NASA and Boeing chase jet contrails with science of climate impact in doubt

Scientific debate is getting heated over what to do about airplane contrails — the wispy lines of water vapor you often see trailing behind a jet.

Those harmless-looking vapor trails sometimes spread out to form thin cirrus clouds.

Environmental activists and nonprofits focused on climate change routinely assert contrails contribute more to global warming than the carbon dioxide emitted from jet engines.

The aviation industry, under pressure to do something, has stepped up research into contrails.