Solar geoengineering might work but local temperatures could keep rising for years

This technique includes Spraying aerosols high up into the stratosphere to cool the planet. It works in a similar way to a large volcanic eruption.

Sulphur dioxide is often proposed as the most likely candidate for aerosol release.

However Sulfuric acid or hydrogen sulphide could also be used.

·         Releasing aerosols could also help to bring back global rainfall patterns to their pre-industrial averages.

·         It has an edge on other proposed forms of solar geoengineering because it would not require a large technological leap to become a reality

·         Other concerns are that that, if aerosols were used to address global warming, the world could be left at risk of a “termination shock”. That is, if aerosols were released and then suddenly stopped – as a result of political disagreement or a terrorist attack, for example global temperatures could rapidly rebound.

·         Using sulphur dioxide in aerosol spray has its own concern. It could come down as acid rain.

In theory, it involves using ships to spray saltwater into the clouds above the sea. Once airborne, the salt particles would act as cloud condensation nuclei, they would facilitate the condensation of water vapour into liquid. As more water droplets are created, clouds would appear larger and brighter. These brighter clouds would reflect away more sunlight. In simple words it means making existing clouds just a little bit brighter which could help cool planet.

·         A few studies based on modelling suggest that marine cloud brightening may be able to restore temperatures and ice cover, and could have a “mixed” impact on global crop yields.

It includes increasing the albedo of buildings in order to reflect more sunlight. This would involve making rooftops and walls brighter – by painting them white, for example.

Scientists have also suggested that the same technique could be applied to crops, possibly by introducing genes that would give plants a waxy sheen.

·         The technique could be used on a smaller scale than other proposed technologies. This means the risk of issues, such as “cross-boundary conflict” and termination shock, could be much smaller.

·         It might hamper crop productivity and, thus, food production.

This would involve using a fleet of sea vessels to churn up millions of tiny microbubbles on the ocean surface. The seafoam formed would reflect away sunlight, cooling the planet

·         In case if anything goes wrong, it is faster and easier to shut ocean foam.

·         creating enough microbubbles at the ocean’s surface to have an overall cooling effect on the planet could require large amounts of energy.

Cloud thinning

It means to “remove” cirrus clouds from the atmosphere.

Cirrus clouds are thin, wispy clouds made of ice crystals, which form at high altitudes. The clouds reflect away some sunlight, but also absorb large amounts of long-wave radiation – meaning that, on balance, they warm the planet.

Aerial vehicles such as drones could be used to deliver and then inject solid aerosol particles, such as desert dust or pollen, into cirrus clouds. Seeding the clouds in this way would cause them to dissipate more quickly, lessening their overall warming effect.

·         If we could remove all cirrus clouds, we could more than offset the warming caused by a doubling of CO2.

·         Overseeding could lead to the formation of thicker and more persistent cirrus clouds. The effect could be additional warming rather than the intended cooling.

·         It involves sending a giant mirror – or fleet of mirrors – into orbit in order to reflect away more sunlight from the Earth

·         Since sunshades are implemented in space and, hence, environmentally they are the least disruptive.

·         It would be a huge technological challenge. Once introduced, it would need to be continually altered to deal with further rises in atmospheric CO2

·         The costs are probably expensive when we compare with other solar geoengineering techniques

·         Geoengineering can hold global warming to 1.5C. These technologies could theoretically lower global warming and help in the effort to fight climate change.

·         Geoengineering could be viewed by many as a quick “technofix” to climate change. If more research and development is channelled into these techniques, people may start to backpedal on their promises to cut their greenhouse gas emissions.

·         Since geoengineering would not affect the climate the same way [as mitigation], a lower global mean temperature anomaly achieved using geoengineering does not necessarily lead to lower aggregate climate risks

·         The technologies involved in this process are very costly.

·         There is also the issue of governance. Though ideas are beginning to emerge, it is still not clear who could be responsible for carrying out and regulating solar geoengineering. At present, research into solar geoengineering is largely restricted to the US, the UK and other parts of Europe. However, developing countries are likely to be the most affected by future climate change, research shows. Therefore, “it is right” for these nations to play “a central role in solar geoengineering.