“The GREENHOUSE Effect”

My term paper in Natural Science is about “The GREENHOUSE Effect”.

In the past several years, we have heard scientists and prominent people talk repeatedly about global warming, claiming that it is among the greatest, if not the greatest threat to human life to date. The latest among these prominent environmentalists is former US Vice President Al Gore, who, in his groundbreaking presentation/movie documentary  “An Inconvenient Truth“, effectively and vividly projected a most plausible scenario of human live in a planet under the conditions of the greenhouse effect. In a website featuring this documentary, it said that “The vast majority of scientists agree that global warming is real, it’s already happening and that it is the result of our activities and not a natural occurrence.”
It was with this presentation/documentary that eventually led him to gain a Nobel Prize in 2004. After him, Leonardo de Caprio jumped into the bandwagon with his “the 11th Hour“ , and a string of documentaries followed which further pushed the work of teaching the world about the greenhouse effect and its impact on live on earth.
Scientifically, the greenhouse effect is defined as the heating of the earth’s surface due to the atmosphere containing gases that absorb and emit infrared radiation. The term greenhouse effect is a simplistic description, even if the analogy is not exactly right. A greenhouse works by isolating heated air inside a structure so that the warmth is not lost by convection. The greenhouse effect, however, traps warmth within the surface-troposphere system, the air, itself.
The greenhouse effect was discovered by Joseph Fourier in 1824, first reliably experimented on by John Tyndall in 1858, and first reported quantitatively by Svante Arrhenius in 1896. Yet, it was only in the mid-90s, particularly with the Rio de Janiero Earth Summit , that governments of the world recognized and accepted the fact and problem of global warming and the greenhouse effect. In fact it was only nearly a whole century after the greenhouse theory was first proposed, that governments decided to adopt what is now known as the Kyoto protocols , which specifies limits to the greenhouse gases that countries may permit their respective industries to spew out into the atmosphere.
Specifically, the greenhouse effect is created by the increase of gases that trap the energy that is released by the sun. The sun, acting like a big radiator, sends a regular stream of energy in the form of light, which reaches the earth and gets absorbed by the atmosphere. Various components of earth's atmosphere absorb ultraviolet and infrared solar radiation before it penetrates to the surface, but the atmosphere is quite transparent to visible light.
Absorbed by land, oceans, and vegetation at the surface, the visible light is transformed into heat and re-radiates in the form of invisible infrared radiation. If that was all there was to the story, then during the day earth would heat up, but at night, all the accumulated energy would radiate back into space and the planet's surface temperature would fall far below zero very rapidly. The reason this doesn't happen is that earth's atmosphere contains molecules that absorb the heat and re-radiate the heat in all directions. This reduces the heat radiated out to space. Called 'greenhouse gases' because they serve to hold heat in like the glass walls of a greenhouse, these molecules are responsible for the fact that the earth enjoys temperatures suitable for our active and complex biosphere.
In normal circumstances, a greenhouse effect is a requirement for life to exist, as it raises the temperature of the surface of a planet permitting it to sustain life. In the absence of the greenhouse effect and an atmosphere, the Earth's average surface temperature of 14 °C (57 °F) could be as low as −18 °C (−0.4 °F), the black body temperature of the Earth. For at least the last 100,000 years atmospheric CO2 naturally generated and consumed by animals and plants was in rough equilibrium. Without this characteristic of holding in heat the globe's mean temperature would be in the 40s rather than a comfortable 59 degress Fahrenheit
Carbon dioxide, water vapor ( ), methane ( ), nitrous oxide ( ), and a few other gases are greenhouse gases. They all are molecules composed of more than wo component atoms, bound loosely enough together to be able to vibrate with the absorption of heat. The major components of the atmosphere ( and ) are two-atom molecules too tightly bound together to vibrate and thus they do not absorb heat and contribute to the greenhouse effect. Carbon dioxide ( ) is one of the greenhouse gases. It consists of one carbon atom with an oxygen atom bonded to each side. When its atoms are bonded tightly together, the carbon dioxide molecule can absorb infrared radiation and the molecule starts to vibrate. Eventually, the vibrating molecule will emit the radiation again, and it will likely be absorbed by yet another greenhouse gas molecule. This absorption-emission-absorption cycle serves to keep the heat near the surface, effectively insulating the surface from the cold of space.
However, with the advent of technology, humans have began burning fossil fuels, thereby increasing the amount of carbon gases in the air. The progress of industry also resulted in the increased cutting down forests, not just pumping billions of tonnes of carbon dioxide (CO2) into the atmosphere, but lessening the ability of the earth to absorb carbon dioxide from the atmosphere. We also add other gasses to the atmosphere in smaller quantities, such as methane, and chlorofluorocarbons, which are released into the atmosphere by burning fossil fuels and by manufacturing.
Over the past 250 years, carbon dioxide levels have increased by 25%. Presently, it is the most abundant trace gas in the atmosphere. This has been due primarily to the use of fossil fuels. Several studies have concluded that CO2 emissions may alter the radioactive balance of the earth, increasing the global temperature and dramatically changing global climate.
The increase in temperature is expected to have significant effects. Deaths from global warming are expected to double in just 25 years -- to 300,000 people a year.6 Global sea levels could rise by more than 20 feet with the loss of shelf ice in Greenland and Antarctica, devastating coastal areas worldwide.7 Heat waves will be more frequent and more intense. Droughts and wildfires will occur more often. The Arctic Ocean could be ice free in summer by 2050.8 More than a million species worldwide could be driven to extinction by 2050.