April 2015 marks the 200th anniversary of the most powerful volcanic eruption in modern times, the eruption of Mount Tambora in Indonesia. \u00a0This eruption is discussed in awe in climatology classes because of what we now know about the impacts of volcanic activity on climate–it depresses global temperatures for up to five years after a major eruption. \u00a0The length of time that the colder than normal temperatures last depend on how big the eruption was and where it occurred. \u00a0If the eruption is near the equator, it is more significant in its impact because the effects travel equally into both the southern and northern hemispheres, while high-latitude eruptions tend to affect one hemisphere more than the other.<\/p>\n
Volcanic eruptions affect short-term climate mainly by its emission of sulfuric acid droplets high into the atmosphere. \u00a0These droplets act like tiny shiny glass beads similar to the ones used in stop signs. \u00a0They are highly reflective and act to reflect sunlight back to space before it can get to earth’s surface. \u00a0This reduces the energy input into the earth’s global climate system. \u00a0With less energy to work with, temperatures are depressed and the atmospheric and oceanic circulations can also change. \u00a0Volcanic ash can also have some effects, but they are less important for global climate and tend to cause more local effects, since ash is heavier and cannot be carried as far away as the sulfuric acid droplets.<\/p>\n
In the case of Tambora, temperatures in the years following the eruption were reduced so much that in 1816, temperatures in the northern hemisphere led to the “Year without a Summer”. \u00a0Frosts occurred in northern locations every month of the year and clothes froze to washing lines in New England summers. \u00a0Famine became a problem in some areas due to the lack of food. \u00a0And it was so cold and cloudy in Europe that Mary Shelley and her friends were forced to sit inside telling stories to each other, leading to the eventual publication of “Frankenstein”. \u00a0Climate events can have impacts far beyond just energy and agriculture!<\/p>\n
The Economist<\/em> has a fantastic story about Tambora in this month’s issue (link<\/a>). \u00a0I encourage you to read it and think about how you would make changes to your farm management if another big eruption occurred. \u00a0Other more recent eruptions have occurred in 1883 (Krakatoa, Indonesia), 1912 (Katmai, Alaska), 1963 (Agung, Indonesia), 1982 (El Chichon, Mexico), and 1991 (Pinatubo, Philippines) One could happen again at any time. \u00a0Fortunately, it usually takes a few months for the effects to be seen in the climate, which gives producers time to make plans for changes in crops and growing season in subsequent years.<\/p>\n
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