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Could ocean geoengineering help to thwart climate change?

Marine scientists across the globe believe ocean geoengineering may offer the means to effectively thwart climate change. But could trapping gigatons of carbon underwater have unforeseen consequences?

With Cop26 fast approaching in November, dozens of ocean geoengineering projects are currently being trialled to test the feasibility of trapping carbon emissions underwater.

Though planting trees has proven an effective way of capturing existing emissions, a growing consensus among environmentalists is that it won’t remove enough carbon dioxide by itself to meaningfully halt climate change.

As Peter Wadhams, head of ocean physics at Cambridge University, states, ‘You’d have to turn Europe into one big primeval forest. It works but it’s not good enough alone.’

For this reason, scientists are looking for the next great natural balancer in the fight against climate change. Able to hold 150 times more carbon than air per-unit of volume, our oceans have long been touted as a potential gamechanger.

The actual solutions on offer, mind, range from all the way from ingenious to downright implausible.

‘Weathering’ and ‘Rewilding’

A solution thought up by British biologist Tom Green is, in theory, relatively simple to orchestrate now on a wide scale.

Farfetched as it sounds on paper, Green’s plan involves locking away atmospheric carbon in pea-coloured sand – made from a volcanic rock called olivine – at the bottom of the ocean.

According to his own calculations, depositing this material offshore in 2% of the world’s coastlines would capture 100% of global carbon emissions every year. Imagine that.

Relying on a natural process called weathering, this sand is said to dissolve a little over time in water causing a chemical reaction which absorbs mass amounts of carbon from the air. Once coaxed into this underwater tomb, the carbon supply will hypothetically be used up by calcifying organisms like shellfish and corals – whose eventual carcasses will sink as sediment and turn into limestone.

Sounds incredible right, so what exactly are we waiting for?

Gathering olivine isn’t a problem for researchers. Unfortunately, we just don’t know exactly how the acceleration of chemical reactions will affect surrounding ecosystems and biodiversity. Until that is figured out for certain, projects like Green’s will never get the go ahead.

Alternatively, scientists are considering the possibility of rewilding our coastlines with carbon hungry plants like kelp or seagrass, though this process would require far more upkeep and organisation to treat all year round. For scope, 90% of seagrass meadows have died out in the UK alone.

If that were to happen on the scale being suggested here, literal gigatons of carbon would be released into the atmosphere at once leading to rapid warming. It goes without saying, but that definitely wouldn’t be good.

The geoengineering approach

While many are focused on using natural methods to store carbon, others are looking to geoengineering technology to lock carbon within our oceans.

In most cases here, researchers are developing ways of keeping the mass of methane already concealed in frozen Arctic waters dormant. That means somehow slowing the melting of glaciers and sea ice, which is occurring at a rate of 1.2 trillion tons a year.

One bizarre trial currently being funded by the Australian government is testing the effect of ‘cloud brightening,’ which hopes to reflect sun directly away from the most vulnerable areas around the edge of the Arctic.

This would see high-tech vessels called Flettner Ships deployed in fixed areas of the ocean. Each of these devices has a floating base, with multiple masts which spray surrounding seawater in a fine mist into the clouds above.

Lead designer Stephen Salter, a professor of engineering design at Edinburgh University, claims the salt vapour actively makes clouds brighter, allowing them to absorb far more sunlight and heat than normal. In the lead up to Cop26, he argues his contraptions should already be in use.

The reason Salter has yet to get his way, however, is because like weathering and rewilding, cloud breaching poses potential red flags of its own.

Extreme weather like monsoons depend on specific shifts in heating between continents and oceans. This means changes in Greenland, for instance, will directly impact precipitation in the tropics. The entire atmosphere is connected, and any notable imbalance in heating and cooling could lead to unpredictable and dangerous weather patterns.

‘If you don’t balance your warming and cooling very carefully, then you get all sorts of changes in the climate system,’ says Oxford professor Ray Pierrehumbert.

For this reason, other companies and inventors are looking into more risk adverse solutions, like cooling the ocean at source. Former navy submariner Olav Hollingsaeter has invented a machine designed to sit on ocean seabeds and blow colder air to the surface, while tech firm Sant is working a machine that mimics the effect of calcium eating seashells.

Both are still in the testing phase and looking for official approval.

The threat of overreliance

Tech has proven an effective tool in the aim of going net zero. Carbon capture has become a more common practice, autonomous devices are maximising farms yields and collecting ocean waste, and satellites are improving our response to natural disasters like wildfires.

However, as previously mentioned, when it comes to directly altering our climate’s ecosystems using technology, we have to be meticulous in our research and testing.

A contingent of physicists describe geoengineering of this nature as ‘weather hacking,’ and are concerned people underestimate how much upkeep these methods would require.

Using cloud brightening as just one example, professor Wadhams stated, ‘Once you emit CO2, its warming effect will continue for thousands of years. Whereas marine cloud brightening relies on particles that fall out of the atmosphere after, maybe, seven days. So, you have to renew them every week.’

In essence, if we were to implement this method as the sole means of saving the Great Barrier Reef, for example, we would have to keep bleaching clouds forever in the surrounding area.

If these processes were put on pause for whatever reason – perhaps political conflicts or drastic technical issues – we’re looking at rapid and catastrophic warming of the climate.

Geoengineering for the planet could yet be huge in our fight against climate change. Right now, however, Wadhams is most optimistic about the overarching desire to innovate for good.

If any of the projects we’ve mentioned manage to get the green light during Cop26, we’ll be first on the scene here at Thred. Stay tuned.


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