A few weeks ago, Mickey McVay wrote a letter to the editor in which he asked if anyone could explain how greenhouse gases could promote global warming. Oddly enough, I happen to know the answer to that question. I hope my explanation is understandable.
Our atmosphere is made up of mostly nitrogen, a lot of oxygen, and other gases in smaller amounts. Most radiation from the sun passes right through our atmosphere because it has a short wavelength. The radiation heats the ground and then is emitted as long wave radiation. This is the same kind of heat you feel from a hot sidewalk. Water vapor, carbon dioxide, and methane molecules in the atmosphere absorb long wave radiation, which causes them to vibrate. The vibration produces heat, which is then radiated throughout the atmosphere.
Water vapor, carbon dioxide and methane are referred to as greenhouse gases (even though the physics behind greenhouses is quite different,) and they are what keeps our planet warm. Without them, the radiation from the sun would bounce right back into space, and Earth would be a much colder place. The opposite is also true, which is what we're concerned about today.
All of this is just basic physics, and has been known since the 1850s. Starting in 1859, an Irish physicist by the name of John Tyndall started publishing papers describing long wave radiation absorption by certain gases, and for a long time he was believed to be the original discoverer of the phenomenon. But recently it was discovered that an American scientist named Eunice Foote had published a paper to that effect in 1856. Swedish physicist Svante Arrhenius postulated in 1896 that a significant increase in carbon dioxide could cause global temperatures to rise, but it wasn't until the 1950s that scientists started getting concerned enough to start monitoring temperatures around the world. By the 1970s, US Department of Energy started getting concerned that increased industrialization would produce global warming, although at the same time, there was also a small group of scientists who believed that the pollution in the atmosphere (aerosols) would reflect the sun's radiation out into space, thereby causing global cooling. But by the 1980s, temperature data showed that cooling was not happening, and the 1980s wound up being the warmest decade on record. By 1997, it was determined that there was enough evidence that action needed to be taken.
This is just the basics, of course. There is a lot of different aspects that get into various scientific disciplines, all of which are interrelated.
Now I mentioned at the top that it was odd that I knew all this. Science, especially physics, is not really my thing. The only reason I know any of this is because I believe that Walt Whitman gives good advice.
