written by: Willie Scott•edited by: Lamar Stonecypher•updated: 4/27/2010
With the ever increasing emission of greenhouse gases and our slow reaction to their mitigation, scientists believe we can reduce their effect on climate change through geo-engineering technology. This consists of reflecting solar radiation away from earth and removal of CO2 from the atmosphere.
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Introduction to Geo-engineering
Geo-engineering has been investigating different methods of reducing the effects of climate change since the early 1990’s.
Scientists believe that methods such as altering the earth’s albedo (the percentage of solar energy absorbed or reflected by earth) can mitigate the consequences of climate change, some methods are still being explored, and some have been tested on a small scale.
Some earth scientists believe geo-engineering will avert industrial nations from the mitigation of greenhouse gases, but geoscientists argue that it will compliment this.
This is an article on geo-engineering, a relatively new concept that hopes to slow down climate change. Here we will examine the methods employed by geo-technology, and we begin with an overview of how greenhouse gases affect the earth’s albedo.
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The Earth’s Albedo
As we have seen from the introduction the earth’s albedo is a relationship between the solar radiance absorbed and reflected by earth; a reflective white body having an incidence starting at 0% with a black absorbent material one of up to 100%.
Greenhouse gases form in the earth’s atmosphere and stratosphere are altering this relationship by preventing some of the reflected solar radiance from re-entering deep space.
Some of the earth’s substances which affect the albedo are listed below;
Clouds – depending on the types of clouds, with dark clouds absorbing the sun's radiance and white clouds reflecting a good percentage of it.
Water – depending on the waters density and whether the water is calm or ruffled.
Forests- deciduous trees have a higher albedo than conifer types so removing forests can increase the albedo (although many factors affect this).
Snow – this reflects the suns radiance.
Soil – depending on the colour of the soil, desserts reflecting more radiance than dark agricultural soil.
We move on now to examine the different technologies used in geoenineering technology.
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It is proposed to spray seawater up into the atmosphere over an ocean, when the droplets of water and salt reach the clouds about 1km above they are absorbed and are known to increase cloud reflectivity. The operation will be carried out by a fleet of satellite controlled unmanned ships powered by wind.
Geo-engineering scientists maintain that the areas under the clouds will become cooler, so this technology can be used to mitigate melting ice sheets and the bleaching of coral reefs caused by rising sea temperatures.
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Scientists have estimated that our oceans remove between fifty and sixty billion tonnes of CO2 a year from the atmosphere, and have a capability to remove more through iron seeding.
At present plankton floating on the top layers of the ocean absorb CO2 through photosynthesis, and it is known that adding iron to the seawater will stimulate this natural process, causing plankton blooms.
However, there are a few problems with this technology, the first one being that the plankton would have to sink to the bottom as normal when they die. If they float to the top and decompose, the CO2 captured will escape back to the atmosphere. Another fear is that the small zooplankton which feed on the plankton will devour them before they reach the ocean floor, emitting the CO2 to atmosphere.
Although iron has been added naturally to the oceans from wind-blown dust, the environmental consequences of adding large quantities to the ocean need further investigation. Some scientists allude to this method of geo-engineering as creating toxins that could possibly poison sea and coastal flora and fauna.
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Anthogenic Removal of CO2 From the Atmosphere
Geo-engineering has come up with a method of removal of CO2 from the ambient air. This consists of special membranes formed into panels which absorb the CO2 and once the panels are filled, it is removed for storage as in Carbon Capture and Storage (see my article on CCS). This method has the advantage of being able to locate the panels on top of airport and city buildings, bus shelters and along motorways to absorb CO2 from exhaust emissions.
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Improving Desert Albedo
The barren deserts of the Sahara and Gobi already reflect a portion of the suns radiance, but according to the geo-engineers it can be improved by the addition of a reflective expanse. This would be in the form of highly reflective plastic sheets laid on top of the sand, however the cost of such a project at present would run to billions of dollars.
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Removal of CO2 Sources using Bio-char
This method is directed at farmers and foresters who burn their unwanted plants or leave them to rot in the fields or forests emitting CO2 to atmosphere.
To prevent this, the scientists have developed a machine that shreds the wood and crops, feeding the resultant matter into an oven converting it into charcoal. This is then buried in the fields, enriching the soil and storing the CO2.
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Screening Using Sulphur Dioxide
It has been known for some time that the emission of sulphur dioxide from volcanoes gathers in layers in the atmosphere and provides a sun screen, filtering solar radiation before it reaches earth.
Scientist claim that injecting sulphur dioxide high into the atmosphere can enhance the natural process. The several suggestions for injecting the sulphur have so far proved too costly.
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CO2 Removal Using Artificial Trees
The artificial tree consists of a box structure about the size of a normal shipping container, filled with carbon absorbing materials
These containers could be used at the same locations as the membrane panels discussed earlier as well as being located on structures above abandoned oil and gas wells, with the captured CO2 being pumped into the depleted reservoirs.
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Increasing Albedo in the City
One of the simplest and inexpensive methods of reflecting solar radiance away from the inner city is to paint the roofs of city buildings white.
This would lower the temperature of inner city areas which is normally 3-4 degrees higher than adjacent rural temperatures. This is due to the urban heat island phenomena, caused by the construction of buildings and infrastructure from thermal mass materials, with the absorbed heat being released at night.