Stratospheric sulfate aerosols (geoengineering)
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Stratospheric aerosol injection is a proposed method of
solar geoengineering Solar geoengineering, or solar radiation modification (SRM), is a type of climate engineering in which sunlight (solar radiation) would be reflected back to outer space to limit or reverse human-caused climate change. It is not a substitute for ...
(or solar radiation modification) to reduce
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. This would introduce
aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
s into the
stratosphere The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...
to create a cooling effect via
global dimming Global dimming is the reduction in the amount of global direct irradiance at the Earth's surface that has been observed since systematic measurements began in the 1950s. The effect varies by location, but worldwide it has been estimated to be of ...
and increased
albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...
, which occurs naturally from
volcanic eruptions Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...
. 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 The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to advance scientific knowledge about climate change caused by human activities. The World Meteorological Organization (WMO) a ...
concludes that it "is the most-researched olar geoengineeringmethod, with ''high agreement'' that it could limit warming to below 1.5°C." 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 Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
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 Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
and
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
are also under consideration. The leading proposed method of delivery is custom
aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
.


Methods


Materials

Various forms of
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
were proposed as the injected substance, as this is in part how volcanic eruptions cool the planet. Precursor gases such as
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
and
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
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 An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of anthrop ...
, every one to four years into the
stratosphere The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...
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 Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
appears to reduce the problem of aerosol growth. Materials such as
photophoretic Photophoresis denotes the phenomenon that small particles suspended in gas (aerosols) or liquids (hydrocolloids) start to migrate when illuminated by a sufficiently intense beam of light. The existence of this phenomenon is owed to a non-uniform d ...
particles, 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 The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere; which are two of the five layers of the atmosphere of Earth. The tropopause is a thermodynamic gradient-stratification layer, that marks the end of ...
, 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 The McDonnell Douglas F-15 Eagle is an American twin-engine, all-weather tactical fighter aircraft designed by McDonnell Douglas (now part of Boeing). Following reviews of proposals, the United States Air Force selected McDonnell Douglas's ...
have the necessary
flight ceiling With respect to aircraft performance, a ceiling is the maximum density altitude an aircraft can reach under a set of conditions, as determined by its flight envelope. Service ceiling Service ceiling is where the rate of climb drops below a pres ...
, but limited payload. Military tanker aircraft such as the
KC-135 Stratotanker The Boeing KC-135 Stratotanker is an American military aerial refueling aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It is the predominant variant of the C-135 Stratolifter family of transpo ...
and
KC-10 Extender The McDonnell Douglas KC-10 Extender is an American aerial refueling tanker aircraft operated by the United States Air Force (USAF). A military version of the three-engine DC-10 airliner, the KC-10 was developed from the Advanced Tanker Cargo A ...
also have the necessary ceiling and have greater payload capacity. * Modified ''
artillery Artillery is a class of heavy military ranged weapons that launch munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during siege ...
'' might have the necessary capability, but requires a polluting and expensive propellant charge to loft the payload.
Railgun A railgun or rail gun is a linear motor device, typically designed as a weapon, that uses Electromagnet, electromagnetic force to launch high velocity projectiles. The projectile normally does not contain explosives, instead relying on the proj ...
artillery could be a non-polluting alternative. *''
High-altitude balloon High-altitude balloons are crewed or uncrewed balloons, usually filled with helium or hydrogen, that are released into the stratosphere, generally attaining between above sea level. In 2002, a balloon named BU60-1 reached a record altitude of . ...
s'' 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 Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
in the atmosphere may require a millennium-timescale commitment to SRM if aggressive emissions abatement is not pursued simultaneously.


Aerosol formation

Primary aerosol formation, also known as homogeneous aerosol formation, results when gaseous combines with oxygen and water to form
aqueous An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be rep ...
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
(H2SO4). This acidic liquid solution is in the form of a
vapor In physics, a vapor (American English) or vapour (British English and Canadian English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critic ...
and
condenses Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...
onto particles of solid matter, either
meteor A meteoroid () is a small rocky or metallic body in outer space. Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...
itic in origin or from dust carried from the surface to the stratosphere. Secondary or heterogeneous
aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
formation occurs when H2SO4 vapor condenses onto existing aerosol particles. Existing aerosol particles or
droplets A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the lower end of a tube or other surface boundary, producing a hanging drop called a pendant d ...
also run into each other, creating larger particles or droplets in a process known as
coagulation Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...
. Warmer atmospheric temperatures also lead to larger particles. These larger particles would be less effective at scattering
sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
because the peak light scattering is achieved by particles with a diameter of 0.3 μm.


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 A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...
), 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 A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of the Sun's radiation, preventing it from hitting a spacecraft or planet and thereby reducing its insolation, which results in reduced heating. Light can be div ...
). * ''Technological feasibility'': In contrast to other proposed solar geoengineering techniques, such as
marine cloud brightening Marine cloud brightening also known as marine cloud seeding and marine cloud engineering is a proposed solar radiation management climate engineering technique that would make clouds brighter, reflecting a small fraction of incoming sunlight ba ...
, much of the required technology is pre-existing: chemical manufacturing,
artillery shells A shell, in a military context, is a projectile whose payload contains an explosive, incendiary, or other chemical filling. Originally it was called a bombshell, but "shell" has come to be unambiguous in a military context. Modern usage so ...
, high-altitude aircraft,
weather balloons A weather balloon, also known as sounding balloon, is a balloon (specifically a type of high-altitude balloon) that carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a ...
, 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 In aeronautics, ice protection systems keep atmospheric moisture from accumulating on aircraft surfaces, such as wings, Propeller (aeronautics), propellers, Helicopter rotor, rotor blades, Intake, engine intakes, and Environmental control system ...
, 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'.


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 Earth's climate system is a complex system having five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). '' ...
. 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 The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere; which are two of the five layers of the atmosphere of Earth. The tropopause is a thermodynamic gradient-stratification layer, that marks the end of ...
. 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 () or the direct release of sulfuric acid () and these face different challenges. If gas is released it will oxidize to form and then condense to form droplets far from the injection site. Releasing 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 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 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 release could be conceived and developed, it would allow control over the particle size to possibly alleviate some of the inefficiencies associated with release.


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 Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...
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 Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...
'': is 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 Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propan ...
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'': There would be an effect on the appearance of the sky from stratospheric aerosol injection, notably a slight hazing of blue skies and a change in the appearance of
sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spring ...
s. How stratospheric aerosol injection may affect clouds remains uncertain. According to a study on cleaner air, the reduction of aerosol pollution has led to solar brightening in Europe and North America, which has been responsible for an increase in U.S. corn production over the past 30 years. * ''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'': An historical study in 2018 found that stratospheric sulfate aerosols injected by the volcanic eruptions of
Chicón Chicón or Chicon (possibly from Quechua ''ch'iqu'' workable stone) is a mountain in the Urubamba mountain range in the Andes of Peru, about high. It is located in the Cusco Region, Calca Province, Calca District and in the Urubamba Province ...
(1982) and
Mount Pinatubo Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon. Its eruptive history w ...
(1991) had mixed effects on global crop yields of certain major crops.


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 David Keith may refer to: * David Keith (novelist) (1906–1994), pen name of American scholar Francis Steegmuller *David Keith (actor) (born 1954), American film and TV performer and director *David Keith (physicist), Canadian-born Harvard Profess ...
and
Gernot Wagner Gernot Wagner (1980 in Austria) is a climate economist at Columbia Business School. He holds an AB and a PhD in political economy and government from Harvard University, as well as an MA in economics from Stanford University. A founding co-direct ...
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. In 2012, the
Bristol University , mottoeng = earningpromotes one's innate power (from Horace, ''Ode 4.4'') , established = 1595 – Merchant Venturers School1876 – University College, Bristol1909 – received royal charter , type ...
-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 The Engineering and Physical Sciences Research Council (EPSRC) is a British Research Council that provides government funding for grants to undertake research and postgraduate degrees in engineering and the physical sciences, mainly to univers ...
, 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 , latin_name = , image_name = Shield of the University of Cardiff.svg , image_size = 150px , caption = Coat of arms of Cardiff University , motto = cy, Gwirionedd, Undod a Chytgord , mottoeng = Truth, Unity and Concord , established = 1 ...
, 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 The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention, is a multilateral treaty. The Convention has three main goals: the conservation of biological diversity (or biodiversity); the sustainable use of its ...
in 2012.


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 The Convention on Long-Range Transboundary Air Pollution, often abbreviated as Air Convention or CLRTAP, is intended to protect the human environment against air pollution and to gradually reduce and prevent air pollution, including long-range ...
(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 The Vienna Convention for the Protection of the Ozone Layer is a multilateral environmental agreement signed in 1985 that provided frameworks for international reductions in the production of chlorofluorocarbons due to their contribution to the ...
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 The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion Ozone depletion consists of two related events observed sinc ...
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 The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
authority to regulate stratospheric sulfate aerosols.


Welsbach seeding

Welsbach seeding is a patented
climate engineering Climate engineering (also called geoengineering) is a term used for both carbon dioxide removal (CDR) and solar radiation management (SRM), also called solar geoengineering, when applied at a planetary scale.IPCC (2022Chapter 1: Introduction and F ...
method, involving seeding the
stratosphere The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...
with small (10 to 100
micron The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...
) metal oxide particles (
thorium dioxide Thorium dioxide (ThO2), also called thorium(IV) oxide, is a crystalline solid, often white or yellow in colour. Also known as thoria, it is produced mainly as a by-product of lanthanide and uranium production. Thorianite is the name of the minera ...
, aluminium oxide). The purpose of the Welsbach seeding would be to "(reduce) atmospheric warming due to the
greenhouse effect The greenhouse effect is a process that occurs when energy from a planet's host star goes through the planet's atmosphere and heats the planet's surface, but greenhouse gases in the atmosphere prevent some of the heat from returning directly ...
resulting from a greenhouse gases layer," by converting radiative energy at near-
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
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 The Hughes Aircraft Company was a major American aerospace and defense contractor founded on February 14, 1934 by Howard Hughes in Glendale, California, as a division of Hughes Tool Company. The company was known for producing, among other produ ...
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 Mikhail Ivanovich Budykorussian: Михаил Иванович Будыко (20 January 1920 – 10 December 2001) was a Soviet and Russian climatologist and one of the founders of physical climatology. He pioneered studies on global climate an ...
is believed to have been the first, in 1974, to put forth the concept of artificial
solar radiation management Solar geoengineering, or solar radiation modification (SRM), is a type of climate engineering in which sunlight (solar radiation) would be reflected back to outer space to limit or reverse human-caused climate change. It is not a substitute for ...
with stratospheric
sulfate aerosol The term sulfate aerosols is used for a suspension of fine solid particles of a sulfate or tiny droplets of a solution of a sulfate or of sulfuric acid (hydrogen sulfate). They are produced by chemical reactions in the atmosphere from gaseous prec ...
s if
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
ever became a pressing issue. Such controversial
climate engineering Climate engineering (also called geoengineering) is a term used for both carbon dioxide removal (CDR) and solar radiation management (SRM), also called solar geoengineering, when applied at a planetary scale.IPCC (2022Chapter 1: Introduction and F ...
proposals for
global dimming Global dimming is the reduction in the amount of global direct irradiance at the Earth's surface that has been observed since systematic measurements began in the 1950s. The effect varies by location, but worldwide it has been estimated to be of ...
have sometimes been called a "Budyko Blanket".


See also

*
Carl Auer von Welsbach Carl Auer von Welsbach (1 September 1858 – 4 August 1929), who received the Austrian noble title of Freiherr Auer von Welsbach in 1901, was an Austrian scientist and inventor, who separated didymium into the elements neodymium and praseody ...
*
Chemtrail conspiracy theory The chemtrail conspiracy theory is the erroneous belief that long-lasting condensation trails are "chemtrails" consisting of chemical or biological agents left in the sky by high-flying aircraft, sprayed for nefarious purposes undisclosed to t ...
*
Climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
*
Climate engineering Climate engineering (also called geoengineering) is a term used for both carbon dioxide removal (CDR) and solar radiation management (SRM), also called solar geoengineering, when applied at a planetary scale.IPCC (2022Chapter 1: Introduction and F ...
*
Cloud seeding Cloud seeding is a type of weather modification that aims to change the amount or type of precipitation that falls from clouds by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical p ...
*
Global dimming Global dimming is the reduction in the amount of global direct irradiance at the Earth's surface that has been observed since systematic measurements began in the 1950s. The effect varies by location, but worldwide it has been estimated to be of ...
*
Solar geoengineering Solar geoengineering, or solar radiation modification (SRM), is a type of climate engineering in which sunlight (solar radiation) would be reflected back to outer space to limit or reverse human-caused climate change. It is not a substitute for ...
*
Termination Shock The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interst ...
*
Weather Modification Operations and Research Board Weather modification is the act of intentionally manipulating or altering the weather. The most common form of weather modification is cloud seeding, which increases rain or snow, usually for the purpose of increasing the local water supply. W ...


References


Further reading

* *


External links


What can we do about climate change?
Oceanography magazine
Global Warming and Ice Ages: Prospects for Physics-Based Modulation of Global Change
Lawrence Livermore National Laboratory
The Geoengineering Option:A Last Resort Against Global Warming?
Council on Foreign Relations The Council on Foreign Relations (CFR) is an American think tank A think tank, or policy institute, is a research institute that performs research and advocacy concerning topics such as social policy, political strategy, economics, mi ...

Geo-Engineering Climate Change with Sulfate Aerosols
Pacific Northwest National Laboratory Pacific Northwest National Laboratory (PNNL) is one of the United States Department of Energy national laboratories, managed by the Department of Energy's (DOE) Office of Science. The main campus of the laboratory is in Richland, Washington. O ...

Geo-Engineering Research
Parliamentary Office of Science and Technology The Parliamentary Office of Science and Technology (POST) is the Parliament of the United Kingdom's in-house source of independent, balanced and accessible analysis of public policy issues related to science and technology. POST serves both Hous ...

Geo-engineering Options for Mitigating Climate Change
Department of Energy and Climate Change The Department of Energy and Climate Change (DECC) was a department of the Government of the United Kingdom created on 3 October 2008, by Prime Minister Gordon Brown to take over some of the functions related to energy of the Department for Busin ...

Unilateral Geoengineering
Council on Foreign Relations The Council on Foreign Relations (CFR) is an American think tank A think tank, or policy institute, is a research institute that performs research and advocacy concerning topics such as social policy, political strategy, economics, mi ...
* * * {{YouTube, id=EnNerOVUOdo, title=As planet warms, scientists explore 'far out' ways to reduce atmospheric CO2
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published on March 27, 2019 animation of SCoPEx Climate change policy Planetary engineering Climate engineering