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Several kinds of scatterers could bring about the desired cooling. The simplest and cheapest per unit mass may be substances that interact minimally with electromagnetic radiation (dielectrics). These include sub-micron oxide particles, including sulfur oxides. These materials are contained in standard volcanic aerosols and Earth crustal ‘dust’, although the particles used in solar radiation management would likely be smaller and without chemical impurities. As such, they may be safe, since materials, such as sulfate and ash, are relatively well understood as one can predict with confidence how their properties change throughout their months-to-years travel time through the stratosphere. The surface properties of other materials must be studied to determine their response to the very acidic and oxidizing environment, in the presence of highly energetic ultraviolet light. Alternatives to dielectrics have been suggested, such as metallic or resonant particles (see, for example, Teller, 1997). Metals interact with electromagnetic radiation strongly and might conceivably require much less particle mass than would non-conducting (dielectric) particles.NASA
Existing small jet fighter planes, like the F-15C Eagle (Figure 2a), are capable of flying into the lower stratosphere in the tropics, while in the Arctic, larger planes, such as the KC-135 Stratotanker or KC-10 Extender (Figure 2b), are capable of reaching the required altitude. Specialized research aircraft such as the American Lockheed ER-2 and the Russian M55 Geophysica, both based on Cold War spy planes, can also reach 20 km, but neither has a very large payload or could be operated continuously to deliver gases to the stratosphere.
The Northrop Grumman RQ-4 Global Hawk can reach 20 km without a pilot but costs twice as much as an F-15C. Current designs have a payload of 1-1.5 tons. Clearly it is possible to design an autonomous specialized aircraft to loft sulfuric acid precursors into the lower stratosphere, but the current analysis focuses on existing aircraft.
Options for dispersing gases from planes include the addition of sulfur to the fuel, which would release the aerosol through the exhaust system of the plane, or the attachment of a nozzle to release the sulfur from its own tank within the plane, which would be the better option. Putting sulfur in the fuel would have the problem that if the sulfur concentration is too high in the fuel, it would be corrosive and affect combustion. Also, it would be necessary to have separate fuel tanks for use in the stratosphere and in the troposphere to avoid sulfate aerosol pollution in the troposphere.
The military has already manufactured more planes than would be required for this geoengineering scenario, potentially reducing the costs of this method. Since climate change is an important national security issue [Schwartz and Randall, 2003], the military could be directed to carry out this mission with existing aircraft at minimal additional cost. Furthermore, the KC-135 fleet will be retired in the next few decades as a new generation of aerial tankers replaces it, even if the military continues to need the in-flight refueling capability for other missions.
Unlike the small jet fighter planes, the KC-135 and KC-10 are used to refuel planes mid-flight and already have a nozzle installed. In the tropics, one option might be for the tanker to fly to the upper troposphere, and then fighter planes would ferry the sulfur gas up into the stratosphere (Figure 2b). It may also be possible to have a tanker tow a glider with a hose to loft the exit nozzle into the stratosphere.
Originally posted by ProudBird
Anthropogenic stratospheric aerosol injection would cool the planet, stop the melting of sea ice and land-based glaciers, slow sea level rise, and increase the terrestrial carbon sink, but produce regional drought, ozone depletion, less sunlight for solar power, and make skies less blue. Furthermore it would hamper Earth-based optical astronomy, do nothing to stop ocean acidification, and present many ethical and moral issues. Further work is needed to quantify many of these factors to allow informed decision-making.
About the Author
Matt Andersson is the President of Aviation Development Holdings and the Founder of Indigo Airlines, backed by American Express and McKinsey & Company. He has been featured in the Financial Times, the Wall Street Journal, the New York Times, Fortune, Time Magazine and BBC Radio. A jet-rated pilot and University of Chicago M.B.A.,
Charlson and colleagues have shown that the cooling effect of sulfate aerosols does not neatly cancel out the effects of greenhouse warming, but rather, makes the situation more complex. "Aerosol cooling and the greenhouse effect have characteristics that prevent them from neatly offsetting each other," note Charlson and colleague Tom Wigley, who heads the Office for Interdisciplinary Earth Studies at the University Corporation for Atmospheric Research in Boulder, Colorado.
First, the cooling and warming occur mostly over different parts of the world: the aerosol effect is focused over industrial areas in the Northern Hemisphere, whereas warming effects may be greatest over subtropical oceans and deserts. There are also temporal variations. Aerosol effects are most pronounced during daylight hours during the summer season; the activity of greenhouse gases differs very little over the course of a day, or over a year.
The work of Charlson and colleagues suggests that forcing by sulfate aerosol is not evenly distributed over the globe--it can vary by roughly a factor of five from region to region. As a result, the world might expect to see dramatic changes in regional weather patterns in the future, not just an increase in average global temperature.
Sulfate aerosol was named by the journal Science as one of nine runners-up for Molecule of the Year in 1995.
Basically, IndiGo airlines is a private airliner. It is a low-cost airlines based at Gurgaon in an Indian state of Haryana. Its main base is Indira Gandhi International Airport in New Delhi, the capital city of India. IndiGo operates domestic flights daily linking over 17 destinations.
Environmentalists said geo-engineering went against the spirit of the Nagoya talks, which aims to set new targets for 2020 to protect nature, such as setting up more land and marine protected areas, cutting pollution and managing fishing. "We are certainly in favor of more (geo-engineering) research, as in all fields, but not any implementation for the time being because it's too dangerous. We don't know what the effects can be," said Francois Simard of conservation group IUCN. "Improving nature conservation is what we should do in order to fight climate change, not trying to change nature."
Why not carry on burning fossil fuels, and instead reduce the amount of CO2 in the atmosphere directly? Better still, allow CO2 levels to rise but restrict the sunlight hitting the earth’s surface.