How do volcanic eruptions impact Earth's radiation balance?

Volcanic eruptions impact Earth's radiation balance by releasing particles and gases that can reflect sunlight and trap heat.

When a volcano erupts, it spews out ash, sulphur dioxide (SO₂), and other particles into the atmosphere. These particles can spread across large areas and form a layer that reflects sunlight back into space. This process, known as "global dimming," reduces the amount of solar energy reaching Earth's surface, leading to a temporary cooling effect. For example, the eruption of Mount Pinatubo in 1991 caused a global temperature drop of about 0.5°C for a couple of years.

In addition to ash and particles, volcanic eruptions release greenhouse gases like carbon dioxide (CO₂) and water vapour. These gases trap heat in the atmosphere, contributing to the greenhouse effect. However, the cooling effect from the ash and sulphur dioxide usually outweighs the warming effect from the greenhouse gases in the short term.

Sulphur dioxide is particularly important because it reacts with water vapour to form tiny droplets of sulphuric acid. These droplets create a haze that can linger in the stratosphere for years, reflecting sunlight and enhancing the cooling effect. This phenomenon is called "aerosol forcing."

The overall impact of a volcanic eruption on Earth's radiation balance depends on the size and duration of the eruption, as well as the types and amounts of materials released. Large eruptions with significant amounts of sulphur dioxide can have a noticeable cooling effect on the climate, while smaller eruptions may have a more limited impact.

In summary, volcanic eruptions can both cool and warm the Earth by reflecting sunlight and trapping heat, but the cooling effect from ash and sulphur dioxide usually dominates in the short term.