In April 1815, Mount Tambora in Indonesia erupted, spewing untold quantities of sulphur, carbon dioxide, and ash into the atmosphere, and causing earthquakes and tsunamis in the area. It was the largest volcanic eruption in recorded history.
As frightening as those effects were for Indonesians, those immediate effects were just a small sample of the Tambora eruption’s impact on the weather.
The cloud of ash, smoke, and volatile gasses entered the stratosphere and literally blocked out the sun, screening the earth from much of the light and warmth necessary to sustain life on Earth, turning the sky a pale, sickly shade of yellow.
For the next year, global temperatures plummeted. The following winter was exceptionally cold in the Northern Hemisphere. Even more troubling, though, was that it dragged on for months longer than usual, resulting in what has since been called “the year without a summer.”
Throughout North America, Northern Europe, and Asia, the summer of 1816 brought storms that dropped a foot or more of snow during May and June and killing frosts in July and August, crippling food production. Many residents of New England and the Canadian Maritimes froze to death, starved, or suffered from severe malnutrition. Rioting and looting became common in the United Kingdom and France.
While only the most severe volcanic eruptions have that kind of effect, it’s clear that volcanic activity can impact the weather in both the immediate area and on a global scale. Weather historians note at least four such occasions in the last few centuries, including the eruption of Mount Pinatubo in the Philippines in 1991, which lowered global temperatures by about 2° F over the next two years. Increased volcanic activity on a global scale is even suspected to be one of the possible causes of the “Little Ice Age” that occurred from about 1550 and 1850.
The greatest impact on weather in the immediate vicinity of a volcanic eruption is often heavy rain, accompanied by thunder and lightning. These severe storms are caused by the large amount of ash particles projected into the atmosphere. Water molecules cling to the ash particles, causing it to rain.
This reaction is why very few eruptions have global repercussions. Most of the volcanic ash and gasses released by an eruption only make it into the troposphere, where they are quickly flushed out by rain.
Another common occurrence is volcanic fog, colloquially known as “vog” in Hawaii and other volcanic regions. Instead of having large, violent eruptions, many volcanoes simply simmer, continually giving off smoke and sulphur-dioxide. These particles and gasses combine to create poor air quality and hazy conditions, similar to smog in crowded cities.
Whether short-term or long lasting, the effect of volcanoes on weather are complex and undeniable, and just one more reminder of how sensitive and interconnected the natural world is.