This is my
paper/poster which has been accepted for the American Geophysical Union meeting
in San Francisco in December 2007
Stratospheric Injection of Reflective Aerosols or Particles
by means of
GC33A-0935
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.
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:
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 http://groups.google.com/group/geoengineering/browse_thread/thread/cfc43d1597f5ae9/f2033973259d7153#f2033973259d7153
3) Flash Point and Chemical
Composition of Aviation Kerosene (Jet A) http://www.galcit.caltech.edu/EDL/publications/reprints/galcit_fm99-4.pdf
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. http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter5.pdf
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. http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter15.pdf
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