From the shores of eastern Canada to the beaches of North Carolina to New Zealand's open sea, companies are exploring a new frontier to fight global warming. Soundbite (English) Will Burt, Planetary: "The problem, of course, at its root is that we've got too much carbon dioxide in the air and the logical storage place for all for some of that excess carbon is going to be the biggest reservoir by far that exists. And that reservoir is the ocean." Climate experts say that even if countries stepped up efforts to reduce greenhouse gas emissions, it wouldn't be enough to cool the planet. Carbon dioxide also needs to be removed from the atmosphere. Oceans naturally absorb heat-trapping gases, but researchers are looking to supercharge that capacity. Soundbite (English) David Ho, (C)Worthy): "I always say that, you know, for this to work—carbon dioxide removal—it has to go from something that most people have never heard of to the largest thing that humanity has ever done in a really short time. Right. And it's daunting. Yeah." Near Halifax, Planetary Technologies is pumping out magnesium oxide, a powdery white mineral used in everything from water treatment plants to heartburn pills. Here, a red dye is added to track how it flows out to sea. The company hopes the chemical reaction caused by the magnesium oxide will allow the ocean to absorb more CO2. Soundbite (English) Will Burt, Planetary: "You add an alkaline or a basic mineral to the ocean and that that mineral is essentially an antacid. This alkaline mineral neutralizes carbon dioxide acid in the ocean." Dozens of other projects have been launched in recent years, including sinking sugarcane waste to the ocean floor to trap carbon. Last summer, another company, Vesta, poured shiploads of the mineral olivine, an ingredient used to manufacture steel, off the coast of North Carolina. GigaBlue is taking a different approach – hoping to increase the growth of algae through added nutrients But some projects are facing strong opposition over concerns that dumping foreign matter into the ocean could have unintended consequences. Planetary paused its project in Cornwall, England, after residents protested. And some locals in New England are fighting a proposed experiment off the coast of Massachusetts. Soundbite (English) Meghan Lapp: "We created the Clean Water Act to ensure that we have clean water, (that) we're not dumping chemicals into the ocean." The Woods Hole Oceanographic Institution plans to study the effects of sodium hydroxide in the North Atlantic Ocean. The scientists have been meeting with the community but Meghan Lapp, who represents a Rhode Island fishing company, is still concerned. Soundbite (English) Meghan Lapp: "To be doing that in the name of carbon capture to me is just irresponsible." The industry is so new that many countries have yet to adopt guidelines and standards for how to dump nutrients, crops or minerals for carbon capture. In the U.S., federal agencies have recently issued some of the first-ever permits for these ocean projects. Soundbite (English) Will Burt, Planetary: "We can't spend half a century digging into the details of how the solution might work, because the whole point here is, is to mitigate against a rapidly accelerating climate crisis. We have to act with safety and integrity, but we also have to act fast." Most of the ocean start-ups are selling carbon credits to finance their work. Soundbite (English) David Ho (C)Worthy): "The experiments that are being done now and the scale at which they're being done, it's pretty safe. The question is what happens when you scale it up to billions of tons every year? And that's still to be determined. I think there's still some work to be done there." AP Video: Alex Turnbull, David Goldman Other video: Ocean Alk-Align, GigaBlue, Vesta PBC, Alban Roinard, Carboniferous Production: Serginho Roosblad