When volcanoes erupt, they release massive amounts of gases and particles into the atmosphere. These particles, referred to by scientists as "aerosols," reflect incoming solar radiation back into outer space, cooling the planet. The influence of volcanic emissions can be felt hemispherically, or globally, if the emissions reach the upper atmosphere (stratosphere). Major explosive volcanic eruptions, such as the 1991 eruption of Mt. Pinatubo, can produce surface cooling on the order of around 0.5 degrees C (0.9 degrees F) for several years.
