Global warming is a problem everybody is familiar with, yet we tend not to be aware of the basics of it. So here it is. In Earth’s atmosphere are certain gases which allow sunlight through but block sunlight from going back out to space when it bounces off of Earth. These gases are called greenhouse gases. They are called that because they make the Earth warm just as a greenhouse makes its inside warm. But the similarity ends there. An actual greenhouse and greenhouse gases do not work in a similar way at all. But what does a greenhouse do?
One of the most worried about dangers for very young children in the modern world, before they are able to do simple things such as open doors, is that they get left in cars outside on a hot day. The car heats up and quickly gets so hot the infant or toddler dies. But how does this happen?
When the Earth’s surface is exposed to sunlight, the air above the ground warms up. Because warmer air is less dense than cooler, the warmed air floats up into the sky while cooler air replaces it, thus keeping all of us cool. The cooler air may come from under clouds, under trees, or half a world away where it is night. But inside a car, the sunlight pours in while the warmed air cannot get out. Thus, the car’s interior heats up until it is the same temperature as the sun’s rays itself, which, in hot days, is a fatal temperature for humans and animals. Glass allows sunlight and warmth in but does not allow air out. Using this principle, greenhouses are buildings made just of glass which house plants that benefit from the warmth.
But this is not at all how greenhouse gases work. Greenhouse gases instead work like a different kind of glass. You know there are some vehicles with black windows? You cannot see into the vehicle but people inside can see clearly what is outside. That is because the glass allows sunlight inside but does not allow it reflected back out. That is the property of greenhouse molecules. They allow sunlight to reach the Earth’s surface. When the sunlight hits Earth, its heat is released in the form of thermal radiation. The greenhouse gases have the chemical property of absorbing thermal radiation, so the radiation is blocked from reaching outer space and Earth is heated up.
The principal greenhouse gases in Earth’s atmosphere are water vapor, carbon dioxide, and methane. Water vapor, which is abundant in the atmosphere, is a weak greenhouse gas. Carbon dioxide is stronger and less abundant. Methane is a very powerful greenhouse gas and is rare in the atmosphere.
Now, the whole global warming problem is that human activity is releasing great amounts of carbon dioxide into the air due to the primary industrial fuel being stores of carbon in the Earth’s crust. The Earth’s vegetation, which removes carbon dioxide from the air, is also being cut down by humans. In addition, methane, which is extremely potent, is being released into the atmosphere by a variety of human means, such as keeping of livestock which emits methane and other activities which release stores of methane into the air.