Scientists at ETH Zurich believe that seeding the atmosphere each year with five million tons of diamond dust could reflect enough of the sun's energy to cool the planet by 1.6ºC (2.9ºF) over 45 years, thereby countering the devastating effects of climate change.

This type of large-scale manipulation of the earth’s climate is called “geoengineering.”

Certainly this strategy comes with a hefty price tag. The scientists at ETH Zurich's Institute for Atmospheric and Climate Science estimated the investment at about $2.6 trillion per year (or $200 trillion over the remainder of this century).

The idea of pumping the atmosphere with lab-grown diamond dust sounds a bit fanciful, but it's rooted in observable, measurable data.

When Mount Pinatubo erupted in the Philippines in 1991, about 20 million tons of sulfur dioxide was blasted into the sky, effectively redirecting some of the sun’s energy and lowering the average temperatures over the next two years by a half degree.

Scientists could have proposed mimicking the action of a volcano by seeding the sky with sulphates, but that strategy has its dangers. Sulfates lead to the production of sulphuric acid, which depletes the ozone layer, negatively affects plant growth and diminishes the effectiveness of solar panels.

Back in 2015, Harvard scientists were the first to propose a massive-scale geoengineering project using diamond dust. They argued that carbon-based diamond dust or alumina (aluminum oxide) would be far more effective and less damaging than sulphates.

In a modeling study published this month in Geophysical Research Letters, the ETH Zurich scientists reported that diamond dust was the best choice for staving off the worst consequences of global warming.

The researchers used a supercomputer to model the effects of seven compounds — including sulfur dioxide, diamond, aluminum, calcite, silicon carbide, anatase and rutile — across 45 years. The results showed that the chemically inert diamond particles were best at reflecting radiation while also staying aloft and avoiding clumping.

The ETH Zurich said that the diamond particles could be injected into the stratosphere using high-altitude aircraft.

Douglas MacMartin, an engineer at Cornell University, who specializes in climate science, told science.org that at $500,000 per ton, synthetic diamond dust is 2,400 times more expensive than sulfur, which he advocates as more viable, cost-effective alternative.

Another issue is whether the international lab-grown diamond manufacturers would be able to ramp up to handle production.

The scientific community understands that the diamond-dust cooling strategy is not without its own risks. First off, it’s never been tested, and second, once the diamonds are up in the sky, the results — positive or negative — would be difficult to reverse.

Credits: Graphic by Scientific Visualization Studio/Goddard Space Flight Center.