Geoengineering is the large-scale manipulation of the Earth in order to mitigate global warming (Lenton & Vaughan, 2009).  The definition is vague, and its broadest uses encompass ideas ranging from carbon capture and sequestration to launching mirrors into space.  Here, we use the term as it is defined above, but exclude carbon capture and sequestration (CCS).  CCS attempts to avoid humanity’s impact on the system; geoengineering attempts change the system to avoid its system’s impact on humanity.

While our plan explores CCS methods to decrease carbon dioxide levels (CO2) to our goal of 350ppm, we have included this section to illustrate the potential for geoengineering in aiding our plan by decreasing any warming that may occur while our plan is in action.  We include geoengineering in our costs only as part of research.

     Proposals for geoengineering projects can be divided into two categories: Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR) (Lenton & Vaughan, 2009).  SRM proposals aim to reduce global warming by reducing the amount of light absorbed by the Earth and its atmosphere.  Commonly cited SRM ideas include spraying sulfur aerosols into the stratosphere, brightening clouds over the ocean, and sending lenses or mirrors into outer space (The Royal Society, 2009). CDR methods try to fix the root cause of global warming by taking CO2 out of the atmosphere.  Methods include biomass burial, biochar burial, and enhanced weathering.

      Geoengineering proposals are highly controversial.  Its proponents claim that we are too close to catastrophic CO2 levels to stop global warming merely by curbing emissions and sequestering carbon.  Once the Earth's climate reaches a tipping point, climate change will progress rapidly and its effects will be irreversible.  Reducing the amount of radiation that is trapped by the atmosphere will give us more time to remove CO2.  Critics argue that ambitious geoengineering projects will be cheaper and easier to implement globally than weaning the world's infrastructure off fossil fuels or sequestering most of the carbon we produce (Keith, 2009).

      Geoengineering is far from having universal approval, however.  Detractors cite the "moral hazard" that public support of geoengineering may cause: people will be less likely to support costly emissions reduction plans if they believe that geoengineering can fix the planet quickly and cheaply (Keith, 2009).  They also point out that the Earth's climate is highly complex, and they don’t believe scientists have been collecting data long enough to be able to predict its fluctuations accurately.  Complex systems can behave nonintuitively.  Small disturbances may trigger unexpected effects, and geoengineering will affect the climate in ways that have never been tested (Wunsch).  We should wait to implement geoengineering, some scientists say, until we are sure that we have reached a tipping point, and that the risks to the environment from inaction are greater than those from geoengineering.

Two geoengineering methods are included in this plan: cool roof technology and biochar burial.

Cool roof technology

     A roofing system that is designed to reflect heat and sunlight is a cool roof.  Cool roofs are an SRM technique because installing them in urban areas globally increases the Earth's albedo and decreases temperature. Decreasing global temperature provides more of a buffer zone before the climate reaches a tipping point, and therefore more time in which to carry out carbon capture and sequestration. Cool roofing also effectively sequesters carbon, because it reduces the energy used for air conditioning.

• If installed in all densely populated urban areas, the equivalent of 24 Gt of CO2 will be offset in temperature (Akbari, 2009) “That is what the whole world emitted last year,” according to Arthur Rosenfeld. “So, in a sense, it’s like turning off the world for a year.”

• Cool roofing costs $3 per square foot (Akbari, 2009).

• Cool roofing saves $0.07 in energy costs per square foot per year (Larson 2007).

• Normal roofs have a lifespan of 20 to 25 years.  If 5% of roofs replaced each year were replaced with cool roofs, this goal could be met in two decades (Barringer, 2009).


Biochar burial

     Biochar is charcoal created by burning biomass in a low-oxygen environment.  Up to 50% of the carbon in plant matter is converted to charcoal during this process, which is called pyrolysis (Lenton & Vaughan, 2009).  Unlike burning in oxygen, pyrolysis avoids releasing CO2 into the atmosphere.  Syngas and bio-oil, both biofuels, are by-products of the pyrolysis process; these can be used in place of fossil fuels.   This biochar would be buried in soil, sequestering the carbon in a stable form. 

• Carbon can be sequestered in charcoal for hundreds to thousands of years, as opposed to decades in decomposing biomass (The Royal Society, 2009).

• Biochar burial has side benefits.

◦ Improves farmability of soil (Lehmann, Gaunt, & Rondon, 2006)

◦ Filters groundwater, and improves water quality (Lehmann, n.d.)

◦ Reduces emissions of nitrous oxide, another greenhouse gas (Lehmann et al., 2006)

• If carbon costs $3.38 under the international cap and trade system, biochar burial will cost from $100 to $230 per ton CO2 sequestered.  This cost is high compared to other sequestration methods, but there are economic incentives for biochar burial (Lehmann et al., 2006).

◦ Biofuel produced by the pyrolysis of biomass can be sold.

◦ Biochar can be sold for about $100 per ton as fertilizer (Lehmann et al., 2006).