Page 21 - GEL 1103 เอกสารประกอบการเรียนบทที่ 2

English for Communication and Study Skills

greenhouse gases, absorb a portion of this heat and then radiated heat
back toward Earth. This keeps Earth warmer than it would be otherwise.

Source: National Geographic, McGraw Hill (2008).

Source: National Geographic, McGraw Hill (2008).

 The Carbon Cycle
Carbon, primarily as carbon dioxide, is constantly recycled in
nature among the atmosphere, Earth’s oceans and organisms that inhabit
he land. Organisms that undergo photosynthesis on land and in the water
take in carbon dioxide and produce and store carbon based food. This
food is consumed by non-photosynthetic organisms. Carbon dioxide is
released as food is broken down to release energy. When organisms die
and decay, some carbon is stored as humus in soil and some carbon is
released as carbon dioxide. This carbon cycle is illustrated in the picture.
Some carbon dioxide in the atmosphere dissolves in the oceans,
and is used by algae and other photosynthetic, aquatic organisms. Just as
on land, aquatic organisms give off carbon dioxide. However, Earth’s
oceans currently absorb more carbon dioxide from the atmosphere than
they give off.

When Earth’s climate changes, the amount of carbon dioxide that
cycles among atmosphere, ocean, and land also can change. Some people
hypothesize that if Earth’s climate continues to warm, more carbon
dioxide may be absorbed by oceans and land.

Source: National Geographic, McGraw Hill (2008).

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