Global Cooling Post-Eruption
A period of Global cooling is also present post-eruption. This is due to the emission of Sulphur Dioxide ejected into the Stratosphere. The SO2 reflects electromagnetic radiation produced by the Sun by the processes of absorption and scattering. Sulphur Dioxide within the atmosphere appears to degrade global temperatures. As SO2 penetrates the Stratosphere it reacts with Oxygen and water vapour to produce microscopic droplets of Sulphuric acid (H2SO4) aerosols. The aerosols often circle the globe weeks after initial eruption predominantly throughout the latitude they erupted at due to convection cells within the atmosphere where they may remain for two to 3 years. The condition is recognised as the haze effect. The haze is often referred to as Vog, a portmanteau between the words volcanic and smog. The haze limits visibility and is prominent throughout the lower troposphere as can be seen in figure 12. Vog in the Stratosphere however, causes greater, global effects on the Earth.
Past eruptions including Mount Pinatubo caused global temperature decreases of 0.4 degrees Celsius supporting that past eruptions have followed theories expected to occur after an eruption. The super volcano Toba is also suggested to have caused a volcanic winter that lasted over 6 years.
The effects of this increased reflection of incoming solar radiation would most likely have been amplified by an increase in albedo. The lower temperatures caused by an increase in SO2 aerosols in the atmosphere may have increased Arctic sea ice, thus increasing the reflectivity of the surface of the Earth, and causing a positive climactic feedback, further decreasing average global temperatures.
In April 1815 Mount Tambora erupted on the island of Sumbawa in Indonesia. The super-colossal eruption measured VEI 7[1] and was the largest eruption in recorded history. The eruption ejected 160 kilometres cubed of ash particles over 37 kilometres into the atmosphere penetrating well into the Stratosphere.[2] The eruption was the cause of, ‘A year without a summer,’ for many countries within the Northern Hemisphere due to the stratospheric veil of aerosols. The estimates of Sulphate aerosols ejected are an ongoing debate as to the multiple methods such as anatomical observations indicating optical depth measurements, a petrological method studying petroleum sources containing sulphur molecules as well as studying the polar ice sulphate concentrations within ice cores taken from Antarctica and Greenland. To insure the concentrations relate to the eruptions the ice cores are dated by quantifying oxygen isotopes variations between seasons.[3] In 1816 the Northern Hemisphere experienced the coldest year since 1601 following the Huaynapuntina in Peru in the year of 1600.[4] Between 1816 and 1818, lower Tropospheric temperature anomalies were -0.51 degrees Celsius, -0.44 and -0.29[5] degrees respectively which relates to figure 13 showing increased sulphate concentrations directly after the large volcanic eruption in 1815. In 1810 a large eruption is also assumed to have occurred but still remains unknown.
The effects of this increased reflection of incoming solar radiation would most likely have been amplified by an increase in albedo. The lower temperatures caused by an increase in SO2 aerosols in the atmosphere may have increased Arctic sea ice, thus increasing the reflectivity of the surface of the Earth, and causing a positive climactic feedback, further decreasing average global temperatures.
In April 1815 Mount Tambora erupted on the island of Sumbawa in Indonesia. The super-colossal eruption measured VEI 7[1] and was the largest eruption in recorded history. The eruption ejected 160 kilometres cubed of ash particles over 37 kilometres into the atmosphere penetrating well into the Stratosphere.[2] The eruption was the cause of, ‘A year without a summer,’ for many countries within the Northern Hemisphere due to the stratospheric veil of aerosols. The estimates of Sulphate aerosols ejected are an ongoing debate as to the multiple methods such as anatomical observations indicating optical depth measurements, a petrological method studying petroleum sources containing sulphur molecules as well as studying the polar ice sulphate concentrations within ice cores taken from Antarctica and Greenland. To insure the concentrations relate to the eruptions the ice cores are dated by quantifying oxygen isotopes variations between seasons.[3] In 1816 the Northern Hemisphere experienced the coldest year since 1601 following the Huaynapuntina in Peru in the year of 1600.[4] Between 1816 and 1818, lower Tropospheric temperature anomalies were -0.51 degrees Celsius, -0.44 and -0.29[5] degrees respectively which relates to figure 13 showing increased sulphate concentrations directly after the large volcanic eruption in 1815. In 1810 a large eruption is also assumed to have occurred but still remains unknown.
http://en.wikipedia.org/wiki/File:Greenland_sulfate.png
In the past, the 'Little Ice Age', a period of lower average temperatures (especially in Europe) and much colder winters, has been attributed to the 'Maunder Minimum', a semi-permanent solar minimum. However, recent research has shown that even during extreme solar minima, the minimum solar irradiance is still too high to explain any global cooling effects. Therefore, scientists are now looking at new causes of the LIA, such as large-scale volcanic activity prior to the dip in global temperatures.
Increased SO2 in the atmosphere certainly does explain short term drops in temperatures, but these effects would only be seen for a couple of years at most. This brings us back to the effects of positive feedbacks such as the increase in albedo that could occur, as previously explained. The increase in albedo would continue the cooling affect over the long term, and therefore may have attributed to the cause of the LIA.
However, the LIA is recorded as lasting for as much as 500 years, and even though albedo effects can be long lasting, they would most likely not account for the entire period of cooling, and therefore we may have to take into account some sort of combination theory.
[1] http://en.wikipedia.org/wiki/Mount_Tambora
[2] http://www.wired.com/science/discoveries/news/2009/04/dayintech_0410
[3] http://en.wikipedia.org/wiki/Mount_Tambora
[4] http://en.wikipedia.org/wiki/Year_Without_a_Summer
[5] http://en.wikipedia.org/wiki/Year_Without_a_Summer
Increased SO2 in the atmosphere certainly does explain short term drops in temperatures, but these effects would only be seen for a couple of years at most. This brings us back to the effects of positive feedbacks such as the increase in albedo that could occur, as previously explained. The increase in albedo would continue the cooling affect over the long term, and therefore may have attributed to the cause of the LIA.
However, the LIA is recorded as lasting for as much as 500 years, and even though albedo effects can be long lasting, they would most likely not account for the entire period of cooling, and therefore we may have to take into account some sort of combination theory.
[1] http://en.wikipedia.org/wiki/Mount_Tambora
[2] http://www.wired.com/science/discoveries/news/2009/04/dayintech_0410
[3] http://en.wikipedia.org/wiki/Mount_Tambora
[4] http://en.wikipedia.org/wiki/Year_Without_a_Summer
[5] http://en.wikipedia.org/wiki/Year_Without_a_Summer