The Effect of Volcanic Eruptions on Climate

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The Effect of Volcanic Eruptions on Climate

Introduction

Recently there has been a lot of research in the field of climate change, and much of it is focused on anthropogenic affects on climate. However, there has also been a great deal of research focused on natural Earth processes and how they affect the climate (Robock 2000). One natural process which significantly impacts climate is volcanic eruptions. Volcanic eruptions affect the climate of the earth in many ways (Zielinski et al 1997). Volcanic ash ejected during eruptions effect climate by reflecting solar rays back into space, and thus cooling the surface of the Earth. Another way volcanoes affect the Earth’s climate, is the emission of many different types of volcanic gasses. Volcanic gasses including CO2, H2O vapour, and different kinds of sulfur gasses such SO2 and H2S, affect the climate in very different ways (Robock 2000). CO2 and H2O vapour generally act as green house gasses and work towards heating the Earth’s surface temperature. Sulfuric gasses affect climate in more complicated ways which is mainly a function of the concentrations of these gasses in the atmosphere (Ward 2009). This paper will examine the role volcanic eruptions have in affecting climate through the ejection of volcanic ash and the emission of different volcanic gasses including CO2, H2O vapour, and sulfuric compounds, and the impact certain historic volcanoes have had on climate by ejecting all of these kinds of particles. Effects of Volcanic Ash on Climate

When Volcanoes erupt they eject large amounts of volcanic ash into the atmosphere (Robock 2000). These particles generally stay in the atmosphere for only a couple of weeks to a couple months. After this time they settle out of the air and become deposited in between sedimentary beds However, while these particles are in the atmosphere they spread around the globe very quickly and affect the earth’s climate for the short term of their suspension.

When the ash is suspended in the atmosphere, it has a strong effect on surface temperatures. Robock (2000) explains that the intensities of the diurnal cycle are reduced for regions under the airborne ash clouds. Diurnal cycles refer to the patterns exhibited on a 24 hour time period that continue day to day such as temperature, tides, etc. He explains that the daily temperatures of the Earth’s surface are lowered by a couple of degrees because there is less solar insulation which is the amount of sunlight falling on a given area. This decrease in solar insulation is due to the volcanic ash’s ability to backscatter the sun’s solar rays back into space; therefore, cooling the surface of the Earth.

Not only does volcanic ash affect surface temperatures, it also affects the Earth’s precipitation levels during its time of suspension. A study by Wallace et al (1994) examines the composition of the magmatic material which gets ejected from a volcano in the form of ash during eruptions. He explains that the main component in this ash is the anhydrite CaSO4. This anhydrite ash will readily absorb water to form the mineral gypsum CaSO4∙2H2O. When the anhydrite absorbs water, it will take it directly from regular rainclouds. This reduction in rain cloud moisture will decrease the amount of precipitation that reaches the Earth’s surface leading to potential droughts in certain regions.

Effects of Volcanic CO2 and H2O on Climate
Volcanoes release many types of gasses when they erupt and within a short amount of time these gasses, like the volcanic ash, circle the globe. According to a study by Bluth et al (1992), the gasses released during the 1982 El Chicho´n eruption in Mexico and the 1991 Mt Pinatubo eruption in the Philippines were scattered around the whole Earth within three weeks. However, unlike volcanic ash which almost always completely settles out in a few months, these volcanic gasses can stay in the atmosphere for many years (Robock 2000). Some gasses like CO2 and H2O...
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