Stanford engineers invent high-tech mirror to beam heat away from buildings into space

[Fumesucker]

8. On a clear night where the air temperature is above freezing you often get frost on the ground

If it's cloudy at the same temperature then there is no frost because the clouds block the infrared from escaping to space.

http://mynasadata.larc.nasa.gov/804-2/1035-2/

Sunlight warms soil, rocks, plants, roads, buildings and bodies of water, all of which then emit the solar energy they absorb in the form of thermal (infrared) radiation that we perceive as heat. If there were no atmosphere, the Earth surface would release as much energy to space as it receives from the sun. But that would keep the Earth much too cold for life as we know it to exist.

The atmosphere is why the Earth is warm enough to support life, for it contains water vapor, a gas that strongly absorbs infrared radiation. This water vapor is the key to why the Earth is warm enough to support life. According to the National Oceanic and Atmospheric Administration, removing water vapor from the atmosphere would reduce the average temperature of Earth to 0 degrees F! The oceans would be frozen solid. The Irish scientist John Tyndall was among the first to explain this, and in 1863 he wrote,

Aqueous vapour [water vapor] is a blanket, more necessary to the vegetable life of England than clothing is to man. Remove for a single summer night the aqueous vapour from the air which overspreads this country, and you would assuredly destroy every plant capable of being destroyed by a freezing temperature. The warmth of our fields and gardens would pour itself unrequited into space, and the sun would rise upon an island held fast in the iron grip of frost.