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Seven Solutions to Global Warming

Space Sunshades (1/7)

Roger Angel at the University of Arizona has proposed launching trillions of space shades into what as known is the L-1 orbit between the sun and Earth. These shades - each about two-feet in diameter and weighing only a gram - would collectively form a long, cylindrical cloud that would ultimately reduce sunlight hitting Earth by about two percent.

The project has been viewed as prohibitively expensive. Angel says the project could feasibly be deployed in 25 years for a few trillion dollars, which includes the cost of producing and blasting 20 million tons of shades into space. (Image: University of Arizona Steward Observatory)

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Seven Solutions to Global Warming

Cloud Seeding (2/7)

Another way to reflect more sunlight back into space is to increase reflectivity of the world's marine clouds, which cover a quarter of the ocean's surface. John Latham and Stephen Salter have proposed wind-powered yachts (pictured) that would spray seawater droplets into the air to produce more clouds.

Latham says that about a thousand of these vessels would be needed to make the plan effective, and that they should be deployed in the southern oceans, where most reflective marine stratocumulus clouds are. But more testing is necessary to better understand the ecological and meteorological consequences of this method. (Image Courtesy: John MacNeill)

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Seven Solutions to Global Warming

Ocean Iron Enrichment (3/7)

Sprinkling iron dust can trigger plankton blooms in ocean waters. More plankton would be able to absorb more carbon dioxide making iron fertilization a potential climate change mitigation strategy. The broader effects on marine ecosystems and food chains, however, are not yet fully understood.

The photo shows a research team aboard the Australian research vessel, Aurora Australis, examining the effects of iron on phytoplankton growth in the Southern Ocean in 2001. (Photo: Ken Buesseler / Woods Hole Oceanographic Institution)

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Seven Solutions to Global Warming

Sulfate Injections (4/7)

A technically feasible proposal is increasing the amount of sulfates in the Earth's atmosphere, which would reflect sunlight back into space. The 1991 eruption of Mount Pinatubo, which belched out 20 megatons of sulfur dioxide and resulted in cooler temperatures worldwide.

Initial proposals have included additives to jet fuels, sending sulphates up in balloons, or even using naval artillery to fire dust shells into the air. Some scientists have warned that a "sulfate sunshade" would destroy the Earth's ozone layer. (Photo: Reuters)

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Seven Solutions to Global Warming

Ocean Tubes (5/7)

British scientists James Lovelock and Chris Rapley have proposed putting thousands of giant plastic tubes in the ocean, which would use wave motion and a one-way valve to push deep water through the tubes to the surface, bringing up essential nutrients to stimulate blooms of tiny marine plants.

The resulting plankton blooms would help draw carbon dioxide from the air and also emit a chemical called dimethyl sulfide, which stimulates the formation of sun-reflecting clouds.(Illustration: Jack Cook / Woods Hole Oceanographic Institution)

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Seven Solutions to Global Warming

Carbon Sequestration (6/7)

Another option is taking carbon dioxide straight out of the air and storing it. The "air capture" devices illustrated here were conceived by Columbia University researcher Klaus Lackner and Global Research Technologies LLC. Sometimes referred to as mechanical trees for their carbon-capturing function, these devices would - unlike trees - be able to work day and night and release the captured CO2 on demand.(Image Courtesy: Global Research Technologies LLC)

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Seven Solutions to Global Warming

Biochar (7/7)

The hand on the left is holding "biochar," a biomass-derived black carbon, which is seen as a promising option to enrich agricultural soils (right) and capture carbon dioxide. This method was inspired by the properties of ancient Amazonian terra preta soils (center) that can store carbon for several thousand years.

Biochar is produced by a process called pyrolysis, which heats organic materials - like crop waste - without oxygen. It can be either burned for fuel or fertilize fields and lock up carbon. (Photo: Johannes Lehmann / Cornell University)

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Geoengineering: Manipulating Nature for a Cooler Planet

With greenhouse gas emissions still rising sharply, some scientists say it’s time to think about "last resort" options to stop and reverse global warming. But most geoengineering proposals have risks of their own.

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