What is the greenhouse effect, and what effect does it have on the Earths surface temperature?
The greenhouse effect was a term coined a few decades ago. A greenhouse is made of material that lets sunlight enter, but doesn’t let the heat that accumulates leave. So a greenhouse building can be very hot even in the coldest winter as long as it is in sunlight. For our planet, when solar radiation reaches the Earth, the atmosphere is transparent to that radiation and it reaches the surface. That heats up the surface. That heat can be radiated back out to space (as infrared radiation), but some atmospheric gases actually stop that infrared radiation from passing through the atmosphere. Those gases are mainly carbon dioxide, methane, and to some degree water vapour. So the greenhouse effect causes the surface temperature of the Earth (the land, the water, and the air) to be warmer than they would be without the effect. Venus’s atmosphere is almost all carbon dioxide (about 96.5%) and that (along with a few other trace gases) has led to what is called a “runaway greenhouse effect”.
