The strategy is inspired by the natural process of chemical weathering of rocks, where rain, which is slightly acidic, “weathers” or erodes the surface of rocks and minerals, and then transfers that alkalinity to the ocean through runoff. ..

It is a process that occurs with or without human intervention, but on geological time scales.

“We need something much faster than nature can generate at the moment,” Rau said.

According Dear All by the National Academies of Sciences, even if the global community meets its emissions reduction targets, by 2050 it will still need to remove an additional 10 gigatonnes of CO2 annually to avoid devastating climate outcomes.

Scientists have to walk a fine line: devising a method that is scalable and effective enough to actually affect the climate without negatively affecting the environment in the process.

«People, for better or worse, perceive the oceans as pristine, and they are going to have serious concerns about interventions of this nature,» Burns said, referring to fears in the scientific community that any negative effects or public mistrust of a ocean-based carbon sequestration method could create a backlash against all other approaches.

Much of that fear stems from a scandal that broke in 2012.

A Canadian company experimented with ocean fertilization by dumping 120 tons of iron-enriched dust into the ocean off the coast of British Columbia to stimulate phytoplankton growth. The experiment caused such a large plankton bloom that it was reportedly visible from space. An international uproar ensued.

While there was no evidence that the experiment did any harm, it was considered a public relations disaster by the international scientific community.

“It just failed massively. So this time, I think we need to be very careful that everyone participates,» said Lennart Bach, a marine biogeochemist at the University of Tasmania in Australia.

In an attempt to preempt safety fears, Planetary is partially funding research at Dalhousie University in Nova Scotia on oyster reproduction and phytoplankton growth.

Dalhousie University oceanographer Hugh MacIntyre helps Mikaela Ermanovics set up an experiment in Dartmouth, Nova Scotia.
Dalhousie University oceanographer Hugh MacIntyre helps student Mikaela Ermanovics set up an experiment on how magnesium hydroxide affects phytoplankton in Dartmouth, Nova Scotia.Riley Smith for NBC News

Oceanographer Hugh MacIntyre, who has studied phytoplankton for more than 35 years, said research begins with microscopic algae for a reason.

«Every organism that you see in the ocean, whether it’s an orca or a fish, a starfish, a lobster, whatever, eats something that was eaten by something that was eaten by phytoplankton,» said MacIntyre, a professor at Dalhousie University.

So far, MacIntyre’s tests have not resulted in any significant negative impacts on plankton growth, and he is using a concentration of magnesium hydroxide that is 10 times higher than Planetary actually intends to use.

“We go to the extreme because we want to know at what point it would make a difference,” he said.

MacIntyre said he can never definitively prove that the antacid won’t have harmful effects on marine life, but he can prove how plankton fare when taken to the extreme.

«Ultimately the question is, at what point are you sure enough there isn’t a problem?» he said.