The climate we live in controls where and when we get our food, what we wear, the houses we live in, and what diseases we might catch. ‘What is climate?’ shows how crucial climate is to human life and explains what influences it. A key cause is that the Equator receives more of the sun's energy than the poles do. About a third of the solar energy we receive is reflected back into space. Climate is mainly controlled by two basic relationships between the Earth and the sun: the tilt of the Earth's axis of rotation, which causes the seasons; and the daily rotation of the Earth.