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8/8/2019 2008Nov, SciAm Shades
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What is
geoengineering? Deliberate actions to slow or reverse global
warming
Instead of reducing emissions, geoengineeringmodifies the natural world to cool the earth.
Old concept, proposed by environmentalscientists advising Lyndon Johnson in 1965.
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Types of Geoengineering
Largely dependent onCO2 in atmosphere
Remove CO2 byfertilizing oceans with
iron.
Takes a long time
Controlling Amount of Heat that Returns to Space
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Problems with RemovingCO2
Iron in the oceans?! Biological effects associated with gigantic
algal blooms
Recreation, natural beauty
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Types of Geoengineering
Sea Mist in theTroposphere
Solar Sunshade SO2 in the stratosphere
Controlling Amount of Solar Energy
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Large, unmanned ships in the ocean
Powered by the wind and shoot smallparticle ocean spray into the atmosphere
Brighten clouds with small particle spray,thereby reflecting more sunlight, reducing
incoming energy.
1500 ships, 3 billion dollars = offsets CO2production twice what we have now.
Sea Mist
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Sea Mist Problems
Unpredictable localclimate changes
Reduced rainfall becauseof more long-livedclouds
No field data
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Space Sunshade
Trillions of disks at theLagrangian point (where the
Earths and Suns gravitational
fields are equal).
Each disk is kept track of by alocal global positioning system
Each disk flies into position byusing tiny solar sails.
Cloud of Disks that can blockout sunlight, cooling the earth.
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Sunshade Problems
5 trillion dollars
Lengthy construction
Reduction of global rainfallbecause of evaporation reduction
Potential weapon use, blottingout sunlight over certain portions
of the earth
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Sulfur in the
Stratos here SO2 in the atmosphere
goes through multiplechemical reactions
Eventually becomessulfate particles made upof sulfuric acid, waterand other impurities.
Deflect incomingsunlight
Already comes fromsome volcanic eruptions
Deployment by plane,balloons, missiles
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Sulfur Problems CO2 warms planet day and night,
independent of seasons.
Sulfur only cools planet when the sunis shining, not during polar winter.
Thus, sulfur may cool tropics morethan the poles.
Wind and precipitation changes
Less evaporation in tropics, sofreshwater may become even morescarce.
Acid rain from sulfuric acid in theatmosphere
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References
Kunzig, Robert 2008. A sunshade for planet earth.Scientific American. Volume 299-5, p.46-55.
20 Reasons Geoengineering May be a Bad Idea.www.thebulletin.org/files/064002006_0.pdf
Some online talks on geoengineeringonline.itp.ucsb.edu/online/climate_c08
http://online.itp.ucsb.edu/online/climate_c08http://www.thebulletin.org/files/064002006_0.pdfhttp://online.itp.ucsb.edu/online/climate_c08http://www.thebulletin.org/files/064002006_0.pdfhttp://www.thebulletin.org/files/064002006_0.pdfhttp://online.itp.ucsb.edu/online/climate_c08