Putting mirrors in space and salting clouds are two of the more outlandish ideas noted by the UN's Intergovernmental Panel on Climate Change (IPCC) as a way to help counteract the consequences of increasing greenhouse gas emissions.
Its report also examines carbon dioxide removal, with ideas such as sowing the seabed with iron to stimulate the growth of plankton that would then absorb carbon, as well as capturing carbon dioxide from the air and storing it in either land or sea.
Solar radiation management could reflect some of the sun's rays (the mirrors) or "brighten" clouds by introducing salt particles to create more droplets of water so the clouds appear whiter. Sulphate particles, or aerosols, injected into the stratosphere could also reflect sunlight – but the report highlights concerns over the potential stratospheric ozone depletion this may cause.
Bob Ward of the Grantham Research Institute says that the IPCC is "right to consider" such measures, but that environmental concerns and cost are big problems to overcome.