THE Independent looks at fake volcanoes, giant space mirrors, oceans of iron filings… One of these ideas might save our planet from the worst effects of global warming – or destroy it.
Heat could be stopped from reaching the Earth’s atmosphere by reflecting some of the sun’s rays back into space. Volcanic eruptions, which release a huge amount of sulphate particles, have led to periods of cooling: the eruption of Mount Pinatubo in 1991 saw global temperatures fall by ½C for 18 months, the released sulphates reflecting light.
Drawbacks: Though this would be among the fastest fixes to global warming, it is also among the riskiest. Global weather patterns could be drastically affected.
Assembling a giant glass sunshade in space then firing it into orbit could reflect a small proportion of the sun’s rays, according to astronomer Roger Angel. He claims a reduction of just 2 per cent in sunlight reaching the Earth could make warming more manageable.
Drawbacks: Asteroids, primarily. Glass discs would be vulnerable to space debris, and maintenance of a “space umbrella” requires time, expertise and money.
Dropping iron filings into the ocean can generate blooms of carbon-absorbing plankton. The plankton then take in CO2 at the surface, then carry it with them as they drift to the ocean floor after death, creating “carbon sinks”.
Drawbacks: It takes a long time for comparatively little effect, and the impact on marine life could be devastating. Where plankton blooms in contained water sources, fish can suffocate. Fertilising the oceans would also marginally acidify them.
Technology already exists to extract CO2 from the air. Klaus Lackner of the Columbia University Earth Institute has developed machinery that can extract 1,000 times more CO2 a day from the atmosphere than a natural tree. Building these structures around the world could add muscle to nature’s blueprint.
Drawbacks: High cost: direct air-capture measures like this would cost a minimum of $600 per tonne of CO2 removed.
Planting real trees has the aesthetic advantage of creating forests, and would satisfy those who believe that “engineering” the climate is madness. Painting the roofs of houses white or covering tranches of desert in reflective material could also bounce back unwanted radiation.
Drawbacks: Geoengineers argue that man is already engineering the climate with pollution from fossil fuels. Also, these methods alone would not be enough to avert the worst of climate change.