Geo-engineering is an umbrella term referring to technologies designed to engineer the natural environment on a huge scale in an attempt to counteract the effects of global warming.
Proposed techniques include attempting to lower temperatures by releasing stratospheric sulfur aerosols into the atmosphere, seeding clouds, painting large urban areas white to reflect the sun's rays, introducing devices to absorb carbon dioxide from the atmosphere, fertilising the ocean to stimulate the growth of carbon absorbing algae, and putting giant mirrors into orbit.
To date, no large-scale geo-engineering projects have been undertaken, although some limited ocean fertilisation and cool roof schemes have been introduced.
Geo-engineering proposals are extremely controversial with some scientists predicting they will prove unworkable and environmental groups maintaining they distract from the urgent need to curb carbon emissions.
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