question: what is geoengineering?

Geoengineering is deliberate, large-scale intervention in Earth’s natural systems to counteract climate change. The two most common forms are:

SOLAR RADIATION MANAGEMENT (SRM)

SRM techniques aim to reflect a small proportion of the Sun’s energy back into space, counteracting the temperature rise caused by increased levels of greenhouse gases in the atmosphere which absorb energy and raise temperatures. Methods include: albedo enhancement, space reflectors and stratospheric aerosols.

CARBON DIOXIDE REMOVAL (CDR)

These techniques aim to remove carbon dioxide from the atmosphere, directly countering the increased greenhouse effect and ocean acidification. These techniques would have to be implemented on a global scale to have a significant impact on carbon(4). Methods include: afforestation, biochar, bioenergy capture and sequestration, ambient air capture, ocean fertilization, enhanced weathering and ocean alkalinity enhancement.

A description of the different forms can be found in the following posts:

SRM:

Albedo Enhancement

Space Reflectors
Stratospheric Aerosols

CDR:

Ambient Air Capture
Afforestation

Biochar
Bioenergy Capture and Sequestration
Ocean Fertilization
Enhanced Weathering
Ocean Alkalinity Enhancement

geoengineering explained: the benefits and challenges of stratospheric aerosols

Stratospheric aerosols are minute particles suspended in the atmosphere designed for solar radiation management (SRM). When these particles are sufficiently large, their presence becomes noticeable as they scatter and absorb sunlight, which can reduce visibility (haze) and redden sunrises and sunsets. Aerosols interact both directly and indirectly with the Earth’s radiation budget and climate. As a direct effect, the aerosols scatter sunlight directly back into space. As an indirect effect, aerosols in the lower atmosphere can modify the size of cloud particles, changing how the clouds reflect and absorb sunlight, thereby affecting the earth’s energy budget. Aerosols can also act as sites for chemical reactions to take place. Stratospheric aerosols introduce small, reflective particles into the upper atmosphere to reflect some sunlight before it reaches the surface of the Earth. This is accomplished by releasing sulfur dioxide into the stratosphere.

BENEFITS

CHALLENGES

  • Very potent method and could off-set all the warming from the doubling of CO2
  • Affordable and relatively easy
  • Proven effective by large, natural volcanic eruptions
  • As with all sunshade schemes, overall rainfall is reduced
  • Regional weather climates will be dramatically affected which may cause dangerous outcomes, such as famine
  • Doesn’t cool poles to pre-industrial temperatures, so polar ice sheets will continue to melt
  • Will not prevent ocean acidification
  • Sky will become whiter
  • Without efforts to reduce overall CO2 production, the planet would warm rapidly if we stopped injecting SO2 into the stratosphere

see also:

Question: What is geoengineering?

Albedo Enhancement

Space Reflectors
Stratospheric Aerosols

Afforestation
Ambient Air Capture
Biochar
Bioenergy Capture and Sequestration
Ocean Fertilization
Enhanced Weathering
Ocean Alkalinity Enhancement

source:
LePage, M. (2012, September 20). The pros and cons of geoengineering. Retrieved from New Scientist: http://www.newscientist.com/gallery/geoengineering/

geoengineering explained: the benefits and challenges of space reflectors

Space reflectors, a form of solar radiation management (SRM), are sun shields positioned in space in order to reduce the amount of solar energy reaching the earth. Options include placing mirrors around the earth, placing millions of reflectors between the earth and the sun where the gravitational attraction between the two bodies is equal, launching a “cloud” of trillions of refracting discs or launching a sunshade of mesh aluminum threads.

BENEFITS

CHALLENGES

  • The theorized sun protection would be enough to stop global warming
  • Expensive [estimated at several trillion dollars]
  • Experimental technology with unforeseen consequences
  • Will take 25 years or longer to complete
  • Effects would be uneven with the tropics cooling and the polar regions warming

see also:

Question: What is geoengineering?

Albedo Enhancement

Space Reflectors
Stratospheric Aerosols

Afforestation
Ambient Air Capture
Biochar
Bioenergy Capture and Sequestration
Ocean Fertilization
Enhanced Weathering
Ocean Alkalinity Enhancement

sources:
Physics, I. I., RSC, & Engineering, T. R. (2009, July 15). Geoengineering: challenges and global impacts. Retrieved from http://www.rsc.org

 

geoengineering explained: the benefits and challenges of albedo enhancement

Albedo is the fraction of the sun’s radiation reflected from a surface. It is quantified as the proportion or percentage of solar radiation of all wavelengths reflected by a body or surface to the amount incident upon it. An ideal white body has an albedo of 100% and an ideal black body is 0%. Albedo enhancement attempts to increase the reflectiveness of clouds, land surfaces, and water so that an increased quantity of the sun’s heat is reflected back into space, ergo albedo enhancement is considered a form of solar radiation management (SRM).

BENEFITS

CHALLENGES

  • The Arctic is cooled, despite being remote from any areas of application, and there is some recovery of sea ice and snow cover
  • Even desert geoengineering is insufficient to return the Arctic sea ice and snow to their pre-industrial conditions
  • Surface albedo modification (SAM) geoengineering gives rise to both near-field and far-field changes in climate
  • Surface albedo modification is strongly seasonal and mostly confined to the areas of application
  • Desert geoengineering produces strong local cooling effects and results in large changes in circulation and precipitation worldwide with a particularly large reduction in the intensity of the Indian and African monsoons
  • The general circulation model is an insufficient tool for predicting the effects of albedo modification schemes
  • Urban and crop geoengineering produce only small to insignificant changes in global average temperatures
  • SAM geoengineering schemes do not offer a full solution to the problems caused by greenhouse gas concentrations, and may, in fact, prove detrimental to the environment

see also:

Question: What is geoengineering?

Albedo Enhancement

Space Reflectors
Stratospheric Aerosols

Afforestation
Ambient Air Capture
Biochar
Bioenergy Capture and Sequestration
Ocean Fertilization
Enhanced Weathering
Ocean Alkalinity Enhancement

sources:
Budikova, D. (2013). Albedo. Retrieved from The Encyclopedia of Earth: http://www.eoearth.org/view/article/149954/
Peter Irvine, D. J. (2011). Climatic effects of surface albedo geoengineering. Journal of Geophysical Research: Atmospheres. Retrieved from http://onlinelibrary.wiley.com/doi/10.1029/2011JD016281/abstract