Former U.S. vice-president Al Gore is warning against massive geoengineering experiments that attempt to reverse climate change, arguing instead that the focus must remain on cutting emissions that are warming the planet.
"I don't think it's a good idea," Mr. Gore told the TED Conference in Vancouver, after he was invited on stage to weigh in on a debate about geoengineering.
"I think it's great to have the exploration of out-of-the-box ideas. But the main idea is we've got to stop putting 110 million tonnes of man-made global-warming pollution up there every day."
Geoengineering is a controversial area of science that involves deliberate, large-scale interventions to alter the planet's climate, such as creating clouds that contain chalk in order to reflect heat from the sun, which was proposed before Mr. Gore took the stage.
B.C. had its own brush with geoengineering several years ago, when a small organization in Haida Gwaii teamed up with a California businessman to dump more than 100 tonnes of iron into the ocean in the belief that "fertilizing" the water could reverse global warming and acidification.
Mr. Gore said such Band-Aids aren't the solution.
"We have to stop the pattern of behaviour that is creating this crisis," said Mr. Gore, who was not on the TED program, but was called up from the audience.
"There is a collision between human civilization as it's presently organized, and the surprisingly fragile ecological system of the earth. The most vulnerable part of it is the very thin shell of atmosphere that we're using as an open sewer."
The annual TED Conference brings together experts, artists and public figures to speak about big ideas and issues that can change the world. A day earlier, the Pope made a surprise video appearance, urging powerful leaders "to act humbly."
Other high-profile speakers on the schedule this week include tennis star Serena Williams and Tesla founder Elon Musk.
The former vice-president took the stage during a session on climate change and protecting the Earth.
Danny Hillis, a computer theorist and inventor who co-founded the company Applied Minds, made the case for geoengineering.
"What if there was a thermostat that allowed you to turn down the temperature of the Earth whenever you wanted?" Dr. Hillis asked.
"The basic idea of solar geoengineering is that we can cool things down just by reflecting a little more sunlight back into space."
He proposed doing that by altering clouds with small amounts of chalk. That would involve creating clouds using water mixed with the equivalent of a handful of chalk in an Olympic-sized swimming pool.
Dr. Hillis acknowledged it was a controversial idea.
"A lot of people don't think that we should be talking about this at all," he said.
"Their concern is that if people imagine that there is some easy way out, that we won't give up our addiction to fossil fuels. And I worry about that."
Climate scientist Kate Marvel, who earlier had lectured about the cooling power of clouds, responded to Dr. Hillis's proposal.
"Danny, you seem so nice, and I hope we can be friends. And you terrify me," she joked, after she was invited back on stage to respond to the chalk idea.
She said reducing the amount of sunlight would be problematic and doesn't address other problems of climate change, such as ocean acidification.
More importantly, Dr. Marvel said, she was worried about being a test subject.
"I'm a physicist, and also a human being and a citizen," she said.
"I'm frightened as a citizen. I feel that what you're proposing to do involves all of us as human subjects, and I'm not sure if I consent to that."