Another step in the search for fusion energy that could be a solution to the global climate crisis was made by scientists in California.

Last year, on a December morning, scientists at the National Ignition Facility at the Lawrence Livermore National Laboratory (LLNL) in California managed, for the first time, to achieve what they called a “huge scientific achievement.” To produce a nuclear fusion reaction that released more energy than was consumed by the lasers used in the experiment, in a process called “ignition.”

Today, scientists report that have successfully re-ignited at least three times within 2023; according to a December report from LLNL. This marks another important step that will likely one day be a major solution to the global climate crisis, which is caused primarily by the burning of fossil fuels.

For decades, scientists have tried to harness fusion energy, essentially recreating the sun’s power on Earth. After they managed to release an infinite source of clean energy last year, the next important step was to prove that this process could be repeated.

Brian Appelbe, a researcher from the Center for Inertial Fusion Studies at Imperial College London, said the reproducibility demonstrates the “robustness” of the process, showing that it can be achieved even when conditions such as the laser or fuel pellet vary.

Each experiment also offers an opportunity to study the nature of ignition in detail, Appelbe told CNN. “This provides valuable information for scientists to address the next challenge to overcome: how to maximize the energy that can be obtained.”

What is nuclear fusion?

Unlike nuclear fission—the process used in the world’s nuclear plants today, which is produced by splitting atoms—nuclear fusion leaves no legacy of long-lived radioactive waste. As the climate crisis accelerates and the urgency of eliminating planet-warming fossil fuels increases, the prospect of an abundant source of safe, clean energy is enticing.

Nuclear fusion, the reaction that powers the sun and other stars, involves the smashing of two or more atoms together to form a denser atom, in a process that releases enormous amounts of energy.

The energy produced in December 2022 was small but enough to make a successful ignition and prove that laser fusion could create energy.

Since then, scientists have done this several times. On July 30, the NIF laser delivered just over 2 megajoules resulting in 3.88 megajoules of energy — the highest output achieved to date, according to the report. Two consecutive experiments in October were also successful.

“These results demonstrated the ability of NIF to consistently produce fusion energy at multi-megajoule levels,” the report said.

However, there is still a long way to go before nuclear fusion reaches the scale needed to power electricity grids and heating systems. Scientists are now focusing on harnessing the progress that has been made and how to scale up fusion experiments and reduce costs significantly.