Question

Why do volcanoes cause Earth's climate to get colder?

Answer 1

Lightweight volcanic ejecta, particularly ash and small cinders cause a "block" in the atmosphere preventing incoming solar radiation from reaching the earth's surface, thus lowering the surface temperature of the planet.

Explanation:

Volcanic eruptions are accompanied by ejection of considerable amounts of matter (pyroclastic materials, lava and ash). If these materials are light enough they are ejected to the atmosphere and may stay there for a while, thus blocking the incoming energy from the sun. This effect causes the surface temperature of the earth to ever so slightly drop.