When the greenhouse gasses weren't there, it was very cold. The sun's radiation came down on the Earth, but it reflected off the Earth so it was still cold.
The earth was at 0 degrees farenheight.
But all that changed when greenhouse gases appeared! The suns rays didn't bounce out anymore. They were trapped in the atmosphere.
As humans started to populate the Earth, and later the demand for energy grew. They used power plants, and gsoline to power things. The amount of greenhouse gases increased.
Shortwave radiation dosen't get stopped by the greenhouse gases but longwave radiation does.
If large amounts of the greenhouse gases accumulate in the atmosphere, the heat cannot get out and Earth will continue to become hotter and hotter. The temperature will affect humans, animals, climate, and ecosystems.THE END