Set 2 | Important Greenhouse Effect and Climate Change MCQs

Correct Answer is D.

• Greenhouse gas in an atmosphere is a gas that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in earth’s atmosphere are carbon dioxide, methane, nitrous oxide and ozone

Correct Answer is E.

• The six major gases identified as Green House Gases by Intergovernmental Panel on climate change include CH4, CFC, and N2O. While sulphur dioxide (SO2) is not a greenhouse gas, it is responsible for acid rain.
• The Chhattisgarh Public Service Commission has marked the correct answer as option (e) whereas they have considered option (c) as correct in the previous answer sheet. Probably this would have been done on the basis of direct and indirectly involved gases in greenhouse effect.
• The gases directly responsible for greenhouse effect are – Carbon dioxide (CO₂), Methane (CH4), Nitrous Oxide (N2O), CFC, SF6, NF3, etc. While the gases indirectly responsible for green house effect include – Nitrogen oxide (NOX), Carbon monoxide (CO), Non-methane volatile organic compounds (NMVOC) and sulphur dioxide (SO₂).

Correct Answer is D.

The relative contributions of greenhouse gases to the Earth’s greenhouse effect are distributed as follows, including all key greenhouse gases:

1. Water Vapor (H₂O):
   • Contribution: Approximately 60%
   • Role: The most abundant greenhouse gas, water vapor amplifies the greenhouse effect by trapping heat. Its concentration is influenced by temperature and atmospheric conditions, acting as a feedback mechanism rather than a direct driver of climate change.
2. Carbon Dioxide (CO₂):
   • Contribution: About 26%
   • Role: A significant contributor to the greenhouse effect, CO₂ is primarily emitted from the burning of fossil fuels, deforestation, and industrial processes. Its long atmospheric lifetime makes it a critical focus of climate mitigation efforts.
3. Methane (CH₄):
   • Contribution: Around 4-9%
   • Role: Although present in smaller quantities, methane is over 25 times more potent than CO₂ in trapping heat over a 100-year period. It is released from sources such as agriculture (livestock), wetlands, landfills, and fossil fuel extraction.
4. Ozone (O₃):
   • Contribution: About 3-7%
   • Role: Ozone in the troposphere acts as a greenhouse gas, contributing to warming. Its formation is largely influenced by industrial emissions and photochemical reactions.
5. Nitrous Oxide (N₂O):
   • Contribution: Around 1.5%
   • Role: Emitted from agricultural activities, fossil fuel combustion, and industrial processes, nitrous oxide is approximately 300 times more effective than CO₂ at warming the atmosphere on a per-molecule basis.
6. Chlorofluorocarbons (CFCs) and Hydrofluorocarbons (HFCs):
   • Contribution: About 0.1-0.4%
   • Role: Synthetic gases with a high global warming potential and long atmospheric lifetimes, CFCs and HFCs are used in refrigeration, air conditioning, and aerosols. Their production is being phased out under international agreements like the Montreal Protocol.
7. Perfluorocarbons (PFCs):
   • Contribution: Trace amounts
   • Role: PFCs are synthetic gases primarily emitted from industrial processes, such as aluminum production. Despite their small concentration, they have extremely high global warming potentials and remain in the atmosphere for thousands of years.
8. Sulfur Hexafluoride (SF₆):
   • Contribution: Trace amounts
   • Role: Used in electrical insulation and industrial applications, SF₆ is the most potent greenhouse gas known, with a global warming potential thousands of times greater than CO₂.
9. Nitrogen Trifluoride (NF₃):
   • Contribution: Trace amounts
   • Role: Emitted during the production of semiconductors and other electronic devices, NF₃ has a high global warming potential and an increasing presence in the atmosphere due to its industrial use.

These gases collectively trap heat in the Earth’s atmosphere, driving the greenhouse effect and contributing to global climate change. Addressing emissions from both natural and anthropogenic sources is critical for mitigating their impact on global warming.

Correct Answer is C.

• When the earth starts frosting after getting heat from the sun, then the heat is dissipated out of the earth. But gases like carbon dioxide, nitrous oxide, water vapour and methane absorb some part of this heat in return of which some additional heat is collected in the lower part of the atmosphere.
• Over the past few years, due to increase in the amount of these gases in the atmosphere, the average temperature of the atmosphere has increased which is called global warming or greenhouse effect and the above- mentioned gases are called greenhouse gases.

Correct Answer is C.

• The primary greenhouse gases are – Water Vapour, Methane, Nitrous Oxide and Ozone.
• Substituting Propane for other fuels such as gasoline and fuel oil is an economical and viable step towards cleaner air. Using Propane reduces greenhouse gas like Carbon- dioxide and air pollutants like carbon monoxide and nitrogen oxide.

Correct Answer is C.

• A layer of greenhouse gases namely carbon dioxide, methane and nitrous oxide acts as a thermal blanket for the earth, absorbing heat and warming the surface known as global warming. Hence, Argon is not responsible for global warming.

Correct Answer is B.

• In the month of February, 2021 the International Energy Agency’s (IEA) released its Net Zero Emissions (NZE) Road map-named ‘Net Zero by 2050’.
• It is the World’s first comprehensive energy road map which came ahead of the United Nations November 2021.
• ‘Net zero emissions’ refers to achieving an overall balance between greenhouse gas emissions taken out of the atmosphere.

What is Net Zero?

• Net-zero, which is also referred to as carbon-neutrality, does not mean that a country would bring down its emissions to zero.
• Rather, net-zero is a state in which as country’s emissions are compensated be absorption and removal of greenhouse gases from the atmosphere.
• Absorption of the emissions can be increased by creating more carbon sinks such as forests, while the removal of gases from the atmosphere requires futuristic technologies such as carbon capture and storage.
• This way, it is even possible for a country to have negative emissions, if the absorption and removal exceed the actual emissions.
• A good example is Bhutan which is often described as carbon- negative because it absorbs more than it emits.

Correct Answer is D.

• Plants use carbon dioxide to produce carbohydrates (sugars and starches) in the process known as photosynthesis. Since humans and all other animals depend on plants for their food, photosynthesis is necessary for the survival of all life on Earth. It is also a greenhouse gas which is very harmful to us. Therefore carbon dioxide is both useful as well as harmful to life on earth.

Correct Answer is A.

According to the data available in the 2020, largest contributor to carbon dioxide emission is China. It emits about 28% of the world’s total carbon emission. The United States is in second place with 15% and India is in third place with 7%. Russia is in fourth place with 5% and Japan is in fifth place in terms of carbon emission with 3% of the world’s total CO₂ emission.

As of 2024, the global distribution of carbon dioxide (CO₂) emissions by country is as follows:

1. China: Approximately 32.88% of global CO₂ emissions, maintaining its position as the largest emitter.
2. United States: Around 12.6% of global emissions, ranking second.
3. India: Contributes about 6.99% of global CO₂ emissions, placing third.
4. Russia: Accounts for approximately 4.96% of global emissions, in fourth place.
5. Japan: Responsible for about 2.81% of global CO₂ emissions, ranking fifth.

• These figures indicate that China remains the largest contributor to global CO₂ emissions, followed by the United States and India. Notably, India’s share has increased compared to previous years, reflecting its rapid economic growth and energy demands. Conversely, the United States and the European Union have reported declines in emissions due to reduced use of coal, oil, and cement.
• It’s important to recognize that these percentages are subject to change as countries implement policies to reduce emissions and transition to renewable energy sources. Additionally, per capita emissions vary significantly, with countries like the United States and Australia having higher per capita emissions compared to nations such as India and China.
• Addressing global CO₂ emissions requires concerted efforts from all nations, especially the top emitters, to adopt sustainable energy practices and mitigate the impacts of climate change.

Correct Answer is B.

• As of 2024, China remains the largest contributor to global carbon dioxide emissions, accounting for approximately 31% of the world’s total CO₂ emissions. The United States ranks second, contributing about 14%, followed by India with 8%, Russia at 4%, and Japan at 3%. Together, these countries make up the bulk of global CO₂ emissions, with the rest distributed among other nations worldwide