Globally, sea levels have risen by between 21 and 24 cm since 1880. Most of this rise is the result of water physically expanding as it warms, but in recent decades meltwater from Greenland and Antarctica has also contributed significantly.
These sea level rises threaten coastal properties and the livelihoods and lifestyles of coastal communities, as well as the very existence of low-lying countries. Rising seas not only erode or flood land, but also allow destructive storm surges to reach areas farther inland. As melting polar ice becomes an increasingly significant contributor to sea level rise, some have begun to embrace the notion that it can be slowed by technological means ranging from underwater curtains to ice-thickening pumps.
let the storm rage on
Climate science has been here before. For years the field has been divided over the promise and pitfalls of solar geoengineering schemes, environmental modifications that attempt to reduce the effects of climate-warming solar radiation. The most controversial methods involve spraying a mist of particles into the stratosphere, which would reflect some of the sun’s energy back into space and cool the planet. Proponents say this could buy the world time to decarbonize without suffering the worst consequences of climate change. Critics say they are too risky. The arguments can get bitter. These battles are now spilling over onto the ice.
In December 2023, NASA climate scientist Ken Mankoff held a workshop on polar geoengineering at a major science conference. Although he warned that doing so would start a “civil war” in the field, he thinks there is much more agreement than disagreement among polar scientists: Whatever their position on geoengineering, all are concerned that the effects of climate change far outweigh efforts to slow or stop them. Given the urgency, it’s no surprise that the new ideas are attracting interest.
Proposed interventions take many forms. One leading suggestion focuses on outlet glaciers, the huge frozen rivers that slowly carry ice away from land masses into the warm waters of the ocean. Many are accelerating. For example, ice loss from the Thwaite Glacier in Antarctica has doubled in 30 years, currently contributing 4% of the 3.5mm of global annual sea-level rise. Glaciologists are concerned that it could eventually collapse, raising sea levels by 65cm worldwide. Warmer water is melting the seaward edge of the ice from below, destroying its “grounding line”, where it grips bedrock for stability. So, some are proposing to install huge underwater curtains to keep warm currents away from the ice edge.
No one can yet say what such curtains would be made of, how they would be kept safe, or how they would be prevented from interfering with other vital local ecosystem services. Currents flowing along the shores of Antarctica drive a vital nutrient pump that nourishes entire marine food chains far and wide. It’s also possible that keeping one glacier cool would speed the melting of its neighbouring glaciers. To try to get some answers, scientists at the University of Cambridge’s Climate Repair Centre are conducting experiments in tanks and planning outdoor trials in local waterways.
Another major idea involves drilling boreholes into vertical kilometres of ice to extract water from the base of ice sheets. The concept is straightforward: When a huge mass of ice sits on a bed of rock, the combined pressure and temperature liquefy a thin layer of water at the interface of rock and ice that helps the ice slide. Removing this lubricant should help keep the ice in place.
For a long time such ideas – and others, including holding outlet glaciers in place with physical barriers, as well as thickening vulnerable sea ice by pumping seawater and freezing it in place – were largely seen as science fiction. But they are gaining momentum. Dr. Mankoff’s workshop was one of three workshops held between October and December to discuss polar geoengineering; the fourth workshop was held earlier this year. More are planned, and several research papers are in preparation.
Yet opposition is growing. Martin Siegert, a climate scientist at Imperial College London, calls the whole discussion “absolute madness.” “This came out several years ago and many of us ignored it. We thought ‘It’s not going to happen, so let’s not waste time thinking about it.'” He and others have been surprised by how much attention these proposals have attracted since the beginning of the year, and they think now is the time to challenge them.
Let it go
Some counter-arguments revisit themes familiar from the solar geoengineering debate – for example, that techno-fixes divert attention from the core task of decarbonising, and that even exploratory research greases a slippery slope towards deployment. “If a government decides to make geoengineering-based research part of its national Antarctic programme, it will send a very strong signal about the state’s intentions,” says Peder Roberts, a historian and member of the Scientific Committee on Antarctic Research, which advises various intergovernmental groups, including the United Nations and the Antarctic Treaty Secretariat. “The more expensive a piece of research is, the harder it is to say it’s not political.”
Even if such research were carried out, there would be practical hurdles to implementation. Unlike solar projects, polar projects are likely to be extremely expensive – costing many billions of dollars. They present unprecedented engineering challenges: a seafloor curtain to protect Thwaite Glacier could be 80km long and would have to be installed, maintained and repaired in some of the most turbulent seas on Earth.
The political and regulatory challenges are also daunting. Antarctica is protected by international agreements known as the Antarctic Treaty System. All 57 member countries, including the US and Russia, must come to an agreement before any geo-engineering can begin. Yet many of these Antarctic Treaty countries have long failed to cooperate on two pillars of climate action: curbing greenhouse-gas emissions and raising climate funds for poor countries. As a result, Dr. Roberts says, “I’m pretty sure we’ll be pretty far out in the water before we can reach such an agreement.”
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From The Economist, published under license. Original content can be found at www.economist.com.
