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Ozone Depletion & Climate Change (Atmospheric Sciences) Solved Questions & Notes (2026) - Apex Rankers

Meteorology & Atmospheric Sciences > Atmospheric Sciences > Ozone Depletion & Climate Change

15 Total Solved Questions
~23 mins Estimated Reading Time
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Ozone Depletion & Climate Change

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Q. 1 Atmospheric Sciences
Difficulty: Hard (1 Mark)
Who formulated the four-reaction photochemical cycle describing the pure oxygen production and destruction of stratospheric ozone in 1930?
A
Sydney Chapman (Chapman Cycle)
✓ Correct
B
Mario Molina
C
F. Sherwood Rowland
D
Paul Crutzen
💡 Step-by-Step Explanation & Concept Rationale
Sydney Chapman formulated the classic Chapman mechanism in 1930: (1) O2 + h*nu -> 2 O, (2) O + O2 + M -> O3 + M, (3) O3 + h*nu -> O + O2, (4) O3 + O -> 2 O2.
Q. 2 Atmospheric Sciences
Difficulty: Medium (1 Mark)
Which scientists won the 1995 Nobel Prize in Chemistry for demonstrating that Chlorofluorocarbons (CFCs) destroy stratospheric ozone via catalytic chlorine radical chain reactions?
A
Albert Einstein and Niels Bohr
B
Paul Crutzen, Mario Molina, and F. Sherwood Rowland
✓ Correct
C
Svante Arrhenius and Guy Callendar
D
Ernest Rutherford and James Chadwick
💡 Step-by-Step Explanation & Concept Rationale
Crutzen, Molina, and Rowland shared the 1995 Nobel Prize in Chemistry for their pioneering work on atmospheric chemistry, particularly the formation and decomposition of ozone by CFCs.
Q. 3 Atmospheric Sciences
Difficulty: Medium (1 Mark)
In the catalytic destruction of stratospheric ozone, approximately how many ozone (O3) molecules can a single free chlorine atom destroy before being sequestered into a reservoir species?
A
Only 1
B
About 10
C
Up to 100,000 ozone molecules
✓ Correct
D
Exactly 1,000,000,000
💡 Step-by-Step Explanation & Concept Rationale
Because chlorine acts as a true chemical catalyst (Cl + O3 -> ClO + O2, and ClO + O -> Cl + O2), a single free chlorine radical can destroy roughly 100,000 ozone molecules before diffusing out.
Q. 4 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What crucial role do Polar Stratospheric Clouds (PSCs, Type I nitric acid trihydrate and Type II water ice) play in the formation of the Antarctic Ozone Hole?
A
They provide heterogeneous surfaces on which inert reservoir species (HCl and ClONO2) are converted into photolytically active chlorine (Cl2 and HOCl)
✓ Correct
B
They freeze the ozone molecules into dry ice
C
They reflect all solar radiation away from Earth
D
They absorb UV radiation directly
💡 Step-by-Step Explanation & Concept Rationale
During polar winter darkness, heterogeneous reactions on PSC surfaces convert stable chlorine reservoirs (HCl, ClONO2) into molecular chlorine (Cl2). When sunlight returns in spring (September), Cl2 rapidly photolyzes into active Cl radicals.
Q. 5 Atmospheric Sciences
Difficulty: Easy (1 Mark)
What landmark international environmental treaty signed in 1987 phased out the production and consumption of ozone-depleting substances (ODSs)?
A
Kyoto Protocol
B
Montreal Protocol on Substances that Deplete the Ozone Layer
✓ Correct
C
Paris Agreement
D
Ramsar Convention
💡 Step-by-Step Explanation & Concept Rationale
The Montreal Protocol (agreed in September 1987) is widely considered the most successful global environmental treaty, universally ratified and successfully putting stratospheric ozone on track to recover by mid-century.
Q. 6 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is the 'Kigali Amendment' (2016) to the Montreal Protocol designed to phase down?
A
Coal-fired power plants
B
Hydrofluorocarbons (HFCs), which do not deplete ozone but are potent greenhouse gases with high Global Warming Potentials
✓ Correct
C
Single-use plastics
D
Nuclear waste
💡 Step-by-Step Explanation & Concept Rationale
The Kigali Amendment (adopted in 2016) mandates the global phasedown of HFCs (hydrofluorocarbons), which were introduced to replace CFCs/HCFCs but are super-greenhouse gases.
Q. 7 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is 'Global Warming Potential' (GWP) of a greenhouse gas defined as?
A
The price of carbon offsets
B
A metric measuring the cumulative radiative forcing of 1 kilogram of a gas relative to 1 kilogram of Carbon Dioxide (CO2, GWP = 1) over a specified time horizon (typically 100 years)
✓ Correct
C
The temperature at which a gas catches fire
D
The percentage of gas in the troposphere
💡 Step-by-Step Explanation & Concept Rationale
GWP measures how much energy the emissions of 1 ton of a greenhouse gas will absorb over a given time period (usually 100 years), relative to 1 ton of CO2.
Q. 8 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is the approximate 100-year Global Warming Potential (GWP100) of Methane (CH4) according to the IPCC Sixth Assessment Report (AR6)?
A
1
B
Approximately 27 to 30
✓ Correct
C
273
D
23,500
💡 Step-by-Step Explanation & Concept Rationale
Methane has a GWP100 of approximately 27 to 30 (approx 80 times more potent than CO2 on a 20-year timescale GWP20).
Q. 9 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is the approximate 100-year GWP of Nitrous Oxide (N2O)?
A
10
B
Approximately 273
✓ Correct
C
1,000
D
10,000
💡 Step-by-Step Explanation & Concept Rationale
Nitrous oxide (N2O, released primarily from agricultural fertilizers and soils) has an atmospheric lifetime of ~114 years and a GWP100 of approximately 273.
Q. 10 Atmospheric Sciences
Difficulty: Hard (1 Mark)
Which synthetic industrial gas has the highest known Global Warming Potential (GWP100 ~23,500) and an atmospheric lifetime exceeding 3,000 years, used in electrical switchgear?
A
Sulfur Hexafluoride (SF6)
✓ Correct
B
Nitrogen gas (N2)
C
Helium (He)
D
Propane (C3H8)
💡 Step-by-Step Explanation & Concept Rationale
Sulfur hexafluoride (SF6) is the most potent greenhouse gas evaluated by the IPCC, with a GWP100 of 23,500 and an atmospheric lifetime of ~3,200 years.
Q. 11 Atmospheric Sciences
Difficulty: Easy (1 Mark)
What is the primary temperature goal agreed upon in the legally binding 'Paris Agreement' (COP21, 2015)?
A
To keep global average temperature rise well below 2.0 °C above pre-industrial levels and pursue efforts to limit the increase to 1.5 °C
✓ Correct
B
To stop the seasons from changing
C
To keep global temperature exactly at 0 °C
D
To allow up to 5.0 °C of warming
💡 Step-by-Step Explanation & Concept Rationale
Article 2 of the Paris Agreement commits parties to holding the increase in global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit it to 1.5 °C.
Q. 12 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What is 'Equilibrium Climate Sensitivity' (ECS)?
A
The long-term increase in global mean surface temperature resulting from a sustained doubling of atmospheric CO2 concentration after the climate system reaches equilibrium
✓ Correct
B
The daily temperature change caused by clouds
C
The thermometer accuracy in the Arctic
D
The rate of ocean sea level rise per year
💡 Step-by-Step Explanation & Concept Rationale
ECS is a fundamental metric in climate science: it represents the eventual steady-state global warming resulting from doubling pre-industrial CO2 (from 280 to 560 ppm), estimated by IPCC AR6 as likely between 2.5 °C and 4.0 °C (best estimate 3.0 °C).
Q. 13 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What is 'Transient Climate Response' (TCR)?
A
The global mean surface temperature change at the exact moment atmospheric CO2 doubles in a simulation where CO2 increases by 1% per year compound
✓ Correct
B
The temperature change during a solar eclipse
C
The annual monsoon rainfall in Pakistan
D
The speed of seismic waves
💡 Step-by-Step Explanation & Concept Rationale
TCR measures the immediate warming response at the time of CO2 doubling (after ~70 years of 1%/yr increase), before deep oceans reach thermal equilibrium.
Q. 14 Atmospheric Sciences
Difficulty: Easy (1 Mark)
What is the 'Keeling Curve'?
A
A continuous graph of atmospheric carbon dioxide concentration measured at the Mauna Loa Observatory in Hawaii since 1958, showing steady upward anthropogenic accumulation and seasonal biospheric oscillations
✓ Correct
B
A curve showing ocean salinity
C
The profile of an airplane wing
D
A graph of earthquake magnitudes
💡 Step-by-Step Explanation & Concept Rationale
Started by Charles David Keeling in 1958 at Mauna Loa, Hawaii, the Keeling Curve provided the first definitive empirical evidence of rapidly rising atmospheric CO2 levels and the Northern Hemisphere photosynthetic seasonal cycle.
Q. 15 Atmospheric Sciences
Difficulty: Medium (1 Mark)
Why does the Keeling Curve show a regular annual sawtooth oscillation (dipping in Northern Hemisphere summer and rising in winter)?
A
Volcanoes only erupt in winter
B
Photosynthetic uptake of CO2 by the vast Northern Hemisphere terrestrial forests in spring/summer, followed by respiration and decomposition in autumn/winter
✓ Correct
C
Solar flares occur in summer
D
Automobiles are driven only in winter
💡 Step-by-Step Explanation & Concept Rationale
Because most of Earth's landmass and forests are in the Northern Hemisphere, global atmospheric CO2 drawdown peaks during Northern Hemisphere summer photosynthesis, rebounding in autumn/winter respiration.
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