Greenhouse Effect: Definition, Meaning, Diagram, Examples, Facts, Causes, Effects

Greenhouse Effect Definition

The greenhouse effect refers to the process by which certain gases in Earth's atmosphere trap heat, preventing it from escaping into space. This natural phenomenon is essential for maintaining Earth's temperature, but human activities, such as burning fossil fuels, have intensified it, leading to global warming and climate change.

What Is the Greenhouse Effect?

The greenhouse effect is a naturally occurring process that plays the important role of ensuring that the Earth maintains the correct temperatures for life to be sustained. It is a process by which some gases in the atmosphere interact with incoming energy from the sun.

The sunrays reach the surface and reflect into space, but it warms the Earth's surface, meaning the heat is radiated. Part of it gets to be diffused back into space, but some bit is retained by the greenhouse gases in the atmosphere. This trapped heat acts like an insulative blanket draped over the planet's surface, keeping it warmer than it would otherwise, thereby maintaining a stable climate fit for life.

Diagram of Greenhouse Effect

Greenhouse Gases

Greenhouse gases are gases in Earth's atmosphere that trap heat, contributing to the greenhouse effect and warming the planet.

Major Greenhouse Gases

The main greenhouse gases include:

• Carbon dioxide (CO2)

• Methane (CH4)

• Nitrous oxide (N2O)

• Fluorinated gases.

Role of Greenhouse Gases

• Absorb infrared radiation

• Re-radiate heat back to Earth

• Maintain thermal balance

Mechanism of the Greenhouse Effect

The mechanism of the greenhouse effect is discussed below:

• Sunlight enters Earth’s atmosphere

• Surface absorbs energy and warms

• Earth emits infrared radiation

• Greenhouse gases absorb this radiation

• Heat is re-radiated back to surface

• Earth’s temperature increases

Causes of Greenhouse Effect

Mainly, the greenhouse effect results from human activities and natural processes that alter the composition of Earth's atmosphere. The causes of the greenhouse effect are discussed as follows-

Human Activities

• Huge amounts of CO2 are emitted into the atmosphere by the burning of fossil fuels for energy, industrial processes, and transportation.

• Deforestation, especially for agriculture and the growth of cities, shrinks the ability of the Earth to consume more CO2 through photosynthesis and overweight the level of greenhouse gases.

Methane Emissions

• Methane emissions, mainly from agriculture (enteric fermentation in livestock and rice cultivation).

• Extraction of fossil fuel energy sources such as natural gas.

• Other gases include nitrous oxide, from agricultural and industrial activity, and fluorinated gases used in refrigeration and air conditioning.

Natural Processes

• Natural events, like volcanic eruptions and fires, can also emit these gases, but the magnitude is generally very small compared with human activities.

• Land-use change, urbanisation and industrialisation alter atmospheric dynamics, which impacts the balance of gases that regulate how much heat is retained

Effects of Greenhouse Effect

The effects of the greenhouse effect are discussed as follows:

• Global warming

• Climate change

• Melting of glaciers and polar ice

• Sea-level rise

• Extreme weather events

• Ecosystem disruption

• Threats to biodiversity and human life

Runaway Greenhouse Effect

The runaway greenhouse effect is a self-enhancing cycle of heating, wherein the temperature increase acts as a catalyst for accelerating greenhouse gas emissions, thereby raising further temperatures. It is a severe process of climate warming that cannot be controlled.

• Cause: Excessive greenhouse gas emissions trap heat.

• Feedback Loop: Warming releases more greenhouse gases, which cause more warming.

• Results: Might give rise to very extreme, inhospitable conditions, as exists on Venus.

• Prevention: Reduction of greenhouse gas emissions and mitigation of climate change impacts.

Greenhouse Gases and their Sources

Some of the major greenhouse gases and their sources are:

Greenhouse Effect NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Major greenhouse gases

• Causes of greenhouse gases

Practice Questions for NEET

Q1.The two gases making the highest relative contribution to greenhouse gases are

1. CO2 and N2O

2. CO2 and CH4

3. CH4 and N2O

4. CFC5 and N2O

Correct answer: 2) CO2 and CH4

Explanation:

The gasses that cause the greenhouse effect are called greenhouse gasses, and they trap radiation and do not allow it to reflect off the Earth's surface. The greenhouse gasses are chlorofluorocarbons (CFCs), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

The approximate percentages of different greenhouse gasses in the atmosphere are:

CFC - 14%, CO2 - 60%, CH4 - 20%, N2O - 6%

Hence, the correct answer is option 2) CO2 and CH4.

Q2. Ozone gas is continuously formed in the stratosphere by

1. Action of UV rays on nascent oxygen

2. Reaction of oxygen with water vapour

3. Action of UV rays on molecular oxygen

4. Action of UV rays on water vapour

Correct answer: 3) Action of UV rays on molecular oxygen

Explanation:

The role of ultraviolet (UV) radiation in ozone formation is essential in the Earth's atmosphere. When UV rays hit oxygen molecules (O₂), they split these molecules into individual oxygen atoms (O). Free oxygen atoms react with other O₂ molecules to form ozone (O₃). This is necessary for creating the ozone layer that protects life on Earth from absorbing harmful UV radiation.

Hence the correct answer is option 3) Action of UV rays on molecular oxygen.

Q3. High concentration of green house gases has resulted in maximum rise of atmospheric temperature in

1. tropic region

2. middle latitude

3. polar region

4. temperate region

Correct answer: 3) polar region

Explanation:

Increases in the level of greenhouse gases have led to considerable heating of the earth leading to global warming. During the past century, the temperature of the earth has increased by 0.6oC, most of it during the last three decades. The temperature rise is slight in the tropics, moderate in middle latitudes and maximum in polar regions. It will lead to the melting of polar ice caps as well as of other places like the Himalayan snow caps.

Hence, the correct answer is option 3) polar region.

Also Read:

• MCQ on Greenhouse Effect

• Types of Pollution

• Air Pollution and its Control

Recommended Video on The Greenhouse Effect