Researchers are working on a way to evaluate and rank the various geoengineering proposals that have been put forward to combat global warming.

A survey of the five most popular, yet risky, geoengineering proposals being floated as a way to address global warming.

Global warming has become such an overriding emergency that some climate experts are willing to consider schemes for partly shielding the planet from the sun's rays. Critics warn that no such scheme is a magic bullet and emission reduction strategies will still have to go forward.

The author looks at the risks that geoengineering techniques being proposed to combat climate change could be weaponized. He argues that there are "[t]wo factors make this a danger we dismiss at our peril: the unequal impact of climate changes, and the ability of small states and even nonstate actors to attempt geoengineering."

It should be possible to counteract the global warming associated with a doubling of carbon dioxide levels by enhancing the reflectivity of low-lying clouds above the oceans, according to researchers in the US and UK. John Latham of the National Center for Atmospheric Research in Boulder, US, and colleagues say that this can be done using a worldwide fleet of autonomous ships spraying salt water into the air.

A growing number of experts say it is time for broad discussion of how and by whom geoengineering should be used, or if it should be tried at all. Similar questions are being raised about nanotechnology, robotics and other powerful emerging technologies. There are even those who suggest humanity should collectively decide to turn away from some new technologies as inherently dangerous.

Pumping sulphur particles into the atmosphere to mimic the cooling effect of a large volcanic eruption has been proposed as a last-ditch solution to combating climate change – but doing so would cause problems of its own, including potentially catastrophic drought, say researchers.

Mars will be transformed into a shirt-sleeve, habitable world for humanity before century's end, made livable by thawing out the coldish climes of the red planet and altering its now carbon dioxide-rich atmosphere, according to one researcher.

A University of Arizona Astronomer is proposing to create a shield between the Earth and the Sun to reduce global warming.

Mirrors in orbit around Mars could create Earth-like conditions on a small patch of the planet's surface, according to a NASA-funded study. The extra sunlight would provide warmth and solar power for human explorers, but some experts say the mirrors may be hard to deploy.