Translator’s Note: Overall, the translation of this article was relatively smooth; I just needed to look up a few unfamiliar words in the software. I would like to mention an issue beyond the translation itself: It is well known that carbon dioxide causes the greenhouse effect, while sulfur dioxide can inhibit it. Unfortunately, almost all atmospheric environmental management methods aim to convert other polluting gases into carbon dioxide, including the treatment of sulfur dioxide. This creates a problem where the more the environment is managed, the stronger the greenhouse effect becomes. Environmentalists should perhaps consider the balance between these two factors.
By Phil Berardelli
On a clear day about 74,000 years ago, a massive volcanic eruption occurred on the island of Sumatra. This volcano, named Toba, erupted with a total volume of rock and other materials more than 1,000 times that of the 1980 eruption of Mount St. Helens in Washington, USA. During that period, Earth’s temperature dropped by at least 10^\circ\text{C}, causing global famine.
But were there even more serious consequences? A new study asks: Did the Toba eruption plunge the Earth into an ice age lasting more than 1,000 years? Could the same thing happen today, pushing us back into an ice age?
Large volcanic eruptions—like Toba—do not exacerbate global warming. On the contrary, although eruptions emit greenhouse gases (such as carbon dioxide, \text{CO}_2), they also emit sulfur dioxide (\text{SO}_2). Sulfur dioxide can combine with water to spread across the globe in the form of sulfate aerosols, which block solar radiation, causing temperatures to drop, and then fall as acid rain or snow.
Paleoclimatic evidence suggests that the Toba eruption, which occurred during the last glacial period, emitted far more sulfur dioxide than Mount St. Helens, and the timing of the eruption coincides exactly with the beginning of a 1,000-year cold period. Consequently, some scientists have proposed that Toba could cause freezing weather and that a similar event today might bring about a new ice age. However, NASA’s modeling centers and the National Center for Atmospheric Research in Colorado have different views.
Alan Robock, a leading climatologist at Rutgers University in New Brunswick, New Jersey, established a volcanic eruption model with sulfur dioxide emissions several times that of Toba. The results, published in the May 27 issue of the journal Geophysical Research Letters, indicate that the low-temperature climate lasted only a few decades. Therefore, the 1,000-year ice age was likely just a result of natural cycles; over the past millions of years, the Earth has already experienced dozens of ice ages.
“The research results almost completely rule out the theory that large volcanic eruptions are one of the causes of global ice ages,” said Ellen Mosley-Thompson, a climatologist at Ohio State University in Columbus. Thompson, who was not involved in the study, added, “Therefore, paleoclimatologists should focus their research on other variable factors, such as changes in ocean circulation or periodic changes in the Earth’s orbit around the sun.”
However, if Toba were to erupt today as it did in the past, the consequences would be catastrophic. Although it is not expected that the volcano would affect the climate for thousands of years, Robock and his colleagues estimate it would still cause global temperatures to drop by 17^\circ\text{C} for several years, taking decades to return to normal. This would deal a double blow to the human population through “massive agricultural crop failures” and “large-scale loss of vegetation.”
Appendix: Introduction to the Eruption of Mount St.
Helens
https://en.wikipedia.org/wiki/Mount_St._Helens
Original English Article (from Science Magazine
website)
http://sciencenow.sciencemag.org/cgi/content/full/2009/707/2
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