Greenhouse Effect and Climate Change

71. Greenhouse gases are known so as:

Greenhouse gases are known so as:

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they trap heat in the high altitudes.
they act like a greenhouse on the surface of the planet.
the colour of some of the gases emanating from industrial plants are green.
these gases are produced by agricultural crops.
This question was previously asked in
UPSC Geoscientist – 2020
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Greenhouse gases are so named because they trap heat in the Earth’s lower atmosphere in a manner analogous to how the glass walls and roof of a greenhouse trap heat.
– Greenhouse gases (such as CO₂, methane, water vapor) are transparent to incoming solar radiation (shortwave).
– The Earth’s surface absorbs this radiation and re-emits energy as infrared radiation (longwave heat).
– Greenhouse gases absorb this outgoing infrared radiation and re-emit it in all directions, including back towards the Earth’s surface, thus trapping heat and warming the planet.
– This process is known as the greenhouse effect, a natural phenomenon essential for maintaining a habitable temperature on Earth.
– An increase in the concentration of greenhouse gases due to human activities enhances this effect, leading to global warming and climate change.
– The analogy with a greenhouse is not perfect (a real greenhouse also traps heat by preventing convective heat loss), but it effectively describes the trapping of infrared radiation.

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72. The broad estimates of sea level rise due to global warming by 2100 is

The broad estimates of sea level rise due to global warming by 2100 is approximately:

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10 cm
20 cm
30 cm
40 cm
This question was previously asked in
UPSC Geoscientist – 2020
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Broad estimates of global mean sea level rise by the year 2100 due to global warming vary depending on emission scenarios and models. While projections range from about 30 cm to over 1 meter, 40 cm falls within the plausible range often cited as a lower-to-mid estimate in various assessments or as a rounded figure representative of a significant, yet not extreme, rise within the century.
– Sea level rise is caused primarily by the thermal expansion of seawater and the melting of glaciers and ice sheets.
– Projections for sea level rise are based on climate models and future greenhouse gas emission scenarios.
– The Intergovernmental Panel on Climate Change (IPCC) reports provide detailed projections with associated uncertainty ranges for different scenarios.
– The IPCC AR6 report (2021) projects a *likely* global mean sea level rise by 2100 (relative to 1995–2014) of 28–55 cm under a very low emissions scenario (SSP1-1.9) and 63–101 cm under a very high emissions scenario (SSP5-8.5).
– The options provided (10, 20, 30, 40 cm) are relatively low compared to the midpoints of even the lowest IPCC ranges, but 40 cm is the highest option and falls within the lower part of the range projected under moderate emission scenarios by earlier reports or as a rounded figure. Given the options, 40 cm is the most reasonable “broad estimate” among the choices.

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73. Which one of the following is the main natural source of Methane?

Which one of the following is the main natural source of Methane?

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Wetlands
Belching by cattle
Leakage from pipelines
Burning of wood
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UPSC Geoscientist – 2020
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Natural wetlands are the largest natural source of methane emissions globally. Methane is produced by anaerobic bacteria in waterlogged soils and sediments where organic matter decomposes in the absence of oxygen.
Anaerobic decomposition of organic matter in waterlogged environments like swamps, marshes, and bogs is the primary natural process generating methane.
Other significant natural sources include termites, oceans, geological seeps, and wildfires. Anthropogenic sources like livestock (belching), rice cultivation, landfills, and fossil fuel production (leakage from pipelines is an example) are also major contributors to the total atmospheric methane concentration, often exceeding natural sources in terms of total emissions. However, the question asks for the *main natural* source.

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74. Which one of the following greenhouse gases is the largest single cont

Which one of the following greenhouse gases is the largest single contributor to anthropogenic radiative forcing?

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Methane
Ozone
Nitrous oxide
Carbon dioxide
This question was previously asked in
UPSC Geoscientist – 2020
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Among the listed greenhouse gases, Carbon dioxide (CO2) is the largest single contributor to anthropogenic radiative forcing since the pre-industrial era. Its high concentration, long atmospheric lifetime, and significant increase due to the burning of fossil fuels and deforestation make it the primary driver of climate change.
Carbon dioxide is the most significant anthropogenic greenhouse gas contributing to the enhanced greenhouse effect and radiative forcing.
Radiative forcing is the change in the balance between incoming solar radiation and outgoing infrared radiation in the atmosphere. While methane (CH4) and nitrous oxide (N2O) have higher global warming potentials per molecule than CO2, the much larger increase in CO2 concentration in the atmosphere results in its dominant contribution to the overall anthropogenic radiative forcing. Ozone (O3) also contributes, but its distribution and lifetime are more variable.

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75. Which of the following statements about National Action Plan on Climat

Which of the following statements about National Action Plan on Climate Change (NAPCC) with reference to India is/are correct ?

  • It emphasises that maintaining a high growth rate is essential for raising the living standards of the vast majority of the people of India and reducing their vulnerability to the impact of climate change.
  • It was released in 2014.

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1 only
2 only
Both 1 and 2
Neither 1 nor 2
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UPSC CDS-2 – 2023
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The correct answer is A) 1 only.
Statement 1 is correct. India’s National Action Plan on Climate Change (NAPCC) emphasizes the importance of sustainable development and maintaining a high rate of economic growth as crucial for poverty eradication and enhancing the adaptive capacity and resilience of the population to the impacts of climate change. This reflects India’s perspective that development and climate action are intertwined.
Statement 2 is incorrect. The National Action Plan on Climate Change (NAPCC) was formally launched in June *2008*, not 2014, by the then Prime Minister of India.
The NAPCC outlines India’s strategy to meet the challenges of climate change. It is guided by the principles of sustainable development and includes eight national missions focused on areas such as solar energy, enhanced energy efficiency, sustainable habitat, water conservation, sustaining the Himalayan ecosystem, green India, sustainable agriculture, and strategic knowledge for climate change.

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76. Which of the following statements about the ‘Race to Zero Campaign’ is

Which of the following statements about the ‘Race to Zero Campaign’ is/are correct ?

  • One of the main objectives of the Race to Zero Campaign is to build momentum around the shift to a decarbonized economy.
  • It is related to the theory of Zero-Sum Game.

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1 only
2 only
Both 1 and 2
Neither 1 nor 2
This question was previously asked in
UPSC CDS-2 – 2023
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The correct answer is A) 1 only.
Statement 1 is correct. The ‘Race to Zero’ campaign is a global initiative that mobilizes actors outside of national governments – including companies, cities, regions, and investors – to commit to achieving net-zero emissions by 2050 at the latest. Its main objective is precisely to build momentum among these non-state actors towards a decarbonized economy to limit global warming.
Statement 2 is incorrect. The Race to Zero Campaign is related to achieving *net-zero carbon emissions*, not the economic concept of a Zero-Sum Game. Climate action is generally viewed as a collective action problem where collaboration leads to a positive outcome for all involved, rather than a scenario where one party’s gain is another’s loss.
The Race to Zero campaign works through various initiatives and networks (like the Marrakech Partnership) to promote credible net-zero commitments and actions from non-state actors, aligned with the goals of the Paris Agreement.

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77. One carbon credit is accepted as equivalent to

One carbon credit is accepted as equivalent to

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100 kg of carbon
100 kg of carbon dioxide
1000 kg of carbon
1000 kg of carbon dioxide
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UPSC CDS-2 – 2017
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One carbon credit is generally accepted as equivalent to 1000 kg (or 1 metric tonne) of carbon dioxide (CO2) equivalent.
Carbon credits represent a measurable amount of greenhouse gas emissions reduced, avoided, or sequestered, standardized to 1 tonne of CO2 equivalent.
Carbon credits are a key component of carbon trading schemes, designed to reduce greenhouse gas emissions. They allow entities that reduce emissions below their cap to sell credits to those who exceed their cap, creating a market incentive for emission reduction. While often expressed in CO2 equivalent, this includes other greenhouse gases weighted by their global warming potential.

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78. Which greenhouse gas has maximum average residence time in the

Which greenhouse gas has maximum average residence time in the atmosphere?

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CFC
CH₄
N₂O
Water vapour
This question was previously asked in
UPSC CDS-1 – 2024
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The correct answer is CFC (Chlorofluorocarbon).
Greenhouse gases have varying residence times in the atmosphere. Among the options provided, Chlorofluorocarbons (CFCs) have the longest average residence times, typically ranging from decades to several centuries.
Water vapour has a very short residence time (days). Methane (CH₄) has a residence time of about 12 years. Nitrous oxide (N₂O) has a residence time of about 121 years. CFCs, though also potent greenhouse gases, were primarily known for their role in ozone depletion and their long atmospheric lifetimes make them persist for a very long time, contributing to warming over extended periods.

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79. Which of the following statements about ‘Marrakech Partnership’ is/are

Which of the following statements about ‘Marrakech Partnership’ is/are correct?

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  • It is an intergovernmental partnership for global climate action.
  • It is not only an intergovernmental partnership for global climate action but also a collaboration between governments and other stakeholders like cities, businesses and investors.
  • This partnership is guided by the 2030 Agenda for Sustainable Development.

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1 and 2 only
1 and 3 only
1, 2 and 3
2 only
This question was previously asked in
UPSC CDS-1 – 2024
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The correct option is C) 1, 2 and 3.
The Marrakech Partnership for Global Climate Action supports the implementation of the Paris Agreement. It mobilizes climate action by Parties (governments) and non-Party stakeholders including cities, businesses, investors, and civil society. Therefore, it is indeed a collaboration that involves governments (making it partly intergovernmental) but is not limited to them (as stated in point 2). The climate action goals under the Paris Agreement are aligned with and contribute to the broader 2030 Agenda for Sustainable Development, particularly SDG 13 on climate action, so the partnership is guided by this agenda.
The Marrakech Partnership aims to accelerate climate action through annual events (like the Global Climate Action High-Level Event at COPs) and various initiatives that foster collaboration between state and non-state actors. Its focus is on demonstrating how non-Party stakeholders can support governments in achieving the goals of the Paris Agreement.

80. Which one of the following is related to global dimming?

Which one of the following is related to global dimming?

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Fall of atmospheric pressure due to increased particulates
Raise of atmospheric pressure due to increased particulates
Raise of temperature due to increased particulates
Fall of temperature due to increased particulates
This question was previously asked in
UPSC CDS-1 – 2024
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Global dimming is the reduction in the amount of solar radiation reaching the Earth’s surface.
This phenomenon is caused by increased levels of particulate matter (aerosols and pollutants) in the atmosphere. These particles reflect sunlight back into space and absorb solar radiation. They also act as cloud condensation nuclei, leading to brighter and more reflective clouds. By reducing the amount of incoming solar energy, global dimming results in a cooling effect, causing a fall of temperature at the Earth’s surface.
Global dimming has, to some extent, offset the warming effects of greenhouse gases. Changes in air pollution levels can therefore influence global temperature trends.

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