The greenhouse effect is a term that describes an increase in the average global temperature and is often associated with global warming which is the subject of great debate and concern worldwide. Although warnings about the human-generated causes of an enhanced greenhouse effect and the subsequent catastrophic outcomes have been sounded for over 100 years, global warming has only recently become an important political matter, at least in the U.S. President Bush, for the first time in his term of office, referred to the subject in his State of the Union speech earlier this year. Even then, he chose his words carefully by calling this phenomenon, ‘global climate change.’ This discussion will first define the greenhouse effect then explain how naturally occurring and man-made gases affect it along with examples of the consequences of these forces.
Essentially, the greenhouse effect functions in the following manner. When sunlight pierces the atmosphere and hits the earth’s surface, not all of the sun’s solar energy is absorbed. Approximately a third of it is reflected back into space. Specific atmospheric gases serve in much the same way as does the glass of a greenhouse, thus the terminology. These gases allow sunlight to penetrate then trap some of the solar energy which heats the earth (Breuer, 1980). It is a delicate balance and because these greenhouse gases have been artificially augmented by man-made sources, more build-up in the atmosphere has occurred thus trapping more of the sun’s energy and reflecting less back into space. This occurrence is causing the earth to warm.
The rising levels of carbon dioxide (CO2) in the atmosphere are becoming increasingly disconcerting. “The concentrations of CO2 in the air around 1860 before the effects of industrialization were felt, is assumed to have been about 290 parts per million (ppm). In the hundred years and more since then, the concentration has increased by about 10 percent” (Breuer, 1980, p. 67). Eighty percent of the world’s population accounts for just 35 percent of CO2 emissions while the United States and Soviet Union combined are responsible for generating half. Worldwide, “carbon dioxide emissions are increasing by four percent a year” (Miller, 1990, p. 450). Motor vehicles are a major cause of air pollution as is fuel burned for the heating of homes and powering industry along with the toxins emitted from stacks at coal-burning power plants. “Vehicles produce high levels of carbon monoxides (CO) and a major source of hydrocarbons (HC) and nitrogen oxides (NOx), whereas, fuel combustion in stationary sources is the dominant source of sulfur dioxide (SO2)” (Breuer, 1980, p. 70).
If the balance between the CO2 levels in the ocean and atmosphere is disturbed by interjecting increasing amounts of CO2, the oceans would continually absorb higher concentrations than it does naturally. The subsequent warming ocean waters are less effective in their ability to absorb CO2 and when the oceans can no longer keep pace with the intrusion of this naturally equalized cycle, then more CO2 will remain in the atmosphere. Increasing the amount of CO2 in the atmosphere is expected to result in a warming of the Earth’s surface accelerating the greenhouse effect. “Currently carbon dioxide is responsible for 57 percent of the global warming trend. Nitrogen oxides contribute most of the atmospheric contaminants” (Miller, 1990, p. 498).
The scientific community agrees that global temperatures are rising due to the burning of fossil fuels which are damaging the protective atmospheric Ozone layer by changing its composition. Human pollution is changing the climate of our earth and has increased global warming in the past half-century. The effects are being felt worldwide, not just in the U.S. where most of the CO2 emissions are generated. In the UK., for example, four of the five warmest years for more than three centuries have occurred in the last 10 years. Scientists predict that in 50 years, annual temperatures in the southeast of England could be at least three degrees (Fahrenheit) warmer, on average, than they are now (Climate Crisis 2000). Global warming is further evidenced by the well-documented melting of glaciers along with the thermal expansion of the oceans, which have contributed to an increase in sea level over the past century of about six inches in that country (Trenberth 1997).
Studies have been conducted by the National Aeronautics & Space Administration (NASA) have demonstrated that the past decade has been the warmest on record. At first thought, especially during the cold winter months, a little warming wouldn’t seem to be such a bad thing. Several varieties of fruits and vegetables could be produced in northern climates that today only grow in warmer climates. Warmer seas are likely to be attractive to more species of fish to the colder habitats as well. This is not to mention additional tourist currency to what would be the warm, sandy beaches of Canada or England (Climate Crisis 2000). However, as in everything, there is a downside and in this case, one of the horrific proportions. Studies in the UK have found that warming could increase rainfall by more than 20 percent during the winter by the 2080s and decrease it by the same amount during summer months in the southern half of that country. This would cause severe droughts in some regions but areas such as East Anglia, a very low-lying region on the east coast of England, could very well be underwater altogether.
One would have to wonder what enormous problems this will cause not only to people and property but to the health of the global economy as a whole. Entire sections of various countries will be forced to abandon their homes and businesses. The process will be a slow and torturous one. Scientists also worry about the effects of a changing climate on the Gulf Stream, a massive ocean current that acts to warm the continent of Europe. “Ocean currents transport large amounts of heat around the world: climatologists call it thermohaline circulation (THC)” (Climate Crisis 2000). If it slows down or moves further south as a result of Greenland melting, Europe could end up with a climate more like that of present-day Greenland. A BBC-produced television program documented recently that Greenland is in fact melting at an alarming rate providing photographic evidence taken in the 1970s in contrast to photographs taken in the present day.
Future scenarios for greenhouse gas quantities, especially regarding CO2 and CH4, are hardly exactly known when attempting to project future climate changes. Formulating the net greenhouse effect is complex because of its associations to supplementary aspects of energy cycles. However, the period of time that records have been kept is sufficient now to make comparative trends regarding the effects of climate change. One of the problems regarding measuring global warming is that the phenomenon is not occurring in a uniform and steady manner. Many areas of the world, in fact, most, experience a wide variation of temperature and climatic effects from year to year (Wunderlich & Kohler, 2001). Thus the feedback from studies is vulnerable to challenges made by a minority of scientists, politicians, and other citizens who have, for whatever reason, an agenda that compels them to rebuke the overwhelming evidence that man-made causes are accelerating the greenhouse effect.
The effects of melting snowcaps and the resulting rise of sea levels have been well documented. Other effects are known but not as universally. A reduction of snow cover in addition to the lake and sea ice will have dire consequences for locations at higher latitudes and lower elevations, especially in the winter and spring months. At increased temperatures, the atmospheric water vapor and resulting precipitation will be proportionately higher (Wunderlich & Kohler, 2001). Cloud compositions will change which will amplify the greenhouse effect. The increased levels of precipitation because of the warming in the polar regions will increase the effect. Shifting vegetation patterns, types, and regional variations will cause major human adaptations, the degree to which is open to speculation.
The elevated evaporation rate will hasten the drying effect of soil subsequent to rainfall which will result in drier conditions in many regions. Places that presently suffer through periodic drought conditions in the warmer months will be the hardest hit. The more rapid water recycling rate will result in heavier rainfall amounts and the number of extreme rainfall events. Higher rainfall rates will cause increased tropical storm intensity in addition to the warmer temperatures. Hurricanes maybe even more frequent and intense than presently predicted. As horrific as this near-future scenario is, it remains the landmasses that will suffer the greatest changes as a result of the greenhouse effect. “Temperatures are expected to increase more rapidly over land compared to oceans because of the ocean’s higher heat capacity and because it can transfer more of the trapped heat to the atmosphere by evaporation. Overland, the warming has been and is expected to continue to be larger during nighttime than during daytime” (Wunderlich & Kohler, 2001).
Most scientists worldwide accept the sufficient evidence that suggests global warming is already well underway and cannot be reversed anytime soon. They and reasonable people of all backgrounds and nationalities agree that if CO2 emissions are not greatly reduced and soon, the resulting greenhouse effect will alter the climate and possibly the sustainability of humankind.
Breuer, Georg. (1980). “Air in Danger: Ecological Perspectives of the Atmosphere.” New York: Cambridge University Press.
“Climate Crisis: All Change in the UK?” (2000). BBC News. Web.
Miller, G. Tyler. (1990). “Living in the Environment: An Introduction to Environmental Science.” Belmont: Wadsworth.
Trenberth, Kevin E. (1997). “Global Warming: It’s Happening.” National Center for Atmospheric Research. Web.
Wunderlich, Gooloo S.; Kohler, Peter O. (2001). “Improving the Quality of Long-Term Care.” The National Academies Press. p.18.