Global warming and its consequence is no news to anybody. But it could be too late before renewable sources of energy are put to work. In order to handle such an emergency Roger Angel, Director of the Steward Observatory Mirror Laboratory and the Center for Astronomical Adaptive Optics from the Department of Astronomy of the University of Arizona and one of the world's foremost minds in modern optics, has been looking for a year at ways to cool the Earth.

He plans to reduce the temperature on Earth by building a massive space sunshade made of a breath taking 20,000 billion tiny spacecrafts weighing about a gram each (a total of 20 million tons) and orbiting a million miles above our heads. The spacecrafts would form a long, cylindrical cloud with a diameter about half that of Earth, and about 10 times longer. About 10 percent of the sunlight passing through the 60,000-mile length of the cloud, pointing lengthwise between the Earth and the sun, would be diverted away from our planet. The effect would be to uniformly reduce sunlight by about 2 percent over the entire planet, enough to balance the heating of a doubling of atmospheric carbon dioxide in Earth's atmosphere.

This plan would cost $100 billion per year and would be deployed over a period of 25 years. NASA Institute for Advanced Concepts has been backing Roger since July 2006 to further research about this idea.

The research work was published by the Proceedings of the National Academy of Sciences under the name "Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)" (November 3, 2006).

Will this idea ever come to reality? If yes, how is it going to be funded remains unanswered.