It sounds like something from B-movie lore. Scientists working to avert global catastrophe invent a terrible technical instrument that could affect the fundamental way that the planet operates. The question is not whether they should use it, but whether they have a choice. In both academic and privately funded laboratories, such techniques are being considered, mostly in response to global warming. Geoengineering, or "ecohacking" - using science to change the environment on a vast scale - could become a reality faster than you think.

The possibility of deliberately, artificially altering the envioronment to address specific threats or reach particular aims is familiar to readers of science fiction (see the 'Red Mars', 'Green Mars', 'Blue Mars' series for perhaps the most famous example), but is being raised ever more often in serious scientific circles. Examples include the proposal to release particles of sulpher into the atmosphere to cool the planet, placing a mesh of tiny refractors into space to deflect light rays away from the planet, and inserting huge tubes into the ocean which will pump cooler water to the surface, bringing nutrients and encouraging phytoplankton to grow.

Needless to say, the ethical implications of these types of actions are momentus, not only in and of themselves (can we? should we?), but because unintented consequences of any such 'tinkering' must be considered.