The Greenhouse Effect and
Global Climate Change
The physical conditions that make the earth a hospitable place for life are similar to the ones that make
greenhouses suitable places to grow plants. The windows of a greenhouse serve two purposes: to allow heat
from the sun into the greenhouse, warming everything inside, and to trap heat inside the greenhouse, which
is especially important. As the interior of the greenhouse becomes warm, like any other warm object, it begins
to emit heat. This heat, emitted by the warm interior of the greenhouse, needs to be trapped in order to keep
the greenhouse warm enough to grow plants. This combination of the transmission and trapping of heat is
called the greenhouse effect.
So how is the earth like a greenhouse? The earth’s atmosphere creates an effect similar to the windows of a
greenhouse. It allows energy from the sun to reach the earth’s surface, while trapping the energy emitted by
the warm objects on the earth. The energy from the sun alone would not be enough to support life; the
trapped energy provides the remaining heat needed to make life on Earth possible. (Of course, the actual
process by which Earth’s greenhouse gases trap heat—shown below—is different from what happens in a
greenhouse, but a greenhouse is a good analogy.)
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Certain gases within the atmosphere, called greenhouse gases, trap the energy emitted by the warm surface
of the earth. The major greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and
carbon compounds, such as hydroflourocarbons and perflourocarbons. Many of these gases occur naturally in
the environment. For example, forest fires produce carbon dioxide. Methane is produced when organic matter
decomposes. However, certain human activities also release greenhouse gases. The greenhouse gases that are
released may increase the concentration of greenhouse gases in the atmosphere. Table 3.1 displays a list of
the most common greenhouse gases and the human activities that produce these gases.
Table 3.1: Greenhouse Gases and Their Sources
Greenhouse Gas Human Activity Source
Carbon dioxide (CO2) • Burning fossil fuels, such as oil, natural gas, and coal, for power generation
• Industrial processes of forest clearing, natural gas flaring, and
• Manufacturing of cement, iron, steel, and aluminum
Methane (CH4) • Use of wetlands for rice cultivation
• Digestion processes of common livestock, such as cattle
• Production and distribution of fossil fuels
• Decomposition of organic waste in landfills
Nitrous oxide (NO) • Fertilization of soil, using nitrogen-based compounds
• Combustion of fossil fuels
Hydroflourocarbons • Processing of aluminum
(HFCs), perflourocarbons • Electric power transmission and distribution
(PFCs), and sulfur • Manufacturing of semiconductors
Global Climate Change
Thanks to the heat trapped by the greenhouse gases, the earth’s temperature in the past averaged close to
60oF, a reasonable temperature to support life. Since the Industrial Revolution, however, the atmospheric
concentrations of carbon dioxide have increased by nearly 30 percent, methane concentrations have more
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than doubled, and nitrous oxide concentrations have increased by close to 15 percent. The higher concentrations
of greenhouse gases have increased the atmosphere’s heat-trapping ability. Many scientists now believe that
this increased capacity to trap heat has led to a gradual increase in the average global temperature, which
is an example of global climate change. The following graph shows how the average temperature of the
earth has changed between 1880 and 2000.
Global Temperature Changes (1880–2000)
Should We Be Concerned?
Rising global temperatures are expected to change precipitation levels and climate patterns in nearly every
part of the world. These changes could affect human and animal health, crop yields, and ecosystems. Though
we can’t be certain to what extent the increased concentration of greenhouse gases due to human activities is
the cause for the rise in global temperatures, we know for sure that an increased average temperature will
change the earth’s climate and weather patterns. Because we depend on the earth for all our natural
resources, it is important to minimize the impact we have on the environment.
What Can We Do?
The most prevalent greenhouse gas in the atmosphere is carbon dioxide. In our current industrialized world,
it is difficult to live a single day without playing a part in the creation of carbon dioxide. Carbon dioxide is
produced when fossil fuels are burned to heat buildings and homes, produce electricity, and power cars.
Throughout the world, generation of electricity from fossil fuels contributes to the concentration of the carbon
dioxide found in the atmosphere.
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Acknowledging the increase in the atmospheric concentrations of greenhouse gases, countries around the
world are beginning to monitor greenhouse gas emissions and work toward reducing the levels of green-
house gases that are being released. Companies and businesses are recognizing that even if they do not
release greenhouse gases from their buildings or facilities, they are responsible for their own energy use and
the emissions that result from their demand for electricity.
What can you do to reduce greenhouse gas emissions? The first step might be to think about the activities
you do that require fossil fuels. Can you carpool to school with a group of friends? How many lights do you
need on at once? Could you turn down your thermostat in the winter and wear a sweater?
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