The revelation that researchers had succeeded in creating a nuclear fusion reaction that generated more energy than it consumed made reassuring reading last week. For almost half a century, I have reported on scientific issues and no decade has been complete without two or three announcements by scientists claiming their work would soon allow science to recreate the processes that drive the sun. The end result would be the generation of clean, cheap nuclear fusion that would transform our lives. Such announcements have been rare recently, so it gave me a warm glow to realise that standards may be returning to normal. By deploying a set of 192 lasers to bombard pellets of the hydrogen isotopes deuterium and tritium, researchers at the US National Ignition Facility (NIF) in Livermore, California, were able to generate temperatures only found in stars and thermonuclear bombs. The isotopes then fused into helium, releasing excess energy, they reported. It was a milestone event but not a major one, although this did not stop the US government and swaths of the world’s media indulging in a widespread hyping jamboree over the laboratory’s accomplishment. Researchers had “overcome a major barrier” to reaching fusion, the BBC gushed, while the Wall Street Journal described the achievement as a breakthrough that could herald an era of clean, cheap energy. It is certainly true that nuclear fusion would have a beneficial impact on our planet by liberating vast amounts of energy without generating high levels of carbon emissions and would be an undoubted boost in the battle against climate change. The trouble is that we have been presented with such visions many times before. In 1958, Sir John Cockcroft claimed his Zeta fusion project would supply the world with “an inexhaustible supply of fuel”. It didn’t. In 1989, Martin Fleischmann and Stanley Pons announced they had achieved fusion using simple laboratory equipment, work that made global headlines but which has never been replicated. To this list you can also add the International Thermonuclear Experimental Reactor (Iter), a huge facility being built in Saint-Paul-lès-Durance in Provence, France, that was supposed to achieve fusion by 2023 but which is over 10 years behind schedule and tens of billions of dollars over budget. In each case, it was predicted that the construction of the first commercially viable nuclear fusion plants was only a decade or two away and would transform our lives. Those hopes never materialised and have led to a weary cynicism spreading among hacks and scientists. As they now joke: “Fusion is 30 years away – and always will be.” It was odd for Jennifer Granholm, the US energy secretary, to argue that the NIF’s achievement was “one of the most impressive scientific feats of the 21st century”. This is a hard claim to justify for a century that has already witnessed the discovery of the Higgs boson, the creation of Covid-19 vaccines, the launch of the James Webb telescope and the unravelling of the human genome. By comparison, the ignition event at the NIF is second-division stuff. Most scientists have been careful in their responses to the over-hyping of the NIF “breakthrough”. They accept that a key step has been taking towards commercial fusion power but insist such plants remain distant goals. They should not be seen as likely saviours that will extract us from the desperate energy crisis we now face – despite all the claims that were made last week. Humanity has brought itself to a point where its terrible dependence on fossil fuels threatens to trigger a 2C jump in global temperatures compared with our pre-industrial past. The consequences will include flooding, fires, worsening storms, rising sea levels, spreading diseases and melting ice caps. Here, scientists are clear. Fusion power will not arrive in time to save the world. “We are still a way off commercial fusion and it cannot help us with the climate crisis now,” said Aneeqa Khan, a research fellow in nuclear fusion at Manchester University. This view was backed by Tony Roulstone, a nuclear energy researcher at Cambridge University. “This result from NIF is a success for science, but it is still a long way from providing useful, abundant clean energy.” At present, there are two main routes to nuclear fusion. One involves confining searing hot plasma in a powerful magnetic field. The Iter reactor follows such an approach. The other – adopted at the NIF facility – uses lasers to blast deuterium-tritium pellets causing them to collapse and fuse into helium. In both cases, reactions occur at more than 100 million C and involve major technological headaches in controlling them. Fusion therefore remains a long-term technology, although many new investors and entrepreneurs – including Bill Gates and Jeff Bezos – have recently turned their attention to the field, raising hopes that a fresh commercial impetus could reinvigorate the development of commercial plants. This input is to be welcomed but we should be emphatic: fusion will not arrive in time to save the planet from climate change. Electricity plants powered by renewable sources or nuclear fission offer the only short-term alternatives to those that burn fossil fuels. We need to pin our hopes on these power sources. Fusion may earn its place later in the century but it would be highly irresponsible to rely on an energy source that will take at least a further two decades to materialise – at best. Robin McKie is the Observer’s science and environment editor