'Serious Negative and Unintended Consequences': Polar Geoengineering Is Not the Answer to Climate Change

A review shows that five major polar geoengineering projects are not feasible in the coming decades. (Image credit: Thomas Barwick via Getty Images)

Our planet continues to warm due to greenhouse gas emissions from human activities. The polar regions are particularly vulnerable to this warming. Sea ice is already shrinking in both the Arctic and Antarctic. The Greenland and Antarctic ice sheets are melting, and both polar regions are experiencing dramatic changes.

These changes have profound implications for society, causing rising sea levels, changes in ocean circulation, and extreme climate events. They also have significant impacts on polar ecosystems, including polar bears and emperor penguins, which have become symbols of the effects of climate change.

The most effective way to mitigate these changes and reduce the risk of widespread impacts is to reduce greenhouse gas emissions. However, decarbonisation is slow, with current projections suggesting a temperature increase of around 3°C by 2100.

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Given the expected changes and the importance of the polar regions to the health of the planet, some scientists and engineers have proposed technological approaches known as geoengineering to soften the blow to the Arctic and Antarctic.

In a study published today in Frontiers in Science, my colleagues and I evaluated five of the most mature geoengineering concepts being considered for the polar regions. We concluded that none of them should be pursued in the coming decades. They are extremely unlikely to mitigate global warming in the polar regions, and are likely to have serious negative and unintended consequences.

What is polar geoengineering?

Geoengineering covers a wide range of ideas for deliberate, large-scale attempts to alter the Earth's climate. Two of the broadest classes include removing carbon dioxide from the atmosphere and increasing the amount of sunlight reflected back into space (called solar radiation modification).

For the polar regions, here are the five most developed concepts.

Stratospheric aerosol injection is a solar radiation modification technique that involves introducing smaller particles (such as sulfur dioxide or titanium dioxide) into the stratosphere to reflect sunlight back into space. The focus here is on the polar regions.

Sea curtains are flexible floating structures anchored to the seabed at depths of 700 to 1,000 m and rising 150 to 500 m. Their purpose is to prevent warm ocean water from reaching and melting ice shelves (floating areas of ice that slow the movement of ice from Greenland and Antarctica into the ocean) and ice sheet abutments (where land, ice sheets, and ocean meet).

Sea curtains are flexible floating structures anchored to the seabed at depths of 700 to 1000 m and rising to a height of 150 to 500 m.

Sea ice management involves two concepts. The first involves scattering glass microbeads on fresh Arctic ice to increase its reflectivity and extend its life. The second involves pumping seawater onto the surface of the sea ice, where it freezes to increase its thickness, or into the air to create snow, with the same effect, using wind pumps.

The outflow of water from the glacier's surface is directed into ice streams located on the Antarctic and Greenland ice sheets. These streams are fast-moving rivers of ice that flow towards the coast, where they can flow into the ocean and raise its level. The water at their base acts as a lubricant. This concept involves pumping water from their base to increase friction and slow the flow. This concept is thought to be particularly relevant in Antarctica, where surface melting is much weaker than in Greenland, and so melting occurs mainly at the base of the ice sheet rather than on its surface.

Ocean fertilization involves adding nutrients like iron to polar oceans to stimulate the growth of phytoplankton. These tiny creatures absorb carbon dioxide from the atmosphere, which accumulates in the deep ocean after they die and sink.

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In our study, we assessed each of these concepts against six criteria, including scale of implementation, feasibility, financial costs, effectiveness, environmental risks, and management complexity.

This framework offers an objective way to evaluate all such concepts on their merits.

None of the proposed polar geoengineering concepts have been tested for viability in the coming decades. The criteria we used show that each of the concepts faces numerous difficulties.

For example, to cover 10% of the Arctic Ocean with frozen seawater pumps for ten years would require installing one million pumps per year. The estimated cost of sea curtains ($1 billion per kilometre) is 6 to 25 times less than similar-sized projects in simpler settings, such as the Thames Barrier near London.

One project to apply glass microbeads to ice was also shut down due to environmental risks. At the last meeting, most of the Antarctic Treaty Consultative Parties made it clear that geoengineering work in the region was not advisable.