In late March, as most of the world was adjusting to lockdown, oceanographer Daniel Harrison was setting sail for the Great Barrier Reef. Though Harrison, a native Australian, had sailed these waters many times before, this particular expedition was different.
On reaching Broadhurst Reef, 100km off the Australian coast, Harrison and his skeleton crew of local scientists – just a few with permission to travel – noticed white corals stretching out in every direction, a sign that the reef was bleaching, and dying, from heat stress. This would be the third mass bleaching of the Great Barrier Reef in just five years, an event that is becoming more likely as the global ocean warms.
Harrison and his team were there to test a radical intervention that, if successful, could spare the world’s largest coral reef from total loss. Known as marine cloud brightening, their approach involves spraying seawater into the air to help form bright clouds that reflect sunlight and cool the waters below. “This is like putting the reef on life support while we deal with the underlying cause. It buys us some time” says Harrison. “Obviously bringing emissions down is the critical thing.”
While Harrison’s project is small in scale, and in its infancy, marine cloud brightening is just one of numerous practices – collectively known as geoengineering or climate intervention – that could cool the planet, offsetting some of the harm caused by greenhouse gas pollution. With global emissions rising, there’s a growing awareness that we’ll likely need such radical measures to avoid dangerous climate change. “Emissions reductions alone are not going to cut it,” says Phillip Boyd, a marine biogeochemist at the University of Tasmania, Hobart. “We’ve got an increasingly fast-moving problem, and so we may need increasingly fast-moving countermeasures,” says Kelly Wanser, founder of US non-profit Silver Lining, which advocates for research into climate intervention.
Using technology to control the climate is undeniably controversial, seen by some as a quick fix with unknown consequences that diverts attention from the harder task of transitioning to a zero-carbon economy. As such, there’s been little funding for research, and few real-world trials. Harrison’s project – focused on curbing a national ecological disaster – is a notable exception. “It’s essential to know whether these things work or not,” says Harrison. “If we find out that they don’t work, it just strengthens the argument for reducing emissions harder and quicker and not delaying”.
Geoengineering – or deliberate climate control – is not new. During the Cold War, both the US and the Soviet Union funded research into cloud seeding, an approach the US eventually used during the Vietnam war to extend the monsoon season and disrupt enemy troops. Since then, the field has expanded into a wide array of schemes mostly intended to mitigate climate change, though some have co-benefits such as boosting fisheries.
Broadly speaking, there are two approaches. The first, Solar Radiation Management (SRM), aims to limit the amount of heat absorbed by the Earth and could be used to quickly cool the surface. This could be achieved, for instance, by sending reflective sulphates into the stratosphere via giant balloons, or by scattering silica beads over Arctic sea ice to make it more reflective.
The alternative, Carbon Dioxide Removal (CDR), focuses on physically extracting CO2 from the atmosphere and storing it, in ecosystems such as mangroves or forests, underground or in the deep ocean. Possibilities here include fertilising the sea surface with iron to promote the growth of plankton – which absorb CO2 from the air – or burning biomass as a source of energy, capturing the CO2 and storing it.
In general, SRM is seen as the more extreme approach that could be deployed with quick results in the case of a regional or global climate emergency.
So far, no single scheme has been proven to work at scale. Most research has focused on land-based solutions, but competing needs, such as ensuring food security, makes these impractical as global solutions. Scientists are now looking to the open ocean as a more pragmatic choice for geoengineering. “This is where it makes most sense, because there’s no conflict of interest with any other issues. These areas are largely unused at the moment and they also make up 50% of the planet’s surface” says Ulf Riebesell, a biological oceanographer at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany.
So far, 27 different marine geoengineering schemes have been proposed. There has been roughly a dozen field tests, mostly focused on ocean iron fertilisation. When a commercial company, Planktos Inc, proposed to test the technology off the Galapagos Islands in 2007, it sparked fears of unregulated interference with the planet’s climate by entrepreneurs looking to turn a quick profit by selling sequestered CO2 as carbon credits.
In response, two intergovernmental bodies sought to outlaw geoengineering. In 2010, the UN’s Convention on Biological Diversity recommended that member states ban the deployment of all large-scale climate intervention technologies, a stance that it reaffirmed in 2016. Meanwhile, in 2013, the UN’s International Maritime Organization (IMO) – which regulates shipping – added ocean iron fertilisation to its list of banned practices. Though the IMO measure is voluntary and yet to be enforced, it symbolises the taboo long associated with climate intervention.
Growing expectations for unproven technologies
With global emissions still growing despite the commitments made in Paris in December 2015, the mood has started to shift. The Intergovernmental Panel on Climate Change has made it clear that we have little chance of avoiding dangerous levels of warming, generally regarded as 1.5C or 2C above pre-industrial temperatures, without geoengineering technologies. Meanwhile, high level organisations such as the UN Environment Programme and the US National Academies of Sciences have started to seriously evaluate options for climate intervention.
“We’re now in a situation where we’re implicitly assuming that we’ll need large-scale CO2 removal, but we really haven’t put the time and money into actually finding out whether we can do it or not”, says Jeffrey McGee, director of the Australian Forum for Climate Intervention Governance at the University of Tasmania, Hobart. “The gap between expectations and knowledge, I think, is getting wider and wider by the day.”
There’s not much time to decide which of these options is useful. We shouldn’t wait another year. The science needs to start now.Ulf Riebesell, Ocean artUp principal investigator
Globally, just a few marine geoengineering projects are ready for field trials. Ocean artUp, being led by Ulf Riebesell, is testing the idea that artificial ocean upwelling – using vertical pumps – can enrich the ocean’s nutrient-poor subtropical gyres, boosting fish production and CO2 uptake. Riebesell’s team is currently testing various pump designs in waters off the north Atlantic island of Gran Canaria.
Arctic Ice Project, an initiative started by Leslie Ann-Field, a lecturer at Stanford University in California, aims to prove that it’s possible to use technology to restore Arctic ice. Field’s method involves scattering tiny glass silica beads on the surface of thin, young Arctic sea ice as a way of boosting its reflectivity by 50%. Field’s team was due to test the method on a small scale at Utqiagvik, Alaska this summer but plans have been scaled back owing to Covid. Follow-on plans to test the method in the Arctic at a larger scale will need additional funding.
Meanwhile, the Marine Cloud Brightening Research Program, a collaboration between the University of Washington, the Pacific Northwest National Laboratory, and a team of retired engineers in Silicon Valley, has emerged as the sole significant US effort in marine geoengineering. With limited funding, the team has designed a bespoke nozzle that can generate three trillion particles of tiny salt particles per second from filtered sea water. The next step, developing this into a system of 400-500 nozzles that can be tested in the field, will need roughly $4-5 million, which the research team is currently raising.
The consequences of deploying any of these technologies at scale is unknown. Already, the ocean has soaked up one third of the roughly 40 billion tonnes of CO2 that we emit annually, as well as 93% of the extra heat from climate change. While this has tempered climate change on land, it has caused the ocean to warm rapidly and become more acidic. Conservationists worry that marine geoengineering could harm marine life, or the health of the ocean.
“Geoengineering is not only complex and unknown, but it has huge potential impact,” says Torsten Thiele, founder of the Global Ocean Trust, a non-profit that focuses on marine conservation, technology and governance. “I’m very sceptical on letting people try things out until we’ve sorted out the other steps and processes. Let’s first figure out the framework, let’s figure out the ethics standards, let’s figure out what happens in the lab. We could create a long list of things that would allow natural scientists to improve knowledge without actually trying these things out in nature.”
With field trials inching forward, attention is turning to how geoengineering research – and deployment, if it ever happens – should be governed. Right now, different laws could be applied to geoengineering on land and in the ocean, but none are comprehensive. The IMO amendment on ocean iron fertilisation, for instance, just applies to a single method and then only if the iron is “dumped” at sea, rather than piped or injected, for instance. “What we have right now is a patchwork of rules” says Kerryn Brent, who researches international environmental law at the University of Adelaide, Australia.
One possibility for governing marine geoengineering is through a new law to protect marine life on the high seas, those waters that are beyond national governance. The law, which is currently being negotiated by the UN, will likely require any activity that takes place on the open ocean to 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 geoengineering. The problem right now, says Brent, is that no single organisation or body has a mandate to gauge the risk of harm caused by geoengineering against the risk of inaction. “One of the big gaps in governance are rules that will enable decision-makers, countries and scientists to weigh up the risks of a specific research activity or deployment versus the risk of not doing it” says Brent. We just don’t have those kind of rules available”, she says.
“Part of the point of all the testing and modelling that we do is to establish the safety, the efficacy and the risks” says Leslie-Ann Field, founder of Ice911. “Our first principle is to do no harm, right? But there’s also just this vast risk of doing nothing,” she says.
According to non-profit Silver Lining, the UNFCCC, which oversees international climate policy talks, could have a role in evaluating both the merits and risks of geoengineering research. The question still remains as to whether one entity, and which, would have the authority to sanction or prevent the deployment of climate intervention. The UN Security Council is one possibility, though with 15 member states, only five of which are permanent, gaining global consensus could be difficult. Meanwhile, scientists say they need regulations urgently for field research to forge ahead. “We need to phase in these technologies in ten years from now. We already know that,” says Riebesell. That’s not much time to decide which of these options is useful. We shouldn’t wait another year. The science needs to start now.”