How do volcanoes affect the climate?

Volcanoes can have both a cooling and warming effect on the planet's climateo See all questions and answerso Read about the projectWhen volcanoes erupt, they emit a mixture of gases and particles into the air. Some of them, such as ash and sulphur dioxide, have a cooling effect, because they (or the substances they cause) reflect sunlight away from the earth. Others, such as CO2, cause warming by adding to the the greenhouse effect.The cooling influence is particularly marked in the case of large eruptions able to blast sun-blocking particles all the way up to the stratosphere - such as Mount Pinatubo in 1991, which caused a significant dip in global temperatures in the following year or two. It's difficult to know for sure that the cooling observed after a particular eruption is definitely the result of that eruption, but examining the average global temperature change after multiple eruptions proves a strong link. Continue reading...