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When a volcanic eruption ejects enough material into the atmosphere, the effects can be local and global climate change.
Volcanic clouds can significantly affect the atmosphere, and therefore the climate, in a variety of ways. Causes of climate effects can be:
- Volcanic gases reacting with atmospheric nitrogen dioxide and ozone
- More solar radiation backscatter due to volcanic ash particles in the atmosphere
- An increase in green house gases such as sulfur and carbon dioxide
The magnitude of these effects is dependent on the size of the eruption and the amount of material ejected into the atmosphere. An estimation of the amount of material ejected can be calculated from the height of the cloud using the equation H = 1.67Q^0.259, where H is the column height in kilometers (km) and Q is the discharge rate of magma in cubic meters per second.
Calculating the Amount of Material Ejected
The 1991 eruption of Mt. Pinatubo was recorded to have a maximum column height (H) of 34 km (18.6 miles) and the explosive event lasted about 1.3 hours, so the estimated amount of volcanic material ejected is 5.27 x 10^8 cubic meters. The 1980 eruption of Mt. St. Helens was recorded to have a maximum column height of 17.5 km and the explosive event lasted about 0.75 hours, so the estimated amount of volcanic material ejected is 2.34 x 10^7 cubic meters.
Both of these historical eruptions had climate impacts, although on very different scales. The Mt. Pinatubo eruption caused global climate change that was especially noticed in the northern hemisphere. For about 1-2 years after the eruption, the surface of the Earth was slightly cooler in the summer and slightly warmer in the winter. Volcanic cloud gases interacting with the atmosphere led to record low levels of stratospheric ozone. Mt. St. Helens, however, caused warming at only the local level immediately after the eruption and temperatures quickly returned to normal levels a day after the eruption.
Will the Chaiten Eruption Affect the Climate?
We can calculate the discharge rate of the Chaiten eruption and compare it to these two historical eruptions. Two heights will be used, due to two separate large explosions on May 2 and May 6, 2008. The May 2 explosion produced an ash cloud to a maximum height of 21 km, giving a discharge rate of 17,500 cubic meters per second. The May 6 explosion produced an ash cloud to a maximum height of 30 km, giving a discharge rate of 69,500 cubic meters per second. Not knowing the length of time of the explosive events, it is difficult at this time to calculate the volume of material ejected into the atmosphere.
Comparing the discharge rates of the Chaiten eruption to those of Mt. Pinatubo and Mt. St. Helens will give some clues as to the climate impact of the Chaiten eruption. Both Chaiten explosive events had discharge rates that were an order of magnitude larger then the Mt. St. Helens discharge rate. They were also both an order of magnitude smaller than the Mt. Pinatubo discharge rate. Climate changes at the local level will most likely occur, as they did at Mt. St. Helens. However, climate changes at the global level may not be noticed for a few months and until global climate data is collected.
Sources:
Smithsonian Institute’s Global Volcanism Program
McCormick, A.P.L., W. Thomason, and C.R. Trepte (1995), Atmospheric effects of Mt. Pinatubo eruption, Nature, 373, 399-404.
Robock, A., and C. Mass, (1982), The Mount St. Helens Volcanic Eruption of 18 May 1980: Large Short-Term Surface Temperature Effects, Science, 216, 628-630.
Sparks, R.S.J., Bursik, M.I., Carey, S.N., Gilbert, J.S., Glaze, L.S., Sigurdsson, H., Woods, A.W., (1997), Volcanic Plumes. West Sussex, England: John Wiley and Sons.
The copyright of the article Climate Change from Chaiten in Volcanoes is owned by Alexandra Matiella Novak. Permission to republish Climate Change from Chaiten in print or online must be granted by the author in writing.
Comments
May 9, 2008 2:45 PM
Guest :
Dear Alexandra,
First my greatest respect for you ability to write in
a way, so that a volcanic greenhorn like myself, who lives on the coastline
around 80 miles away from the Chaiten, had no problem to understand the
overall issue.
Especially your indication of the sunami risk, even
very unlikely to happen as I understood, has given me the exact information
I needed. For us over here, the earthquake and disastrous sunami in MAY!
1960 is always present in our minds, even I wasn’t even born.
Please
go on offering this kind of information that will help us to take the right
decisions.
Yours sincerely
J. Joaquin Hannig
May 11, 2008 4:48 AM
Guest :
Something not metioned but appears important is that Pinatubo was in
equitorial region while Chaiten is 42S and eruptions are just a month and
half from shortest day in southern hemisphere. This means much less effect
from backscatter of sunlight and outgoing infrared radiation is much more
important. If there is an insulating effect of the ash which near the
equator is much less important than backscatter of incoming radiation then
it is possible there could be a warming effect on the southern hemisphere
for a few months then a cooling effect.
May 12, 2008 9:19 AM
Guest :
Alexandra,
As you have stated the length of the second
eruption is unknown. Clearly an order of magnitude of less material
ejected (compared to Pinatubo) is significant and the event may not cause
as great of a change in the climate (again comparing to Pinatubo). But, if
the volcano continues to erupt the material ejected into the air would
approach that of Pinatubo. Now to my question, will you continue to update
this article or write a follow-up after the major eruptions have ceased?
These types of events are interesting. Thank you for your great
insight.
-Aaron
May 15, 2008 10:41 PM
Guest :
Alexandra,
Based on reports from the area the second explosive
event not only was much more energetic as you said, but apparently had a
much longer duration. Looking at the MODIS images soon after the second
event it looks to me like the "track" of the plume is not only
higher than for the first event, but that the higher portion of the plume
has a longer track as well.
(see
http://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2008-05-07)
I'm a geologist but know very little about volcanology, but would
it not be possible to estimate a rough minimum duration for this eruption
based on a conservative estimate of plume speed (say ~150 mph) and length
of highest portion of the plume. For the above image it looks to my
untrained eye like the highest part of the plume extends at least 140 miles
to the east of Chaiten and (based on the shadow cast by the plume) it looks
as if the volcano is still undergoing very violent eruption. Based on my
kindergarden approach it looks to me as if the main eruptions lasted at
least one hour, does this make sense to you?
Haven't had a
chance to review the newer sat images, but I would like to think that there
are some images from a few hours later that might be used in a similar way
to reach a better estimate.
On a related note, the volcano has
apparently remained active and continues to release major amounts of ash
(at slower rate) since the 05/06 explosion. Ash concentrations were high
enough (at ~3,000m) to disrupt flights as far away as Buenos Aires (5/9
http://www.mercopress.com/vernoticia.do?id=13367&formato=HTML) --
surprisingly to the north of what I would have expected.
Recent
media reports (last 12 hours or so) also hint at increasingly energetic
action from the volcano.
Thanks and keep up the good work,
Pablo
May 18, 2008 7:00 PM
Alexandra Matiella Novak :
Readers,
Thank you for your comments. I am getting requests for
updates concerning the fact that the current Chaiten eruption event is
still ongoing and therefore still contributing aerosols and gases to the
atmosphere.
I invite anyone with more expertise to please post
comments to this article to assist in publicizing as much information as
possible about the possible climatic impacts of the Chaiten eruption.
As pointed out in previous comments, the fact that Chaiten is still
emitting material could cause the amount of material ejected to surpass the
amount ejected by Pinatubo. I'm not sure, however, of the implications of
one extremely large event (Pinatubo) versus multiple smaller events
(Chaiten). Anyone with insight is encouraged to participate in the
discussion.
Thank you,
Alexandra Matiella Novak
5 Comments
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May 8, 2008
