Throwing Shade: Solar Geoengineering

Image Credit: Monsterkoi in Pixabay

As the harsh realities of climate change set in, Thomas Walsh probes the controversial realm of geoengineering, questioning whether our urgent need to cool the planet justifies tampering with the atmosphere.

On November 30th, leaders will gather in the United Arab Emirates for the 2023 United Nations Climate Change Conference. More commonly referred to as COP28, it is the 28th Conference of the Parties to the UN Framework Convention on Climate Change. It’s the only show in town to discuss collective action on climate change, though the COP process tends to underwhelm. The target of 1.5°C warming is seen as increasingly farcical. A warmer-than-ever world poses the question: how far is humanity willing to go to protect itself and the natural world?

Scientists and activists are starting to call for research into solar geoengineering, specifically methods like Marine Cloud Brightening (MCB) and Stratospheric Aerosol Injection (SAI). MCB involves spraying sea salt into the air to beef up clouds over oceans, reflecting incoming light back to space. SAI takes inspiration from volcanic eruptions, like the 1991 Mount Pinatubo blast, which chilled the Northern hemisphere by half a degree for four years, by releasing sulphate particles high into the stratosphere. Would it work? Yes, these methods mimic nature's own cooling tricks. 

Hardline environmentalists might argue that it’s immoral and too dangerous to meddle with natural systems to this degree. Many scientists agree with the latter. Little is known about the likely effects on the water cycle, or any cycle. Adverse effects are expected on the ozone layer. Other studies have shown that spraying calcium carbonate instead of sulphates could have the beneficial side effect of reversing ozone depletion. However, these studies are exclusively based on simulations. The consensus view is that the biggest risk is ‘moral hazard’ – if this is considered a serious climate solution, what imperative is there to reduce emissions? Carbon emissions are, after all, not just the leading cause of global warming, but of ocean acidification. Fossil fuel combustion is also the leading source of air pollution, linked by some studies to 7 million deaths annually. It would be myopic to use geoengineering to justify business-as-usual fossil fuel consumption.

Climate tipping points are fast approaching. One such point of no-return in earth systems is the collapse of large ice sheets whereby the more ice collapses, the quicker the remaining ice melts and the harder it is for new ice to form, leading to an unstoppable cascade. One model suggests that in the absence of rapid emissions cuts, near-term deployment of solar geoengineering could be required to stabilise the West Antarctic Ice Sheet. On current trajectories, launching geoengineering in 2060 wouldn’t be enough to halt the collapse of the ice sheet, but a combination of drastically reduced emissions and geoengineering before the 2040s could save it. 

Temporarily lowering temperatures would yield carbon benefits, such as reducing the need for air conditioning, decreasing wildfire frequency, and slowing permafrost thaw. Geoengineering could be considered a harm reduction strategy, buying humanity time to reduce emissions and stabilise temperatures.

Regarding technical feasibility, aircraft exist that can reach the necessary height, others can carry the payload, but none currently can do both. Specially designed planes would be needed. Spreading enough sulphur particles to halve the rate of global warming would require only about 100 of these aircraft, each flying twice daily. Sourcing the sulphur wouldn’t be difficult. All in, it would cost about $2.25 billion per year. Even if these figures are significant underestimates, geoengineering probably wouldn’t be prohibitively expensive to any medium sized country, especially one in a desperate situation.

Given that geoengineering could be taken out of the toolbox in the future, whether that be its careful, considered use alongside emissions cuts or its erratic deployment in response to a climate doomsday scenario of droughts and superstorms, it might be a good idea to conduct tests and gather more data. 

Assistant Professor of Geology at UCD, Sam Kelley, speaking to The University Observer says that “natural systems, the climate system in particular, are inherently complex and frequently non-linear. Thus, any attempt at geoengineering would require significant research and testing to mitigate the risk of unintended consequences [such as the events of 1816]”, referring to the volcanic eruption in Indonesia that yielded a year without summer.

Assistant Professor of Geology at UCD, Sam Kelley, speaking to The University Observer says that 'natural systems, the climate system in particular, are inherently complex and frequently non-linear. Thus, any attempt at geoengineering would require significant research and testing to mitigate the risk of unintended consequences.'

The shipping industry, albeit inadvertently, has conducted a large-scale geoengineering experiment through its use of dirty fuels linked to air pollution. In 2020, the International Maritime Organization (IMO) decided to clean up its act. It reduced the permissible sulphur content in shipping fuels from 3.5% to 0.5%. This was good news for public health, but with a climate caveat: the sulphur emissions had been producing cooling effects over the ocean akin to those proposed by geoengineering. This loss of sulphate emissions could heat the earth by 0.05°C, roughly equal to two years of warming due to current carbon emissions. A phase out of coal power, another major source of sulphate emissions, will have a similar effect. 

Harvard scientists teamed up with Sweden’s space agency to plan a test in 2021. Plans were made to launch a balloon capable of releasing reflective particles into the stratosphere. Although this experiment would not have involved actual particle release, it was cancelled after coming under fire from environmental and indigenous groups. Another trial in Mexico prompted the government to ban all geoengineering experiments.

The trial was conducted by Make Sunsets, a company planning to release 1 gram of sulphur dioxide into the stratosphere to offset one tonne of carbon dioxide, selling ‘cooling credits’. The idea is to release a balloon full of helium and sulphur dioxide that will burst when it reaches the stratosphere. Given the trivial relative costs of geoengineering, many think that private companies have no role in geoengineering. In the words of EU Climate Commissioner Frans Timmermans, "Nobody should be conducting experiments alone with our shared planet". He suggests the UN as a venue for global talks on solar geoengineering.

In the words of EU climate commissioner Frans Timmermans, 'Nobody should be conducting experiments alone with our shared planet.'

The effect of solar geoengineering couldn’t be localised as particles would be distributed around the globe once in the stratosphere. Geoengineering would require unprecedented global consensus and cooperation. One complication is the risk of termination shock; if the geoengineering were employed for a number of years but abruptly ended, there would be a period of intense, rapid warming. A geoengineering endeavour, once started, couldn’t be cancelled by one country opting out due to adverse consequences, no matter how bad. As complicated as the process could be, establishing a framework might be an easier option than waiting for a rogue state to launch a unilateral geoengineering effort in response to deadly heat or mass crop failure.

Geoengineering stands at the crossroads of a fundamental dilemma: should our priority be safeguarding humanity or honouring the natural world? Recently, both viewpoints have converged, with contemporary environmentalism coalescing around the belief that combating climate change and preserving biodiversity is paramount to minimising human suffering. Geoengineering may prove modern environmentalism right or pry the two sides apart again. In the meantime, geoengineering remains an idea on paper; its benefits are as theoretical as its woes.