Diamond Dust in the Sky Could Cool Planet, Say Climate Scientists

Recently published research suggests that spraying diamond nanoparticles into the atmosphere could help combat global warming — but that the cost, ultimately, could prove prohibitive. Yves Herman/Reuters

Spraying billions of dollars' worth of diamond particles into the atmosphere could be an effective method of combating global warming, according to a recent analysis by climate scientists.

The technique, which has not been tested, is a form of geoengineering whereby scientists intervene directly in the planetary environment in order to reduce global temperatures. Another proposed method of geoengineering, for example, is spraying sulfur particles into the atmosphere; the particles would reflect some of the Sun's rays before they reach Earth.

Now a team of climate scientists from Harvard University have calculated that diamond nanoparticles would be at least 50 percent more effective than sulfates at reflecting solar energy and thereby cooling the Earth, Nature reported.

However, in their analysis, published on Monday in the journal Atmospheric Chemistry and Physics, the researchers also noted that there could be unknown consequences to using the particles in this way, given that the process has not yet been trialed.

The cost of pumping ground-up diamonds into the atmosphere could also be prohibitive. The authors noted that synthetic diamond particles are available at less than $100 per kilogram, but the technique would require hundreds of thousands of tons of diamond dust to be sprayed each year, racking up a huge bill.

The proposed method—a form of geoengineering known as solar radiation management—mimics the cooling effects of volcanic eruptions. According to NASA, global temperatures dipped by about 0.6 Celsius for around two years following the 1991 eruption of Mount Pinatubo in the Philippines, which ejected more than 20 million metric tons of sulfur dioxide into the atmosphere. Afterwards, the sulfates remained in the atmosphere and reflected solar radiation away from the Earth for months.

The recent Harvard analysis also found that aluminum oxide nanoparticles would be at least as effective as sulfates at reducing global temperatures. The researchers suggest that using solid dusts could have less negative side effects than using sulfates, which produce sulfuric acid that damages the ozone layer. Debra Weisenstein, an atmospheric modeling expert at Harvard and one of the study authors, told Nature that using diamond or aluminum oxide nanoparticles instead of sulfates "could have significantly less impact on ozone" and lead to "less heating of the stratosphere." She also said that using solid dust particles would lead to less diffusion of light, which has the impact of lowering the potential power output of solar panels.

Other geoengineering proposals include increasing the reflectivity of clouds by spraying seawater into the air so that the salt particles in the water increase the concentration of rain droplets and thereby the whiteness of the clouds. Another proposal is adding minerals such as iron to the oceans, which would stimulate the growth of algae that suck carbon dioxide out of the air.

However, there are worries that the effects of geoengineering could be disastrous, with measures that block the Sun's rays having potential unforeseen impacts on precipitation patterns. Piers Forster, professor of physical climate change at the University of Leeds, told the BBC that geoengineering could adversely affect up to 4.1 billion people through changes to rainfall patterns and could lead to the complete drying out of the Sahel region in sub-Saharan Africa.