through the release of a precursor gas (SO
₂) or the direct release of sulfuric acid (H
₂SO
₄) and these face different challenges. If SO
₂ gas is released it will oxidize to form H
₂SO
₄ and then condense to form droplets far from the injection site. Releasing SO
₂ would not allow control over the size of the particles that are formed but would not require a sophisticated release mechanism. Simulations suggest that as the SO
₂ release rate is increased there would be diminishing returns on the cooling effect, as larger particles would be formed which have a shorter lifetime and are less effective scatterers of light. If H
₂SO
₄ is released directly then the aerosol particles would form very quickly and in principle the particle size could be controlled although the engineering requirements for this are uncertain. Assuming a technology for direct H
₂SO
₄ release could be conceived and developed, it would allow control over the particle size to possibly alleviate some of the inefficiencies associated with SO
₂ release.
Strength of cooling: The magnitude of the effect of forcing from aerosols by decreasing insolation received at the surface is not completely certain, as its scientific modelling involves complex calculations due to different confounding factors and parameters such as optical properties, spatial and temporal distribution of emission or injection, albedo, geography, loading, rate of transport of sulfate, global burden, atmospheric chemistry, mixing and reactions with other compounds and aerosols, particle size, relative humidity, and clouds. Along with others, aerosol size distribution and hygroscopicity have particularly high uncertainty due to being closely related to sulfate aerosol interactions with other aerosols which affects the amount of radiation reflected.As of 2021, state-of-the-art CMIP6 models estimate that total cooling from the currently present aerosols is between 0.1 °C (0.18 °F) to 0.7 °C (1.3 °F); the IPCC Sixth Assessment Report uses the best estimate of 0.5 °C (0.90 °F), but there's still a lot of contradictory research on the impacts of aerosols of clouds which can alter this estimate of aerosol cooling, and consequently, our knowledge of how many millions of tons must be deployed annually to achieve the desired effect.

Hydrological cycle: Since the historical global dimming from tropospheric sulfate pollution is already well-known to have reduced rainfall in certain areas, and is likely to have weakened Monsoon of South Asiaand contributed to or even outright caused the 1984 Ethiopian famine,^] the impact on the hydrological cycle and patterns is one of the most-discussed uncertainties of the different stratospheric aerosol injection proposals. It has been suggested that while changes in precipitation from stratospheric aerosol injection are likely to be more manageable than the changes expected under future warming, one of the main impacts it would have on mortality is by shifting the habitat of mosquitoes and thus substantially affecting the distribution and spread of vector-borne diseases. Considering the already-extensive present-day mosquito habitat, it is currently unclear whether those changes are likely to be positive or negative.

Cost

Other possible side effects

Solar geoengineering in general poses various problems and risks. However, certain problems are specific to or more pronounced with stratospheric sulfide injection.

Ozone depletion: a potential side effect of sulfur aerosols; and these concerns have been supported by modelling. However, this may only occur if high enough quantities of aerosols drift to, or are deposited in, polar stratospheric clouds before the levels of CFCs and other ozone destroying gases fall naturally to safe levels because stratospheric aerosols, together with the ozone destroying gases, are responsible for ozone depletion. The injection of other aerosols that may be safer such as calcite has therefore been proposed. The injection of non-sulfide aerosols like calcite (limestone) would also have a cooling effect while counteracting ozone depletion and would be expected to reduce other side effects.
Whitening of the sky: Volcanic eruptions are known to affect the appearance of sunsets significantly, and a change in sky appearance after the eruption of Mount Tambora in 1816 "The Year Without A Summer" was the inspiration for the paintings of J. M. W. Turner. Since stratospheric aerosol injection would involve smaller quantities of aerosols, it is expected to cause a subtler change to sunsets and a slight hazing of blue skies. How stratospheric aerosol injection may affect clouds remains uncertain.
Stratospheric temperature change: Aerosols can also absorb some radiation from the Sun, the Earth, and the surrounding atmosphere. This changes the surrounding air temperature and could potentially impact the stratospheric circulation, which in turn may impact the surface circulation.
Deposition and acid rain: The surface deposition of sulfate injected into the stratosphere may also have an impact on ecosystems. However, the amount and wide dispersal of injected aerosols means that their impact on particulate concentrations and acidity of precipitation would be very small.
Ecological consequences: The consequences of stratospheric aerosol injection on ecological systems are unknown and potentially vary by ecosystem with differing impacts on marine versus terrestrial biomes.
Mixed effects on agriculture: A historical study in 2018 found that stratospheric sulfate aerosols injected by the volcanic eruptions of Chicón (1982) and Mount Pinatubo (1991) had mixed effects on global crop yields of certain major crops. Based on several studies, the IPCC Sixth Assessment Report suggests that crop yields and carbon sinks would be largely unaffected or may even increase slightly, because reduced photosynthesis due to lower sunlight would be offset by CO2 fertilization effect and the reduction in thermal stress, but there's less confidence about how the specific ecosystems may be affected.
Inhibition of Solar Energy Technologies: Uniformly reduced net shortwave radiation would hurt solar photovoltaics by the same 2-5% as for plants. the increased scattering of collimated incoming sunlight would more drastically reduce the efficiencies (by 11% for RCP8.5) of concentrating solar thermal power for both electricity production and chemical reactions, such as solar cement production.

Outdoors research

Almost all work to date on stratospheric sulfate injection has been limited to modeling and laboratory work. In 2009, a Russian team tested aerosol formation in the lower troposphere using helicopters. In 2015, David Keith and Gernot Wagner described a potential field experiment, the Stratospheric Controlled Perturbation Experiment (SCoPEx), using stratospheric calcium carbonate injection, but as of October 2020 the time and place had not yet been determined. SCoPEx is in part funded by Bill Gates. Sir David King, a former chief scientific adviser to the government of the United Kingdom, stated that SCoPEX and Gates' plans to dim the sun with calcium carbonate could have disastrous effects.

In 2012, the Bristol University-led Stratospheric Particle Injection for Climate Engineering (SPICE) project planned on a limited field test in order to evaluate a potential delivery system. The group received support from the EPSRC, NERC and STFC to the tune of £2.1 million and was one of the first UK projects aimed at providing evidence-based knowledge about solar radiation management. Although the field testing was cancelled, the project panel decided to continue the lab-based elements of the project. Furthermore, a consultation exercise was undertaken with members of the public in a parallel project by Cardiff University, with specific exploration of attitudes to the SPICE test. This research found that almost all of the participants in the poll were willing to allow the field trial to proceed, but very few were comfortable with the actual use of stratospheric aerosols. A campaign opposing geoengineering led by the ETC Group drafted an open letter calling for the project to be suspended until international agreement is reached, specifically pointing to the upcoming convention of parties to the Convention on Biological Diversity in 2012.

Governance

In the United States, the Clean Air Act might give the United States Environmental Protection Agency authority to regulate stratospheric sulfate aerosols.

Welsbach seeding

Patent

The method was patented by Hughes Aircraft Company in 1991, US patent 5003186. Quote from the patent:

"Global warming has been a great concern of many environmental scientists. Scientists believe that the greenhouse effect is responsible for global warming. Greatly increased amounts of heat-trapping gases have been generated since the Industrial Revolution. These gases, such as CO₂, CFC, and methane, accumulate in the atmosphere and allow sunlight to stream in freely but block heat from escaping (greenhouse effect). These gases are relatively transparent to sunshine but absorb strongly the long-wavelength infrared radiation released by the earth."
"This invention relates to a method for the reduction of global warming resulting from the greenhouse effect, and in particular to a method which involves the seeding of the earth's stratosphere with Welsbach-like materials."

Feasibility

History

In popular-culture

Climate movement

Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Climate_movement

The climate movement is a global social movement focused on pressuring governments and industry to take action (also called "climate action") addressing the causes and impacts of climate change. Environmental non-profit organizations have engaged in significant climate activism since the late 1980s and early 1990s, as they sought to influence the United Nations Framework Convention on Climate Change (UNFCCC). Climate activism has become increasingly prominent over time, gaining significant momentum during the 2009 Copenhagen Summit and particularly following the signing of the Paris Agreement in 2016.

Environmental organizations take various actions such as Peoples Climate Marches. A major event was the global climate strike in September 2019 organized by Fridays For Future and Earth Strike. The target was to influence the climate action summit organized by the UN on 23 September. According to the organizers four million people participated in the strike on 20 September. Youth activism and involvement has played an important part in the evolution of the movement after the growth of the Fridays For Future strikes started by Greta Thunberg in 2019. In 2019, Extinction Rebellion organized large protests demanding to "reduce carbon emissions to zero by 2025, and create a citizens' assembly to oversee progress", including blocking roads.

History

Since the early 1970s, climate activists have called for more effective political action regarding climate change and other environmental issues. In 1970, Earth Day was the first large-scale environmental movement that called for the protection of all life on earth. The Friends of Earth organisation was also founded in 1970.

Activism related to climate change continued in the late 1980s, when major environmental organizations became involved in the discussions about climate, mainly in the UNFCCC framework. Whereas environmental organizations had previously primarily been engaged at the domestic level, they began to increasingly engage in international campaigning.

The largest transnational climate change coalition, Climate Action Network, was founded in 1992. Its major members include Greenpeace, WWF, Oxfam and Friends of the Earth. Climate Justice Now! and Climate Justice Action, two major coalitions, were founded in the lead-up to the 2009 Copenhagen Summit.

Between 2006 and 2009, the Campaign against Climate Change and other British organisations staged a series of demonstrations to encourage governments to make more serious attempts to address climate change.

The 2009 United Nations Climate Change Conference in Copenhagen was the first UNFCCC summit in which the climate movement started showing its mobilization power at a large scale. According to Jennifer Hadden, the number of new NGOs registered with the UNFCCC surged in 2009 in the lead-up to the Copenhagen summit. Between 40,000 and 100,000 people attended a march in Copenhagen on December 12 calling for a global agreement on climate. Activism went beyond Copenhagen, with more than 5,400 rallies and demonstrations took place around the world simultaneously.

In 2019, activists, most of whom were young people, participated in a global climate strike to criticise the lack of international and political action to address the worsening impacts of climate change. Greta Thunberg, a 19-year-old activist from Sweden, became a figurehead for the movement.

Methods

Climate activists are sometimes depicted as dangerous radicals, but the truly dangerous radicals are the countries that are increasing the production of fossil fuels.

António Guterres, Secretary-General of the United Nations, 2022

Presenting data and other facts is less effective in motivating people to act to mitigate climate change, than financial incentives and social pressure involved in showing people climate-related actions of other people.

The strongest factors in self-reported changes in opinion about global warming were Republican party identification, seeing others experience impacts of global warming, and learning more about global warming.^[16]

These are several approaches that have been used in the past by climate advocates and advocacy campaigns:

the provision of information,
framing of information about aspects of global climate change, and
challenging the terms of political debates.

All three of these methods have been implemented in climate campaigns aimed at the general public. The information about the impacts of global climate change plays a role in forming climatic beliefs, attitudes, and behavior, while the effects of other approaches (e.g. provision of information about solutions to GCC, consensus framing, use of mechanistic information) is yet mostly unknown.^[17] The third approach is to create space for discussions that move beyond questions of economic interests that often dominate political debates to emphasize ecological values and grass-roots democracy. This has been argued to be crucial to bringing about more significant structural change.^[18] Some politicians, such as Arnold Schwarzenegger with the slogan "terminate pollution", say that activists should generate optimism by focusing on the health co-benefits of climate action.^[19]

Climate disobedience

Climate disobedience is a form of civil disobedience, deliberate action intended to critique government climate policy. In 2008, American climate activist Tim DeChristopher posed as a bidder at an auction of US Bureau of Land Management oil and gas leases of public land in Utah, won the auction, reneged on payment, and was imprisoned for 21 months. In September 2015, five climate activists known as the Delta 5 obstructed an oil train in Everett, Washington. At trial, the Delta 5 were allowed the necessity defense, that is, breaking a law in the service of preventing a greater harm. After testimony, the judge determined the grounds for the necessity defense were not met and instructed the jury to disregard testimony admitted under the necessity defense. The Delta 5 were fined for trespassing but were acquitted of more serious charges.^[20]^[21]^[22]^[23]

The first example of a judge accepting the climate necessity defense was on March 27, 2018 when Judge Mary Ann Driscoll acquitted all 13 defendants of civil charges from a protest held in 2016 in Boston, Massachusetts.^[24]

Declaring emergency state

Artwork of a distressed polar bear stranded on the tip of an iceberg, morphing into the Earth below the waterline. The Earth submerged in a pot of boiling water above the flames of a gas stove.

Enacting a state of emergency may be composed of two elements: declaring a state of emergency that has formulated real-world i.e. legal effects and the associated enabling or ensuring of rapid complementary large-scale changes in human activity for the articulated purposes. To date, many governments have acknowledged, sometimes in the form of tentative text-form "declarations", that humanity is essentially in a state of climate emergency.

In November 2021 Greta Thunberg with other climate activists begun filing a petition to the United Nation calling it to declare a level 3 global climate emergency. This should lead to the creation of a special team that will coordinate the response to the climate crisis in the international level. The response should be at least as strong as the response to the COVID-19 pandemic.^[25]

It has been proposed that the national security sector could play a unique role in the development of a global climate-emergency mobilisation of labour and resources to build a zero-emission economy and enact decarbonization.^[26]

Commentators and The Climate Mobilization have suggested mobilisation of resources on the scale of a war economy and other related exceptional or effective measures.^[27]^[28]^[29]^[30]^[31]

Focus on climate justice

Shifting away from a focus on impacts on the natural environment, in recent years people have called on decision-makers to move towards equitable mitigation strategies for all people.^[32]^[33] Climate justice acknowledges that some regions and populations are more vulnerable to climate change than others,^[34] and that in addressing climate solutions we must consider "existing vulnerabilities, resources and capabilities."^[35]

In the United States, organizations such as the Climate Justice Alliance work towards the goal of resilient economies and communities, placing "race, gender and class at the center of the solutions" by working to unite the voices of frontline communities.^[36]

Legal action

In some countries, those affected by climate change may be able to sue major greenhouse gas emitters. Litigation has been attempted by entire countries and peoples, such as Palau^[37] and the Inuit,^[38] as well as non-governmental organizations such as the Sierra Club.^[39] Investor-owned coal, oil, and gas corporations could be legally and morally liable for climate-related human rights violations.^[40]^[41] Litigations are often carried out via collective pooling of effort and resources such as via organizations like Greenpeace,^[42] which sued a Polish coal utility^[42] and a German car manufacturer.^[43]

Proving that some weather events are due specifically to global warming is now possible, and methodologies have been developed to show the increased risk of other events caused by global warming.^[44]

For a legal action for negligence (or similar) to succeed,^{[clarification needed]} "Plaintiffs ... must show that, more probably than not, their individual injuries were caused by the risk factor in question, as opposed to any other cause. This has sometimes been translated to a requirement of a relative risk of at least two."^[45] Another route (though with little legal bite) is the World Heritage Convention, if it can be shown that climate change is affecting World Heritage Sites like Mount Everest.^[46]^[47]

Of countries' governments

Besides countries suing one another, there are also cases where people in a country have taken legal steps against their own government.^[48]

In the Netherlands and Belgium, organisations such as the foundation Urgenda and the Klimaatzaak^[49] in Belgium have also sued their governments as they believe their governments are not meeting the emission reductions they agreed to. Urgenda have already won their case against the Dutch government.^[50]

In 2021, Germany's supreme constitutional court ruled that the government's climate protection measures are insufficient to protect future generations and that the government had until the end of 2022 to improve its Climate Protection Act.^[51]

Held v. Montana was the first constitutional law climate lawsuit to go to trial in the United States, on June 12, 2023.^[52] The case was filed in March 2020 by sixteen youth residents of Montana, then aged 2 through 18,^[53] who argued that the state's support of the fossil fuel industry had worsened the effects of climate change on their lives, thus denying their right to a "clean and healthful environment in Montana for present and future generations"^[54]^{:Art. IX, § 1} as required by the Constitution of Montana.^[55] On August 14, 2023, the trial court judge ruled in the youth plaintiffs' favor, though the state indicated it would appeal the decision.^[56]

Of companies

In May 2021, in Milieudefensie et al v Royal Dutch Shell, the district court of The Hague ordered Royal Dutch Shell to cut its global carbon emissions by 45% by the end of 2030 compared to 2019 levels.^[57]

Fossil fuel divestment

Fossil fuel divestment or fossil fuel divestment and investment in climate solutions is an attempt to reduce climate change by exerting social, political, and economic pressure for the institutional divestment of assets including stocks, bonds, and other financial instruments connected to companies involved in extracting fossil fuels.

Fossil fuel divestment campaigns emerged on college and university campuses in the United States in 2011 with students urging their administrations to turn endowment investments in the fossil fuel industry into investments in clean energy and communities most impacted by climate change.^[58] In 2012, Unity College in Maine became the first institution of higher learning to divest^[59] its endowment from fossil fuels.

The divestment movement against fossil fuels has shed a different light on conversations surrounding fossil fuel finance. Banks and investors have been increasingly questioning the viability of the fossil fuel sector in the long-term. This is because this disinvestment movement is stigmatizing fossil fuels and is raising uncertainty around continued use of fossil fuels, thus reducing the financial desirability of fossil fuel assets. Because the extraction, exploration, and mining of fossil fuels are all capital-intensive activities, uncertainty around their financial risks can reduce investment. If there is a reduction in the supply of capital or a rise in the costs of capital, fossil fuel projects will end up being uneconomical. This will make the valuation of fossil fuel companies go down making them to go out of the market.^[60]

The main argument behind fossil fuel divestment campaigns is that earning profits from investments in activities associated with fossil fuels is unethical owing to the fact that fossil fuel emissions are the primary drivers responsible for global climate change.^[61] Fossil Fuel divestment campaigns such as the Go Fossil Free campaign by 350.org are pleading with the investors to divest by immediately freezing any new investments that they might make in any fossil fuel companies and to divest from any direct ownership and commingled funds, such as fossil fuels public equities together with corporate bonds, in the next five years.^[61]

Fossil fuel divestment campaign have three primary aims. One of them is to pressure government across the globe to put legislation in place including carbon tax or banning any further drilling of fossil fuels. The second aim is to pressure fossil fuel companies to enact transformative change in their companies by switching to forms of energy supply that are less carbon-intensive in nature. The third aim is to ensure transparency when it comes to the carbon exposure that is caused by fossil fuel companies and also to put pressure on governments across the globe to play an active role in restricting the extraction of fossil fuels.^[61]

Fossil fuel divestment campaigns thus seek to cut everything that would be required for the growth and survival of the fossil fuel industry.^[62] These include the social license that this industry requires to operate, the political license that the fossil fuel industry needs to grow and to survive, and the financial investments that support its existence, survival, and growth.^[63] These campaigns also seek to pressure governments to play their role in trying to limit emissions. In these campaigns, campaigners demand so see that the public institutions server their ties that they have always had with this fossil fuel industry for the main purpose of tarnishing the reputation of the fossil fuel industry and to challenge the power that the industry has.^[64] By doing these, these campaigners thus want to starve fossil fuel companies of the badly needed capital and to remove both the infrastructure and the influence that this industry has.^[65]

Divestment campaigns have been used for a variety of social justice issues in the past. For example, divestment campaigns have been launched to end investment in South Africa during apartheid, Israel, and Sudan, and against the tobacco industry. Most recently, divestment campaigns have focused on private prisons and the fossil fuel industry. These divestment calls have received a lot of attention with varying outcomes.^[66]

The good news for the fossil fuel divestment campaigns is that their strategy could be effective. This owes to the fact that there has been an increase in the fossil fuel divestment commitments since 2000. These divestment commitments have resulted in reductions in the flow of capital into the gas and oil sector, as experienced in 33 countries across the globe between the years 2000 and 2015. Research has found that increasing gas and oil divestment pledges in various countries has also been influenced by divestment campaigns. More stringent environmental policies have also been enacted by regimes that recognize climate change as a threat to their country.^[67]

Fossil fuel divestment has indeed gained remarkable traction over the last few years. It has transformed from being a fringe idea to becoming a movement currently valued at around $14.5 trillion. It has over one thousand endowments, pension plans, and major investors committed. It has made many of today’s retail investors and institutional investors channeling their money towards environmentally conscious funds.^[60]

Public environmental activism

This type of citizen activism is important to creating a path to systemic change that will benefit the environment. This change can be assisted through government involvement by way of making more environmentally-conscious policies and all-encompassing changes that will be needed to make substantial environmental change. Different strategies, actions, and systems are used by citizen environmental activists for the purpose of supporting and in some cases demanding these environmental changes. There are however, issues that this type of activism faces. Issues such as potential decline in favorability and participation in environmental movements in BRIC countries, barriers to environmental citizen involvement and mobilization, and divergence in goals between environmental movements.

Creating change

Individual, voluntary activism is not enough to make a substantial difference in prominent climate change issues, systematic change is.^[68] Carol Booth puts forward that the harm in "bystanding to inadequate laws, policies and programs warrant greater moral concern" than individual harm by way of personal emissions and similar negative actions contributing to climate change (pg. 412).^[68] In order for emissions reduction, one of many climate change issues, to occur at a scale that has positive environmental effects government action will be needed.^[68] Overall, environmental reform is best supported and advanced by activism and movements.^[69] Frederick Buttel theorizes that the reasons for this are that environmental activism and movements fight back against countermovement groups and that they ensure responsibility in regards to environmental protection.^[69]

Government systems can both shape and constrain what public activists are able to do, particularly systems found in countries like the U.S and European Union.^[70] Constraints come from institutional aspects of the government systems that make it difficult to produce legislation and other prominent changes that fight against climate change issues.^[70] The progression of mobilization in some cases depends on activists to find ways to move past barriers found in these government systems.^[70] The general public has influence over certain outcomes. "...[L]atent civic behavior, attitudes towards society, and historical patterns of expectations for institutional performance can exert surprisingly important influence on political, and even economic outcomes(pg. 33).^[71] When looking at Californian policy, it was found that the influence of citizen activism leads to systematic choices that are favorable to the environment from influential and powerful members, like policy and community figureheads.^[71]

A 2023 review study published in One Earth stated that opinion polls show that most people perceive climate change as occurring now and close by.^[72] The study concluded that seeing climate change as more distant does not necessarily result in less climate action, and reducing psychological distancing does not reliably increase climate action.^[72]

Systems and actions in public activism

Different strategies, systems, and actions are utilized in public environmental activism. Certain actions may be unavailable to different types of public activists depending on economic standpoint.

Erik Wright's theories of social transformation were used to analyze environmental movements and in part the actions that these movements took in their activism that connected to Wright's "transformational strategies".^[73] This includes "interstitial strategies", which are strategies that try to alter or challenge the current system, are seen in citizens actions like buying more efficient appliances and other environmentally-friendly focused consumer actions.^[73] "Ruptural strategies" "smash the current system through confrontation".^[73] Strategies like these connect to the practice in environmental movement to hold protests and resistance demonstrations.^[73] Lastly, "symbiotic strategies" are focused on collaboration through social reformation such as promoting and reforming policy to prioritize the climate's health as opposed to profit.^[73] Other types of strategies that citizen activists take are "awareness building, alliance building, and network foundation."^[70] "Conservation behavior", the public's willingness to life more environmentally-sustainable lifestyles, has been seen to become increasingly more popular both in developed and "developing democracies."^[74] In an examination of the BRIC countries, of which they are still considered developing, it is posited that if work being done by environmentalists in these countries is seen as not enough, citizens may take it upon themselves to "turn their efforts to lifestyle adjustments as an alternative form of contribution."^[75]

The United States' "citizen suit provision" is a type of system that is accessible for the use in public environmental activism.^[76] These are used in many major U.S environmental laws, are important to environmental enforcement, and deter noncompliance from agencies at fault as well as demonstrate public interest and demand.^[76] Another environmental system is "China's environmental complaint system".^[76] This system takes in citizen's reports of violations in regards to environmental issues and is used typically for the public to voice "concerns and frustrations with environmental problems and has been successful in promoting environmental awareness and engaging the public"(pg 330).^[76] The study suggested that "the role of public participation is greatly dependent on the broader governance [system] within which it is embedded, and that channeling environmental activism into [government] can significantly influence its effectiveness"(pg 326).^[76]

Obstacles

Public activism faces challenges due to differences in economic development as well as differences in government and law. There have been "signs of declining confidence and membership in environmental [organizations]"^[75] in the BRIC countries as well as "barriers to public involvement and social [mobilization] due to close monitoring and censorship, notably in China and Russia.^[75] Issues facing more long-term environmental discourse are feelings of unconcern and helplessness are cited as obstacles that public activist groups face in trying to promote change.^[73] In addition, mainstream environmental movements are "increasingly being challenged by environmental counter-movements"(pg 309).^[69] There are also many different goals and gaps between these types of movements, as well as barriers to producing an effective, influential message to inspire other to enact change.^[69] This prevents a solid, widespread message and specific goal from all environmental groups being produced.

Targeting of activists

The United States government through its domestic intelligence services targeted, as "domestic terrorists," environmental activists and climate change organizations, including by investigating them, questioning them, and placing them on national "watchlists" that makes it more difficult for them to board airplanes and that could instigate local law enforcement monitoring.^[78] Unknown actors also secretly hired professional hackers to launch phishing hacking attacks against climate activists who were organizing the #ExxonKnew campaign.^[79] On September 16, 2022, over fifty climate protesters were arrested and jailed in the U.K. for blocking roads, with many of them going through court hearings, and some being released on bail. Alice Reid, a spokesperson for the group Rebels in Prison Support, claims that many of these protestors are young adults with no connection to the judicial system before becoming activists.^[80]

Activities

2014 People’s Climate March

The climate movement convened its largest single event on 21 September 2014, when it mobilized 400,000 activists in New York during the People’s Climate March (plus several thousand more in other cities), organized by the People's Climate Movement, to demand climate action from the global leaders gathered for the 2014 UN Climate Summit.^[81]^[82]

Institutional Climate Activism

There have been coalitions of institutional investors that have promulgated climate activism.^[83] These initiatives have sometimes included expansive group efforts, such as Climate Action 100+ - a coalition over 300 institutional investors (including some of the largest greenhouse emitters).^[84] Institutional activism is not uncommon, despite the common assumption that shareholder interests would be averse to such action.^[83] However, industry-wide efforts to mitigate climate risks is often in the interest of heavily diversified firms, as climate change can have a strong effect on the global economy.^[83]

Climate Mobilization

Since 2014, growing portions of the climate movement, especially in the United States have been organizing for an international economic response to climate change on the scale of the mobilization of the American home front during World War II, with the goal of rapidly slashing carbon emissions and transitioning to 100% clean energy faster than the free market is likely to allow. Throughout 2015 and 2016, The Climate Mobilization led grassroots campaigns in the U.S. for this scale of ambition, and in July 2016, activists succeeded in getting text adopted into the Democratic Party's national platform calling for WWII-scale climate mobilization.^[85] In August 2015, environmentalist Bill McKibben published an article in the New Republic rallying Americans to "declare war on climate change."^[86]

School strikes for climate

School Strike for Climate (Swedish: Skolstrejk för klimatet), also known variously as Fridays for Future (FFF), Youth for Climate, Climate Strike or Youth Strike for Climate, is an international movement of school students who skip Friday classes to participate in demonstrations to demand action from political leaders to prevent climate change and for the fossil fuel industry to transition to renewable energy.

Publicity and widespread organising began after Swedish pupil Greta Thunberg staged a protest in August 2018 outside of the Swedish Riksdag (parliament), holding a sign that read "Skolstrejk för klimatet" ("School strike for climate").^[87]^[88]

A global strike on 15 March 2019 gathered more than one million strikers in 2,200 strikes organised in 125 countries.^[89]^[90]^[91]^[92] On 24 May 2019, in the second global strike, 1,600 protests across 150 countries drew hundreds of thousands of strikers. The May protests were timed to coincide with the 2019 European Parliament election.^[91]^[93]^[94]^[95]

The 2019 Global Week for Future was a series of 4,500 strikes across over 150 countries, focused around Friday 20 September and Friday 27 September. Likely the largest climate strikes in world history, the 20 September strikes gathered roughly 4 million protesters, many of them schoolchildren, including 1.4 million in Germany.^[96] On 27 September, an estimated two million people participated in demonstrations worldwide, including over one million protesters in Italy and several hundred thousand protesters in Canada.^[97]^[98]^[99]

Youth Climate Movement

Youth all over the world have been striking, advocating, and volunteering for climate solutions. Youth climate action groups such as SustainUS, Fridays for Future, and the Sunrise Movement have called on young people to hold leaders accountable, whether through attending conferences,^[100] striking from school and pressuring politicians to listen to scientists,^[101] or calling for greater green jobs and consolidating voting power.^[102]

In 2020 the United Nations Secretary General launched the global Youth Advisory Group on Climate Change, selecting seven members who meet to represent the changes youth are demanding globally.^[103]^[104]

Youth involvement in pro-climate action movements has increased significantly in the 21st century, and has intensified over the past few years.^[105] Youth climate activists have used social media platforms as a vehicle to engage and protest with the current environmental issue. After Greta Thunberg started the youth movement "Strikes for Climate" by protesting outside the Swedish Parliament in 2018, she documented her journey on Twitter, where she built a network to promote her cause and call people to action.^[106] The youth climate movement starts shifting from the traditional way to the social media platforms and it will continue in the future.

Younger generations are paying more attention to global events, particularly climate change. Research shows that climate change is of greater concern among younger people than older people. Over 70% of Americans aged 18 to 34 worry about global warming compared with 62% of those 35 to 54 and 56% who are 55 or older.^[107] Corner claims that across European countries, young people tend to have similar or higher levels of concern than adults and have a higher sense of risk perception.^[107] Younger generations are more likely to have learned through general education about climate change in their schooling, and to be aware of the negative effects that climate change has brought to the Earth. In addition, they also see climate change as a more serious global event that is relevant to themselves because they will be more impacted, and thus should take the lead on addressing climate change.

When the pandemic hit, most school strikes movements around the world continued to be held, but moved more onto social media platforms (Twitter, Facebook, etc), resulting in lower participation rates. However, participation in youth climate movement on social media continued to rise. Social media provided an outlet for youth to share their concerns, generate knowledge, and be more politically active since they are not yet able to vote and face logistical limitations in face-to-face participation.^[108]^[109]

The research found that activists in their study created a sense of connection to other young people and other climate change activists.^[110] They usually post their activist identities on their social media account profile. (For example, @GretaThunberg, a young climate activist #climatechange#climatestrike #youthmovement). What they share in common is that they try to inspire others to do the same in their communities by showcasing themselves as climate activists with a strong voice. The strategy for younger activists is to situate themselves within a specific role to create a relevant identity to others and make connections with other people on the internet. Thus, regardless of which side the activists are going to support, they are utilizing their social media as a medium to communicate with others in a shared way. They are playing an important role focused on engaging a range of supporters worldwide to join in the youth climate movement.

The Youth Climate Movement (YouNGO)^[111] or International Youth Climate Movement (IYCM) refers to an international network of youth organisations that collectively aims to inspire, empower and mobilise a generational movement of young people to take positive action on climate change.

YOUNGO is the official children and youth Constituency of the UNFCCC, with members up to 35 years old. One of the main tasks of this group is to draft a Global Youth Position Statement to hand officials at the annual UNFCCC Conference of Parties.^[112]^[113]

2019 Global Climate Strike

The September 2019 climate strikes, also known as the Global Week for Future, were a series of international strikes and protests to demand action be taken to address climate change, which took place from 20 to 27 September 2019. The strikes' key dates were 20 September, which was three days before the United Nations Climate Summit, and 27 September.^[114]^[115] The protests took place across 4,500 locations in 150 countries.^[116]^[117] The event stemmed from the Fridays for Future school strike for climate movement, inspired by Swedish climate activist Greta Thunberg.^[118]^[119] The Guardian reported that roughly 6 million people participated in the events,^[120] whilst 350.org – a group that organised many of the protests – claim that 7.6 million people participated.^[121]

The 20 September protests were likely the largest climate strikes in world history.^[122]^[123] Organisers reported that over 4 million people participated in strikes worldwide,^[122] including 1.4 million participants in Germany.^[124]^[125] An estimated 300,000 protesters took part in Australian strikes,^[126] a further 300,000 people joined UK protests^[127] and protesters in New York – where Greta Thunberg delivered a speech – numbered roughly 250,000.^[115]^[123] More than 2,000 scientists in 40 countries pledged to support the strikes.^[128]

A second wave of protests took place on 27 September,^[129] in which an estimated 2 million people took part in over 2,400 protests.^[120]^[130] There were reported figures of one million protesters in Italy,^[131] and 170,000 people in New Zealand.^[132] In Montreal, where Greta Thunberg spoke, the Montreal school board cancelled classes for 114,000 of its students.^[133]^[134] An estimated 500,000 protesters, including several federal party leaders, joined the march in Montreal.^[135]^[136]

2023 Climate Protests

In November 2023 around 70,000 people participated in a climate march in Amsterdam, Netherlands, 10 days before the elections in the country. This was the biggest climate march in the history of the Netherlands.^[137]

Many climate protests are scheduled for the 2023 United Nations Climate Change Conference including a climate march in London. The conference has created many protests, as the head of the conference is at the same time the head of the oil company ADNOC which according to one research "is planning the largest expansion of oil and gas production of any company in the world."

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Friday, February 16, 2024

Stratospheric aerosol injection

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