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21 Aug 2025, 21:36
Kudos
Bookmarks
Scientists have speculated about how volcanoes influence climate since the early 1900s, yet only after satellite sensors became routine in the 1990s did they confirm that large eruptions can loft vast plumes of sulfur dioxide (SO₂) into the stratosphere. There the gas oxidizes into sulfate aerosols that brighten Earth’s albedo, reflecting a fraction of incoming sunlight and lowering surface temperatures for one to three years. Balloon observations after Krakatoa in 1883 and after El Chichón in 1982 hinted at this link, but the evidence was fragmentary and often disputed. Today researchers label this sunlight-blocking mechanism volcanic forcing.
The benchmark case is the 1991 eruption of Mount Pinatubo in the Philippines. Pinatubo hurled roughly 20 million tons of SO₂ well above the tropopause, and, carried by fast stratospheric winds, the resulting aerosol veil circled the globe within weeks. Its peak aerosol optical depth reached about 0.15, values once cited in early nuclear-winter simulations, and global mean temperature fell by nearly 0.5 degrees Celsius over the next two years. The episode persuaded many climatologists that any eruption of comparable size would deliver a predictable, though temporary, planetary chill.
That expectation faltered in 2010 when Iceland’s Eyjafjallajökull volcano, famous for grounding trans-Atlantic flights, released millions of tons of SO₂ yet produced virtually no measurable cooling. Detailed lidar and aircraft surveys showed that most of the plume topped out near nine kilometres, below the eleven-to-seventeen kilometre band where stratospheric circulation accelerates, so aerosols settled out within months and remained confined to the North Atlantic basin.
The 2014 Holuhraun fissure, also in Iceland, deepened the puzzle. Although Holuhraun emitted even more SO₂ than Eyjafjallajökull, reanalysis data recorded only a faint minus 0.07 degree Celsius signal. Together the two Icelandic events underscored that latitude and plume height can outweigh sheer emission volume; high-latitude eruptions often vent below the altitude needed for long-lived, planet-circling aerosol layers.
Accumulating data now support a refined pattern. Tropical eruptions such as Pinatubo or El Chichón inject SO₂ directly into swift equatorial circulation, spreading aerosols worldwide, whereas most high-latitude eruptions remain regionally bottled and short lived. Current climate models therefore couple plume-height dynamics with aerosol chemistry, water-vapour interactions, and circulation thresholds to predict which future eruptions will matter for global forecasts and which will be climatic footnotes. Clarifying those thresholds is increasingly crucial for risk assessments of geoengineering proposals that would deliberately mimic volcanic injections.
A volcano at 65° N erupts and releases a large plume of SO2 that peaks at roughly 10 km, below the eleven-to-seventeen km band where stratospheric circulation accelerates. Based on the passage, which outcome is most likely?
A. Global mean temperature will fall by about 0.5 °C for one to two years, mirroring the Pinatubo record.
B. The aerosol cloud will remain largely confined to high-latitude regions and dissipate within a few months, yielding only modest or localized cooling.
C. Stratospheric winds will distribute the aerosols worldwide regardless of the eruption’s latitude or plume height.
D. Climate models will disregard the eruption entirely because it has no measurable effect on either regional or global climate.
E. Because of its high latitude, the eruption will cool the planet more strongly than Pinatubo even though its plume is lower.
The benchmark case is the 1991 eruption of Mount Pinatubo in the Philippines. Pinatubo hurled roughly 20 million tons of SO₂ well above the tropopause, and, carried by fast stratospheric winds, the resulting aerosol veil circled the globe within weeks. Its peak aerosol optical depth reached about 0.15, values once cited in early nuclear-winter simulations, and global mean temperature fell by nearly 0.5 degrees Celsius over the next two years. The episode persuaded many climatologists that any eruption of comparable size would deliver a predictable, though temporary, planetary chill.
That expectation faltered in 2010 when Iceland’s Eyjafjallajökull volcano, famous for grounding trans-Atlantic flights, released millions of tons of SO₂ yet produced virtually no measurable cooling. Detailed lidar and aircraft surveys showed that most of the plume topped out near nine kilometres, below the eleven-to-seventeen kilometre band where stratospheric circulation accelerates, so aerosols settled out within months and remained confined to the North Atlantic basin.
The 2014 Holuhraun fissure, also in Iceland, deepened the puzzle. Although Holuhraun emitted even more SO₂ than Eyjafjallajökull, reanalysis data recorded only a faint minus 0.07 degree Celsius signal. Together the two Icelandic events underscored that latitude and plume height can outweigh sheer emission volume; high-latitude eruptions often vent below the altitude needed for long-lived, planet-circling aerosol layers.
Accumulating data now support a refined pattern. Tropical eruptions such as Pinatubo or El Chichón inject SO₂ directly into swift equatorial circulation, spreading aerosols worldwide, whereas most high-latitude eruptions remain regionally bottled and short lived. Current climate models therefore couple plume-height dynamics with aerosol chemistry, water-vapour interactions, and circulation thresholds to predict which future eruptions will matter for global forecasts and which will be climatic footnotes. Clarifying those thresholds is increasingly crucial for risk assessments of geoengineering proposals that would deliberately mimic volcanic injections.
A volcano at 65° N erupts and releases a large plume of SO2 that peaks at roughly 10 km, below the eleven-to-seventeen km band where stratospheric circulation accelerates. Based on the passage, which outcome is most likely?
A. Global mean temperature will fall by about 0.5 °C for one to two years, mirroring the Pinatubo record.
B. The aerosol cloud will remain largely confined to high-latitude regions and dissipate within a few months, yielding only modest or localized cooling.
C. Stratospheric winds will distribute the aerosols worldwide regardless of the eruption’s latitude or plume height.
D. Climate models will disregard the eruption entirely because it has no measurable effect on either regional or global climate.
E. Because of its high latitude, the eruption will cool the planet more strongly than Pinatubo even though its plume is lower.
21 Aug 2025, 21:36
Kudos
Bookmarks
Official Solution:
Scientists have speculated about how volcanoes influence climate since the early 1900s, yet only after satellite sensors became routine in the 1990s did they confirm that large eruptions can loft vast plumes of sulfur dioxide (SO₂) into the stratosphere. There the gas oxidizes into sulfate aerosols that brighten Earth’s albedo, reflecting a fraction of incoming sunlight and lowering surface temperatures for one to three years. Balloon observations after Krakatoa in 1883 and after El Chichón in 1982 hinted at this link, but the evidence was fragmentary and often disputed. Today researchers label this sunlight-blocking mechanism volcanic forcing.
The benchmark case is the 1991 eruption of Mount Pinatubo in the Philippines. Pinatubo hurled roughly 20 million tons of SO₂ well above the tropopause, and, carried by fast stratospheric winds, the resulting aerosol veil circled the globe within weeks. Its peak aerosol optical depth reached about 0.15, values once cited in early nuclear-winter simulations, and global mean temperature fell by nearly 0.5 degrees Celsius over the next two years. The episode persuaded many climatologists that any eruption of comparable size would deliver a predictable, though temporary, planetary chill.
That expectation faltered in 2010 when Iceland’s Eyjafjallajökull volcano, famous for grounding trans-Atlantic flights, released millions of tons of SO₂ yet produced virtually no measurable cooling. Detailed lidar and aircraft surveys showed that most of the plume topped out near nine kilometres, below the eleven-to-seventeen kilometre band where stratospheric circulation accelerates, so aerosols settled out within months and remained confined to the North Atlantic basin.
The 2014 Holuhraun fissure, also in Iceland, deepened the puzzle. Although Holuhraun emitted even more SO₂ than Eyjafjallajökull, reanalysis data recorded only a faint minus 0.07 degree Celsius signal. Together the two Icelandic events underscored that latitude and plume height can outweigh sheer emission volume; high-latitude eruptions often vent below the altitude needed for long-lived, planet-circling aerosol layers.
Accumulating data now support a refined pattern. Tropical eruptions such as Pinatubo or El Chichón inject SO₂ directly into swift equatorial circulation, spreading aerosols worldwide, whereas most high-latitude eruptions remain regionally bottled and short lived. Current climate models therefore couple plume-height dynamics with aerosol chemistry, water-vapour interactions, and circulation thresholds to predict which future eruptions will matter for global forecasts and which will be climatic footnotes. Clarifying those thresholds is increasingly crucial for risk assessments of geoengineering proposals that would deliberately mimic volcanic injections.
A volcano at 65° N erupts and releases a large plume of SO2 that peaks at roughly 10 km, below the eleven-to-seventeen km band where stratospheric circulation accelerates. Based on the passage, which outcome is most likely?
A. Global mean temperature will fall by about 0.5 °C for one to two years, mirroring the Pinatubo record.
B. The aerosol cloud will remain largely confined to high-latitude regions and dissipate within a few months, yielding only modest or localized cooling.
C. Stratospheric winds will distribute the aerosols worldwide regardless of the eruption’s latitude or plume height.
D. Climate models will disregard the eruption entirely because it has no measurable effect on either regional or global climate.
E. Because of its high latitude, the eruption will cool the planet more strongly than Pinatubo even though its plume is lower.
A) Incorrect: This repeats the Pinatubo pattern, but the passage explains that similar SO₂ quantities produce global cooling only when the plume rises high enough to enter rapid stratospheric circulation, which a 10 km plume does not.
B) Correct Answer: The passage notes that high-latitude eruptions venting below the fast-circulation band create aerosols that “settled out within months and remained confined,” leading to limited, short-lived cooling. This choice mirrors that description.
C) Incorrect: Global distribution depends on both latitude and altitude; winds near the poles are too sluggish to spread low plumes worldwide, contrary to this claim.
D) Incorrect: The author treats even regionally confined eruptions as important data for refining models, so climatologists would not ignore such an event outright.
E) Incorrect: The passage argues that plume height, not latitude alone, determines the strength of volcanic forcing; a lower plume at 65° N would not out-cool Pinatubo.
Answer: B
Scientists have speculated about how volcanoes influence climate since the early 1900s, yet only after satellite sensors became routine in the 1990s did they confirm that large eruptions can loft vast plumes of sulfur dioxide (SO₂) into the stratosphere. There the gas oxidizes into sulfate aerosols that brighten Earth’s albedo, reflecting a fraction of incoming sunlight and lowering surface temperatures for one to three years. Balloon observations after Krakatoa in 1883 and after El Chichón in 1982 hinted at this link, but the evidence was fragmentary and often disputed. Today researchers label this sunlight-blocking mechanism volcanic forcing.
The benchmark case is the 1991 eruption of Mount Pinatubo in the Philippines. Pinatubo hurled roughly 20 million tons of SO₂ well above the tropopause, and, carried by fast stratospheric winds, the resulting aerosol veil circled the globe within weeks. Its peak aerosol optical depth reached about 0.15, values once cited in early nuclear-winter simulations, and global mean temperature fell by nearly 0.5 degrees Celsius over the next two years. The episode persuaded many climatologists that any eruption of comparable size would deliver a predictable, though temporary, planetary chill.
That expectation faltered in 2010 when Iceland’s Eyjafjallajökull volcano, famous for grounding trans-Atlantic flights, released millions of tons of SO₂ yet produced virtually no measurable cooling. Detailed lidar and aircraft surveys showed that most of the plume topped out near nine kilometres, below the eleven-to-seventeen kilometre band where stratospheric circulation accelerates, so aerosols settled out within months and remained confined to the North Atlantic basin.
The 2014 Holuhraun fissure, also in Iceland, deepened the puzzle. Although Holuhraun emitted even more SO₂ than Eyjafjallajökull, reanalysis data recorded only a faint minus 0.07 degree Celsius signal. Together the two Icelandic events underscored that latitude and plume height can outweigh sheer emission volume; high-latitude eruptions often vent below the altitude needed for long-lived, planet-circling aerosol layers.
Accumulating data now support a refined pattern. Tropical eruptions such as Pinatubo or El Chichón inject SO₂ directly into swift equatorial circulation, spreading aerosols worldwide, whereas most high-latitude eruptions remain regionally bottled and short lived. Current climate models therefore couple plume-height dynamics with aerosol chemistry, water-vapour interactions, and circulation thresholds to predict which future eruptions will matter for global forecasts and which will be climatic footnotes. Clarifying those thresholds is increasingly crucial for risk assessments of geoengineering proposals that would deliberately mimic volcanic injections.
A volcano at 65° N erupts and releases a large plume of SO2 that peaks at roughly 10 km, below the eleven-to-seventeen km band where stratospheric circulation accelerates. Based on the passage, which outcome is most likely?
A. Global mean temperature will fall by about 0.5 °C for one to two years, mirroring the Pinatubo record.
B. The aerosol cloud will remain largely confined to high-latitude regions and dissipate within a few months, yielding only modest or localized cooling.
C. Stratospheric winds will distribute the aerosols worldwide regardless of the eruption’s latitude or plume height.
D. Climate models will disregard the eruption entirely because it has no measurable effect on either regional or global climate.
E. Because of its high latitude, the eruption will cool the planet more strongly than Pinatubo even though its plume is lower.
A) Incorrect: This repeats the Pinatubo pattern, but the passage explains that similar SO₂ quantities produce global cooling only when the plume rises high enough to enter rapid stratospheric circulation, which a 10 km plume does not.
B) Correct Answer: The passage notes that high-latitude eruptions venting below the fast-circulation band create aerosols that “settled out within months and remained confined,” leading to limited, short-lived cooling. This choice mirrors that description.
C) Incorrect: Global distribution depends on both latitude and altitude; winds near the poles are too sluggish to spread low plumes worldwide, contrary to this claim.
D) Incorrect: The author treats even regionally confined eruptions as important data for refining models, so climatologists would not ignore such an event outright.
E) Incorrect: The passage argues that plume height, not latitude alone, determines the strength of volcanic forcing; a lower plume at 65° N would not out-cool Pinatubo.
Answer: B
