NORMAN — In his Sept. 25 Letter to the Editor, “Global warming is happening,” John Baugher asked, “Does the CO2 layer influence the flow of heat only in one direction?”
In short, the earth radiates heat outward to space by emitting infrared (IR) light, and CO2 in the atmosphere reduces the Earth’s emissions, making the Earth warmer. Sunlight hitting Earth’s atmosphere has a wide spectrum of high energy, short wave radiation including UV, visible and IR light.
About 30 percent of this sunlight is reflected back into space, and the rest is absorbed by the earth, warming the planet. Earth re-emits this energy but only as low energy, long wave IR light. CO2 and other greenhouse gases mixed in our atmosphere absorb Earth’s IR energy, and re-emit it in all directions — some back to Earth — further warming the planet.
It’s a little like compound interest, or maybe more like a compounding mortgage rate. When IR light is emitted into space, it is from higher, colder altitudes where emission is less efficient, so excess IR is trapped closer to the surface, causing more heating. Satellites orbiting outside our atmosphere have measured emitted IR light, and have observed striking decreases in emissions precisely at wavelengths absorbed by greenhouse gases.
The balance between incoming light energy from the sun and outgoing IR light from the Earth regulates global temperature in a life-enabling balance. Without this greenhouse effect, Earth would be a frigid ice-ball of a planet. But an overactive greenhouse effect causes an excess energy gain by the Earth, and the overheating climate we are now experiencing.
Our Earth has a finespun atmosphere less than 2 percent as thick as the Earth is deep – like the skin on an apple. We rely on it to sustain our lives, our cultures, and civilization as we know it, along with the other multitude of species sharing this planet.