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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 gases into the stratosphere where they undergo a series of reactions to create sulfuric acid which can nucleate and form aerosols.[1] Volcanic stratospheric aerosols cool the surface by reflecting solar radiation and warm the stratosphere by absorbing terrestrial radiation.[2] The variations in atmospheric warming and cooling result in changes in tropospheric and stratospheric circulation.[1]

Historic examples

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

1991
The 1991 eruption of Mount Pinatubo, a stratovolcano in the Philippines, cooled global temperatures for about 2–3 years.[3]
1883
The explosion of Krakatoa (Krakatau) may have contributed to volcanic winter-like conditions. The four years following the explosion were unusually cold, and the winter of 1887–1888 included powerful blizzards.[4] Record snowfalls were recorded worldwide. However, the period of cold winters started with the 1882-1883 winter, months before the Krakatoa eruption.
1815
The 1815 eruption of Mount Tambora, a stratovolcano in Indonesia. The eruption had a Volcanic Explosivity Index of 7. The eruption was the largest in recorded human history and one of largest in the holocene (10,000 years to present). The eruption led to global cooling and worldwide harvest failures caused what came to be known as the "Year Without a Summer" of 1816. Europe, still recuperating from the Napoleonic Wars, suffered from food shortages. Food riots broke out in the United Kingdom and France, and grain warehouses were looted. The violence was worst in landlocked Switzerland, where famine caused the government to declare a national emergency. Huge storms and abnormal rainfall with flooding of Europe's major rivers (including the Rhine) are attributed to the event, as is the August frost. A major typhus epidemic occurred in Ireland between 1816 and 1819, precipitated by the famine. An estimated 100,000 Irish people perished during this period. A BBC documentary, using figures compiled in Switzerland, estimated that the fatality rates in 1816 were twice that of average years, giving an approximate European fatality total of 200,000 deaths. The corn crop in Northeastern North America failed, due to mid-summer frosts in New York State and June snowfalls in New England and Newfoundland and Labrador. The crop failures in New England, Canada, and parts of Europe also caused the price of wheat, grains, meat, vegetables, butter, milk, and flour to rise sharply.
1783
The eruption of the Laki volcano in Iceland released enormous amounts of sulfur dioxide, resulting in the death of much of the island's livestock and a catastrophic famine which killed a quarter of the Icelandic population. It has been estimated that 23,000 British people died from the poisoning.[5] Northern hemisphere temperatures dropped by about 1 °C in the year following the Laki eruption. The winter of 1783–1784 was very severe, and estimated to have caused 8,000 additional deaths in the UK. The meteorological impact of Laki continued, contributing significantly to several years of extreme weather in Europe. In France, the sequence of extreme weather events contributed significantly to an increase in poverty and famine that may have contributed to the French Revolution in 1789.[6] Laki was only one factor in a decade of climatic disruption, as 1991 eruption of Mount Pinatubo, a stratovolcano in the Philippines, cooled global temperatures for about 2–3 years.[3]
1883
The explosion of Krakatoa (Krakatau) may have contributed to volcanic winter-like conditions. The four years following the explosion were unusually cold, and the winter of 1887–1888 included powerful blizzards.[4] Record snowfalls were recorded worldwide. However, the period of cold winters started with the 1882-1883 winter, months before the Krakatoa eruption.
1815
The 1815 eruption of Mount Tambora, a stratovolcano in Indonesia. The eruption had a Volcanic Explosivity Index of 7. The eruption was the largest in recorded human history and one of largest in the holocene (10,000 years to present). The eruption led to global cooling and worldwide harvest failures caused what

The causes of the population bottleneck – a sharp decrease in a species' population, immediately followed by a period of great genetic divergence (differentiation) among survivors – is attributed to volcanic winters by some researchers. Such events may diminish populations to "levels low enough for evolutionary changes, which occur much faster in small populations, to produce rapid population differentiation".[20] With the Lake Toba bottleneck, many species showed massive effects of narrowing of the gene pool, and Toba may have reduced the human population to between 40,000 and 15,000 or even fewer.[20]

See also

References

  1. ^ a b Robock, Alan (May 2000). "Volcanic eruptions and climate". Reviews of Geophysics. 38 (2): 191–219. Bibcode:2000RvGeo..38..191R. doi:10.1029/1998RG000054.
  2. ^ Santer, Benjamin D.; Bonfils, Céline; Painter, Jeffrey F.; Zelinka, Mark D.; Mears, Carl; Solomon, Susan; Schmidt, Gavin A.; Fyfe, John C.; Cole, Jason N. S.; Nazarenko, Larissa; Taylor, Karl E.; Wentz, Frank J. (March 2014). "Volcanic contribution to decadal changes in tropospheric temperature". Nature Geoscience. 7 (3): 185–189. Bibcode:2014NatGe...7..185S. doi:10.1038/ngeo2098. hdl:1721.1/89054.
  3. ^ Brohan, P.; Kennedy, J. J.; Harris, I.; Tett, S. F. B.; Jones, P. D. (2006). "Uncertainty estimates in regional and global observed temperature changes: A new data set from 1850". Journal of Geophysical Research. 111 (D12): D12106. Bibcode:2006JGRD..11112106B. CiteSeerX 10.1.1.184.4382. doi:10.1029/2005JD006548.
  4. ^ University of Minnesota. "With a Bang: Not a Whimper" (PDF). Archived from the original (PDF) on 2010-06-22.
  5. ^ Walker, Dan (19 January 2007). "When a killer cloud hit Britain". BBC Two's Timewatch.
  6. ^ Wood, C.A. (1992). "The climatic effects of the 1783 Laki eruption". In Harrington, C. R. (ed.). The Year Without a Summer?. Ottawa: Canadian Museum of Nature. pp. 58–77.
  7. ^ Grove, Richard H. (May 1998). "Global impact of the 1789-93 El Niño". Nature. 393 (6683): 318–319. Bibcode:1998Natur.393..318G. doi:10.1038/30636. S2CID 205000683.
  8. ^ James Hansen (January 1997). "Pinatubo Climate Investigation". NASA Goddard Institute for Space Studies.
  9. ^