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Summer Snow?
Volcanic aerosols can have a huge effect on Earth's climate.
For example, global cooling often has been linked to aerosols created from
major volcanic eruptions.
The year 1816 often has been referred to as "the year without a summer."
That year there were significant weather-related disruptions in New England
and in Western Europe, and there were killing summer frosts in the United States
and Canada.
These strange phenomena were thought to result from a major eruption
of the Tambora volcano in Indonesia in 1815. The volcano threw sulfur
dioxide gas into the stratosphere, and the aerosol layer that formed led to brilliant
sunsets that were seen around the world for several years.
The Dust Veil Index (DVI) for the Tambora eruption was extremely high:
1500. This index tells scientists how heavy an impact an eruption will
have on the climate. Contrast Tambora's DVI with that of Mt. St. Helen's,
which had a DVI of only 1, indicating a very light impact on the climate.
What Causes Aerosols to Form?
Did you know that oceans and volcanoes have something in
common? They both can create aerosols that stay suspended in the air for
long periods of time.
Some of the other natural sources of aerosols are:
- Dust storms
- Forest and grassland fires
- Living vegetation
Human activities, such as the burning of fossil fuels and the
alteration of natural surface cover, also generate aerosols.
People Particles!
Averaged over the globe,
aerosols resulting from human activities (not volcanic or oceanic aerosols) currently
account for about 10 percent of the total amount of aerosols in our atmosphere. Most of
that 10 percent is concentrated in the Northern Hemisphere,
especially downwind of industrial sites, slash-and-burn agricultural regions, and overgrazed grasslands.
What Next?
Scientists still have much to learn about the way
volcanic aerosols affect regional and global climate. They need to
find ways to learn the following:
- The relative impacts of
natural aerosols compared with those that humans produce.
- Where on the planet the amount of atmospheric aerosols is generally
increasing, decreasing, or remaining the same.
- Whether aerosols in general are warming or cooling
our planet.
NASA satellites provide much data for them to examine,
and new instruments enable the collection of data that wasn't
available previously.
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Aerosols in History
Mayon Eruption - 2000
The Mayon volcano, which erupted in February 2000, spewed ash
and steam as far as 5 miles into the atmosphere and forced tens of thousands of people
in the Philippines to leave their homes. View the Satellite image.
Pinatubo Eruption - 1991
Scientists study effects of the aerosols ejected by this volcano. Their studies may
help them to better understand climate change and learn to predict future climate
variations.
The spreading of sulfur dioxide in the upper atmosphere following the eruption of Mt. Pinatubo, 1991.
Krakatoa Eruption - August 27, 1883
This volcano (also called Krakatau) is on a small island in the Pacific. When Krakatoa blew up, it caused a
massive tidal wave 40 meters high, killed some 36,000 people, and destroyed about 75 percent of the island.
The massive eruption was heard as far away as Alice Springs, Australia.
Because of the huge amount of ash and aerosols spewed
into the stratosphere, the sun looked greenish blue for 15 days afterward, and
global temperatures were lowered by around 1.5 degrees Celsius.
Tourists have been barred from the island since 1999 because the volcano became active again!
Tambora Eruption - 1815
The Tambora volcano is on Sumbawa Island in Indonesia. The eruption was responsible for the unusual weather patterns that followed. Large amounts of ash and aerosols caused winter to come in August, destroying crops in Sumbawa.
About 92,000 people died in Sumbawa and the nearby island of Lombox: 10,000
were killed by the eruption, and about 82,000 more died from starvation, disease,
and hunger as a result of conditions after the eruption.
Even the Northern Hemisphere was affected:
completely unexpected cold spells disturbed crops and livestock. This in turn
caused more hunger and disease worldwide during 1815 and 1816.
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