The climate system is a composite system consisting of five components: the atmosphere, the hydrosphere, the cryosphere, the lithosphere, and the biosphere. These components interact and thereby maintain an always changing, yet relatively stable environment that sustains life --the most precious and complex thing in the universe .
The most fundamental question about the climate system is why its state is always changing, and yet has so far avoided a runaway instability that could destroy all life. It is also against this background that the importance of understanding human impact on the state of the climate system better emerges. With our industrial activity changing the chemical composition of the atmosphere, are we prodding a "lamb" who poses no harm, or a "beast" who may react to devour all of us?