The energy balance between earth and sun has been studied for years. The image summarizes a report by J. T. Kiehl and Kevin E. Trenberth of the National Center for Atmospheric Research, Boulder, Colorado in 1997. Click the image to view the report. For a simpler explanation click here.

The amount of power is enormous totalling 1.76 x 10¹⁷ watts when the sun is directly overhead and averaging 4.4 x 10¹⁶ watts across the 24 hour day. As long as the balance over time is maintained the temperature is unchanged.

Global climate change theorists have argued that increases in greenhouse gases are increasing the Back Radiation component shown on the lower right of the diagram. They believe the evidence is strong enough to act on with urgency and believe they are proposing effective albeit expensive measures.

As you can see this is a big complicated system with lots of moving parts. Global change skeptics argue the mechanics are not well enough understood to draw the kind of conclusions the mainstream is suggesting and certainly not enough to try to fix it at great expense.

The Frequencies are proportional to the temperature of the emitting body

0.25-3 micrometer  -  Shortwave - coming from the sun (6000K temperature)
3-20 micrometer - Longwave - radiated by the earth and air (250-300K temperature)

5.8 and 6.5 micrometer captured by H2O greenhouse gas
4 and 15 micrometer captured by CO2 greenhouse gas

0.4-0.7 micrometer visible light (our eyes evolved to see in this range because the atmosphere was transparent to these frequencies giving us a good chance of finding food and avoiding predators)