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 FOR almost 20 years, I’ve been spending time on a craggy stretch of British Columbia’s shoreline called the Sunshine Coast. This summer, I had an experience that reminded me why I love this place, and why I chose to have a child in this sparsely populated part of the world.

It was 5 a.m. and my husband and I were up with our 3-week-old son. Looking out at the ocean, we spotted two towering, black dorsal fins: orcas, or killer whales. Then two more. We had never seen an orca on the coast, and never heard of their coming so close to shore. In our sleep-deprived state, it felt like a miracle, as if the baby had wakened us to make sure we didn’t miss this rare visit.

The possibility that the sighting may have resulted from something less serendipitous did not occur to me until two weeks ago, when I read reports of a bizarre ocean experiment off the islands of Haida Gwaii, several hundred miles from where we spotted the orcas swimming.

There, an American entrepreneur named Russ George dumped 120 tons of iron dust off the hull of a rented fishing boat; the plan was to create an algae bloom that would sequester carbon and thereby combat climate change.

Mr. George is one of a growing number of would-be geoengineers who advocate high-risk, large-scale technical interventions that would fundamentally change the oceans and skies in order to reduce the effects of global warming. In addition to Mr. George’s scheme to fertilize the ocean with iron, other geoengineering strategies under consideration include pumping sulfate aerosols into the upper atmosphere to imitate the cooling effects of a major volcanic eruption and “brightening” clouds so they reflect more of the sun’s rays back to space.