Volcanism

MEMBERS OF THE scientific community by and large concur that the Earth is undergoing a change in climate and that global warming is occurring at an increasing rate. In fact, scientific modeling suggests that Earth will experience an increase in temperature during the next 100 years at a pace up to four times greater than that in the previous 100 years. To a large extent this acceleration in the late 20th century is attributed to carbon dioxide (CO2) emissions generated by human activity. Carbon dioxide acts like a glass barrier over the Earth, preventing heat from leaking into the environment, and thus creating a greenhouse effect. Human activity has counteracted global warming to a small degree by emitting aerosols in the environment, causing global cooling.

Volcanism is another contributing factor to climate change. Each volcano affects the climate based on its location and the nature and extent of an eruption.

Similar to human activity, volcanism leads to both global warming and cooling. The effect of volcanism on climate depends on the interaction between the sun's heat and the volcanic debris. In essence, scientists believe that ongoing volcanic eruptions have maintained the Earths temperate climate for millions of years. Circumstantial evidence suggests that volcanism can influence short-term weather patterns in addition to having an effect on long-term climate change.

Volcanic dust blown into the atmosphere can remain for months and produce temporary cooling, the degree to which is dependent on the volume of dust, and the duration of which is dependent on the size of the dust particles. The strength of gases can vary greatly among volcanoes. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride.

Volcanoes that discharge great quantities of sulfur compounds affect the climate more significantly than those that release only dust. In fact, the greatest volcanic effect on the Earth's short-term weather patterns is caused by sulfur dioxide gas. Sulfur dioxide can form sulfuric acid aerosols that reflect the sun's heat and trigger cooling of the Earth's surface for as long as two years. Scientific literature frequently refers to the drop in global temperature after the eruption of Mount Pinatubo, Philippines, in 1991 and the very cold temperatures leading to crop failures and famine in North America and Europe for two years following the eruption of Mt. Tam-bora, Indonesia, in 1815 as examples of this effect. Furthermore, sulfuric dioxide can form acid rain, a combination of sulfuric acid and nitric acid. Acid rain, which is also caused by the burning of fossil fuels, is a critical environmental problem that can [Page 1067]injure lakes, streams, and forests and the inhabitants of these ecosystems.

Yasur volcano in Vanuatu is one of the world's most active volcanoes, erupting dozens of times a day for about 800 years.

In addition, volcanoes discharge water and carbon dioxide in large quantities in the form of atmospheric gases, and can absorb and retain in the atmosphere heat radiation emanating from the ground. Estimates suggest that water makes up to 99 percent of gas in volcanic expulsions. This short-term warming of the air leads the water to become rain within a matter of hours or days and the carbon dioxide to dissolve in the ocean or to be absorbed by plants. The majority of the heat energy connected to global warming exists in the ocean. If the oceanic depth at which heat is stored is decreased, then global temperature increases are expected to be greater than predicted.

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