The world’s oceans are heating up. The average surface temperature of our seas has increased by 0.9C compared to preindustrial levels, with 0.6C happening in the last 40 years alone. While this is still less than the increase in global air temperatures – which have risen by more than 1.5C – our oceans are nonetheless in danger.
While oceans have a very high heat capacity – the top few metres of the sea store as much heat as Earth’s entire atmosphere – warmer oceans cause havoc for our planet. Hotter water results in rising sea levels due to thermal expansion, coral bleaching, accelerated melting of Artic ice sheets, intensified hurricanes and changes in ocean health and biochemistry.
In this context, geo-engineering, the deliberate large-scale manipulation of Earth’s environment, has emerged as a potential approach to cool our oceans and reduce carbon dioxide levels in the atmosphere.
The idea of humans controlling nature is not something that sits well with many people. However, as it becomes clearer that we are unlikely to meet global carbon reduction targets, geo-engineering as a solution to rising temperatures is gaining traction.
Shading Our Oceans
A popular theory to cool the water is the possibility of shading our oceans from the sun by identifying materials that could reflect its rays. Many suggestions have been put forward on how to create this artificial reflective surface, ranging from launching mirrors into space to painting the tops of mountains or creating an artificial reflective sea foam.
Nature’s way, and the most effective, of shading the ocean is via clouds. They reflect sunlight back into space, thereby reducing the amount of solar energy absorbed by the Earth’s surface and oceans. By creating greater cloud coverage or making existing clouds brighter, it is possible to create a cooling effect on the planet.
One of the companies trialling this approach is California-based start-up Make Sunsets whose approach involves using aircraft tethered to balloons to spray reflective aerosols into the atmosphere – known as a stratospheric aerosol injection (SAI). The aerosols contain sulphate dioxide, a substance released by erupted volcanoes, including Mount Fuji, which famously erupted in 1991 and was thought to have cooled the planet by 0.5C for one year. According to Make Sunsets, just one gram of clouds offsets the warming effect of one ton of CO₂ for a year.
Marine cloud brightening is another technology that attempts to manipulate cloud formation to form a cooling effect. It is a form of solar geo-engineering technique that would make clouds brighter by spraying tiny sub-micrometer seawater particles into the air, reflecting a small fraction of incoming sunlight back into space in order to offset anthropogenic global warming.
The Marine Cloud Brightening Project, based out of Washington University, is currently using small-scale field experiments to test this model. Along with stratospheric aerosol injection, it is one of the two solar radiation management methods that may feasibly have a substantial climate impact.
Beyond clouds, scientists have considered altering the composition of ocean water to discourage the retention of heat. For example, increasing the salinity of the ocean’s surface would facilitate the flow of warmer and less salty North Atlantic Ocean currents on the surface, significantly raising the temperature of the Arctic atmosphere which would remove the sea ice cover and result in an overall cooling effect on the Arctic Ocean.
Some researchers propose the idea of fertilising specific regions of the ocean with nutrients like iron. This approach stimulates the growth of phytoplankton, which absorb carbon dioxide during photosynthesis. By reducing atmospheric carbon dioxide levels, this method could potentially mitigate global warming and cool the oceans.
The Ocean: A Test Bed for Technology?
Proposals to geo-engineer the ocean are shrouded with controversy. One fear is that even if geo-engineering was successful, it would reinforce human ignorance and the view that human being’s relationship with nature is one of dominance. This could lead to a misplaced confidence in our ability to ‘fix’ any destruction we choose to inflict on the planet.
Other risks include termination effect (a rapid rebound in global temperatures if interventions were to suddenly stop) and internal governance challenges that could result in geopolitical tensions and disagreements about its deployment, regulation and potential side effects. As a result, at this point in time only small-scale geo-engineering tests are permitted.
With that said, the ungovernability of the High Seas makes it the perfect testing ground for wild new experiments.
With no government to oversee their activities, companies are increasingly heading to the deep ocean as a test bed for new ideas. As such, new laws are under discussion to protect marine life in high waters. The UN has proposed that any activity that takes place on the open ocean must first undertake an environmental impact assessment, a formal process to gauge potential damage to marine life. While this would limit the possibility of harmful experimentation in the open ocean, some feel there is a need for more structured, high-level governance of geo-engineering. The question of ‘who pays’ for what is considered to be a global problem is also a big concern.
The lack of progress that has been made in curbing the world’s carbon emissions requires governance issues to be addressed with haste. Covering 70 per cent of the planet, the ocean holds vast potential for climate mitigation and carbon storage, with technology the key to unlocking these opportunities.
If implemented successfully, the cooling effect of many geo-engineering solutions is expected to be felt rapidly and to be reversible in fairly short time scales. As the impacts of climate change become more visible, tolerance for more unconventional interventions seems to be growing, but questions remain as to how they will be actioned and by who.