Climate: Could moon dust keep Earth cool?

Blocking one to two per cent of the Sun's rays is all it would take to lower Earth's surface by a degree or two Celsius.

Whether out-of-the-box thinking or a sign of desperation, scientists on Wednesday proposed the regular transport of moon dust to a gravity point between Earth and Sun to temper the ravages of global warming.

Ideas for filtering solar radiation to keep Earth from overheating have been kicking around for decades, ranging from giant space-based screens to churning out reflective white clouds.

But the persistent failure to draw down planet-warming greenhouse gas emissions has pushed once-fanciful geoengineering schemes toward centre stage in climate policy, investment and research.

Blocking one to two per cent of the Sun's rays is all it would take to lower Earth's surface by a degree or two Celsius -- roughly the amount it has warmed over the last century.

The solar radiation technique with the most traction so far is the 24/7 injection of billions of shiny sulphur particles into the upper atmosphere.

So-called stratospheric aerosol injection would be cheap, and scientists know it works because major volcanic eruptions basically do the same thing. When Mount Pinatubo in the Philippines blew its top in 1991, it lowered temperatures in the northern hemisphere by about 0.5C for nearly a year.

But there are serious potential side-effects, including the disruption of rain patterns upon which millions depend for growing food.