Since the beginning of the industrial revolution some 200 years ago, machinery and fossil fuels have saved inestimable amounts of time and labor, while substantially raising the standard of living around the world. It is perhaps ironic that the same technology could change the Barth’s climate and threaten its future.
In 1896, a Swedish chemist, Svante Arrhennius estimated that the carbon dioxide concentration would double and the Earth’s surface would warm by approximately five degrees. Today we realize that his estimate and concern for the environment may not have been very far off the mark. In 1990, the U.S. government had allocated five hundred million dollars for research into global warming. (Davies, 1990)
Global warming is a great topic to include in a curriculum unit. Aside from the fact that global warming has received wide media coverage and all students have heard or read about it in the news, analysis of the problem also shows that pollutants affect more than one part of our environment. Substances which may contribute to global warming include; CFC’s, methane , nitrogen oxides and carbon dioxide (this has received the most press). Lastly, students will be able to see how a basic principle supporting life on Earth can go “haywire.” See appendix page 17.
The surface of the Earth is heated by incoming solar radiation. The earth then remits some of this energy as infrared radiation (ex. radiation of much lower frequency). Some of this infrared radiation escapes directly into space, but much is absorbed by gases in the atmosphere like water vapor, carbon dioxide and ozone. The absorption process traps energy and heats the atmosphere much like a greenhouse traps heat. Therefore, this atmospheric process is known as the “greenhouse effect.” The amount of energy trapped by greenhouse gases is equivalent to sixty-five percent of the energy received from the sun, and is therefore critical for establishing the average surface temperature of the Earth. The average temperature on earth is 15 degrees centigrade. (U.S. D.C. & NOAA, 1989)
If we didn’t have an atmosphere, the temperature on earth would be 33 degrees centigrade cooler (60 degrees Fahrenheit) colder. Venus with a thick atmosphere of carbon dioxide has an average surface temperature of 470 degrees centigrade. Mars, with a thin atmosphere has an average surface temperature of -60 degrees centigrade. (NOAA & UCAR, 1991)
A greenhouse effect is essential to life. If there were no global warming or trapping of radiation by the greenhouse gases, our planet would be covered by ice. Past temperature fluctuations on earth before the industrial age have occurred naturally, and have included ice ages and desertification. Most scientists foresee a doubling of carbon dioxide occurring in the next century and are concerned about the resulting global warming leading to great changes in the earth’s climate. (Albritton, 1990)
Due to increases in the greenhouse gases, some computer models show a possible rise of 1-3 degrees centigrade (1.95.7 F) in temperature. (UDC & NOAA, 1989)
According to the World Resources Institute, various human activities involving energy use (49%), industrial processes (24%), deforestation (14%) t and agriculture (13%) all contribute to global warming by increasing the amount of the following greenhouse gases: methane, ozone, carbon dioxide and the man-made gases CFC’s and nitric oxide. (World Resources Institute, 1990-1991)
Carbon dioxide today comes into the atmosphere from the burning of fossil fuels, deforestation, soil processes, and wood burning. It has a lifetime in the atmosphere of 2-3 years and is increasing at a rate of .3% per year. Carbon dioxide contributes 49% to global warming. (Gawell, 1989)
Methane comes from rice paddies, cattle and other livestock, termites, deforestation, wood burning and landfills. It has a lifetime of 5-10 years. Methane is increasing by .8-1.0% per year and contributes 18% to global warming. (Gawell, 1989)
CFC’s, chemicals used in refrigeration, insulation, foams, aerosol propellants and in other parts of industry, have a lifetime of 75- 400 years and are increasing by 4% per year and contribute to heating by 14%. (Gawell, 1989)
Nitric oxide comes from fertilizers, land-use changes, wood burning, coal and oil combustion. It has a lifetime of 100- 175 years. It is increasing by .2% per year and contributes to warming by 6%. (Gawell, 1989)
Ozone (tropospheric) at lower elevations adds to the warming process. Its formation is catalyzed by other gases such as nitric oxide. In the troposphere, ozone has a lifetime of 5 months and is increasing by .2-1% per year. Ozone is responsible for 3% of the total global warming. (Gawell, 1989)
We need the greenhouse effect and global warming to live, but what if these artificial increases in the greenhouse gases (caused by man) raise the earth’s temperature? Is this already occurring? This is where the controversy lies.
The years 1987 and 1988 were the hottest on record. (atmosphere, 1992) With the heat wave and floods of 1993 the question of global warming will take center stage again.
The earth does have a natural buffering or neutralization system to get rid of carbon dioxide, but will it be enough or be able to work fast enough? The oceans contain 95% of the carbon actively circulating in the biosphere and the carbon cycle found within it provides the main long-term control of atmospheric carbon dioxide. This determines the strength of the natural greenhouse effect and has been closely involved in previous climate changes. (American Chemical Society, 1990)
Presently, the net oceanic uptake of carbon is not keeping pace with the increasing carbon dioxide emissions, and is causing great uncertainty. Human activities currently release about 7-8 GT (1 GT=10
12
kg.) of carbon per year and the atmosphere accumulates around 3.5 GT per year. Net oceanic absorption is approximately 1-3 GT per year. (American Chemical Society, 1990)
Carbon dioxide is withdrawn from the ocean’s surface by photosynthesis (phytoplankton). Also, the ability of the ocean to absorb carbon dioxide is strongly related to ocean temperature. Thus, oceans are key players in future global warming. (American Chemical Society, 1990)
While the jury’s still out on whether the increase in carbon dioxide in the atmosphere will add to the warming of the earth should we take the chance? Global warming receive attention in the media until a couple of years ago Pinatubo exploded. Mt. Pinatubo spewed gases into the atmosphere and cooled the atmosphere by a degree or two. With its gases now dissipated, and a very hot and dry spring/summer in 1993, will this controversy be renewed in the media?
What if the oceans and other parts of the biosphere cannot absorb all the extra gases? Do we really need to find out and shouldn’t we get rid of all the possibilities? Many articles and even a TV movie this past year have focused on the possible consequences of a rise in the earth’s temperature. These possibilities include extinction of plants and animals, failed crops, deforestation, a rise in sea levels and thus flooding, droughts, tropical diseases, monsoons and hurricanes. (Gawell, 1989)
The media has been giving much attention to the disappearing rainforests in South America, but what about other places on earth. Each tree absorbs as much as 36 pounds of carbon dioxide per year and thus are vital to maintaining the earth’s climate. (World Resources, 1990-1991)
As stated previously, our government as well as some others are trying to reduce air pollution and thus greenhouse gas emissions through a variety of laws and regulations; but not every country is pursuing the same goal. An example is China. China’s fast growing economy is primarily due to the burning of coal. Carbon emissions in China have increased by 65% in the past decade and China now contributes 11% of global carbon emissions. (Lenssen, 1993) See appendix page 18
CFC’s are 10,000 times better at blocking radiation than carbon dioxide, but there are 35,000 times more carbon dioxide molecules in the atmosphere. The U.S. is responsible for the
largest portion of man-made contributions to the greenhouse effect—21%, USSR- 14%, Europe- 14%, China 7% (this figure all gases), Brazil—4%, India-4% and others 36%. (Morgenstern & Tirpac, 1990)
Cows, coal mines and landfills are major sources of methane which is second only to carbon dioxide in contribution to the greenhouse gases. 1 gram of methane in the atmosphere absorbs infrared radiation about 70 times more effectively than one gram of carbon dioxide lifetime of 10 years and is considered an excellent target for reduction. More than 3 billion animals (cattle, sheep, goats, buffalo, camels, and others) account for 15-20% of the annual methane emissions. Recommendations include ; better control of animal feed and waste. In coal mining there is capability to recover 50% of the methane produced. Removal of methane from landfills is also suggested. Reduction of methane from-rice paddies by better irrigation, fertilizer practices and cultivation is also possible. (Gibbs & Hogan, 1990)
Skeptics of global warming include Richard S. Lindzen a professor at MIT. He believes that the present fluctuations in the earth’s temperature are part of normal patterns and should not be a concern. (Lindzen, 1990)
Should we take the chance?