domingo, 17 de julio de 2011
A greenhouse gets warm because the glass prevents the sun warmed air from moving away. Greenhouse gases do not warm the Earth in that way. Unfortunately, the phrase has currency and it will be used here.
The Sun emits radiation which warms the Earth. The Earth also emits radiation which cools it. The Earth is surrounded by the vacuum of space and so there is no other possibility. The physics for this was worked out around more than 100 years ago and it is very well understood. Incoming and outgoing radiation are always nearly in balance. If this were not the case, the Earth would be cooling or warming. If you want to know what the temperature of the Earth should be, you use Stefan's law of 1884. It tells you how many watts of energy is incoming or outgoing.