As world leaders vow to accelerate climate action to avert catastrophic changes to the planet, nuclear fusion is gathering momentum as a zero-emission energy source that is considered safer than current nuclear fission technology.

Though the next-generation energy source may face opposition in Japan, which suffered a major nuclear accident triggered by a massive earthquake and tsunami in 2011, experts say the nation should stay updated on new developments, as the technology may be viable as soon as the 2040s.

Fusion energy is produced when light atomic nuclei are merged to form a heavier nucleus. The mass of the resulting nucleus is less than that of the original two, and the leftover mass becomes energy.