Actually, this is my argument for global warming concern. If you can convince yourself of it's invalidity, .....
1) Earth operates as a radiant black body in a vacuum. It absorbs radiant energy from the sun, which heats it up until it can re-radiate as much radiant energy as it receives. This is by far the GREATEST factor which establishes its average surface temperature. Other minor influences include variations in albedo, and in insolation. Insolation hasn't varied by more than 0.1% over at least the past 400 yrs, and very likely not for the past 2000 yrs. ["More recently, a study and review of existing literature published in Nature in Sept. 2006 suggests that the evidence is solidly on the side of solar brightness having relatively little effect on global climate, and downplays the likelihood of significant shifts in solar output over long periods of time." - http://en.wikipedia.org/wiki/Solar_variation
2) At earth’s average temperature, all of it’s re-radiation occurs in the infrared band.
3) Anything which interferes with earth’s ability to radiate infrared will cause earth’s “radiating surface” temperature to rise in order to compensate by increasing its radiant temperature, so shifting the radiation to a higher-energy frequency.
4) Certain gas molecules can absorb infrared radiation and immediately re-emit it at approximately the same frequency, or perhaps lower. Problem is the photons they absorb are all outbound, the ones they re-emit are emitted in a random direction, 50% back toward the surface. These are the “Greenhouse gasses”, responsible for a 37 deg C higher temperature on earth compared to the moon. There are four main GHG’s in earth’s atmosphere, Water, CO2, Methane, Oxides of Nitrogen.
5) Water is currently responsible for perhaps 95% of the greenhouse effect. Problem is that the atmosphere’s water content is almost entirely dependent on earth’s surface temperature. Therefore, earth’s surface temperature is almost entirely controlled by its content of the other three, mainly CO2.
6) There are some complicating issues, such as an individual molecule’s average residence life in the atmosphere etc. Methane is about 20 times better at trapping heat than carbon dioxide, but it only stays in the atmosphere for about 10 years, before breaking down to CO2 and water. (CH4 + 2O2 -> CO2 + 2H20) Then it is an ordinary CO2 molecule (in the atmosphere). Overall, releasing a methane molecule traps about 6 times more heat compared with releasing a CO2 molecule.
7) Surface temp also influenced by earth's albedo, eg. reflectivity which varies according to cloud and snow/ice coverage, and for short periods by particulate matter loading (particles at high altitude tend to intercept incoming radiation and re-radiate it randomly, eg. 50% outward, therefore cooling the surface). Volcanoes cool earth by inserting heavy particulate loadings into upper atmosphere, but effect only lasts for short times, eg. one or two yrs.