Al Gore in his book “an inconvenient truth” begins his book with this picture and the statement “This is the first picture most of us ever saw of the Earth from space. It was taken on Christmas Eve, 1968 by one of the astronauts aboard the Apollo 8 spacecraft.” Thus, this is the way I begin this essay.
It is essential that that we understand some terms before proceeding further.
- Greenhouse effect: light and heat from the sun enters the atmosphere striking the earth’s surface where some is absorbed by surface features and converted into other forms of energy such as chemical energy of food. QUIZ TIME: What Is the process called? Answer at end of essay. Some is radiated back into space, and some is trapped in the atmosphere by clouds and various pollutants thereby raising the temperature similar to a hothouse or greenhouse; thus the term “greenhouse effect”.
- Global warming: the cumulative result of the greenhouse effect on a worldwide basis
The greenhouse effect exists all the time, maintaining the average climate of the world at about 60 ͦ F. The earth’s atmosphere is what keeps us at an “average temperature”. Global warming and the greenhouse effect are phrases that appear regularly in the mass media. Quoting from an earlier essay, “The transfer rate of carbon from the atmosphere by photosynthesis just about equals the rate at which respiration and decay return carbon to the atmosphere. However, when fossil fuel burning is added to the equation, the rate of CO2 returned to the atmosphere is greatly favored.”
In 1991 the National Association of Biology Teachers (NABT) adopted the following position.
Causes of Climate Change
- Increased use of fossil fuels
- Increased rate of deforestation, resulting in less carbon “locked up” in the forest
- Increased amount of “greenhouse gases” (CO2,CH4 (methane), N2O (nitrous oxide), CFCs (chlorofluorocarbons)) causing the atmosphere to absorb radiant heat
- Growth of the human population as it affects all of the above
Consequences of Global Warming .
- Shifting of agriculture zones
- Desertification and local mass extinction
- Changes in animal migration patterns
- Sea levels rise as a result of melting polar ice and thermal expansion in the oceans, which can cause destruction of human structures and natural habitats along sea coasts
Possible Actions to Reduce Climate Change
- Reduce fossil fuel consumption by increasing efficient use of energy
- Decrease deforestation and encourage reforestation
- Use education to increase public awareness
- Control human population growth, possible reversing it
- Use alternative energy resources and recycle
- Promote education, awareness, political priorities and international efforts and cooperation
Stephen Schneider writing in the Scientific American (September 1989) recalls that in 1957 Roger Revelle and Hans E. Suess of the Scripts Institution of Oceanography noted that “humanity is performing a great geophysical experiment” not in a laboratory or on a computer, but on our own planet. Al Gore in his book “an inconvenient truth” includes a graph of Revelle’s work. It indicates a steadily increasing CO2 in the atmosphere which continues today. Revelle also explains why the CO2 level varies from one hemisphere to the other and why it changes seasonally. As stated in an earlier essay, the majority of land masses lies north of the equator which contains the most vegetation. The levels decrease in summer when photosynthesis is rapidly occurring and increases in fall and winter when deciduous trees drop their leaves
This experiment essentially began at the beginning of the Industrial Revolution. Since then we have increased the atmospheric content of carbon dioxide by about 25 percent by burning oil, coal, and other fossil fuels. This along with clearing forests and decomposition of dead organic matter removes a source of CO2 sequestration from the atmosphere. Carbon dioxide makes only about 0.03% of the atmosphere but along with water vapor and other greenhouse gases such as methane (CH4) greatly affects the earth’s climate. Even as early as the early 1800’s people knew that like a greenhouse which allows sunlight to enter but traps the heat inside, such gases absorb the longer wavelength infrared rays thereby trapping the heat and gradually raising the temperature, Think about which nights trap the heat the most and keep the temperature warmer, cloudy nights or clear?
The following graphs compares the levels of carbon dioxide equivalent in megatonnes in 2005 and 2013 and the worst culprit.
The following diagram indicates how some of the solar radiation strikes the earth and is absorbed, some is radiated back into space, and some is trapped in the atmosphere and the role of greenhouse gasses including water (vapor in the form of clouds). In a later essay I will compare the absorption and reflectivity rates of soil, blacktopped and paved areas, and glaciers including glaciers that have disappeared leaving brown areas
Answer to quiz question: photosynthesi
References
National Association of Biology Teachers (NABT) 1991
Schneider, S. (1996) Laboratory Earth Weidenfeld & Nicolson London
Gore, A. (2006) an inconvenient truth Viking, Rodale New York, NY
