Volcanic Gases and Climate Change OverviewVolcanoes can impact climate change. During major explosive eruptions huge amounts of volcanic gas, droplets, and ash are injected into the stratosphere. Injected ash falls rapidly from the stratosphere -- most of it is removed within several days to weeks -- and has little impact on climate change. But volcanic gases like sulfur dioxide can cause global cooling, while volcanic carbon dioxide, a greenhouse gas, has the potential to promote global warming.

Droplets of volcanic sulfuric acid increase the reflection of radiation from the Sun back into space, cooling the Earth's lower atmosphere or troposphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years.

The eruption of Mount Pinatubo on June 15, 1991, was one of the largest eruptions of the twentieth century and injected a 20-million ton sulfur dioxide cloud 20 kilometers high into the stratosphere. The Pinatubo cloud was the largest sulfur dioxide cloud ever observed in the stratosphere. It caused what is believed to be the largest aerosol disturbance of the stratosphere in the twentieth century. Consequently, it cooled the Earth's surface for three years following the eruption, by as much as 1.3 degrees.

While sulfur dioxide released in more recent volcanic eruptions has occasionally caused measurable global cooling of the lower atmosphere, the carbon dioxide released in modern day volcanic eruptions has never caused detectable global warming of the atmosphere. This is probably because recent volcanoes have not been big enough to produce detectable global warming

Volcanic versus man-made CO2 emissions

Do the Earth’s volcanoes emit more CO2 than human activities? Research findings indicate that the answer to this frequently asked question is a clear and unequivocal, “No.” Human activities release approximately 35 billion metric tons of CO2. All of the volcanoes on the planet release a total of approximately 0.4 billion metric tons.

In recent times, about 70 volcanoes are normally active each year on the Earth. One of these is Kīlauea volcano in Hawaii, which has an annual CO2 output of about 0.0031 billion metric tons per year. It would take a huge addition of volcanoes to the earth —the equivalent of an extra 11,200 Kīlauea volcanoes—to scale up the global volcanic CO2emission rate to the man-made CO2 emission rate.

Volcanic Gases and Climate Change Overview. U.S. Geological Survey, n.d. Web. 20      May 2014. <http://volcanoes.usgs.gov/hazards/gas/climate.php>. 

Mount Pinatubo, June, 1991 1

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by Jason Wolfe

September 5, 2000

When Mount Pinatubo erupted in the Philippines June 15, 1991, an estimated 20 million tons of sulfur dioxide and ash particles blasted more than 12 miles (20 km) high into the atmosphere. The eruption caused widespread destruction and loss of human life. Gases and solids injected into the stratosphere circled the globe for three weeks. Volcanic eruptions of this magnitude can impact global climate, reducing the amount of solar radiation reaching the Earth's surface, lowering temperatures in the troposphere, and changing atmospheric circulation patterns. The extent to which this occurs is an ongoing debate. Large-scale volcanic activity may last only a few days, but the massive outpouring of gases and ash can influence climate patterns for years. Sulfur gases convert to sulfate aerosols, very small droplets containing of sulfuric acid. Following eruptions, these aerosol particles can linger as long as three to four years in the stratosphere.Major eruptions alter the Earth's climate because volcanic aerosol clouds absorb terrestrial radiation (heat being given off by the Earth), and scatter a significant amount of the incoming solar radiation (heat from the sun), an effect known as "radiative forcing" that can last from two to three years following a volcanic eruption."Volcanic eruptions cause short-term climate changes and contribute to natural climate variability," says Georgiy Stenchikov, a researcher at Rutgers University. "Exploring effects of volcanic eruption allows us to better understand important physical mechanisms in the climate system that are initiated by volcanic forcing."NASA's Upper Atmosphere Research Satellite (UARS) enables study of the chemistry, dynamics and energy balance in the atmosphere layers above the troposphere. UARS provides measurements of the atmosphere. UARS has data from September 18, 1991 through August 31, 1999. Stratospheric Aerosol and Gas Experiment II (SAGE II), launched in October 1984, uses a technique called solar occultation to measure solar radiation and to determine the distribution of stratospheric aerosols, ozone, nitrogen dioxide, and water vapor around the globe. Multi-Channel Sea Surface Temperature (MCSST) data are taken from measurements of emitted and reflected radiance by the five-channel Advanced Very High Resolution Radiometers (AVHRR) onboard the NOAA -7, -9. -11 and -14 polar orbiting satellites. MCSST data currently extend from November 11, 1981 through June 7, 2000, and are updated as new data become available.

Stenchikov and Professor Alan Robock of Rutgers University with Hans Graf and Ingo Kirchner of the Max Planck Institute for Meteorology performed a series of climate simulations. They combined volcanic aerosol observations (taken from the SAGEII, the

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UARS, and MCSST).

The research team tested the impact on the climate with and without Pinatubo aerosols for the two years following the Pinatubo eruption. They conducted calculations with mean sea surface temperature to see how sensitive climate change is to volcanic aerosols.

By comparing the climate simulations from the Pinatubo eruption, with and without aerosols, the researchers found that Pinatubo caused a general cooling of the global troposphere, but also caused a winter warming pattern of surface air temperature over Northern Hemisphere continents. The temperature of the tropical lower stratosphere increased by 4°C because of aerosol absorption of radiation. The experiment demonstrated that the direct radiative effect of volcanic aerosols causes general stratospheric heating and tropospheric cooling, with a tropospheric warming pattern in the winter.

"The modeled temperature change is the same as the temperature changes observed after the eruption," Stenchikov says. "The pattern of winter warming following the volcanic eruption is practically identical to a pattern of winter surface temperature change caused by global warming. It shows that volcanic aerosols force fundamental climate mechanisms that play an important role in the global change process."

This temperature pattern is consistent with the existence of a strong phase of the Arctic Oscillation, a natural pattern of circulation in which atmospheric pressure at polar and middle latitudes varies, bringing higher-than-normal pressure over the polar region and lower-than-normal pressure at about 45 degrees north latitude. It is forced by the aerosol radiative effect, and circulation in winter is stronger than the aerosol radiative cooling that dominates in summer.

Man-made, or "anthropogenic" emissions can make the consequences of volcanic eruptions on the global climate system more severe, Stenchikov says. For instance, chlorofluorocarbons (CFCs) react with aerosols to destroy ozone molecules in the mid-latitude stratosphere, reducing our protection from harmful ultraviolet radiation from the Sun.

"In 1991 after the Pinatubo eruption, the ozone content in the mid-latitudes decreased by 5 percent to 8 percent, affecting highly populated regions," says Stenchikov.

By understanding the impact of large volcanic eruptions on Earth's climate system in more detail, perhaps scientists will be in a better position to suggest measures to lessen their effects on people and natural resources.

Volcanoes and Climate Change. NASA Earth Observatory, n.d. Web. 20 May 2014.      <http://earthobservatory.nasa.gov/Features/Volcano/>. 

Volcanoes and Global Climate Change

Volcanoes are the most dramatic and rapid agents of geologic change. An erupting volcano can eject vast amounts of ash and gases into the atmosphere, and cover the ground with tons of lava flows and ash. Eruptions create new mountains, and tear down old ones as we watch. Large eruptions are dangerous, sometimes killing tens of thousands of people at one time. But the most extreme impact of eruptions is their effect on Earth’s climate.

Our planet’s climate results from a complex and always changing mixture of processes and events. The basic source of energy is radiation from the Sun. The incoming radiation interacts with the Earth’s atmosphere and surface, so that changes to either can affect the climate. For example, a dark lava flow absorbs more of the solar energy than a desert soil, so a large enough lava flow could warm a local region. But a much larger influence on climate comes from volcanic gases erupted into the atmosphere that spread out and encircle the planet.

The most abundant gas typically erupted is water vapor, which has been measured to be as high as 97% of gases erupted from some volcanoes. The water has very little impact on climate because it usually rains out of the atmosphere fairly quickly. In fact, it is very common to find volcanic ash deposited that preserve rainfall splash marks.

The greenhouse gas carbon dioxide (CO2) is the second most common gas (varying from 1% to 50% in different types of eruptions). Carbon dioxide is heavier than air and commonly collects in low-lying areas; it can poison and kill animals that breathe it. The CO2

does not significant influence climate because volcanic CO2 is only about 1% of what is released by burning of fossil fuels.

The gas that does have a noticeable climate impact is sulfur dioxide (SO2). Unlike greenhouse gases, SO2

cools the atmosphere. Magma contains a small amount of SO2, typically less than 10% by volume. Large eruptions thrust the SO2 into the upper atmosphere (the stratosphere) where it is transported around the planet and comes in contact with abundant water changes the SO2 gas into sulfuric acid (H2SO4) droplets called aerosols. Even though they are microscopic, there are billions of such aerosols following a big eruption, so that they actually affect the climate. Each aerosol absorbs some of the radiation from the Sun, and thus heats itself and the surrounding stratosphere. But each ray of sunlight that hits an aerosol does not strike the Earth, robbing the surface of that small amount of heat. During the 1900s there were three large eruptions that caused the entire planet to cool down by as much as 1°C. Volcanic coolings persist for only 2 to 3 years because the aerosols ultimately fall out of the stratosphere and enter the lower atmosphere where rain and wind quickly disperse them.

Volcanoes and Global Climate Change. NASA: Exploring the Environment, n.d. Web.      20 May 2014. <http://ete.cet.edu/gcc/?/volcanoes_teacherpage/>. 

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Eruption of Mt. Stromboli, Italy

1991 Mount Pinatubo, Philippines

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Climate change could increase volcanic

eruptionsLast updated on 19 May 2014 By Kieran Cooke

Iceland names its commercial aircraft after its volcanoes – ironic, given that ash blown into the atmosphere by the 2010 eruption of the country’s Eyjafjallajökull volcano resulted in much of Europe’s airspace being closed for days, with 100,000 flights cancelled and ten million passengers stranded.

Volcanoes are deeply embedded in the Icelandic culture. They are everywhere in the landscape. In many ways, the whole country is a volcano. Eruptions of one sort or another are going on all the time. The locals tend to ignore the odd rumble and giant cloud of fire and ash, which would have those of us living in less explosive regions disappearing under our beds.

The Laki volcanic eruption in 1783 was a very different matter, one of the most devastating in recent history, an event that has even the Icelanders quaking at the Earth’s explosive power. Island on Fire, a new book by Alexandra Witze and Jeff Kanipe, details the local and global impact of Laki’s eruption. Hot ash and cinders burned skin and poisoned pastures. At least one-fifth of Iceland’s population was killed, and half the country’s livestock wiped out.

“What made Laki particularly deadly was how long its eruption went on and what poisons it spat into the atmosphere,” they write. “Over the course of eight months, Laki produced one of the largest lava flows in historic times − enough to bury Manhattan 250 meters deep.

“Over the first 12 days, it disgorged the equivalent of two Olympic swimming pools full of lava every second. Along with the lava came the gas: Laki belched out an estimated 122 million tons of sulfur dioxide, 15 million tons of fluorine, and 7 million tons of chlorine. It was one of the biggest atmospheric pollution events in the past 250 years.”

As with climate change-related greenhouse gases, volcanic gases and ash clouds obey no borders. Laki first started erupting in June 1783. Throughout the summer of that year, it heaved and spewed particles that spread across Europe. “All summer, people all over the continent choked on this caustic smog … people could neither avoid nor escape the malignant haze, which manifested itself as a bluish or reddish ‘dry fog’ that smelled strongly of sulphur. It dimmed the sun and instilled panic across the continent.”

Today, we know far more about volcanic eruptions, but, as Witze and Kanipe point out, we are none the less vulnerable. The 2010 eruption of Eyjafjallajökull was relatively small in volcanic terms, yet it showed that in our “just-in-time” world, with its highly-integrated transport and trading systems, one major kink in the network can lead to chaos on a global scale.

The smog of the European summer of 1783 gave way to the worst winter in decades as Laki’s aerosols chilled the continent. Studies show a large spike in death rates in England over the period. Often, not enough attention is paid to climatic issues in analyzing the course of historic events. Witze and Kanipe say that as crops failed and famine spread in France, Laki could well have contributed to the French revolution of 1789 – in the same way that a prolonged drought in the eastern Mediterranean has, in part, driven events behind the uprising in Syria.

Volcanoes are a lesson in what can happen when pollutants and greenhouse gases build up in the atmosphere. Witze and Kanipe estimate that, overall, millions of people around the world could have died as a result of Laki’s belching and heaving.

At the moment, although Laki is relatively quiet, Iceland’s volcanoes are becoming more active. This, say the authors, is due in part to climate change. As the country’s ice has melted, the overlying weight of ice on its volcanoes has been reduced, and the loss of ice is creating geological stresses in the crust beneath.

It’s not a question of if but when the next big blast will come.

Ash plume from an Iceland volcano, 2010

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Climate change could increase volcanic eruptions. Responding to Climate Change,  n.d. Web. 20 May 2014. <http://www.rtcc.org/2014/05/19/   climate-change-could-increase-volcanic-eruptions/>. 

Volcanoes and Climate ChangeBy Jack Dini

The impact of volcanic eruptions on global warming could provide a new explanation for the so-called ‘pause’ in climate change. According to a recent study, models for predicting the rate at which temperatures around the world would rise from 1998 onwards did not take into consideration the measurable impact volcanoes can have. Rather than contributing to global warming, eruptions release particles into the air that reflect sunlight—causing temperatures to drop. This phenomenon was not taken into account when predictions were made—offering an explanation for why the world seemed to stop heating up. Some Examples:• Mount Laki is a large volcano in Iceland that has a history of producing climate changing eruptions. In 1783, Laki erupted, releasing vast rivers of lava. The explosive eruption was so violent that ash and sulfur dioxide were injected into the stratosphere some 8 miles up. This cloud was then swept around the world by stratospheric winds. The result was a significant decrease in the amount of sunlight reaching the earth’s surface for several years. That reduction in sunlight brought about bitter cold weather across the northern hemisphere. The winter of 1784 was one of the coldest ever seen in New England and in Europe. The Mississippi river froze all the way down to New Orleans. Historical records show that similar conditions existed during the following winter. • Mount Tambora in Indonesia erupted with cataclysmic force in April 1815. It was the largest volcanic eruption in over 1,600 years. The following year was called ‘the year without a summer.’ In June of 1815, a foot of snow fell on Quebec City. In July and August, lake and river ice were seen as far south as Pennsylvania. Frost killed crops across New England with resulting famine. During the brutal winter of 1816/17, the temperature fell to -32 F in New York City. • Krakatoa in Southeast Asia erupted in August 1883 resulting in 36,000 deaths. An estimate of the force of the blast that pounded five cubic miles of volcanic rock into dust is that the explosion equaled somewhere between 10,000 to 30,000 megatons of pure TNT. For comparison purposes, the Hiroshima bomb was 20 kilotons of TNT (note that mega refers to millions of tons, while kilo refers to thousands). After Krakatoa, weather around the world was affected for three years because of dust in the upper atmosphere. • In 1991 the second largest volcanic eruption of the 20th century occurred when Mount Pinatubo in the Philippines exploded with enormous force, killing almost 1,000 people and causing widespread damage. Millions of tons of ash and gas were blasted into the atmosphere, reaching an altitude of 21 miles. Over the next two years, average temperatures across the Earth fell by up to 0.5 degrees C. Mount Pinatubo and the earlier major eruption of El Chicon in Mexico in 1982 had important impacts on decadal changes in warming rates. In addition, 17 ‘small’ eruptions occurred after 1999 which had a cumulative effect increasing the reflective effect of aerosols in the upper atmosphere by up to 7% per year from 2000 to 2009. So, where are we today?Volcanic CO2 emissions are much higher than previously estimated, leading to the conclusion that we cannot assume that the increase of atmospheric CO2 is exclusively man-made.

As for volcanoes stopping, a recent National Science Foundation report stated that magma stored for thousands of years in places can erupt in as little as two months. Magma sitting 4-5 kilometers beneath the surface of Oregon’s Mount Hood has been stored in near-solid conditions for thousands of years. The time it takes to liquefy and potentially erupt however, is surprisingly short—perhaps as little as a couple of months.

Alan Caruba sums this up well, “The fundamental scientific fact that, as opposed to all the nonsense about human control or effect on the Earth’s temperatures, volcanoes by comparison render the human component infinitesimal. What Americans need to worry about is the eruption of a super volcano with a large caldera such as the Yellowstone Caldera in Yellowstone National Park and the Valles Caldera in New Mexico. Both have been dormant for thousands of years.

And lastly, we can’t lay all the blame on volcanoes. As Benjamin Santer has reported, “There is not a single culprit as some scientists have claimed. Multiple factors are implicated.”

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Volcanoes and Climate Change. Canada Free Press, n.d. Web. 20 May 2014.      <http://canadafreepress.com/index.php/article/61705>. 

Volcanic eruptions ‘contributed to global warming pause’, scientists claimResearch could explain why rate of climate change appeared to slow down after 1998 – but experts say volcanoes only offer ‘temporary respite’ from rising temperaturesADAM WITHNALL   SUNDAY 23 FEBRUARY 2014

The impact of volcanic eruptions on global warming could provide a new explanation for the so-called “pause” used by sceptics to deny climate change is happening, scientists have said.

According to a study in the US, models for predicting the rate at which temperatures around the world would rise from 1998 onwards did not take into consideration the measurable impact volcanoes can have.

Rather than contributing to global warming, eruptions release particles into the air that reflect sunlight – causing temperatures to drop.

Experts from the Lawrence Livermore National Laboratory in California said this phenomenon was not taken into account when predictions were made – offering an explanation for why the world seemed to stop heating up.

Powerful volcanic eruptions send small sulfur droplets, or aerosols, high into the atmosphere where they act as a mirror to reflect the sun's rays and prevent them warming the ground.

In 1991, the second largest volcanic eruption of the 20th century occurred when Mount Pinatubo in the Philippines exploded with enormous force, killing almost 1,000 people and causing widespread damage. Millions of tons of ash and gas were blasted into the atmosphere from the mountain, reaching an altitude of 21 miles. Over the next two years, average temperatures across the whole of the Earth fell by up to 0.5C.

The research showed that Mount Pinatubo and the earlier major eruption of El Chichon in Mexico in 1982 “had important impacts on decadal changes in warming rates”.

In addition, 17 “small” eruptions occurred after 1999 which had a cumulative effect increasing the reflective effect of aerosols in the upper atmosphere by up to 7% per year from 2000 to 2009.

Scientists have provided a number of explanations in recent years as to why the apparent global warming “pause” came about, including natural climate variability to failures in accurate surface temperature measurement.

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British climate expert Professor Piers Forster, from the University of Leeds, said: “Volcanoes give us only a temporary respite from the relentless warming pressure of continued increases in CO2.”

Volcanic eruptions ‘contributed to global warming pause’, scientists   claim. The Independent, n.d. Web. 20 May 2014.    <http://www.independent.co.uk/environment/climate-change/volcanic-eruptions-contributed-to-global-warming-pause-scientists-claim-9147856.html>. 

The Science of Global Warming

Greenhouse gases that become trapped in the Earth's atmosphere act like a blanket, preventing outgoing terrestrial radiation from escaping back into space. Average air temperatures rise and the secondary effect is an increase water temperatures.

If global temperatures continue to increase many or all of the following concerns can and will become a reality:

Melting of Glacial Ice, most importantly the Greenland Ice Sheet and Polar Ice Caps, leading to… Global sea level rise due to warm water expansion and incoming fresh water from melting glaciers

resulting in… Coastal flooding and erosion. An increase in precipitation, especially at middle and high latitudes, with an increase in river runoff. A decrease in ocean salinity and a subsequent change in ocean current circulation patterns. Major shifts in ocean currents would affect both climate and species survival and possibly result in the

extinction of many species, especially marine life. It is estimated that more than a million species may become extinct by the year 2050.

Declining crops resulting in global starvation. Drinking water is less available. Changes in weather patterns including an increase in violent storms, winds, hurricanes and tornadoes

and extreme El Niño events. Climate shifts - Droughts in areas that once experienced measurable rainfall amounts and higher than

normal precipitation for other locations. Higher death tolls from:

Malnutrition Heat stress Widespread disease

In fact, the year 2005 set the all-time greenhouse gas record and levels continue to spiral upward. Scientific data shows that present-day changes, caused by increased temperatures, include the following:

A substantial decrease in ocean salinity has been recorded over the last 30 years. This may be caused by the following…

o Polar sea ice has thinned by 40% over the last 40 years.o The melting of the Greenland Ice Sheet has accelerated to the point equivalent to a

.13mm/year rise in sea level.o Warm water expands and so sea levels have risen 4 to 8 inches (10-20 centimeters).o Precipitation and river runoff have measurably increased 7-12% over the last 100 years, mainly

between the 30°N and 85°N latitudes.

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o Sea levels have risen 0.3 to 0.7 feet over the last century.

If fossil fuel emissions continue at present or even higher rates, computer generated climate models predict an additional warming of about 2-10 °F over the next 100 years would be possible.

Can Global Warming lead to Global Cooling?

Yes it can. Over geologic time Earth has gone through several ice ages followed by inter-glacial warming periods.

Shorter periods of much cooler temperatures have also occurred due to:

A major volcanic eruption that causes volcanic material to block and reduce incoming solar radiation resulting in cooler temperatures and a "year without a summer". The ash from the 1816 eruption of Tambora in Indonesia cooled Earth so significantly that New England experienced June snowfalls and, throughout the summer months, crop failures were the norm in New England and also in northern Europe.

A change in the circulation of ocean currents due to the melting of major Ice Sheets resulting in decreased salinity caused by the addition of large volumes of fresh melt water. The Younger Dryas and the "8200 years before present" events were both drier periods with much colder temperatures. They are believed to have resulted from melting glaciers and the subsequent alteration of the Gulf Stream current.

Oceanic Circulation Patterns - Thermohaline Circulation

Why is the melting of glacial ice such a problem for the Gulf Stream? Fresh water is less dense than salt water therefore, when a large volume of fresh water mixes with a salt water current, it may no longer be dense enough

The climates of North America and Europe are influenced by the Gulf Stream, a warm ocean current. An interruption in this pattern of flow, either a decrease in the temperature of the Gulf Stream or a cessation of flow altogether would result in dramatic lowering of average temperatures for both continents. The melting of Arctic sea ice and resulting disturbance of the Gulf Stream ocean current, could bring colder weather to Europe and North America and a rise in temperature for the southern hemisphere.

to sink. This would slow down, if not stop, the Gulf Stream from continuing its present course, the end result being that temperatures, normally modified by its path, would drastically change...for the colder.

In the past retreating glaciers dumped enough water into oceans to cause the North Atlantic branch of the Gulf Stream current to stop. This occurred around 8,200 and 12,700 years ago and both times the climate cooled. Exactly how much fresh water is necessary to totally shut down the Gulf Stream is uncertain.

Experts say, "Watch the ice!" Continued melting of glacial ice is the most important telltale sign that Global Warming is taking place.

Cloud Cover and Aerosols

Higher temperatures increase the amount of cloud cover due to an increase in higher evaporation rates of surface water.

Initially, the clouds will trap heat re-radiating from Earth's surface, adding to global warming and the continued rise in temperatures. However, cloud cover actually works against global warming. Clouds tend to block and reflect back into space any incoming solar radiation. After some time, global cooling conditions are a threat. Some models suggest this cooling will occur after approximately 50-100 years, but it could come much sooner.

Another critical factor in both the formation of thicker, denser clouds and the blocking of solar radiation is small particulates such as ash, soot, skin cells, sea salt, sulfates, pollutants and dust. Since the industrial revolution however, humans have introduced an excessive amount of pollutants into the air through the burning of fossil fuels. It has been estimated that cloud cover may have increased up to 5% solely based on aerosol emissions contributed by humans.

Global Temperatures 1770-1805

The top of this graph shows the increase in acidity (sulfuric acid) during the actual eruption of Mount Laki in Iceland in 1783.

The bottom of this graph shows the average global temperatures for the 15 years before the eruption and the 20 years after the eruption.

Laki, Iceland 1783. Volcano World, n.d. Web. 21 May 2014.      <http://volcano.oregonstate.edu/laki-iceland-1783>. 

Global Warming – Since When, and Says Who?

Mount Pinatubo erupted in 1991. How did that affect global temperatures?

El Chinchon erupted in 1982. How did that affect global temperatures?

There were 17 smaller volcanoes that erupted in 1999. How did that affect temperatures?

Global Warming – Since When, and Says Who? Asheville Tribune, n.d. Web. 21 May      2014. <http://www.ashevilletribune.com/asheville/global%20warming/      Global%20Warming%20DM%20Main%20Story%20March%2031%20Update.htm>. 

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Global Temperatures 1700-1800

Global Warming - Man or Myth? N.p., n.d. Web. 21 May 2014.      <http://www2.sunysuffolk.edu/mandias/global_warming/global_cooling.html>. 

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Using global temperature data, is there a correlation between the eruption of Mount Tamboro in 1815 and global temperatures? Is there a correlation between the eruption of Krakatoa in 1883 and global temperatures?