Geoengineering is defined as the deliberate large-scale intervention in the Earth's natural systems to counteract climate change. And, as part of the intervention, geoengineering refers to a set of emerging technologies. The category of technologies include afforestation and enhanced weathering. Both use natural guardrails on the effects of emissions through absorbed carbon dioxide. The category of technology also include biochar and carbon capture technologies which work to remove carbon from the air and safely store it in the ground.
The technologies of geoengineering is generally split into two broad categories: carbon geoengineering, also called carbon dioxide removal, and solar geoengineering, often called solar radiation management or sunlight reflection. Both technology categories are different methods of approaching the same goal of reducing or mitigating emissions and coping with the effects of increased emissions and carbon dioxide in the atmosphere.
Carbon Geoengineering, also called carbon dioxide removal or greenhouse gas removal, is a category of technologies that work to reverse or mitigate the effects of carbon dioxide on the atmosphere through its removal.
Natural methods for carbon geoengineering includes reforestation, afforestation, commercial plantations, natural regeneration or agroforestry projects to increase the available greenspace for the offset of emissions. Forestation projects suffer from the amount of time needed for a natural absorption cycle to take effect. Commercial plantations also have a limited impact since the plantations are harvested periodically for the natural resources, though they offer an economic upside for users. And if the harvested wood from a commercial plantation is burned for fuel, the captured carbon dioxide is released back into the environment. Whereas if the harvested lumber is used for construction, the material will continue to hold on to the carbon dioxide.
There is an estimated 7.7 million square miles of existing damaged and degraded forests which could be recovered.
Biochar is the processing of burning organic waste in a container with little oxygen in a process called pyrolysis. Through this process, the organic waste is burned into a charcoal-like substance which can be used as a type of fertilizer. And the pyrolysis process reduces the amount of gas emitted during the burn and keeps the carbon dioxide stored in the biochar.
Carbon capture and storage refers to technologies which work to reduce emissions through point source capture, which gathers carbon dioxide emissions at industrial exhaust points, and direct air capture, which works to pull carbon dioxide directly from the air. Both store the carbon dioxide underground, though there are emerging technologies which work to reuse the captured carbon dioxide.
Another proposed method of carbon capture and storage is artificial trees. In the method, artificial trees are a series of resin-covered filters that convert captured carbon dioxide to a carbonate called soda ash. The soda ash would be periodically washed off the filters and collected for storage.
Enhanced weathering refers to a natural process in which carbon dioxide is naturally pulled out of the atmosphere through a process called chemical weathering. In chemical weathering, carbon dioxide trapped in rainfall breaking down rocks is washed out as bicarbonate, and is then dissolved in seawater or stored on the ocean floor. Enhanced weathering tries to speed up and increase the possibility of this natural occurrence. In terrestrial applications, enhanced weathering uses silicate materials like olivine which are crushed and spread across agricultural soil where it is absorbed into the microbes and plant roots. The pulverized powder, especially across a large surface area, is capable of capturing carbon dioxide and storing it into those microbes and plant roots. In oceanic applications, similar silicate materials are dissolved on the ocean coasts to take advantage of the tides.
Solar geoengineering, often called solar radiation management or sunlight reflection, refers to the use of technology to reflect a small fraction of sunlight back from the planet in order to cool the planet. These technologies work to cool the planet to mitigate the effects of carbon dioxide and warming without effecting the root cause of the issue. Solar geoengineering would also not address ocean acidification.
One of the simpler solar geoengineering technologies, albedo enhancement is a process of increasing the reflectivity surfaces. This is especially useful in larger cities where there are more surfaces which can have increased reflectivity. The intended effect of increased surface reflectivity is to return solar radiation to the atmosphere rather than absorbing the heat.
Stratospheric aerosols refers to the process of introducing tiny reflective particles, such as calcium carbonate, into the upper atmosphere where they can scatter a small amount of solar radiation back into space. This use of sulfates would mimic the effect of large volcanic eruptions, similar to the eruption of Mount Pinatubo in the Philippines in 1991 which threw a large amount of sulphate particles and caused a global cooling of up to 0.6 degrees over the following two years. While the use of sulfates would mimic the impact of a volcanic eruption, and presents one of the least expensive methods of combating rising global temperatures, the suppression of solar radiation could cause other changes in weather systems and rainfall patterns and could increase the acidifying of the oceans.
Space-based technologies would attempt to reflect a fraction of sunlight from earth through the positioning of large reflective mirrors in space. The subject of space mirrors have been discussed since the 1980s, and the first designed space mirror was developed by engineer James Early. This early model consisted of a 2,000 kilometer-wide shield initially recommended to be installed on the moon. More modern designs include solar shields manufactured from thousands of small mirrors and parasol-like spacecraft to shade parts of earth. Underpinning the idea of using space-based technologies for solar reflection comes from scientist Lowell Wood who proposed the deflection of 1% of solar radiation could be sufficient to halt global warming. Other estimates have the necessary deflection of solar radiation at 2% to 4%.
Cloud-based technologies refer to technologies for manipulating clouds. Cirrus cloud thinning is one such method which attempts to reduce the thin, high-altitude clouds to emit more long-wave radiation from earth to space. Cirrus clouds do not reflect sunlight, but they are largely responsible for trapping the solar radiation on earth and thinning them would theoretically help cool the earth. One proposed method of reducing cirrus clouds is to seed them with water-depleting aerosols.
Cloud seeding is another proposed method for increasing cloud cover and reducing solar radiation. The technology introduces silver ions into the atmosphere which collects moisture around them and develop rain or snow clouds. Cloud seeding has been tested by the governments of China, Russia, and the United Arab Emirates. According to the Pacific Standard Magazine, cloud seeding was used in 2015 in Texas to reduce drought.
Another method would include marine cloud brightening which would attempt to brighten marine clouds to reflect more sunlight back into space. Marine cloud brightening was first proposed by British physicist John Latham in 1990. His proposal saw tiny salt particles from seawater sprayed into low-lying clouds which could form additional droplets and increase the surface area, and the reflectivity, of the clouds.
The idea of geoengineering can be dated back to 1965, when President Lyndon Johnson's Science Advisory Committee warned it might be necessary to increase the reflectivity of the earth to offset the rising greenhouse emissions. But it was in 1982, when Soviet climatologist Mikhail Budyko proposed the idea of filling the stratosphere with sulphate particles to reflect sunlight back into space.
In 1992, British researchers undertook an experiment to test the idea of fertilizing the ocean with iron to stimulate the growth of carbon dioxide absorbing algae.
Geoengineering gained further traction in 2006 when Paul Crutzen, a Nobel Prize-winning atmospheric chemist, suggested geoengineering was necessary to combat the rising global temperatures in an article in Climactic Change.
In 2009, Russian scientists conducted what is believed to be the first outdoor geoengineering experiment. In the experiment, they mounted aerosol generators on a helicopter and sprayed particles as high as 200 meters (660 feet). In a paper published in Russian Meteorology and Hydrology, the scientists claimed their experiment had reduced the amount of sunlight that reached the surface.
The Oxford Principles were authored in 2009 by Steve Rayner, Tim Kruger, and Julian Savulescu of the Oxford Geoengineering Programme, with Catherine Redgewell from University College London and Nick Pidgeon from University of Cardiff. These principles were submitted to the UK House of Commons Science and Technology Select Committee, which endorsed the principles and recommended they be developed further. The United Kingdom's government likewise endorsed the document. This represents one of the first official national-level policy statements on geoengineering.
The principles put forth by the authors are a proposed set of initial guiding principles for the governance of geoengineering, with the intention to guide the development of geoengineering techniques from research to deployment and stipulate that any decision with respect to deployment is taken with governance structures in place.
Geoengineering to be regulated as a public good. This principle suggests any geoengineering projects should be regulated and undertaken in the public interest at the state and international levels without the profit motive expected of private sector companies.
Public participation in geoengineering decision-making. This principle stipulates that when and where possible, any research into geoengineering should notify, consult, and obtain informed consent from those affected by research activities. Which would mean a company capturing and storing carbon in a specific geographic location would require the agreement at the national or local level within the territory or state the carbon would be stored. Whereas a larger scale aerosol in the stratosphere would require global agreement.
Disclosure of geoengineering research and open publication of results. This principle intends to achieve transparency in the research to facilitate a better understanding of the associated risks and reassure the public of the integrity of the research process.
Independent assessment of impacts. This principle intends to put the assessment of the possible impacts of geoengineering research into independent hands, rather than those of the researcher, and include the interests of involved parties where research crosses regional or national lines. The authors want these assessments to address the environmental and socio-economic impacts of research, as well as mitigating the risks of lock-in to particular technologies or vested interests.
Governance before deployment. This principle recommends any decisions with respect to deployment of any research or technology be taken only with governance structures in place, respecting existing rules and institutions where possible.
