Diamonds in the sky: A pricey plan to cool the planet

Although scientists are still divided on the topic and the cost of implementation is estimated to reach hundreds of trillions of dollars, it's undeniable that geoengineering with SAI could have immediate visible effects on climate change by reducing the amount of solar energy that reaches Earth. This approach could buy us time in the long run until we achieve net-zero carbon dioxide emissions. The United Nations warns that we are now "walking on a planetary tightrope" and carbon emissions must be cut in half immediately to prevent a climate catastrophe.

Scientists initially considered a range of materials for atmospheric dispersal, including calcite, aluminum, silicon carbide, and sulfur dioxide, as well as diamond dust. However, in a study published on December 16 in the scientific journal Environmental Research: Climate, researchers from the Institute for Atmospheric and Climate Science at ETH Zurich in Switzerland confirmed that diamonds are the most effective material for this purpose.

They calculated that thanks to diamonds' reflective properties, dispersing 5 million metric tons of diamond dust into the stratosphere annually could cool the planet by 1 degree Celsius. According to NASA data, this degree of cooling could significantly help limit global warming, which began in the latter half of the 19th century and currently stands at around 1.36 degrees Celsius.

The team also compared diamond particles' cooling efficiency with aluminum and calcite particles. They found that producing the 5 million tons of diamond dust needed to cool the planet by 1 degree Celsius would require only one-third the amount of other materials needed to achieve the same effect.

Researchers found that diamond particles have the highest ability to reflect light and heat, allowing them to stay in the atmosphere longer without clumping together. "This happens because diamond dust is extremely reflective and does not stick together, which is why some other materials absorb heat instead of sending it back into space," explained study co-author Sandro Vattioni, a researcher in experimental atmospheric physics at ETH Zurich, as quoted by Live Science.

In previous research, scientists considered using sulfur dioxide in the stratosphere to combat climate change. However, they found that although sulfuric acid aerosols can absorb significant amounts of solar and terrestrial heat, they also lead to undesirable side effects, such as acid rain and damage to the ozone layer. In contrast, diamond dust is chemically inert. Scientists have discovered that diamond particles would not cause stratospheric warming or other major disruptions.

The study did not estimate the cost of producing 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 materials remain unclear. A previous study from 2020 estimated that using sulfur dioxide for SAI from 2035 to 2100 would cost $18 billion annually, with aluminum and calcite likely falling into a similar cost range, Vattioni noted. The projected cost for diamonds would be significantly higher — the 2020 study calculated a total cost of $175 trillion over 65 years.

For now, there is significant uncertainty surrounding geoengineering with SAI, and scientists are far from ready to implement it. Some experts argue against this type of research due to potential unforeseen consequences and because they claim it diverts funds from other vital climate research.

"We really run the danger of passing some irreversible climate tipping points and ecological tipping points, and SAI could potentially help to avoid passing these tipping points until we have reached the net zero goal," remarked Sandro Vattioni on the Live Science portal, a researcher in experimental atmospheric physics at ETH Zurich.