The hot Sun emits visible short waves, and the cool Earth re-emits infrared long waves - terrestrial radiation. Not all of the re-emitted infrared long waves are bounced back to space. Some are absorbed and trapped in the atmosphere by greenhouse gases. In this way, the greenhouse gases act like a blanket that warms the lower atmosphere. What is the role of greenhouse gases in the greenhouse effect?
1) They reflect the short waves emitted by the Sun back into space
2) They absorb and trap the re-emitted infrared long waves from the Earth
3) They cool down the lower atmosphere
4) They have no effect on the greenhouse effect