Ok, here's the question. Without the greenhouse gases in earth's atmosphere the temperature would be 250K. With them it is 40K higher (290K). Using the Stefan-Boltzman equation for flux ( F = σT4) what is the percentage of infrared radiation leaving the earth's surface taht is absorbed by the greenhouse gases? I spent awhile on this and the best I could come up with is 18%. But if someone else knows how to do this, help will be appreciated. Thanks!