37 Geoengineering
Geoengineering is a “prime example of our arrogance in our capacity to shape nature to our whims with technology.
Hansen
A promising – and probably necessary – approach to overcome humanity’s harmful geo-transformation of Earth is temporary solar radiation management (SRM). Risks of such intervention must be defined, as well as risks of no intervention; thus, the U.S. National Academy of Sciences recommends research on SRM.
An example of SRM is injection of atmospheric aerosols at high southern latitudes, which global simulations suggest would cool the Southern Ocean at depth and limit melting of Antarctic ice shelves. The most innocuous aerosols may be fine salty droplets extracted from the ocean and sprayed into the air by autonomous sailboats. This approach has been discussed for potential use on a global scale, but even use limited to Southern Hemisphere high latitudes requires research and forethought to avoid unintended adverse effects.
The present decade is probably our last chance to develop the knowledge, technical capability, and political will for the actions needed to save global coastal regions from long-term inundation.
Hansen (2023) PipelinePaper230705 (pdf)
37.1 A desparate idea
McKibben
The scientists who study solar geoengineering don’t want anyone to try it. But climate inaction is making it more likely.
There are at least three initiatives under way that are studying the potential implementation of solar-radiation management, or S.R.M., as it is sometimes called: a commission under the auspices of the Paris Peace Forum, composed of fifteen current and former global leaders and some environmental and governance experts, that is exploring “policy options” to combat climate change and how these policies might be monitored; a Carnegie Council initiative of how the United Nations might govern geoengineering; and Degrees Initiative, an academic effort based in the United Kingdom and funded by a collection of foundations, that in turn funds research on the effects of such a scheme across the developing world. The result of these initiatives, if not the goal, may be to normalize the idea of geoengineering. It is being taken seriously because of something else that’s speeding up: the horrors that come with an overheating world and now regularly threaten its most densely populated places.
Unless we find a way to remove carbon in quantities not imaginable presently, this would be the only way to stop or reverse rapidly rising temperature.
The enormous step of dimming the sun could turn out to be very easy, at least from a technological point of view. Filling the air with carbon dioxide took close to three hundred years of burning coal and oil and gas, millions of miles of pipelines, thousands of refineries, hundreds of millions of cars. That enormous effort, carried out by just a fraction of the world’s population, has, with increasing speed, pushed the atmospheric concentration of CO2 from about 275 parts per million, before the Industrial Revolution, to about 425 parts per million now. It would take only a tiny fraction of that effort to inject aerosol particles into the stratosphere.
Any country with a serious air force could probably release sulfur from planes in the upper atmosphere. You might not even need a country: it would cost Elon Musk, currently the world’s richest man, far less to fund such a mission than it did to buy Twitter—and he’s already got the rockets.
The scientific evidence suggests that it would “likely produce a substantial, rapid cooling effect worldwide” and that it “could also reduce the rate of sea-level rise, sea-ice loss, heatwaves, extreme weather, and climate change-associated anomalies in the water cycle.” The question is more: what else would it do?
On a global scale it could, at least temporarily, turn the sky hazy or milky (hence the title of Kolbert’s book); it could alter “the quality of the light plants use for photosynthesis” (no small thing on a planet basically built on chlorophyll—studies have shown that U.S. corn production increased as polluting aerosols went down in the wake of amendments to the Clean Air Act); and it might damage the ozone layer.
The most likely problems, though, would probably be not global but regional. Lowering the temperature, precisely because it would affect global weather patterns, would produce different and hard-to-predict outcomes in different places.
A climate “solution” that helps some and harms others could spark its own kind of crisis. A Brookings Institution report last December began with a scenario—it’s 2035, and a country begins unilateral deployment of S.R.M.: “the country has decided that it can no longer wait; they see geoengineering as their only option.” Initially, “the decision seems wise, as the increase in global temperatures starts to level off. But soon other types of anomalous weather begin to appear: unexpected and severe droughts hit countries around the world, disrupting agriculture.” In response, “another large country, under the impression it has been severely harmed . . . carries out a focused military strike against the geoengineering equipment, a decision supported by other nations who also believe they have been negatively impacted.” This development, however, becomes even more devastating—with no one putting chemicals into the stratosphere, they decline rapidly in the course of a year, and “temperatures dramatically rebound to the levels they would have reached on their previous trajectory.” The result, they conclude, is “disastrous.”
Imagine if India started pumping sulfur into the atmosphere only to see a huge drought hit Pakistan: two nuclear powers, already at odds. Or maybe it’s China—driven by a series of summers like the one it just endured—that starts down this road, and it’s India that suddenly faces unrelenting floods.
Geoengineering is a “prime example of our arrogance in our capacity to shape nature to our whims with technology. It should not be the answer to a disaster which we have caused and now seek to remedy.” And yet, he added, “Geoengineering as a possible solution to this catastrophe will definitely become the only option of last resort if we as a global community continue on the path we have been going. There will be a point when it has to be either geoengineering or total destruction.”
The fossil-fuel industry, which filled the atmosphere with carbon, may now help force us to fill it with sulfur, as well.
McKibben (2022) Dimming the Sun to Cool the Planet Is a Desperate Idea, Yet We’re Inching Toward It
37.2 Solar Geoengineering
NAS Recommendations
The US should establish a multimillion-dollar research programme on solar geoengineering, according to the country’s national science academy.
It recommends funding of $100m (£73m) to $200m over five years to better understand the feasibility of interventions to dim the sun, the risk of harmful unintended consequences and how such technology could be governed in an ethical way.
The National Academies of Sciences (NAS) said cutting fossil fuel emissions remained the most urgent and important action to tackle the climate crisis. But it said the worryingly slow progress on climate action meant all options needed to be understood.
Outdoor experiments should be allowed only if they provide critical knowledge that cannot be obtained by other means, said the report, and the research programme “should not be designed to advance future deployment of these interventions”.
Proponents of geoengineering argue that impacts of global heating could be so great that every option to limit these must be explored. Opponents argue that such research increases the risk that such technologies could be deployed, perhaps by rogue states, instead of cutting emissions. Critics also warn that solar geoengineering could cause damage such as crop failures, and would need to be maintained to avoid a sudden hike in temperature, unless carbon emissions fall rapidly.
“Solar geoengineering is an extremely risky and intrinsically unjust technological proposal that doesn’t address any of the causes of climate change,” said Silvia Ribeiro, Latin America director for the ETC campaign group. “The report asking for more research into a technology we don’t want is essentially flawed.”
37.3 Ocean Geoengineering
Guardian
Tom Green has a plan to tackle climate change. The British biologist and director of the charity Project Vesta wants to turn a trillion tonnes of CO2 into rock, and sink it to the bottom of the sea.
Green admits the idea is “audacious”. It would involve locking away atmospheric carbon by dropping pea-coloured sand into the ocean. The sand is made of ground olivine – an abundant volcanic rock, known to jewellers as peridot – and, if Green’s calculations are correct, depositing it offshore on 2% of the world’s coastlines would capture 100% of total global annual carbon emissions.
The plan relies on a natural process called weathering. “Weathering has been working on the planet for billions of years,” says Green, a graduate of Harvard Business School who runs Project Vesta from San Francisco. “When rain falls on volcanic rocks, they dissolve a little in the water, causing a chemical reaction that uses carbon dioxide from the atmosphere. The carbon ends up in the ocean, where it’s used by marine-calcifying organisms like corals and shell-making animals, whose skeletons and shells sink to the bottom of the ocean as sediment and eventually become limestone.”
Olivine weathers easily, and allowing ocean currents to churn it up, says Green, “will make it dissolve much more quickly, to happen on a human-relevant timescale”. It is not a rare mineral: there are beaches in the Galapagos islands and in Hawaii that are green with olivine-rich sand.
The idea of using the sea to absorb excess carbon is not far-fetched, says Green. Ocean water can hold 150 times more CO2 than air, per unit of volume. “The ocean has already taken up about 30% of the excess carbon dioxide that we’ve emitted as a society,” he says. He and his colleagues are gearing up to test their process in two similar Caribbean coves, one acting as an untouched “control” in the experiment.
Nobody knows if these concepts will work, or what consequences there could be.
UCLA engineers have developed a machine that mimics how seashells form. Called a flow reactor, the machine sucks seawater in, and an electrical charge makes it alkaline, which triggers the CO2 to react with the seawater’s magnesium and calcium, producing limestone and magnesite (like forming shells). The water then flows out and, depleted of its captured CO2, is ready to take up more. A byproduct of this process – hydrogen – can be extracted for fuel.
It’s a similar concept to weathering olivine in the ocean, and Sant’s plan is for initial small studies before a gradual scaling up. The team aims to remove between 10 and 20 gigatonnes of CO2 from the atmosphere, starting in 2050. It will be a huge challenge to build a system large enough – and then to build thousands more.
Jean-Pierre Gattuso, research director at the Laboratoire d’Océanographie de Villefranche in Paris, says the latest research suggests the idea is not viable. “Ocean fertilisation experiments were performed at sea demonstrating that iron addition can trigger a phytoplankton bloom,” he says. “However, the amount of CO2 permanently sequestered appears to be small, because most of the organic matter produced is respired back to CO2 before it has a chance to be stored in the deep ocean. An unintended consequence may also be the creation of low-oxygen areas of water.”
“Marine cloud-brightening” is spraying a fine mist of seawater into clouds so that the salt makes them brighter, and more reflective of the sun’s heat.
It is already being trialled as part of an Australian government-funded research programme to limit damage to the Great Barrier Reef, and Wadhams believes it could be used on a mass scale. However, he thinks the most urgent need is to deploy it “on a more restricted scale, around the edges of the Arctic” where the methane escape risks are highest.
Ray Pierrehumbert, professor of physics at Oxford University, sees red flags. “A lot of weather patterns like monsoons depend on the difference in heating between the continents and the oceans,” he says. “If you do something to cool down the North Atlantic, let’s say to preserve the sea ice or Greenland glaciers, that shifts precipitation in the tropics. Every part of the atmosphere is connected, so if you don’t balance your warming and cooling very carefully, then you get all sorts of changes in the climate system, some of which are difficult to predict.” A graver risk, he says, is viewing technology such as this as a way to avoid reducing emissions. “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. And if you come to rely on it for something like keeping the Great Barrier Reef from dying, you have to continue doing it for ever. But all sorts of things could happen to force you to stop – wars, whatever – and if you do stop, then you get this extremely rapid, catastrophic warming.”
cloud-seeding rarely appears without the accompanying phrase “playing god”. But that isn’t deterring the people behind another new ocean geoengineering project to tackle hurricanes by cooling the surface water where they form.
In 2017, with his brother Bjorn, Olav Hollingsaeter, a former Norwegian navy submariner, started OceanTherm to repurpose established technology to reduce storm intensity. During Norwegian winters, OceanTherm uses “bubble curtains” to release compressed air into deep water. These push warmer water to the surface, which stops harbours freezing over. Deploying bubble curtains in warmer waters shoots colder deep water upwards, cooling the surface.
Hollingsaeter is in talks with decision-makers in areas affected by hurricanes around the Gulf of Mexico, but his quest is complicated by legal and ethical concerns. A similar “hurricane slayer” project by Alan Blumberg, the oceanographer behind an attempt to cool surface water by pumping colder water up, told the Washington Post in 2019 that his research stalled over fears it might change the landfall of a storm, or increase its flooding impact.
Hollingsaeter claims his design improves on Blumberg’s . “When you’re pumping colder water to the surface, the cold water is much heavier and will sink. But the bubble curtain mixes the water temperatures all the way up, so there’s a thick layer of cooler water.”
He admits that nobody knows if cooling surface water could change a storm’s trajectory or power but argues that the potential benefits make it worth further research.
Rewilding coastlines is perhaps an easier climate crisis mitigation plan to get behind. There are three types of “blue carbon” coastal ecosystems that store carbon in sediment or soil: mangroves, salt marshes and seagrasses. Together, they absorb more carbon than land forests, and the carbon escapes only if the ecosystems are destroyed. Unfortunately, this is what has happened to half of the world’s mangroves and many salt marshes, as coastlines are cleared of natural landscapes. In the UK alone, more than 90% of seagrass meadows have been lost to coastal development, anchor damage and algae-feeding pollution.