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IMPACTS OF VOLCANOES ON CLIMATE

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IMPACTS OF VOLCANOES ON CLIMATE

HISTORICAL ERUPTIONS THAT HAVE THE MOST INFLUENCE ON THE CLIMATE

 

IMPACTS OF VOLCANOES ON CLIMATE

A volcanic eruption of high magnitude can influence the climate in a major way for several years. Although the eruptions themselves are not predictable, however, one can get an idea of their effect on climate. Benjamin Franklin (1706-1790) was the first to see that volcanic eruptions affect climate with the harsh winter of 1783-1784 caused by the eruption of Jökull and Eldeyjar in Iceland. In the South of France the stars located above 40° of angular height in relation to the horizon were only been seen.

 

  • EXPLANATION

In the history of the Earth, the largest volcanic eruptions were followed by a cooling of few years. This is due to the large amount of sulfur dioxide (SO2) and ash ejected by these volcanic eruptions. Much of the dust and particles ascend to the stratosphere at 20.km of altitude and sometimes at even more of 50.km. At these altitudes, the winds are strong and the gas can often make several times around the planet. As the stratosphere is stable and reduced vertical movements, the ejected gas may remain for several years.

The ashes sent into the atmosphere fall gradually in the stable high stratosphere, and helps to increase the creation of clounds and precipitations in the lower atmosphere. But this is not the ashes that have the greatest effect on climate.

    • THE FALL OF TEMPERATURE

When sulfur dioxide ejected into the stratosphere is mixed with water vapor in the atmosphere, then this gas turns into liquid sulfuric acid (H2S04) and becomes what is named "aerosol", ie fine droplets of a few tenths of microns in diameter.

These sulfuric acid aerosols, absorb and reflect back to space solar radiation while warming occurs in the stratosphere, it can reach a few degrees at the height of the layer.Then tropospheric temperature tends to fall as was the case during many eruptions. And sometimes this can last 2 to 3.ans after the eruption. In general, there is a net reduction of 5 to 10% of the energy received on the surface of the Earth. While the temperature may fall by 0,10°C to 1°C sometimes. The global cooling triggered by these eruptions would always initially detected under the tropics, shortly after the eruption. Then he then propagate at mid-latitudes over the following years.

Estimates of the fraction of sunlight transmitted through the
aerosols of the Stratigraphic after the major volcanic eruptions.
Rosa refers to a basalt eruption flooding the US Northwest.
According Rampino and al (1988).

 

Click here to see an animation of the effects of a volcanic eruption

The scale of climate disruption will depend on the place the eruption. A volcanic eruption at the equator like the Pinatubo, has the opportunity to reach the global climate of the Earth since the product aerosols may extend in both hemispheres. Aerosols prevent the heat of the sun of crossing the lowest layer of the atmosphere (the troposphere) by cooling then the temperature of regions near the tropics but by warming the stratosphere. The temperatures of North and South are reduced and AO is accelerated. Cold air remains in the North during the winter and much of the US Northeast is experiencing mild weather..

According to NASA studies of of the explosion of Katmai in Alaska, volcanic eruptions located in high-latitude have less impact on the earth as the majority of aerosols have remained largely in the North where they have not been as much exposed to heat. Accordingly, the lower stratosphere very little heated therefore cools less the troposphere and the influence on the Arctic Oscillation is limited.

As can be seen in this diagram the large eruptions lead to global cooling,
as was the case in El Chichon eruption of Mount Pinatubo in 1982 and in 1991

    • DECREASE OF THE OZONE LAYER STRATOSPHERIC

The sulfuric acid aerosols formed in the stratosphere when the sulfur dioxide combines with water particles accelerate the destruction of the ozone layer. The years following the eruption of Mount Pinatubo in 1991, the mapping of the ozone layer and other observations showed reductions of ozone more important than previous years as many in mid-latitudes and high latitudes of the northern hemisphere.

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