VOLCANIC WINTER (Syllabus: GS Paper 1 – Geography)

Context: Researchers from NASA used advanced computer modelling to simulate super-eruptions like the Toba event and found that volcanic winter would probably not exceed 1.5 degrees Celsius.

Volcanic Winter

• About: It is a reduction in global temperatures caused by droplets of sulfuric acid obscuring the Sun and raising Earth's albedo after a large, sulfur rich, particularly explosive volcanic eruption.
• Formation: SO2 and H2S react with hydroxyl (OH) and water (H2O) in the stratosphere, forming sulfuric acid (H2SO4) droplets, which contribute significantly to Earth's albedo.
• Radiative Effects and Surface Cooling: The resultant H2SO4 aerosols increase Earth's albedo, reflecting solar radiation back into space, thereby cooling the surface temperature of the planet.
• Stratospheric Warming and Prolonged Cooling: While volcanic aerosols cool the surface, they warm the stratosphere by absorbing terrestrial radiation, creating a complex interplay of atmospheric dynamics.
• Stratosphere-Troposphere Interaction: The air between the troposphere and stratosphere eventually mixes, causing the volcanic particles to fall into the troposphere.

oSubsequent precipitation brings these particles down to Earth.

• Occurrence: A massive volcanic eruption can deposit enormous amounts of ascending light colored volcanic ash and sulfur aerosols above the troposphere and into the lower stratosphere.
• Historical Impact: The ash produced from the eruption of Mount Etna in 44 B.C. dimmed the Sun's rays, causing a cooling effect.

oThis cooling led to crop failure, famine, and significant challenges in ancient Rome and Egypt.