After 1-3 years, the aerosol falls into the troposphere and then onto the surface. Volcanic eruptions in the tropics affect climate in both hemisphere. Volcanic eruptions at mid or high latitudes only affect the hemisphere in which they sit. However, within 2 years the cooling has disappeared. Record of acidity in the Greenland Ice Sheet and alpine snow line depression.
Acidity is used as a proxy for volcanic eruptions.
These are events that are inherent to the climate system and occur as a result of dynamic processes. La Nina is a great example. These events results from natural coupled interactions between the tropical Pacific Ocean and the atmosphere. These same modeling studies indicate that solar and volcanic forcing can not, by themselves, explain the warming of the 20th century. The best simulations of the period since 1850 include anthropogenic, solar, and volcanic forcing.