The interaction between the Sun's heat and Earth's atmosphere creates our weather. Other vital ingredients are the 23.5 degree tilt of Earth's axis, and the combination of land and water on Earth's surface. Because of its tilt, the Earth is heated unevenly, and this is accentuated by the different heat-absorbing characteristics of land and water.
In its quest for equilibrium, the atmosphere directs warm air to cold places, and cold air to warm, creating our basic system of weather patterns.
Today, Earth has a benign, stable climate with a narrow range of temperatures. In the past, however, there have been periods of rapid and dramatic climate change. Small variations in Earth's orbit around the Sun or in the tilt of its axis could be enough to drastically alter our climate, creating conditions far less conducive to life than those that currently exist.