The red outlined curve represents a blackbody emission spectrum at 294 degrees K. The average surface temperature of the earth is about 288 degrees K or 15 degrees C. The blackbody spectrum of the earth with no greenhouse gases has a similar shape with an average temperature of 255 degrees K. or -18 degrees C. When greenhouse gases are added to the Earth's atmosphere, the emission spectrum seen from space has the shape of the blue curve with several "bites" taken out of it. This is because carbon dioxide, ozone, and methane are emitting radiation at a cooler temperature than the Earth's surface. In the case of carbon dioxide its blackbody radiation occurs at the top of the atmosphere where the temperature is 220 degrees K so its radiance is greatly attenuated. Likewise, methane's and ozone's spectrums are attenuated to a lesser extent because they radiate from a lower altitude than CO2. In order for the earth-atmosphere system to radiate the same amount of energy to space with a greenhouse, its surface temperature must increase.to raise the level of non-attenuated emissions. There is no violation of the conservation of energy, the same amount of energy leaves the earth-atmosphere system as before with no greenhouse gases and the solar radiance absorbed by the earth is the same. The radiance of the Earth is decreased in the portions of the curve where greenhouse gases emit and it is increased in the other portions. Note that carbon dioxide's emission spectrum, and therefore its absorption spectrum, occurs near the peak of the blackbody curve and that is one reason why it is an important greenhouse gas. The "bites" taken out of the top of the atmospheric blackbody radiation for the earth have been shown to increase with rising levels of greenhouse gases and the amount of downward radiation characteristic of carbon dioxide and other greenhouse gases has increased with rising GH gas levels.