Geoengineering

Steph DidasMatt Kollman

Ran Yin

EAS 6410April 19, 2012

• “Global Warming is too serious to be left to the politicians” [Edward Teller]

• “Global Warming is too important to be left to the scientists” [Michael Glantz]

Justification

Feasibility

Cost

Side effect

One rule is: The activity must be within the natural variability.

e.g. Volcanic eruption effect of dust and sulfur acid aerosol

Definition

Large-scale engineering in order to combat or counteract the effect of change in atmospheric chemistry

National Academy of Sciences, 1992.

Geoengineering

Proposed strategies

Three Schemes:

Sunshade Scheme

Ocean Scheme

Greenhouse Gas Remediation

G.Bala, Current Science, 2009.

Solar radiation management

Good: Quick

Bad: Less sunlight

Ocean acidification

ΔTemperature Statistical significance

2xC

O2

2xC

O2 m

inu

s1

.84

% s

un

Caldeira and Wood, 2008

Model Simulation Results (NCAR Atmospheric Model)

Decreasing sunlight by 1.8% will offset the global mean temperature effect of CO2 doubling

ΔPrecipitation

2xC

O2

2xC

O2 m

inu

s1

.84

% s

un

Caldeira and Wood, 2008

Statistical significance

Stratospheric Aerosol

1). Why stratosphere?

2). Sulfur, Dust or Reflective metal flakes

3). Side effect:

More surface area → Chlorine Compounds absorbed → Ozone depletion

Heat the strat.

4). How to distribute the aerosol

Mimic a volcano, like Mt Pinatubo 1991

Engineered nanoparticles:

Stay above strat. (how?)

Uniform size distribution

A thin disk (minimize forward scattering)

Increase particle lifetime

Drift poleward (magnetic dipole)

Drawback:

1. Long lifetime → Irreversible

2. High cost

3. Lack direct natural analog

Fp: Photophoretic force

Keith, David, PNAS, 2010

ΔT Δα

Change cloud abundance (Cloud seeding)

Increasing low-level marine cloud coverage by 4% offsets the CO2 doubling

1). Method:

SO2 emission↑ → H2SO4 CCN ↑

Nature: Sulfur from DMS from ocean algae

2). Side effect:

Acid rain

a. Avoid to fall on land b. (NH4)2SO4

National Academy of Sciences, 1992.

Space Mirror

At the L1 Lagrange point (gravitational force vanished)

Surface Albedo Enhancement

Replace forest with whiter surface?

Which method do you prefer?

Oceanic Hydrosols

• Dispersion of microbubbles with void volume small enough to form a stable suspension

• Reflectance increase will aid in cooling the planet

Seitz, Climatic Change, 2011.

Oceanic Hydrosols: Why and How

• 93% of incident solar radiation is absorbed by Earth’s bodies of water

• Similarly to droplets in clouds, microbubbles cause back scattering of light that increases the albedo of water

• Proposed project: deploy microbubble generators to increase albedo of oceans– Possible deployment on cargo ships to increase wake

reflectance– Possibly deploy only in certain areas where effect

would be greatest– Small scale deployment on terrestrial waters

Seitz, Climatic Change, 2011.

Oceanic Hydrosols: Effects

• Microbubble generation could be sustained at mW/m2 to increase reflectance by 100 W/m2 leading to several Kelvin decrease in temperature

• A 0.05 increase in albedo leads to a 2.6 K drop in average global surface temperature

• Deployment of generators for lakes and reservoirs will slow rate of evaporation

Seitz, Climatic Change, 2011.

Oceanic Hydrosols: Effects

Reduction in average global surface temperature by 2.6 K

Seitz, Climatic Change, 2011.

Oceanic Hydrosols: Challenges

• Cost and logistics of deployment– More feasible if deployed locally on a small

scale

• Optimizing production and lifetime through engineering and surface chemistry– Lifetime is a function of diffusion, convection,

solubility, surfactants present, salinity of water

Seitz, Climatic Change, 2011.

Bering Strait Dam

Photo credit: NASA

Bering Strait Dam: Motivation

• Ice melting

• Rising global temperatures means the melting will only increase

• Albedo decreases when ice melts

• 2008 estimates by NASA: Arctic sea ice may be gone by the summer of 2013

www.cleverclimate.org

Bering Strait Dam: Proposed Project

Photo credit: NASA

Bering Strait Dam: Optional Project

Bering Strait Dam: Effects

• Temperature– Will stop transfer of warm Pacific waters north to

the Arctic ocean.

• Dynamics– The dam will stop water currents and create a

stable ice sheet prolonging its life.

• Salinity– The only flow northward will be due to freshwater

from rivers because all ocean water from Pacific is stopped. A decrease in salinity lowers the freezing point of the water and will allow ice to form and remain longer into the spring.

www.cleverclimate.org

Bering Strait Dam: Concerns

• Ecological impact: interruption of migratory patterns and flow of nutrients from Pacific

• Thermohaline circulation disruption. May stabilize circulation but uncertainty is large

www.cleverclimate.orgPhoto credit: BBC

Bering Strait Dam: Concerns

• Engineering such a structure will be a challenge– The volume of the dam is estimated to be 1.5

billion m3

– Ships and wildlife must pass through

• Requires international cooperation• Cooling effect may be too large. It is also

possible the dam will have no effect, especially on salinity

www.cleverclimate.org

Greenhouse Gas Remediation

Removal of Greenhouse Gases (GHG) from the atmosphere

Greenhouse Gas Remediation Projects

• Carbon sequestration• Biological processes

– Ocean iron fertilization– Ocean mixing– Reforestation

• Physical processes– Biochar burial– Bio-energy with carbon storage– Carbon capture and storage (CCS)

• CFC laser photochemistry• Chemical techniques

– Carbon negative cement– Oil shale ash– Carbon air capture

www.biocharsolutions.comhttp://novacem.com

Biochar

www.biocharsolutions.com

Biochar Amendments Decrease GHG’s

Spokas et al., Chemosphere. 2009.

- Decrease of GHG production from soil

- Decreased herbicide dissipation

- Moisture dependent

- Cause unknown

“All Biochar is Not Created Equally”

www.biocharsolutions.comGaunt & Lehmann, Environ. Sci. Tech. 2008.

www.biochar-international.org

Air Capture

Approximately 6 Gt CO2 emitted in 2005.5% increase projected for 2035.

U.S. CO2 Emissions by sector, 2005

Choi et al., Environ. Sci. Tech, 2011.www.climeworks.com

EIA, Annual Energy Outlook 2011, 2011.

CO2 rich air

CO2 lean air

amine-oxide

CO2-amine-oxide

Sorbent regen &

CO2 recovery

CO2 removal from air

CO2

Regeneration

Aqueous alkaline solutions

Supported Amine Adsorbents

Jones, Annual Reviews of Chemical & Biomolecular Engineering, 2011.

Choi et al., ChemSusChem, 2009.

Process differences:

Solution vs. solid Regeneration conditions Equipment needs

All contribute to cost of air capture

Air Capture Technologies

Material Development Needed for Commercial Success

Choi et al., ChemSusChem, 2011.Bollini et al., Energy Fuels, 2011.

Key FactorsCheap production costMaterial stability to:-Regeneration-Oxidation

Commercial Geoengineering Technologies

Summary

• A lot of avenues for climate change mitigation– Manipulation of radiative forcings

– Direct removal of CO2

• Continued research needed as well as economic motivation for implementation

Questions?