Coldest Decade on Earth in the Past 500 Years
Unknown, Mystery Volcano Explains the Coldest Ten Year Period
Nov 10, 2009
Reports of beautiful sunsets the color purple and the presence of summer frosts and snow throughout temperate regions of the northern hemisphere resulted in 1816 being named the year without a summer. A subsequent famine became known as the worst famine of the century after crops were ruined by the cold temperatures and reduced sunlight.
Global temperature changes in the past must be understood in order to predict the effects of atmospheric changes on global temperature and climate changes in the future. A major problem for climatologists has been their inability to explain why the period from 1810 to 1819 was the coldest decade in the last 500 years.
Tambora: Largest & Deadliest Volcano
Not surprisingly, the second part of the coldest decade is attributed to the largest volcanic eruption ever recorded, that of the Indonesian volcano Tambora on April 10, 1815. Also the deadliest volcanic eruption in recorded history, this catastrophe killed more than 70,000 people and released enormous quantities of volcanic debris into the atmosphere. The heavier ash fell to earth within several weeks but the finer ash particles and sulfur gases reached into the stratosphere (33,000-100,000 feet) and formed sulfuric acid that blocked solar radiation from reaching the earth. While the Tambora eruption certainly helped to explain the second half of the coldest decade, it was not adequate to account for the below average temperatures during the first half of this period.
Ice Cores Contain Volcanic Sulfuric Acid
Now scientists have discovered a likely explanation for the first half of the cold spell. Researchers from South Dakota, San Diego, California, and Grenoble and Aix-en-Provence in France have discovered evidence for an unknown volcanic eruption estimated to be about half as powerful as Tambora that occurred in the year 1809. Appropriately, the cold, hard evidence for this cold spell was found in ice.
Drilled ice core samples collected in Greenland and Antarctica about three years ago were chemically analyzed. Ice that was deposited during the years 1809 and 1810 in both locations at opposite poles of the earth contained unusually large amounts of sulfuric acid. The data suggested that the sulfuric acid came from the same source, most likely a volcano. The sulfur isotopes indicated that the sulfate had spent time in the stratosphere, a requirement for such fine particles to affect the earth's temperature and climate.
Mystery Volcano Explains Coldest Period
Together, the mystery volcano of 1809 and the Tambora volcano of 1815 can explain why the period from 1810 to 1819 was the coldest decade in the past 500 years. The scientists published their study in the journal Geophysical Research Letters in October 2009 and suggested that the unknown volcano may have been in the tropics because that location could explain the deposition of sulfuric acid at both the north and south poles, based on knowledge of prevailing atmospheric winds. The fine sulfurous ash in the stratosphere is eventually removed by precipitation. The analysis of global temperatures during the last 500 years, shows that the temperature and climate quickly return to normal after the ash is removed.
Global Climate Change
The study provides information that correlates atmospheric and temperature changes in the past that is important for understanding and predicting global climate change in the future.
Sources
Oppenheimer, Clive, Climatic, environmental and human consequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815. Progress in Physical Geography 27(2):230-259, 2003.
Cole-Dai, J., D. Ferris, A. Lanciki, J. Savarino, M. Baroni, and M. H. Thiemens, Cold decade (AD 1810-1819) caused by Tambora (1815) and another (1809) stratospheric volcanic eruption, Geophys. Res. Lett., doi:10.1029/2009GL040882, 2009.
 |
