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There is always an easy solution to every human problem – neat, plausible and wrong.H. L. Menken
A new warm period due to CO2
emission?
Impact on CO2 equilibrium conditions, which maintain the present status quo in climate !
The goal: albedo increaseor CO2 reduction
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to reflect more of the incoming total radiation or leak more of the emitted IR radiation
1. Solar reflectors in orbit2. Cloud Seeding
1. Carbon sequestration in rocks2. Carbon sequestration in ocean3. Carbon scrubbing and artificial trees4. Iron fertilization of phytoplankton5. Reforestation and desert greening6. Genetic engineering of plants
1. Aerosols in stratosphere
Proposals for changing or increased inflection of solar radiation or reduced absorption of earth IR radiation
Changing the albedo
• Reflecting mirrors
in orbit
• Cloud seeding
and whitening
Cloud seeding and whitening
Generating condensation points (aerosols) in atmosphere generates clouds.If condensation particles are small, cloud will appear white rather than dark!
10 ships are proposed to distribute 3800 square miles of ocean for a pilotproject. An efficacy estimate claims a requirement of a 1,900 ship fleetcosting $7.5 billion to maintain temperature balance. (supported by Bill Gates)
Clouds are a major component in the albedo estimates of the earthclimate system. Vaporizing seawater and ejecting it into high altitude toincrease cloud density and condensation capability. One Flettner ship hasthe capability of processing an amount 10 tons of water/sec. Aerosolparticles injected into water spray create more droplets with a smaller sizedistribution. This increases the cloud albedo as clouds appear whiter andlarger, leading to a projected cooling effect of between -0.3 and -1.8 Wm−2
.
Efficacy
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this requires an increase ofcloud cover from 50% to about75%, dim days to come!!!
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200 220 240 260 280 300 320
temperature
d/dT
• Atmosphere doping
with aerosols
Changing albedo by photon scattering
Smoke and steam hang over theEyjafjallajokull volcano in Iceland!
Doping the atmosphereNatural examples are volcano eruptions emitting large amounts of dust and sulfuric aerosols into the atmosphere which increase the scattering probability of incoming solar radiation and therefore the albedo factor.
El Chichon 1982 Pinatubo 1991
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The idea- mimic the cooling effect of
Pinatubo eruption
Manually inject aerosols into the
stratosphere by plane
1.5-5 Tg S per yr needed to offset
warming [Rasch et al. (2008)] Paul Crutzen
Nobel Laureate
advocate of sulfate aerosols
Mie scattering on aerosol ordust sized particles is moreefficient for high energy (smallwave length) solar radiationthan Rayleigh scattering for lowenergy (high wavelength) IRradiation from earth. Increasesreflection of incoming light withlimited effect of IR emission!
absorptionscatteringextinction KKK
Removal probability:
rx
2
The parameter x corresponds to the ratio of sizeof scatter medium to scattered wavelength; x islarge for large particles and short wavelengths.Maximum scattering probability is at x=3-5!
Mie scattering is preferably in forwarddirection, it generates halo around sun ormoon or other light sources
m: index of refraction fordifferent scatteringmedia, m=0 means noscattering.
Sulfate delivery systems
Sulfate particle injector mounted aboard aircraft platform
Sulfur-enhanced fuel additives, emit aerosol precursors in jet exhaust stream
Jet-fighter carrying 10 metric tons
each jet distributes payload in 4 hrs, over 2500 miles
would require 1 million such flights per year!
would cost $25 to 50 billions annually
A schematic of the processes that influence the life cycle of stratospheric aerosols (adapted with permission from SPARC 2006).
Sulfate fall-out would eventually be deposited in polar regions
The surface temperature difference from during June, July and August with the2×CO2 simulation and the geoengineering simulation using 2 Tg S yr−1 emission(which is not sufficient to entirely balance the greenhouse warming).
Rasch P J et al. Phil. Trans. R. Soc. A 366, 4007 (2008)
The simulations indicatean efficient cooling effect!
Conversion of ejected gaseous SO2 into H2SO4 within six months, production of hydrosulphuric acid, that translates into acid rain
OHSOHOHOHSO 24222 23
Clear increase of stratospheretemperature by ~4o, while observinga limited decrease of temperature inhemisphere by only ~0.2o. Longterm balance between atmosphericand surface temperature willrequire new seeding.
Natural washout from the atmosphere with rain after some months
Changing the atmosphere absorption by carbon sequestration
• Carbon Storage
• Artificial trees and
carbon scrubbing
Problem of site identification with no leakage
Carbon sequestration by “artificial trees”
Ca(OH)2 + CO2 → CaCO3 + H2O
One solution, long termstorage in undergroundcavities; could also beinjected into declining oilfields to increase oilrecovery!
Second solution is thechemical processing forconverting the CO2 intobuilding material or morecomplex, useful chemicalsubstances!
Possible position near oilfields, chemical plans or otherconvenient locations of high CO2
emission probability(highways, industries) to increase theoverall collection efficiency.
The present tree design absorbs5000_tons of CO2 per year. For anannual CO2 emission of about1010_tons/year roughly 2,000,000trees are required. The estimatedoperation costs of about $50 per tontranslates into annual costs of US$25_trillion annually (worldwide)!
With a world population of 7 billionpeople this translates into annualcosts of $3600/person.
Ocean fertilization
Phytoplankton: basis of food chain, major absorber for CO2
Fast growth rate of phytoplankton makes it more efficient than land based plants,
Smaller fraction of absorbed CO2 is reemitted by respiration process
( deep sea mixing, CaCO3 skeleton structure)
Riebesell et al. Nature 361, 249 (1993)
Efficient up-take of Dissolved Inorganic Carbon (DIC) molecules such as CO2
Iron fertilization of cool ocean waterareas is expected to stimulate aphytoplankton bloom. This is intendedto enhance biological productivity, tostrengthen the marine food chain andremove CO2 from the atmosphere sinceiron is a trace element for plant basedphotosynthesis and is often a limitingnutrient for phytoplankton growth. Itwas demonstrated in the 1995 IronEX IIexperiment that large phytoplanktonblooms can be created by supplying ironto iron-deficient ocean waters. In theexperiment 450 kg of FeS have beendistributed over 18 days into the Pacificocean. A plankton bloom developedrapidly turning the waters brown. It wasestimated from plankton densitysamples that the plankton consumednearly 2500 tons of CO2, significantlyreducing the concentration of CO2 inthe ocean patch from its original value.Southern Atlantic coast of South America
IronEX II Experiment 1995
Vertical temperature
SF6 tracer
Iron concentration
Chlorophyll bloom
Nitrate generation
CO2 fugacity
K. Coale et al. Nature 383, 495 (1996)
Model prediction are promising (http://www.esse.ou.edu/~gromine/iron.html)but a large number of potential site effects primarily from secondary oceanchemistry are envisioned associated with the release of chemicals fromplankton and algae growth and algae death and decay processes.
Additional experiments have been carried out in the last decade:SOIREE, EisenEx, SEED, SOFeX, Planktos, SERIES, and EIFEX, primarily in theSouthern Pacific and Indian Ocean to explore the biogeochemistry of ironfertilization in iron limited waters .
Based on the IronEX II results itwas estimated that a fraction of20% of the ocean area needs tobe fertilized to induce sufficientCO2 absorption for reducingatmospheric CO2 levels to year2000 values.
Long term effects are still unknown!
The 1999 Southern Ocean Iron RElease Experiment SOIREE experimentsuggests dangers of fertilization tothe ecosystem structure. Theclearly visible curved planktongrowth distribution in thesatellite picture is due to oceancurrents .
Results indicate that efficacy of CO2
absorption is smaller than originallyanticipated. Potential dangers arein algae bloom due to overnitrationas consequence of ironfertilization, which could reduceoxygen levels seriously affectingmarine life!
Cost benefit analysisThe ranking of “promising“ geoengineering proposals interms of efficacy and promise (based on theoreticalprediction and pilot studies), costs and affordability, riskand safety (in terms of possible site effects).
P. W. Boyd, Nature Geoscience 1, 722 (2008)
The political and science community is prepared and remains optimistic ...
CR
