Geoengineering Steph Didas Matt Kollman Ran Yin EAS

Geoengineering Steph Didas Matt Kollman Ran Yin EAS 6410 April 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]

Geoengineering Definition Large-scale engineering in order to combat or counteract the effect of change in atmospheric chemistry Justification Feasibility Cost Side effect One rule is: The activity must be within the natural variability. e. g. Volcanic eruption sulfur acid aerosol effect of dust and National Academy of Sciences, 1992.

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

Model Simulation Results (NCAR Atmospheric Model) Decreasing sunlight by 1. 8% will offset the global mean temperature effect of CO 2 doubling Statistical significance 2 x. CO 2 minus 1. 84% sun 2 x. CO 2 ΔTemperature Caldeira and Wood, 2008

Statistical significance 2 x. CO 2 minus 1. 84% sun 2 x. CO 2 ΔPrecipitation Caldeira and Wood, 2008

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? ) ΔT Δα Uniform size distribution A thin disk (minimize forward scattering) Increase particle lifetime Fp: Photophoretic force Drift poleward (magnetic dipole) Drawback: 1. Long lifetime → Irreversible 2. High cost 3. Lack direct natural analog Keith, David, PNAS, 2010

Change cloud abundance (Cloud seeding) Increasing low-level marine cloud coverage by 4% offsets the CO 2 doubling 1). Method: SO 2 emission↑ → H 2 SO 4 CCN ↑ Nature: Sulfur from DMS from ocean algae 2). Side effect: Acid rain a. Avoid to fall on land b. (NH 4)2 SO 4 National Academy of Sciences, 1992.

Space Mirror At the L 1 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 m. W/m 2 to increase reflectance by 100 W/m 2 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. org Photo 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 m 3 – 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. com http: //novacem. com

Biochar www. biocharsolutions. com

Biochar Amendments Decrease GHG’s - Decrease of GHG production from soil - Decreased herbicide dissipation - Moisture dependent - Cause unknown Spokas et al. , Chemosphere. 2009.

“All Biochar is Not Created Equally” www. biocharsolutions. com Gaunt & Lehmann, Environ. Sci. Tech. 2008. www. biochar-international. org

Air Capture U. S. CO 2 Emissions by sector, 2005 Approximately 6 Gt CO 2 emitted in 2005. 5% increase projected for 2035. Choi et al. , Environ. Sci. Tech, 2011. www. climeworks. com EIA, Annual Energy Outlook 2011, 2011.

Air Capture Technologies Aqueous alkaline solutions Process differences: Solution vs. solid Regeneration conditions All contribute to cost of air capture Equipment needs Supported Amine Adsorbents CO 2 rich air amine-oxide Sorbent regen & CO 2 recovery CO 2 removal from air CO 2 lean air Regeneration CO 2 -amine-oxide CO 2 Jones, Annual Reviews of Chemical & Biomolecular Engineering, 2011. Choi et al. , Chem. Sus. Chem, 2009.

Material Development Needed for Commercial Success Key Factors Cheap production cost Material stability to: - Regeneration - Oxidation Choi et al. , Chem. Sus. Chem, 2011. Bollini et al. , Energy Fuels, 2011.

Commercial Geoengineering Technologies

Summary • A lot of avenues for climate change mitigation – Manipulation of radiative forcings – Direct removal of CO 2 • Continued research needed as well as economic motivation for implementation

Questions?