Why are some greenhouse gases more powerful than others?
In: Chemistry
Greenhouse gases warm the planet by absorbing infrared radiation from the surface of the planet. There are three important properties that define how effective a greenhouse gas is at any given moment. (In other words, not accounting for how long it remains in the atmosphere.)
1. How effectively it absorbs the infrared energy. This should be obvious.
2. At which wavelengths is absorbs the infrared energy. The reason this is critical is because water vapor is a highly effective greenhouse gas. (Providing something like 95% of the net warming of the greenhouse effect.) Some gases may be very effective at absorbing infrared but they can still have a low impact on temperature because so much energy at that wavelength is already being absorbed by water vapor. Since the wavelengths where CO2 absorbs energy only partially overlap with water vapor, it also affects energy absorption.
3. How much of the gas is already present in the atmosphere. The more of a greenhouse gas you have in the atmosphere, the less effect a marginal increase will have on absorption. In other words, going from 300 ppm of CO2 to 400 ppm of CO2 (increase of 100 ppm) has a much bigger impact on energy absorption than going from, say 800 ppm to 900 ppm.
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