BBC News | In graphics: Climate change and the Sun: three theories, Space shield

Space shield

Cosmic rays, high-energy particles from space, can stimulate the production of clouds in the lower atmosphere. These clouds mainly cool the Earth. High solar activity blocks some of the cosmic rays, and could warm the world.

The effect may have been a powerful influence on past climate, but is swamped by modern-day greenhouse warming.


�In graphics:�Climate change and the Sun: three theories

	Space shield Cosmic rays, high-energy particles from space, can stimulate the production of clouds in the lower atmosphere. These clouds mainly cool the Earth. High solar activity blocks some of the cosmic rays, and could warm the world. The effect may have been a powerful influence on past climate, but is swamped by modern-day greenhouse warming.