Impact of Tonga Volcano’s Eruption on Weather

• Context (TH): The Hunga Tonga-Hunga Ha’apai (Hunga Tonga for short) eruption in 2022 in the Pacific Kingdom of Tonga could cause unusual weather for the rest of the decade.

Cooling Effect by Volcanic Smoke

• Volcanic smoke, particularly its sulfur dioxide, usually causes short-term cooling of the Earth’s surface.
• Sulfur dioxide forms sulfate aerosols that reflect sunlight back into space before it reaches the surface. This shading effect cools the surface until the sulfate settles or is washed away by rain.

Why Hunga Tonga’s Eruption in an Outlier?

• The Hunga Tonga’s eruption will not cause a cooling effect on the Earth’s surface. This is because it was an underwater volcano, so it produced little smoke but a lot of water vapour.
• The eruption’s immense heat turned large amounts of seawater into steam, which was propelled high into the atmosphere.
• All that water had reached the stratosphere (15 to 40 km above the surface), which is a dry atmospheric layer that produces neither clouds nor rain.
• Water vapour in the stratosphere has two main effects:
  1. It helps in the chemical reactions which destroy the ozone layer.
  2. It is a very potent greenhouse gas.

How Water Vapour in Stratosphere Destroys Ozone? Water vapour breaks down in the stratosphere, releasing reactive hydrogen oxide molecules that destroy ozone. These molecules also react with chlorine-containing gases, converting them into forms that destroy ozone.

Effects of Hunga Tonga’s Eruption

• Last year’s extraordinarily large ozone hole.
• Much wetter than expected summer of 2024.

Source: Phys.org