The risks of geoengineering could outweigh the benefits in fighting climate change
TECHNOLOGICAL FIX
Geoengineering concepts, such as blocking out sunlight, could in theory cut the cost and time needed to counteract climate change UNKNOWN RISKS
Proposed schemes do not address the underlying causes of climate change and their risks are poorly understood KEY QUOTE
Let’s do the homework on this and then put it in a box and hope we never have to smash the glass and reach in John Grant, of Sheffield Hallam University in England, has a plan to combat climate change. There are parts of the Antarctic, he says, where temperatures sometimes drop to under -80ºC. When it is that cold, carbon dioxide turns into a solid. In such a place, “If you carve caverns kilometres long, then run air through them and drop the temperature using refrigeration, carbon dioxide will just fall out of the air like snow,” he says. “You build caverns, filled with carbon dioxide.” Grant reckons this deep freeze concept could remove carbon dioxide from the atmosphere at a cost of just $5 a tonne. The catch? The conditions are “just beyond brutal,” Grant says. “I am talking about expending men’s and women’s lives. Because they are going to die. Military personnel are the only ones that will take the risks.” This is one example of the problems that face technology-led climate intervention ideas under the heading of “geoengineering”. Widespread climate intervention has been touted as a tool to use against global warming. Geoengineering concepts fall into two categories: those that involve removing carbon dioxide from the air and those that involve cutting the amount of sunlight that reaches the Earth.
CUTTING OUT CARBON
The first category includes ideas that go from the mundane to the outlandish. Grant’s polar carbon storage concept sits at the extreme end of the range. A more mainstream idea involves fertilising oceans to stimulate the growth of algae—although it is unclear how such tinkering might affect ocean ecosystems. An even simpler strategy would of course be to plant trees. But “they have got a 20-year lead time, [which] is just too slow,” Grant says. “In the 1990s, we should have been planting trees like they were going out of… well, whatever.” There are other vegetation-based geoengineering concepts but their effectiveness is hampered by the time and space needed for plants to grow and the possibility that not all the carbon they capture will necessarily end up being sequestered away. In between adding greenery and freezing Antarctic caverns, the carbon abatement school of geoengineering also encompasses a number of physical and chemical removal methods. One of these is direct air capture (DAC) of carbon dioxide using chemical reactions. So-called “solid sorbent” DAC systems could be powered by low-carbon energy sources, such as geothermal or nuclear, to capture millions of tonnes of carbon dioxide a year, according to the World Resources Institute. DAC plants require a lot less land than forests and can be placed near geological storage sites to reduce the need for carbon storage and transport. The cost could eventually be as low as $94 per tonne30225-3.pdf) of carbon dioxide captured. But each tonne of carbon dioxide would need between one and seven tonnes of water and would require a major buildout of infrastructure to operate at a scale to make a difference. Another option is to enhance the natural process of carbon removal via the weathering of carbonate and silicate rocks but this would require roughly two tonnes of rock to store a tonne of carbon dioxide and may also increase the alkalinity of the oceans, the effects of which are unknown. When it comes to carbon removal, the ideal is to have a mechanism that is cheap, safe, scalable, socially acceptable, easy to manage and harmless to natural ecosystems. In 2009, the Royal Society, the UK’s national academy of sciences, concluded that none of the carbon sequestration methods proposed at the time met all these criteria. “Significant research is … required before any of these methods could be deployed at a commercial scale,” it said.
BLOCKING THE SUN
Other geoengineering proposals look at stopping the sun’s warming rays from becoming trapped in the Earth’s atmosphere. Most of the ideas involve reflecting sunlight back into space—which, in some instances, is not as science-fiction as it sounds: the main difference between the suggestions is the nature and position of the reflecting material. On land, proposals range from simply covering roofs, roads and pavements with reflective white paint to cloaking deserts with reflective material. At sea, meanwhile, one proposal involves firing seawater into the sky to increase the cloud cover over sunny areas of the ocean. Higher up, another idea suggests adding to an existing layer of sulphuric acid particles that reflect sunlight in the Earth’s low stratosphere. This process has occurred naturally in the past following volcanic eruptions, so there is a fair degree of confidence that it could result in rapid, effective and potentially affordable climate cooling. The problem is that volcanic eruptions have also shown that changes to the stratospheric sulphate zone can have worrying side effects, such as depleting the ozone layer. Finally, there have been several proposals to try to block some of the sunlight out in space by putting thousands of mirrors into random orbit. Although theoretically interesting, the Royal Society was doubtful of the viability of space-based schemes. They “contain such great uncertainties in costs, effectiveness (including risks) and timescales of implementation that they are not realistic potential contributors to short-term, temporary measures for avoiding dangerous climate change,” it said. While many of these ideas are far-fetched, geoengineering concepts continue to attract attention. In part, due to the sheer audacity of some of the ideas—but some observers feel that humanity should not shy away from planet-sized engineering projects. Trying to freeze carbon dioxide in the Antarctic sounds crazy, Grant says, but that is exactly the sort of thing we should be doing if we want to travel to other planets. “It is just technology we are already developing for a Mars mission, employed now,” he says. “The reason we push engineering to the limit for something like going to Mars is because we might need to push engineering to the limit here on Earth.”
MONEY MATTERS
Although the viability of many geoengineering concepts is questionable, on paper there are a number of ideas that appear cheaper, quicker and easier than the mainstream attempts to decarbonise our economy as we are doing at the moment. Increasing stratospheric aerosol particles, for instance, could be achieved with a custom-built fleet of aircraft within a few years and at an annual cost in the tens of billions of dollars. That is a fraction of the cost of conventional mitigation, which the 2006 Stern Review on the Economics of Climate Change put at around 2% of global gross domestic product (GDP)—roughly $1.7 trillion in 2020. Additionally, there is a school of thought that says we cannot afford to overlook geoengineering because we are running out of other options. “I don’t think we have a choice,” says Audun Abelsnes of Techstars, an American start-up accelerator. “I admire guys like Breakthrough Energy, the Bill Gates fund. They only invest in stuff that can take gigatons of CO2 out of the atmosphere. I love funds who are so ambitious on behalf of the planet, because we need them. We have to do everything. The planet will fail if we don’t,” Abelsnes adds. “I think the advocates of geoengineering would say, ‘No-one is advocating that we do not make planes safer because we have parachutes,’” says Zeke Hausfather of the Breakthrough Institute, an environmental research centre unrelated to Gates’ fund. “So, let’s do the research. Let’s do the homework on this, and then put it in a box and hope we never have to smash the glass and reach in. Even if there is a 99% chance that we are never going to need it, we want to have it there just in case.”
SIGNIFICANT RISKS
Thoughts are turning such dramatic interventions as the climate crisis becomes more apparent. New reports conclude that climate change is responsible for 37% of global heat deaths and could be endangering a third00236-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2590332221002360%3Fshowall%3Dtrue) of the world’s food production. However, caution is still needed as climate engineering schemes cannot guarantee success. Certain geoengineering techniques, such as artificially increasing the reflective area of the Earth’s surface, seem doomed from the start in terms of cost and scalability. Others, such as afforestation and using vegetation to capture carbon as charcoal, will probably take too long to be of much use. Although unlikely, geoengineering could also work too well, tipping the climate into an ice age. But much more likely is that there could be detrimental side effects. Global warming is a side effect of a climate-altering release of carbon emissions from fossil fuel consumption. Similarly, loading the stratosphere with sulphuric acid particles “turns the sky whiter,” says Hausfather. “It affects agriculture [because] there’s less light reaching the surface. There’s a lot of regional effects on weather patterns that come out of the modelling. A world with a lot of sulphate aerosols in the stratosphere has effects on the surface,” he adds.
RESEARCH NEEDED
A problem with these ambitious solar radiation management techniques is they counteract global warming but do not get rid of the carbon dioxide that is causing it. “If you ever were to stop putting sulphate aerosols into the stratosphere, you suddenly would have massive warming over the course of six months to two years—pretty much everything you’ve been masking,” Hausfather explains. “Once you start doing it, you’re stuck doing it forever until you can suck out enough CO2 from the atmosphere through other means to bring things back down to what you consider [are] safe levels.” The most worrying consideration about putting effort and investment into geoengineering projects is that if people start to believe climate change could be solved in a few years and with a few trillion dollars then they might stop taking the energy transition seriously. Already, the Earth’s climate is being forced into uncharted territory and scientists warn of increasingly dire consequences. “My real concern [with global warming] is that there might be ‘unknown unknowns’ where we end up pushing the climate well out of the bounds of what it has been for the last few million years,” Hausfather says. “There has been a bit of modelling that suggests there could be some really nasty surprises there.” It is because of this that further research into geoengineering might yet be warranted, he says. It is important to understand how climate engineering might work in case current efforts fail and we have to act quickly to prevent a global catastrophe.
TEXT
Jason Deign
PHOTO
Climeworks