One of the most radical ideas scientist are now considering to slow down global warming involves spraying tiny particles into the sky to reflect sunlight and cool the Earth. This method is known as solar geoengineering or stratospheric aerosol injection (SAI). While the concept dates back decades, new studies are pushing the limits of what might be possible—like cooling the planet with five million tons of lab-grown diamond dust every year.

The idea behind SAI is simple: mimic what happens during major volcanic eruptions. When Mount Pinatubo erupted in 1991, it blasted 20 million tons of sulfur dioxide into the stratosphere. That gas formed particles that reflected sunlight and cooled the planet by about half a degree Celsius for two years. Scientists took note. Maybe it was possible to recreate that effect intentionally, using high-flying aircraft to release reflective aerosols high above Earth.

But sulfur dioxide has serious downsides. It turns into sulfuric acid, which damages the ozone layer and leads to acid rain. It can also warm the stratosphere, shifting wind patterns, changing rainfall, and even disrupting the jet stream. These side effects could worsen global weather systems, rather than stabilize them.

To avoid these risks, researchers are investigating alternatives. A recent study, published in the journal Geophysical Research Letters, led by climate scientist Sandro Vattioni at ETH Zurich tested seven different materials to see which one could cool the planet most effectively with the fewest side effects. The researchers used a supercomputer to model how each compound—sulfur dioxide, aluminum oxide, calcite, silicon carbide, anatase, rutile, and diamond—would behave in the stratosphere over 45 years.