Climate Engineering

There is always an easy solution to every human problem –neat, plausible and wrong.
H. L. Menken

The goal: albedo increase
or CO 2 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 orbit
1. Carbon sequestration in rocks
2. Cloud Seeding
2. Carbon sequestration in ocean
3. Carbon scrubbing and artificial trees
4. Iron fertilization of phytoplankton
p
1. Aerosols in stratosphere
5. Reforestation and desert greening
6. Genetic engineering of plants

Proposals for changing or
increased inflection of solar radiation or
reduced dabsorption of earth IR radiation

Changing the albedo
• Reflecting mirrors
in orbit
• Cloud seeding
and whitening

Cloud seeding and whitening
d ( l ) h l d
Generating condensation points (aerosols) in atmosphere generates clouds.
If condensation particles are small, cloud will appear white rather than dark!

Clouds are a major component in the albedo estimates of the earth
climate system. Vaporizing seawater and ejecting it into high altitude to
increase cloud density and condensation capability. One Flettner ship has
the capability of processing an amount 10 tons of water/sec. Aerosol
particles injected into water spray create more droplets with a smaller size
distribution. This increases the cloud albedo as clouds appear whiter and
larger, leading to a projected cooling effect of between ‐0.3 and ‐1.8 Wm −2
.
10 ships are proposed to distribute 3800 square miles of ocean for a pilot
project. An efficacy estimate claims a requirement of a 1,900 ship fleet
costing $7.5 billion to maintain temperature balance. (supported by Bill Gates)

Efficacy
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Reduction of temperature by 5 K
requires an increase in albedo of:
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200 220 240 260 280 300 320
temperature
this requires an increase of
cloud cover from 50% to about
75%, dim days to come!!!

Changing galbedo by photon scattering
• Atmosphere doping
with aerosols
Smoke and steam hang over the
Eyjafjallajokull volcano in Iceland!

Doping the atmosphere
Natural 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)]
Removal probability:
Paul Crutzen
Nobel Laureate
advocate of sulfate aerosols
K
extinction
K
scattering
K
absorption
Mie scattering on aerosol or
dust sized particles is more
efficient for high energy (small
wave length) solar radiation
than Rayleigh scattering for low
energy (high wavelength) IR
radiation from earth. Increases
reflection of incoming light with
limited effect of IR emission!

Mie scattering is preferably in forward
direction, it generates halo around sun or
moon or other light sources
x
r
2 m: index of refraction for
different scattering media,
m=0 means no scattering.
The parameter x corresponds to the ratio of size
of scatter medium to scattered wavelength; x is
large for large particles and short wavelengths.
Maximum scattering probability is at x=3‐5!

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 the
2×CO 2 simulation and the geoengineering simulation using 2Tg Syr −1 emission
(which is not sufficient to entirely balance the greenhouse warming).
The simulations indicate
an efficient cooling effect!
Rasch P J et al. Phil. Trans. R. Soc. A 366, 4007 (2008)

Natural washout from the atmosphere with rain after
some months
SO2 OH 3H
2O
H
2SO4
2H
2O
Conversion of ejected gaseous SO 2 into H 2 SO 4 within
six months, production of hd hydrosulphuric lh acid, that
translates into acid rain
Clear increase of stratosphere
p
temperature by ~4 o , while observing
a limited decrease of temperature in
hemisphere by only ~0.2 o . Long
term balance between atmospheric
and surface temperature will
require new seeding.

Changing the atmosphere absorption
by carbon sequestration
• Carbon Storage
Problem of site
identification
with no leakage
• Artificial trees and
carbon scrubbing

Carbon sequestration by “artificial trees”
One solution, long term
storage in underground
cavities; could also be
injected into declining oil
fields to increase oil
recovery!
Ca(OH) 2 + CO 2 → CaCO 3 + H 2 O
Second solution is the
chemical processing for
converting the CO 2 into
building material or more
complex, useful chemical
substances!

Possible position near oil fields,
chemical plans or other convenient
locations of high CO 2 emission
probability (highways, industries) to
increase the overall collection
efficiency.
The present tree design absorbs
5000 _ tons of CO 2 per year. For an
annual CO 2 emission of about
10 10_ tons/year roughly 2,000,000
trees are required. The estimated
operation costs of about $50 per ton
translates into annual costs of US
$25 _ trillion annually (worldwide)!
With a world population of 7 billion
people this translates into annual
costs of $3600/person.

Ocean fertilization
Phytoplankton: basis of food chain, major absorber for CO 2

‣ Fast growth rate of phytoplankton makes
it more efficient i than land dbased plants,
‣ Smaller fraction of absorbed CO 2 is
reemitted by respiration process
( deep sea mixing, CaCO 3 skeleton structure)
‣ Efficient up‐take of Dissolved Inorganic
Carbon (DIC) molecules l such as CO 2
Riebesell et al. Nature 361, 249 (1993)

Southern Atlantic coast of South America
Iron fertilization of cool ocean water
areas is expected to stimulate a
phytoplankton bloom. This is intended
to enhance biological productivity, to
strengthenthemarinefoodchainand
remove CO 2 from the atmosphere since
iron is atraceelement for plant based
photosynthesis and is often a limiting
nutrient for phytoplankton growth. It
was demonstrated in the 1995 IronEX II
experiment that large phytoplankton
blooms can be created by supplying iron
to iron‐deficient ocean waters. In the
experiment 450 kg of FeS have been
distributed over 18 days into the Pacific
ocean. A plankton bloom developed
rapidly turning the waters brown. It was
estimated from plankton density
samples that the plankton consumed
nearly 2500 tons of CO 2 , significantly
reducing the concentration of CO2 in
the ocean patch from its original value.

IronEX II Experiment 1995
K. Coale et al. Nature 383, 495 (1996)
Vertical ltemperaturet
SF 6
tracer
Iron concentration
Chlorophyll bloom
Nitrate generation
CO 2 fugacity

BasedontheIronEXIIresultsit
was estimated that a fraction of
20% of the ocean area needs to
be fertilized to induce sufficient
i
CO 2 absorption for reducing
atmospheric CO 2 levels to year
2000 values.
Model prediction are promising (http://www.esse.ou.edu/~gromine/iron.html)
but a large number of potential site effects primarily from secondary ocean
chemistry are envisioned associated with the release of chemicals from
plankton 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 the Southern
Pacific and Indian Ocean to explore the biogeochemistry of iron fertilization in
iron limited waters .

Long term effects are still unknown!
The 1999 Southern Ocean Iron RElease Experiment SOIREE experiment
suggests dangers of fertilization to
the ecosystem structure. The
clearly visible curved plankton
growth distribution in the
satellite picture is due to ocean
currents .
Results indicate that efficacy of CO 2
absorption is smaller than originally
anticipated. Potential dangers are
in algae bloom due to overnitration
as consequence of iron fertilization,
which could reduce oxygen levels
seriously affecting marine life!

Cost benefit analysis
The ranking of “promising“ geoengineering proposals in
terms of efficacy and promise (based on theoretical
prediction and pilot studies), costs and affordability, risk
and 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 isti ...
CR