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.