2008Nov, SciAm Shades

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

2008Nov, SciAm Shades

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