Greenhouse Effect

The greenhouse effect is the name given to the trapping of heat in the lower atmosphere and the warming of Earth's surface that results. Although a natural phenomenon, this warming effect tends to increase as more human-produced gases are released into the atmosphere. This increased warming could result in climate changes that affect crops, as well as melting glaciers and coastal flooding.

Only in the past few decades has the term "greenhouse effect" implied something bad for the environment. In fact, the phenomenon that it describes is absolutely essential to life on Earth. Without it, Earth would be a cold and lifeless planet. What this phenomenon does is hold on to some of the heat given off by the Sun. Specifically, Earth's atmosphere is the mixture of gases and water vapor that surrounds the entire Earth. Composed mainly of oxygen and nitrogen as well as small amounts of other trace gases, the atmosphere is essential to photosynthesis (the process a plant uses light to make food). It also protects organisms from the Sun's infrared rays because it absorbs much of these. Since the atmosphere is located physically between the surface of Earth and the Sun, the molecules of gas that make it up act somewhat like a pane of glass in a greenhouse, which is where the name "greenhouse effect" originates. The glass on a greenhouse lets light in and out but holds in its heat. What the atmosphere does is allow wavelengths of visible light from the Sun to reach Earth's surface. While doing that, however, the atmosphere blocks the escape into space of the longer infrared wavelengths. That is, they trap the light's heat by reabsorbing these wavelengths, much of which get sent back down to Earth again. Overall, this makes Earth a warm place that is hospitable to life.

Human activities have begun to alter this process of capturing heat, however. The result of these activities may be the experiencing of too much of a good thing. Too much of a greenhouse effect means that things are heating up too fast. In the past few decades, human activities have begun to change, if not harm, the atmosphere, so that it is trapping more heat than it should. Specifically, our steady burning of fossil fuels (coal, oil, natural gas) has increased the amount of carbon dioxide in the atmosphere. Carbon dioxide is the most important gas in the greenhouse effect, since it is the molecules of carbon dioxide that do the actual absorbing of long-wave infrared radiation. The more carbon dioxide in the atmosphere, the more heat it keeps in. Besides all of the carbon dioxide being pumped into the air by car exhausts and factories, there is the added problem that humans

are vastly reducing the world's forests, whose trees and plants take in carbon dioxide and give off oxygen as part of photosynthesis.

Since humans are artificially warming Earth this way, many scientists feel that Earth is already beginning to experience the negative consequences. Climatologists (scientists who study Earth's climate or weather) now believe that Earth's long-term climate patterns are changing. Some project as much as a 4 or 5 degree increase by the middle of the twenty-first century. This could have disastrous effects, since such global warming could cause the polar ice caps and the mountain glaciers to melt. This could result in mass flooding, making many islands disappear, and putting coastal cities completely under water. Since it is climate that mostly determines what will grow where, crops also could be seriously affected. A global temperature rise could produce entirely new patterns and extremes of rainfall or drought in certain areas.

SVANT AUGUST ARRHENIUS

Swedish chemist Svant Arrhenius (1859–1927) is considered to be the founder of physical chemistry, a fairly new field which blends chemistry and physics. He not only contributed to the founding of a new branch of science, but added a new concept, now called the "greenhouse effect," to the study of the life sciences.

Svant Arrhenius was a child prodigy (exceptionally smart) who taught himself to read at three years of age. Born at Vik, Sweden, the youngster is said to have become interested in mathematics while watching his father, a surveyor (a person who determines boundaries), add columns of figures. Naturally brilliant in school, he earned a bachelor's degree from the University of Uppsala at the age of nineteen while studying physics, mathematics, and chemistry. For his doctoral dissertation in 1884, he offered a theory that explained what occurred when electricity passes through a solution at the atomic level. His ideas were so revolutionary, however, that his committee gave him the lowest passing grade possible. Nineteen years later, Arrhenius would receive the Nobel Prize in Chemistry for the same work that had barely earned him a degree.

All his life, Arrhenius was regularly pushing the limits of science, and in 1908 he published a book titled Worlds in the Making that marked him as one of the forerunners of molecular biology. Molecular biology is the study of the complex chemicals, like proteins and nucleic acids, that make up living things. In this work, Arrhenius offered what he called the universality of life, meaning that life was not to be found only on Earth. It was his belief that life on Earth had sprung from "spores" that had been driven though outer space by radiation pressure from other planets. This meant to him that life had been spread throughout the universe and took hold wherever conditions were favorable. There are now many physical reasons why his spore theory is not correct, and it also offers no explanation as to where or how life originated in the first place.

It was in this book, however, that Arrhenius also suggested what we now call the greenhouse effect. There he speculated that carbon dioxide gas in the atmosphere heats Earth by first allowing sunlight to reach its surface, and then trapping much of the heat radiation or preventing the heat from escaping back into space. He argued that because of this phenomenon, any rise in the amount of carbon dioxide in the atmosphere would raise Earth's temperature since it would act like a greenhouse and trap even more of the heat. He also argued that the reverse could happen and that a major decrease in carbon dioxide could result in a cooling effect that might even cause another Ice Age. Today, many scientists think that global warming is in fact occurring, and that it is caused by the carbon dioxide released when fossil fuels, like coal, are burned in factories and power plants. Arrhenius was certainly a man ahead of his time.

Steps are being taken to prevent possible disastrous effects from happening. Efforts to reduce the pumping of greenhouse gases (carbon dioxide, methane, and nitrous oxide) into the atmosphere have begun in certain countries. This involves making automobile engines more efficient and clean, or better still, encouraging the use of public transportation. Electric cars soon may become practical. The use of nitrogen-based fertilizers can be reduced, and the destruction of entire forests can be stopped. International agreements have already been made to reduce the production of such gases by industry. Many scientists point to the nearby planet Venus as an example of what could happen if a "runaway" greenhouse effect ever occurs. The atmosphere around Venus keeps its surface temperatures as high as 932°F (504°C). To date, there is no evidence of life on Venus.

[See alsoCarbon Dioxide; Forests; Ozone; Pollution; Rain Forests ]