The Earth's atmosphere plays a very important role of temperature maintenance, primarily achieved through convection. Warmer parts of air rise creating high and low atmospheric pressures and in turn winds which travel around the Earth, maintaining a state where temperatures do not fluctuate too rapidly or too quickly. In addition to this, the heat generated by the Sun also cause water to evaporate and form clouds which are transported by the winds generated though convection. These clouds are also helpful in providing a perhaps more noticeable form of temperature insulation as they stop heat energy being lost through radiation, which is why nights are colder when the sky is clear. This form of heat insulation is not dissimilar to that of a green house, light from the Sun above passes through the clouds and as it does it is refracted, it is then reflected off the Earth's surface at angle back towards the clouds. Depending on this angle, it may not be able to pass through the clouds due to the refractive index being too great, thus it is reflected back to the earth wherein this process is repeated.