We’ve talked before about how lightning breaks nitrogen molecules into nitric oxide—which falls to Earth in rainwater and nourishes plants.

But we now know that lightning storms have another essential function.

After forming nitric oxide, a secondary reaction makes oxidants, which clean the atmosphere.

Oxidants are essentially water molecules that lost a hydrogen atom. To replace it, they react with other compounds, including methane and CO2.

They oxidize these into other forms that also fall to Earth in rain, thereby reducing greenhouse gases in the atmosphere.

The volume of oxidants was thought to be tiny—a few parts per trillion.

Until, in 2012, some brave atmospheric scientists flew their research plane directly into electrical storms in Texas and Oklahoma. They were stunned to find oxidant levels thousands of times higher even though no lightning was present.

Eventually, they figured out that invisible electrical discharges in the top of a thunderhead, before lightning is formed, produce huge volumes of oxidants directly—without first forming nitric oxide.

Their new estimates suggest that electrical storms could produce a sixth of our atmosphere’s cleansing oxidants.

Studies suggest that, if Earth continues to warm, we’ll have more lightning, which could increase atmospheric oxidants and help counter rising greenhouse gas levels.