In the early 1980s scientists began raising concerns about global warming and climate changes. Initially these concerns about human-induced climate changes were met with skepticism because there are natural cycles of climate changes that occur over hundreds of years. Those who tried to raise the importance of this issue, and suggest that perhaps we were over-consuming or unsustainably using our resources, were faced with a lot of criticism and ridicule (Shah, 2005). That early skepticism of the 1980s and 1990s has been replaced with a mainstream scientific consensus on global warming--that changes in our climate are real and that continued human-induced global warming cannot be ignored. Today, the body of research accumulated over the past 25 years indicates that humans are a major factor in the current climate changes. More and more we are realizing that the Industrial Revolution has changed forever the relationship between humanity and nature. There is real concern that by the middle or the end of the next century, human activities will have changed the basic conditions that have allowed life to thrive on earth. The results are uncertain, but if current predictions prove correct, the climatic changes over the coming century will be larger than any since the dawn of human civilization (UNEP/WMO, 1994).
What is Global Warming?
Global warming is the progressive, gradual rise of the earth's average surface temperature, thought to be caused in part by increased concentrations of "greenhouse" gases (GHGs) in the atmosphere. According to the National Academy of Sciences, the Earth's temperature has risen by about one degree Fahrenheit in the past century, with accelerated warming during the past two decades. Analysis of the various human and natural influences on the global climate indicates that this warming cannot be explained without taking into account human emissions of GHGs. Current scientific data indicates that these "greenhouse" gases have been the dominant force driving temperature increases over the past 50 years. Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases--primarily carbon dioxide, methane, and nitrous oxide. The heat-trapping property of these gases is undisputed, although uncertainties exist about exactly how earth's climate responds to them (Environmental, 2005).
The Greenhouse Effect
The term greenhouse is used in conjunction with the phenomenon known as the "greenhouse effect." Energy from the sun drives the earth's weather and climate and heats the earth's surface; in turn, the earth radiates energy back into space. Roughly 30 percent of the total solar energy that strikes the earth is reflected back into space by clouds, atmospheric aerosols, reflective ground surfaces, and ocean surfaces, Figure 2. The land, air, and the oceans absorb the remaining 70 percent. Atmospheric greenhouse gases (water vapor, carbon dioxide, methane, nitrous oxide, and other gases) trap some of the out-going energy, retaining heat much like the glass panels of a greenhouse. Without this natural "greenhouse effect," temperatures would be much lower than they are now and life as we know it would not be possible. Greenhouse gases are responsible for maintaining the earth's average temperature at approximately 60 degrees Fahrenheit. What has many people worried now is that, since the Industrial Revolution, humans have been artificially raising the concentration of greenhouse gases in the atmosphere, causing the greenhouse effect to get stronger, trapping more heat than needed and raising the average temperature of the earth's surface, which, if left unchecked, could eventually cause the planet to become much less habitable for humans, plants, and animals.
[FIGURE 2 OMITTED]
Our factories, power plants, and cars burn coal and gasoline, pumping millions of tons of carbon dioxide into our atmosphere. …