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Sore Throat
Joined: 01 Sep 2000
Posts: 1802
Location: x |
Volcanoes help unleash El Nino disaster: study
 Sat Nov 22, 2003 5:57 pm
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...regarding the role of the release of fine particulates into the atmosphere:
http://story.news.yahoo.com/news?tmpl=story&u=/afp/20031119/sc_afp/climate_elnin o_031119190559
Volcanoes help unleash El Nino disaster: study
PARIS (AFP) - Volcanoes are a prime cause for El Nino, the climate phenomenon that can catastrophically disrupt weather patterns across the Pacific and beyond, a study says.
A major eruption doubles the chance that an El Nino will be unleashed in the following winter, according to the research, which is published on Thursday in the British scientific journal Nature.
The research is the first to supply statistical flesh to the theory that volcanic fallout may affect the world's climate system, spewing out billions of tonnes of fine ash that lingers in the upper atmosphere, reflecting back solar heat.
Climate experts led by Brad Adams of the University of Virginia looked at so-called geological indicators -- dust preserved in polar ice cores as well as tree rings and coral growth that reflect sudden changes in the climate -- and compared this with the dates of major known eruptions from 1649 onwards.
They found a "significant, multiyear El Nino-like response" that kicked in just after big volcanic activity in the tropics.
"The results imply roughly a doubling of the probability of an el Nino event occurring in the winter following a volcanic eruption," they write
El Ninos occur in cycles that vary from three to 11 years, when the sea surface temperature in the western tropical Pacific Ocean is warmer than usual.
The prevailing east-west trade winds die, causing a huge buildup of warm water in the western part of the ocean.
This has effects on climate that can reverberate around the southern hemisphere, inflicting snowfalls and landslides in South America, drought in southern Africa, a weak hurricane season in the Atlantic and forest fires in Indonesia.
The shift in weather is so abrupt that crops and fish migrations are hit, having a dramatic effect on human life.
Adams' team believes that the fine shroud of volcanic ash kick-starts the process.
A thin layer of "aerosolised" particles hangs in the stroposphere, causing an overall cooling of the planet's atmosphere of a few tenths of a degree Celsius (about half a degree Fahrenheit).
But the effect regionally is different.
There is a complex interaction between atmospheric temperatures and vast, circulating masses of water. Athough the rest of the world cools, there is a slight warming in the tropical zone of the Pacific, fuelled in part by a convection of warm water from elsewhere.
That small rise is is enough to trigger an El Nino, which is highly susceptible to small changes in sea surface temperatures.
According to the study, the El Nino usually lasts for the first three years after a big tropical volcanic eruption, and then goes into reverse, with the so-called El Nina phenomenon, for the three years after that.
But the researchers add a big caveat: eruptions themselves are not the only factor. Man-made global warming (news - web sites) -- the spewing out of greenhouse gases by the burning of fossil fuels -- is also likely to play a role.
"Volcanic eruptions, such as that of Mount Pinatubo (in the Philippines) in 1991 may have a larger effect on Earth's climate than previously thought," says Shanaka de Silva of the Department of Space Studies at the University of North Dakota, in a commentary.
"If they influence the (El Nino) cycle as proposed, then explosive volcanism is a vital catalyst in global climatic interconnections, and a major player in Earth's climate system."
[Edited 1 times, lastly by Sore Throat on 11-22-2003] |
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Deborah
Joined: 30 Jul 2000
Posts: 731
Location: East Coast |
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Sat Nov 22, 2003 6:47 pm
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Excerpt:
.....There is a complex interaction between atmospheric temperatures and vast, circulating masses of water.....
This is a very important point of fact.
It is not conjecture, speculation or the product of flawed, extremist thinking. It is a basic tenet of atmospheric physics.
Whenever large swaths of the atmosphere are warmed or cooled, whether via natural processes or via artificial processes, there are going to be disturbances in atmospheric circulation and disturbances in atmospheric hydrology patterns. |
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Wolf_Larson
Joined: 08 Aug 2003
Posts: 442
Location: The Sea |
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Sat Nov 22, 2003 7:38 pm
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quote:
Originally posted by Deborah:
Whenever large swaths of the atmosphere are warmed or cooled, whether via natural processes or via artificial processes, there are going to be disturbances in atmospheric circulation and disturbances in atmospheric hydrology patterns.
Please define what you consider to be an artificial process and just how much energy is required to produce detectable warming or cooling of a "large swath" of the atmosphere.
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Deborah
Joined: 30 Jul 2000
Posts: 731
Location: East Coast |
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Sun Nov 23, 2003 2:40 am
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I would define an artificial process as one that is implemented or facilitated by human activity, such as the burning of fossil fuels in the industrial and transportation sectors.
The emissions generated as a result of these artificial processes contain particulate matter that can either warm or cool large regions of the atmosphere depending on its chemical composition and color and its capacity to mix with other atmospheric constituents including other particulates.
As for how much energy is required to produce detectable warming or cooling of a large swath of the atmosphere, I would say this is a regional issue which is best evaluated by looking at the measurements being taken by researchers in the region(s) of interest.
[Edited 1 times, lastly by Deborah on 11-22-2003] |
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