It may sound like a sci-fi movie — scientists mimic the effects of a volcanic explosion in a desperate bid to reverse global warming — but it's really happening. As this Doc Zone program reveals, scientists are experimenting with radical schemes to cool the planet. Could these remedies be a form of technological suicide?Salting the ocean with iron dust to trigger plankton blooms, shooting salt crystals into clouds to make them brighter, genetically-engineering "robo trees" to hoover carbon from the air — these are just a few of the big ideas under consideration. But the one form of "solar radiation management" likely to work fastest in a climate emergency would be to mimic the effects of a huge volcano by spraying clouds of sulphuric acid into the stratosphere. Jet drones or high-altitude balloons could do the job. Quick and cheap compared to breaking our addiction to carbon and retooling the industrial revolution. The problem? We might cause unintended consequences by reducing rainfall, causing drought and mass starvation. Will geoengineering save the day — or trigger disaster on a planetary scale?