What is nuclear fusion and what does the breakthrough mean for the climate crisis?

Since the 1950s, the prospect of nuclear fusion has remained tantalisingly close, yet just out of reach.

Fusion’s promise – of a steady torrent of zero-carbon energy with no toxic waste – has seemingly remained just a couple of decades away, but has never quite come to fruition.

Meanwhile, over the seven decades scientists have spent working to replicate the same process that powers the sun, our world has steadily entrenched its dependency on climate-altering fossil fuel combustion, which is now taking a devastating toll on the natural world and our own species.

But could that be about to change more quickly than was thought possible? US scientists are believed to be on the verge of announcing a breakthrough in energy generation through nuclear fusion.

According to reports, which are not yet backed up by published research, over the past two weeks, a process at the federal Lawrence Livermore National Laboratory in California has achieved net energy gain through a process called “inertial confinement fusion”.

The process involves using the world’s biggest laser inside a gold-plated chamber to bombard a tiny quantity of hydrogen plasma, stripping the hydrogen atoms of their electrons. The superheating of these electron-free hydrogen nuclei causes them to fuse, releasing energy as it leaves the resulting bonded nuclei with less mass than before the reaction.

If this occurs rapidly enough, the energy output from this process can exceed the heat energy put in through the lasers. This is known as “ignition”.

A formal statement is yet to be put out by the research team, but according to “two people with knowledge of the results” who spoke to the Financial Times, the energy output from the reactor was higher than the input, and was even greater than expected, causing some of the critical measuring equipment to be damaged and complicating the efforts of the team to analyse the reaction.

Nonetheless, the US Department of Energy has said that energy secretary Jennifer Granholm will announce “a major scientific breakthrough” on Tuesday, prompting speculation that the world could be on the cusp of seeing genuine nuclear fusion.

The long-held promise of nuclear fusion is that it could provide energy in such abundance that it would effectively replace all other forms of power, bringing free, unlimited energy to people around the world, revolutionising our societies, and helping to bring the emissions driving the climate crisis to heel.

Scientists are now cautiously optimistic that we could be witnessing a major breakthrough with the potential to radically alter the energy landscape.

Professor Sir Robin Grimes, of Imperial College London, said on Monday: “This is a key step on a possible pathway to commercial fusion. It demonstrates and underpins our basic understanding of the physics, and is an engineering triumph.

“Nevertheless, extracting this energy in a way that it can be harnessed, and developing the materials that can stand up to continuous operation, are massive challenges. There is no doubt, the prize is worth the effort. Success, however long it takes, would be transformational.”

The professor’s comments seem to indicate that despite the recent success, which should be applauded, viable power from fusion remains a considerable way off, and all the time, the emissions going into the atmosphere are continuing to rise.

The risk posed by unguarded optimism about the prospect of unlimited free energy is that it could undo the small steps that have already been taken to decarbonise the energy sector and other industries that have largely depended on fossil fuels.

Just as polluting industries are already factoring in scarcely adequate carbon capture technology in pursuit of their own net zero targets, fusion must not be treated as a climate crisis “get out of jail free” card.

The technology cannot be ready within the time window required to meet the climate targets governments are already failing to meet. Our society’s priority must remain the rapid curtailment of greenhouse gas emissions.

It may not be as sexy, but a combination of energy efficiency, insulation, heat pumps and a broader rollout of renewables remains our best shot for tackling the climate crisis and building greater energy security.