Diamond dust dimming: Geoengineering's costly climate fix

Although scientists remain divided, and the cost of implementation could run into hundreds of trillions of pounds, it cannot be denied that geoengineering (SAI) - with its most prominent technique being stratospheric aerosol injection - would have immediate visible effects on climate change by reducing the solar energy that reaches the Earth. In the long term, this could provide us with precious time until we achieve net-zero carbon dioxide emissions. The UN warns that we are now "walking on a planetary tightrope" and that carbon emissions must be halved immediately to prevent a climate catastrophe.

Scientists did not only consider dispersing diamond dust into the atmosphere; they also explored other materials such as calcite, aluminium, silicon carbide, and sulphur dioxide. In a new study, published on 16 December in the scientific journal Environmental Research: Climate, researchers from the Institute for Atmospheric and Climate Science in Zurich, Switzerland (ETH), confirmed that diamonds offer the best option for atmospheric dispersal.

They calculated that launching 5 million metric tonnes of diamond dust into the stratosphere each year could cool the planet by 1 degree Celsius due to the reflective properties of these precious stones. This level of cooling would play a significant role in mitigating global warming, which began in the latter half of the 19th century and currently stands at about 1.36 degrees Celsius, according to NASA data.

The team also compared the cooling efficiency of diamond particles with that of aluminium and calcite particles. They found that the amount of diamond dust needed to cool the planet by 1 degree Celsius — 5 million tonnes annually — was about one-third of the amount required by other materials to achieve the same cooling effect.

Researchers stated that diamond particles have the highest capacity to reflect light and heat, allowing them to remain suspended in the atmosphere for an optimal period without clumping. "This occurs because diamond dust is extremely reflective and does not adhere, which is why some other materials absorb heat instead of redirecting it back into space," said study co-author Sandro Vattioni, a researcher in experimental atmospheric physics at the Swiss Federal Institute of Technology in Zurich (ETH Zurich), as quoted by Live Science.

Previously, scientists explored the possibility of introducing sulphur dioxide into the stratosphere to curb climate changes. They found that although sulphuric acid aerosols could absorb a considerable amount of solar and terrestrial heat, they could lead to adverse effects, such as causing acid rain and damaging the ozone layer, whereas diamond dust is chemically inert. Scientists have now discovered that diamond particles would not cause stratospheric warming or other significant disruptions.

The new study did not estimate the production costs of diamonds for geoengineering purposes. Still, synthetic diamonds would likely be cheaper than mined diamonds, according to Vattioni, as quoted by Live Science. However, the costs and energy demands of these different materials remain unclear. A previous study (from 2020) estimated that SAI with sulphur dioxide from 2035 to 2100 would cost around £15 billion annually, and the costs of aluminium and calcite would likely be similar, Vattioni said. The expenditure for diamonds would be significantly higher—the 2020 study calculated a total cost over 65 years at approximately £140 trillion.

Currently, there is considerable uncertainty surrounding geoengineering (SAI), and scientists are far from implementing it. Some experts oppose conducting this type of research altogether due to its potential unforeseen consequences and argue that it diverts funds away from other climate research.

Sandro Vattioni, a researcher in experimental atmospheric physics at ETH Zurich, highlighted the significant risk of reaching irreversible climate and ecological tipping points. He noted that SAI might temporarily prevent surpassing these thresholds while working toward achieving net-zero emissions, as reported by the Live Science portal.