Question

Which of the following is a greenhouse gas?
A. Methane
B. CO
C. Water vapour
D. oxygen

Answer 1

Hint: The term Greenhouse effect has been driven by a phenomenon that occurs in a greenhouse. It looks like a small glasshouse and is used for growing plants especially during winter. In a greenhouse, the glass panel lets the light in, but does not allow the heat to escape. Therefore, the greenhouse warms up, very much like inside a car that has been parked in the sun for a few hours.

Complete answer:
Let us first know about the mechanism of the Greenhouse effect.
Clouds and gases reflect about one-fourth of the incoming solar radiation and absorb some of it, but almost half of the incoming solar radiation falls on Earth’s surface heating, while a small portion is reflected.
Earth surface re-emits heat in the form of infrared radiations but part of this does not escape into space as atmosphere gases absorb a major fraction of it.
The molecules of these gases radiate heat energy and a major part of it again comes to earth's surface, thus, heating it once again. This downward flux of radiation is called greenhouse flux. This cycle is repeated many times. The gases like carbon dioxide and methane are commonly known as greenhouse gases because they are responsible for the greenhouse effect.

Hence, the correct answer is option (A).

Additional information:
Greenhouse gas effect
-Carbon dioxide fertilization effect: Increase in the atmospheric concentration of carbon dioxide increases the productivity of some plants and decreases the rate of transpiration due to partial stomatal closure.
-Melting of polar ice caps.
-Rising of sea level, changes in rainfall pattern
-Warming of the troposphere and cooling of the stratosphere and thermosphere.
-The temperature of the earth has increased by 0.6-degree Celsius.

Note: Apart from carbon dioxide and methane, the other gases are CFCs (chlorofluorocarbons) and nitrous oxide. The relative contribution of various greenhouse gases to the total global warming is
Carbon dioxide- 60%
Methane- 20%
CFCs- 14%
Nitrous oxide- 6%
The IPCC or Intergovernmental panel on climate change periodically monitors the atmospheric concentration of greenhouse gases.