At TED, a conference about big ideas that's largely attended by tech luminaries, it was inevitable that geoengineering — the idea of changing the earth's atmosphere to halt or reverse climate change — would come up. During the 2017 TED talks in Vancouver, Canada, multiple speakers brought up geoengineering ideas — but one climate scientist pushed back.

have to put chalk up at a rate of 10 teragrams a year to undo the effects of CO2 we’ve already released," he said. Here's how he visualized that on stage:

"It would be like one hose for the entire Earth," he said.

There are countless reasons why geoengineering schemes like this could be dangerous. There's a fear that people will stop trying to reduce emissions if they think there's a quicker fix for the problem, and there are also many risks that come with messing with the planet in ways we don't fully understand. Even advocates tend to acknowledge these issues.