In the online textbook, the materials used to discuss the meaning of the
term being defined are called:
Sources of definition
Short definitions
Formal sentence definitions
Sources of description
Description
The next questions are based on the following extended definition:
The so-called greenhouse effect is an atmospheric process by which a
portion of the sun's heat is trapped within the earth's atmosphere, making
the earth's surface warmer than it would otherwise be. Life on earth is
possible because there is liquid water, a blanket of life-supporting gases,
and a climate neither too warm nor too cold. Human beings may now be
altering this balance by adding unusual amounts of carbon dioxide to the
atmosphere. This could make the global climate warmer than at any other
time in human history. And this change would be irreversible.
The atmosphere contains 75% nitrogen, 23% oxygen, with argon, water vapor,
and trace gases--including carbon dioxide--making up the remaining 2%.
Carbon dioxide is an odorless, colorless gas which constitutes about 0.035%
by volume of the atmosphere but whose significance far exceeds its relative
scarcity. It is essential for photosynthesis, the process by which the
sun's energy is converted into forms usable by plants and animals. It also
helps regulate the critical heat balance of the planet, thus maintaining
liquid water.
Carbon dioxide affects the heat balance by acting as a one-way screen. It
is transparent to incoming visible sunlight and allows the sun's heat to
warm the ocean and the land. But carbon-dioxide molecules block some of the
infrared heat radiated back into space. This reflected heat is absorbed
into the lower atmosphere. This is the so-called greenhouse effect . . .