Geoengineering is a hotly contested topic both among scientists and policymakers. While some call it an innovative solution that could buy a warming world some time, others believe it’s a reckless cop out that could further environmental exploitation. A new study, led by University of Exeter geoscience professor Martin Siegert, has now tipped the balance in favour of its opponents by reporting that five prominent geoengineering concepts, proposed for the earth’s polar regions, fail to meet essential criteria for responsible climate interventions.
The researchers also added that these methods could render severe environmental damage with far-reaching global consequences.
Their findings were published in Frontiers in Science on September 9.
The five methods in question are:
1. Stratospheric aerosol injection (SAI): deliberately releasing aerosols into the earth’s atmosphere to reflect sunlight and cool the earth’s surface
2. Sea curtains/sea walls: blocking warm ocean water from reaching the ice sheets in polar regions using large buoyant structures attached to the seabed
3. Sea ice management: scattering glass microbeads over sea ice to boost their reflectivity and artificially thicken them
4. Basal water removal: reducing ice loss by removing subglacial water from under glaciers to slow the movement of ice sheets and decelerate sea level rise
5. Ocean fertilisation: drawing more CO2 from the atmosphere into the ocean by adding nutrients like iron to polar oceans to stimulate phytoplankton growth.
Where SAI stumbles
Currently, research on SAI is focused on four aerosol species: sulphur dioxide, sulphur aerosols, titanium dioxide, and calcium carbonate.
Scientists however have raised concerns that injecting these aerosols into the upper atmosphere will create more problems than it promises to solve. In polar winters, there’s no sunlight to reflect, rendering the injection useless for half the year. Even during summers, the ice and snow masses in polar regions already reflect most of the sunlight naturally, so adding more reflective particles couldn’t help much.
SAI also comes with the threat of termination shocks. Research has found that if a geoengineering project is stopped suddenly, global temperatures could skyrocket in only 10-20 years as the greenhouse effect that the aerosols’ consequences were masking will return. Taken together, an SAI project once implemented will have to run continuously for a long time. There is also no international instrument at present that guarantees to pay for such an undertaking or determines who will bear responsibility if it backfires.
Using SAI to ‘only’ cool polar regions can also disrupt seasons worldwide because weather and climate phenomena are influenced by far-flung effects, with potentially drastic implications on nutritional and national security.
Finally, of course, SAI is not cheap. The new study estimated that if 30 countries were to split the cost, they’d each have to cough up $55 million a year — in addition to dealing with legal issues.
On shaky legs
Similarly, plans to build large underwater ‘curtains’ pose considerable technical and environmental hurdles. Installing the heavy foundations is a difficult job even on land, let alone in seafloor sediments and rugged bedrock hundreds of metres below the surface. Such engineering activity may also slow melting in some areas, according to some models.
Another major obstacle to the proposal to add sea curtains is the logistics. The Amundsen Sea in Western Antarctica is one of the most remote and hostile places on the earth’s surface and is accessible for only a few months each year. Few ships can even attempt such work; building the vessels of the requisite class would cost around half a billion dollars each as well.
Similar proposals for Greenland may be somewhat more feasible but their overall consequences on sea level rise remain uncertain.
This geoengineering method has also been associated with extreme potential marine environmental consequences, including negative effects on oceanic circulation and sea ice levels. Barriers in the water will also stand in the way of marine life like fish and marine mammals, which feed at depth in these regions, the researchers said.
At present, it’s also not clear which materials can be used for this purpose. They will have to be selected such that their wear and tear over time doesn’t release toxic compounds into the water, polluting it and further disrupting natural nutrient cycles that are already fragile.
Based on previous research, the new study estimated that this method could cost a lot more than $1 billion (Rs 8,783 crore) per kilometre.
Inefficient interventions
The principal challenge with managing sea-ice levels is ecotoxicity. While some tests and modelling exercises are currently underway, there’s no real clarity on how it will affect invertebrate organisms, especially zooplankton. The glass microbeads may also dissolve quickly in seawater, limiting their usefulness. To have any impact, in fact, the study has estimated that 360 million tonnes of beads will be required every year — roughly equal to the world’s annual production of plastics, thus creating tremendous logistical, supply chain, and emissions challenges.
A free-floating pyrosome made up of hundreds of individual bioluminescent tunicates, a form of zooplankton, off East Timor, 2005.
| Photo Credit:
Nick Hobgood (CC BY-SA)
Worse yet, some studies have also found that the microbeads could absorb sunlight and have a net warming effect on Arctic Sea ice. The new study also concluded that managing sea ice in this way could prove economically unviable compared to mitigating the emissions of greenhouse gases and adopting efficient adaptation strategies.
The aim of Arctic sea-ice freezing is to thicken the ice by pumping seawater either onto the ice surface, where it will freeze, or into the air so that it precipitates as snow and is deposited on the surface of extant ice.
According to experts, this method is neither practical nor effective. Research has estimated that up to 100 million pumps will be needed to cover the Arctic, which will draw a million units of electricity every year for a decade, representing a counterproductive draw on international energy production and finance. The pumps will also have to be pinned in place to keep them from drifting and will need to be maintained at regular intervals, increasing the local carbon footprint. Even if such a massive effort were possible, researchers have cautioned that it will only preserve late-summer sea ice for a few decades and will have little overall impact on slowing global warming.
The method is also expected to incur production and transportation costs of $500 billion a year for the whole Arctic — an infeasible investment for a project that’s barely expected to work.
Scaling issues
Subglacial water in Antarctica is mostly generated by frictional and geothermal heating. However, according to research, drawing this water away with the aim of slowing the rate at which glaciers slide into the oceans is flawed, not to mention a highly emissions-intensive exercise that will demand continuous monitoring and maintenance.
Finally, while adding iron filings to stimulate the growth of phytoplankton in the ocean could work, there’s no way to control which species will dominate. This creates critical uncertainties in local food chains and food web dynamics. For example, if the filings enhance biological productivity in artificially fertilised regions, organisms there might be driven to consume more and more nutrients that might otherwise have circulated to lower latitudes.
The authors of the new study also said that this isn’t a viable strategy because of the scale it will need to be deployed at.
Beyond geoengineering
Per the new study, protecting and even reversing the damage caused by global warming will need “climate-resilient development”, which in turn requires changes in the relationship between humans and the planet. The most common components of this are decarbonisation and better maintenance of protected areas.
However, protected areas — which have long been touted as bulwarks against ecological decline — have attracted criticism for their fortress-like model of conservation. By displacing local communities, these areas can cut off centuries-old relationships between people and ecosystems and undermine traditional knowledge and livelihoods. Experts have also found that militarised enforcement in such areas could foster rather than discourage human-wildlife conflicts, breeding resentment in the local (human) population.
Protected zones can also strain local governments by diverting resources from broader environmental reforms while sealing off habitats could overlook ecological processes that cross artificial boundaries, potentially reducing ecosystem resilience.
Global efforts to decarbonise also face a host of intertwined challenges. Foremost among them is the continued reliance on fossil fuels, which still account for over 80% of global energy use despite decades of policy commitments. Transitioning away from coal, oil, and natural gas also demands large upfront investments in renewable infrastructure, grid modernisation, and storage capacity — costs that many developing economies can’t easily shoulder.
And even where funds exist, political resistance has loomed large, especially in the form of entrenched fossil-fuel lobbies and voter anxieties over rising energy prices. Scaling up renewable energy production, storage, and uptake also needs to surmount supply chain bottlenecks for critical minerals like lithium, cobalt, and rare earths. In addition, the global energy divide persists: while industrialised countries seek to cut emissions, many poorer nations have argued that their developmental needs have yet to be met, creating diplomatic rifts at climate negotiations.
Even so, lowering carbon emissions remains the most promising way to avert catastrophic climate change. Unlike geoengineering or delayed adaptation strategies, decarbonisation can directly address the root cause by curbing the accumulation of greenhouse gas in the atmosphere. Lowering emissions can also improve air quality and minimise environmental pollution. In fact, every tonne of emissions avoided today will translate to fewer shocks tomorrow, buying humankind the sort of stability that some are currently looking for with geoengineering.