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For more than nine decades scientists have tried to replicate the process that produces energy for the sun and stars-fusion. On Tuesday, researchers at the National Ignition Facility (NIF) in California, USA, announced a milestone in this endeavour. They merged two nuclei to produce a heavier nucleus. Their reactor produced about 1.5 times more energy than what was used in the process. In all the earlier attempts to harness the power of fusion, the reactors used up more energy than what was produced. But scientists say that it will be at least two decades before the process pioneered in the California laboratory can be scaled up. Even then, in a world desperately searching for technologies that can power the developmental needs of nations adding to the GHG load, the break-through at NIF has generated excitement.

Several countries are shifting to renewable energies to meet their international climate-related commitments. Yet, power generation currently is responsible for 25-30 percent of global GHG emissions. The inherently unstable nature of renewables means that countries find it very difficult to jettison fossil-fuel energy sources. Conventionally-produced nuclear energy-that uses fission technology-is relatively cleaner. But accidents at Chernobyl in 1986 and Fukushima in 2011 have raised serious questions over the safety of fission-powedered plants.