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Stratospheric Injection of Reflective Aerosols or Particles

 
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02/09/2010 08:13 AM
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Stratospheric Injection of Reflective Aerosols or Particles
Stratospheric Injection of Reflective Aerosols or Particles by means of Aviation Fuel Additives

Various suggestions have been made for stratospheric aerosols or particles to simulate the observed cooling effect of major volcanic eruptions. The best known is the detailed proposal of Paul Crutzen for sulphur dioxide (1). Also proposed by Gregory Benford is diatomous earth, injected as individual diatoms. (Silica particles originating as marine shells. Brief description below ‘Saving the Arctic’)(2)



This paper describes the selection and preliminary testing of chemicals that might be used as aviation fuel additives to inject these two products, sulphur dioxide and micron sized silica particles into the stratosphere, from a commercial or military aircraft.



The Jet Engine.

Although very highly developed, the Jet engine is essentially simple. There is a fan at either end and a combustion chamber similar to a domestic oil central heating boiler in the middle. It also burns a similar type of oil. The oil or kerosene is a mixture of many hydrocarbon type compounds having from 8 to 20 carbon atoms per molecule. (3) Some of these compounds already contain sulphur and other elements.



This type of burner is more or less capable of burning anything flammable, which can be sprayed through the atomising nozzle. There is no reason to believe that a small proportion of a chemical very similar to the chemicals already present in the kerosene will have any undesirable effects.



The Chemicals.

The two chemicals tested are dimethyl sulphide to produce sulphur dioxide and tetra ethyl silicate to produce silica particles.



In a closed glass jar both of these chemicals are indistinguishable from jet aviation fuel. Both are clear, colourless, oily liquids. Both dissolve in aviation fuel in any proportion.



Solutions of each of these chemicals have been burned in a paraffin blowlamp as a simple simulation of a jet engine combustion chamber. Observation of the combustion suggests that the desired chemicals are produced and that the silica particles are of smoke or mist (micron) size.( description of experiments at www.naturaljointmobility.info/experiments.htm )(4)



It is suggested that the solutions would probably have no detrimental effects on the fuel tanks, pipes, pumps or combustion chambers of the jet engine.



Flight Plans etc.

We would want to burn fuel containing the additive specifically when the aircraft was cruising in the stratosphere. Obviously we would not want to release these products at other phases of the aircraft flight so it is not suggested that an additive should be put generally into aviation fuel.



The following information comes from a 747-400 captain flying regularly from the Far East to Europe and the West Coast of United States. Being near retirement, and having started his career with the RAF, he describes the flight plan provided to him for a long flight now as amazingly comprehensive and accurate. Such plans rely on detailed knowledge of weather along the whole route including lower stratospheric winds.



In addition he tells me that it is perfectly possible for the pilot to select, for instance, the outer starboard wing tank to feed the outer starboard engine at a particular time during the flight.



It would seem therefore to be perfectly possible to put the additive into one tank only and to use that tank when the plane was defined in the flight plan to be in the stratosphere. Aircraft cruising altitudes vary between about 30 and 40,000 ft (9 to 12km). The lower boundary of the stratosphere varies from about 20,000 ft. (6 km) near the pole to close to 55,000 ft. (17km) at times on the equator. These heights also vary considerably with weather conditions so careful planning as part of the flight plan would obviously be necessary.



For the testing phase commercial aircraft would of course not be used. Instead it is probable that military aircraft could be made available. If so, injection could be done at higher altitudes than would be possible with most commercial aircraft. The B-52 for instance flies up to 50,000 ft.(15km) Such an aircraft would probably also have a military arrangement of fuel tanks with some smaller emergency tanks and greater flexibility to connect tank to engine. This could be very convenient in testing.


Testing

There will have to be detailed testing of both additives in a jet engine. This would be done at a static engine test facility where the exhaust could be analysed with regard to particle size and type. Safety and the effects on the engine, the pumps, the fuel tanks etc. would all have to be checked. Such testing is however the bread and butter of the aviation industry and could be completed very quickly.



Assuming satisfactory completion of such engine testing, atmospheric testing could be started almost immediately.



Atmospheric Testing.

Atmospheric testing scenarios have already been defined by experts in the field and could be implemented almost immediately following the jet engine test facility phase. For example the suggestion of Gregory Benford of the University of California, outlined below in “Saving the Arctic”(5)



Such testing could be of each of the additives proposed, in different areas or at different times, at different altitudes to compare effectiveness.



Why Might Particles Be Better?

-- they won't react with the ozone layer. (SO2 forms sulphuric acid droplets with water by taking oxygen from ozone. However, since Paul Crutzen's Nobel prize is for his work on the ozone layer he is a good position to say that this effect is small.)

-- they might be more reflective and therefore require less material injected.

-- it might be possible to choose particle size for maximum reflectivity in the ultraviolet.

-- they won't produce acid rain and will come to earth in rain as small sand particles.



Possible Dangers of Silica Particles.

-- just as silica is sand it is also chemically asbestos. However particles in the stratosphere will almost certainly form rain condensation nuclei high in the troposphere and never form breathable dust at ground level. The quantities are also tiny in comparison with other particulates from vehicles, industrial processes and natural windblown dust.

-- the silica particles might cause an abrasion or erosion problem at the tail end of the jet engine as they condense from the hot gases. (They might even condense as silicon carbide! Only testing will show up possible problems.)



Saving the Arctic.

The original suggestion for the injection of silica particles was by Gregory Benford, a planetary atmospheric scientist at the University of California at Irvine. He suggested the use of diatomous earth (Micron sized silica particles originating as sea creatures) without defining a distribution system. “Saving the Arctic” by Gregory Benford. on googlegroups/geoengineering(2)



The jet fuel additives proposed here provide a way of distributing similar particles without the need to develop any new equipment. This means that experimental injection could be started almost immediately.



This complements the rest of Gregory Benford’s document which lays out a scenario for "regional reversible experiments" -- using "tiny harmless particles at such altitude that they will rain out within, say, six months"



He also suggests, in choosing the region, that "The Arctic is particularly vulnerable. The warmer ocean melts ice, exposing more ocean, which is darker than ice. So the ocean absorbs more sunlight. This and other effects are warming the Arctic more than other regions-about 5 degrees Centigrade in the last 30 years."



Benford lists the actual experimental steps thus:

* “ * Deploy the particles by airplane in the Spring.( In the Arctic the atmospheric circulation patterns tend to confine the deployed particles, sweeping them around the pole but not far southward.)
* Measure the cooling below, using local sensors and space monitoring of the sea ice.
* Detect if the present retreat of sea ice toward the North Pole slows or even reverses. This will be a clear, visual signature than the region is cooling. Ground measurements will give more refined understanding.
* The particles can rain or snow out in fall (autumn), ending the experiment."(Because of this limited time scale, lower stratospheric injection might be desirable at passenger jet cruising altitudes)



Obviously the experiment could include sulphur dioxide and particles in different areas and altitude for comparison.



As Gregory Benford said "This describes a Particulate Shield Experiment, designed to understand the complex climate system, not the beginning of an engineering project." But it does obviously lead directly to a geoengineering project, which might lead to slowing or reversing of the Arctic melting which many now feel is the most urgent and immediate danger from global warming. Since there is no need to design and develop any new equipment, limited experiments could be done during the summer of 2008.



Do We Need to Save the Arctic?

The present level of temperature rise, and sea ice melting, will eventually result in the loss of most of the Greenland ice sheet and 4 1/2 metres (15 ft.) of sea level rise. The question is only how quickly this will occur. The I. P. C. C. estimate is 40 centimetres by 2100.(5) This is based largely on data up to 2004. Many recent observations and papers suggest that melting might be occurring much more quickly than predicted. There are also strong arguments that the loss of the summer sea ice will so transform the albedo of the whole Arctic as to make the melting irreversible even by using the methods proposed here.



The IPCC report, based partly on a 2006 paper (Zhang and Walsh) does not predict total loss of Arctic sea ice this century. The maximum prediction is a 33% reduction by 2080-2100.(6) The actual loss for summer 2007 is already close to this at 22%.(7) If the same method of prediction is used, based on the most recent trends including this figure, the North Pole could be free of sea ice by 2013, a full century earlier than predicted.

The IPCC prediction of 40 cm of global sea level rise is similarly based on past trends. In the decade from 1993 to 2003 there was a rise of about 4cms.(5) This has been extrapolated to 40 cms for the ten decades of this century. It could easily transpire that this calculation to predict sea level rise this century is as optimistic as the prediction of summer sea ice loss is turning out to be.





References

1) ALBEDO ENHANCEMENT BY STRATOSPHERIC SULFUR INJECTIONS: A CONTRIBUTION TO RESOLVE A POLICY DILEMMA? An Editorial Essay by Paul Crutzen

Climatic Change (2006) DOI: 10.1007/s10584-006-9101-y

2)email to geoengineering –by Gregory Benfold [link to groups.google.com]

3) Flash Point and Chemical Composition of Aviation Kerosene (Jet A) [link to www.galcit.caltech.edu]



4) Description of experiments at www.naturaljointmobility.info/experiments.htm



5)IPCC 2007 Working Group I Report "The Physical Science Basis" chapter5. Observations:

Oceanic Climate Change and Sea Level. Page 409 on. Click to download 15 Mb pdf. [link to www.ipcc.ch]



6)IPCC 2007 Working Group 2 Report “Impacts, Adaptation and Vulnerability” Chapter 15 “Polar Regions (Arctic and Antarctic)” Page 662 (--- based on the IPCC model, projected mean reductions --–of sea ice area in the Arctic by 2080-2100 of 31%, 33% and 22% ---) Click to download 8Mb pdf. [link to www.ipcc.ch]


7) The big melt: lessons from the Arctic summer of 2007 [link to www.carbonequity.info]

[link to www.naturaljointmobility.info]





GLP