Volcanic winter

A volcanic winter is a reduction in global temperatures caused by volcanic ash and droplets of sulfuric acid and water obscuring the Sun and raising Earth's albedo (increasing the reflection of solar radiation) after a large particularly explosive volcanic eruption. Long-term cooling effects are primarily dependent upon injection of sulfur gasses into the stratosphere where they undergo a series of reactions to create sulfuric acid which can nucleate and form aerosols. Volcanic stratospheric aerosols cool the surface by reflecting solar radiation and warm the stratosphere by absorbing terrestrial radiation. The volcanic aerosols, resulting from the 1991 Pinatubo eruption and others, have been shown to contribute to anthropogenic ozone depletion. The variations in atmospheric warming and cooling results in changes in tropospheric and stratospheric circulation.

The effects of volcanic eruptions on recent winters are modest in scale, but historically have been significant.

Most recently, the 1991 explosion of Mount Pinatubo, a stratovolcano in the Philippines, cooled global temperatures for about 2–3 years.

In 1883, the explosion of Krakatoa (Krakatau) created volcanic winter-like conditions. The four years following the explosion were unusually cold, and the winter of 1887-1888 included powerful blizzards. Record snowfalls were recorded worldwide.

The 1815 eruption of Mount Tambora, a stratovolcano in Indonesia, occasioned mid-summer frosts in New York State and June snowfalls in New England and Newfoundland and Labrador in what came to be known as the "Year Without a Summer" of 1816.

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