In some decidedly welcome good news, it appears that the best weapon in humanity’s fight to mitigate climate change is also one that remains relatively untapped: the ocean. That’s according to a new study published October 4 in Frontiers in Marine Science by an international team of researchers for The Ocean Solutions Initiative.

Indeed, even without human interference, the ocean already removes 25 percent of the carbon emissions we create. And until now, we’ve pretty much taken this for granted, focusing our research on land-based methods (massive solar farms, wind turbines, etc). But with the all-too-real possibility that the rate of global temperature increases isn’t falling fast enough to fulfill promises made to the Paris Agreement, researchers decided whether there’s anything more we can do climate change-wise with the water that covers 71 percent of the Earth’s surface.

To figure this out, researchers evaluated 13 different approaches based on the potential impact of a method to combat ocean warming, acidification, and sea level rise. The study also unpacked the advantages and disadvantages of each method, weighing factors like cost effectiveness, technological feasibility, and governmental feasibility. Although many methods are promising, we’re paying for the lack of research on ocean-based methods with a flurry of unknowns.

Graphs comparing ocean-based methods to combat climate change
Researchers compared the 13 methods across five main categories, leaving renewable energy as the clear overall winner. 

Of the 13 methods the team reviewed, tapping the ocean for renewable energy came out on top, followed by local methods like vegetation that holds the potential to be scaled up. Lesser-researched methods like cloud brightening or stripping carbon dioxide from seawater, although exciting, are unfortunately still closer to science fiction than execution.

Why We Need to Tap the Oceans for Renewable Energy

Given the sheer amount of research performed on renewable energy both on and off land, it should come as no surprise that that may be the lowest hanging fruit.

“Not only do offshore wind farms, wave energy and other ocean renewables have a very large potential to reduce carbon emissions, but they are also cost-effective and ready to be implemented at a large-scale,” explains researcher Dr. Alexandre Magnan of France’s Institute for Sustainable Development and International Relations in a press release.

The ocean may in fact be even better suited to house wind energy in particular, as wind speeds tend to be both faster and more reliable than those on land, according to the American Geosciences Institute. Small differences add up: A turbine produces twice as much energy from a 15-mph wind as it does from a 12-mph wind. But off-shore wind farms can be incredibly expensive, given the underwater equipment, and must withstand wear and tear by waves.

That said, what will be the world’s largest water-based wind farm, named Hornsea Project One, is already under construction near Yorkshire, UK. Scheduled for completion in 2020, the farm, once completed, is projected to generate 4.1 TWh of electricity per year. In one rotation, an 8MW turbine can generate enough electricity to power a house for 29 hours, according to the developer Ørsted. Although Hornsea Project One’s turbines will be slightly smaller, at 7MW, the 75-meter-long blades will still pack a punch.

Hornsea Project One installation ship with cables
The project, once completed, will be the largest off-shore wind farm in the world. 

How Plants Are Our Quiet Heroes

The study also pinpoints great potential in using vegetation on a local level with the goal of eventually scaling it up. Vegetation involves rebuilding and protecting coastal ecosystems like salt marshes, mangroves and seagrass to store the CO2, affectionately dubbed “blue carbon,” in their systems.

The largest population of mangroves, located in Indonesia, holds vast possibilities in reducing emissions. About 30 million tons of carbon emissions, approximately the amount emitted by New Zealand, would be reduced if not for mangrove loss, according to a 2016 carbon study by Conservation International.

Mangroves from Indonesia
Apart from helping with carbon sequestration, mangroves also prevent soil erosion.

Local measures like vegetation are only mildly effective at combatting warming and moderately effective in reducing ocean acidification and sea rise. But on the other hand, they’re also technologically feasible and friendlier to the ocean’s ecosystems, meaning it’s an option worth scaling up. Systems that benefit marine life can pass on benefits to the human communities living nearby by enhancing food security and storing carbon instead of emitting it. But, unfortunately, this is another area where the research is limited.

Is Cloud Brightening in Our Future?

One of the more moon-shot proposals that the researchers investigated was cloud brighting.

Cloud brightening stays true to its name. In a feat of geoengineering, atmospheric scientists would spray water into clouds in hope of making clouds whiter, according to the Marine Cloud Brightening Project (MCBP). Whiter clouds would theoretically reflect more sunlight back to space, letting less sunlight through to warm the Earth’s surface. But again, even if we knew it was effective, the limited research we have predicts the effects may not last. As a controversial, untested technology it would also likely be difficult to sell, meaning cloud brightening may remain a dream.

With insufficient research, and a vast ocean, decision paralysis seems inevitable. But with research from The Oceans Solution Initiative, the map forward can finally be drawn.