On Mon, 4 Oct 2004 18:26:19 +0100, Alan LeHun wrote:


Just had a minor eruption which started about half an hour ago if
anybodies interested.

http://www.fs.fed.us/gpnf/volcanocams/msh/

Fascinating ; thanks for that link. However looks pretty quiet at the
moment!

understand
that to have world-wide impact, the event would need to be in the
tropical/sub-tropical belt? However, would be glad to be corrected if
anyone has got more on this.

ISTR HH Lamb saying that in "Climate, History and the Modern World."
--
Found this on the CRU site which might help .... they imply that for
*maximum* effect such activity should be at lower latitudes etc.

I think the idea is that tho tropical eruptions cause cooling at the surface,aerosol injection
causes heating in the stratosphere thus enhancing the equator pole temperature gradient.Sulphur is
the key aerosol ingredient.In NH winter a stronger polar vortex results -ie +ve NAO/AO mode and
continental warming.This 'advective' effect outweighs the radiative cooling at low latitudes and in
the summer.
Injection into the stratosphere at high latitudes (presumably dispersion by the jet wld be rapid)
causes high latitude heating and a reduced meridional temperature gradient.ie -ve NAO/AO mode and
continental cooling.
..IIRC the 1980 eruption was largely confined locally at the surface causing strong daytime cooling
(and conversely high night time temps locally)-as much as 10C (?),

--
regards,
david
(add 17 to waghorne to reply)

However, did it really cause changes to the regional/European climate in
the years 1783, 1784 etc?

Yes,see
http://www.cosis.net/abstracts/EGU04...04-J-05244.pdf
and
Atmospheric impact of the 1783-1784 Laki Eruption: Part II Climatic effect of sulphate aerosol
E. J. Highwood and D. S. Stevenson
ACP V3 Page(s) 1177-1189. SRef-ID: 1680-7324/acp/2003-3-1177
freely available at
http://www.cosis.net/members/journal...j_id=2&i_id=28


--
regards,
david
(add 17 to waghorne to reply)

"Waghorn" wrote in message
...
However, did it really cause changes to the regional/European
climate in
the years 1783, 1784 etc?

Yes,see
http://www.cosis.net/abstracts/EGU04...04-J-05244.pdf
and
Atmospheric impact of the 1783-1784 Laki Eruption: Part II Climatic
effect of sulphate aerosol
E. J. Highwood and D. S. Stevenson
ACP V3 Page(s) 1177-1189. SRef-ID: 1680-7324/acp/2003-3-1177
freely available at
http://www.cosis.net/members/journal...j_id=2&i_id=28

.... many thanks for those: I originally did not query the effect, then I
found a couple of years ago some remarks (haven't got the refs) that
cast doubt ... and the following in the CRU extract also is confusing:

" Benjamin Franklin, in 1783, first postulated that major volcanic
eruptions affect climate, after the eruption of the Laki volcano in
Iceland. Ironically, most of the ejected material from this eruption
remained in the lower parts of the atmosphere, so Franklin had the right
idea but the wrong volcano. "

These extracts you have posted though are later than the CRU information
sheet, so obviously follow-up work has confirmed the original (i.e.
Franklin) ideas for Laki specifically.

Whatever, a fascinating area of research and one of the teasing
'variables' in the GW debate!

Martin.


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

In article ,
Martin Rowley writes:
I originally did not query the effect, then I
found a couple of years ago some remarks (haven't got the refs) that
cast doubt ... and the following in the CRU extract also is confusing:

" Benjamin Franklin, in 1783, first postulated that major volcanic
eruptions affect climate, after the eruption of the Laki volcano in
Iceland. Ironically, most of the ejected material from this eruption
remained in the lower parts of the atmosphere, so Franklin had the right
idea but the wrong volcano. "

That suggests that there might have been some other major eruption in
1783 (or conceivably 1782) that was responsible for an effect on climate
(should one properly talk of climate or weather, when talking about a
period of a year or so?). Does anyone know of another major eruption?
--
John Hall "Hard work often pays off after time, but laziness always
pays off now." Anon

,That suggests that there might have been some other major eruption in
1783 (or conceivably 1782) that was responsible for an effect on climate
(should one properly talk of climate or weather, when talking about a
period of a year or so?). Does anyone know of another major eruption?

Asama,Japan,1783.But prob low in sulphur.
The Highwood study is littered with understandable caveats.
The summer of !783 was v warm ,but this may not have been due to volcanic effects any way.
Also see,but I can't find it free online,-

Thorvaldur ThordarsonStephen Self
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D1, 4011, doi:10.1029/2001JD002042, 2003
Atmospheric and environmental effects of the 1783-1784 Laki eruption: A review and reassessment

The 1783-1784 Laki flood lava eruption in Iceland emitted ?122 megatons (Mt) SO2 into the atmosphere
and maintained a sulfuric aerosol veil that hung over the Northern Hemisphere for 5 months. The
eruption columns extended to 9-13 km and released ?95 Mt SO2 into the upper troposphere/lower
stratosphere (i.e., the polar jet stream), enforcing a net eastward dispersion of the plumes which
reacted with atmospheric moisture to produce ?200 Mt of H2SO4 aerosols. Away from source, the Laki
aerosols were delivered to the surface by subsiding air masses within anticyclones. We show that
?175 Mt of H2SO4 aerosols were removed as acid precipitation and caused the extreme volcanic
pollution (i.e., dry fog) that effected Europe and other regions in 1783. The remaining ?25 Mt
stayed aloft at tropopause level for 1 year. The summer of 1783 was characterized by extreme and
unusual weather, including an unusually hot July in western Europe, most likely caused by
perseverance of southerly air currents. The following winter was one of the most severe winters on
record in Europe and North America. In these regions, the annual mean surface cooling that followed
the Laki eruption was about ?1.3°C and lasted for 2-3 years. We propose that the upper
troposphere/lower stratosphere aerosols from Laki disrupted the thermal balance of the Arctic
regions for two summers and were the main mechanism for the associated climate perturbations.
Eruptions of Laki magnitude have occurred in the recent past in Iceland and will occur again. If
such an eruption were to occur today, one of the most likely immediate consequences would be
disruption to air traffic over large portions of the Northern Hemisphere.

Published 8 January 2003.
http://www.agu.org/pubs/crossref/200...JD002042.shtml

--
regards,
david
(add 17 to waghorne to reply)

Whatever, a fascinating area of research and one of the teasing
'variables' in the GW debate!

Martin.
yes,it's been found GCM simulations don't have realistic 'scaling' statistics,but adding volcanic
forcing proxies improves this considerably.A recent study found effects on global ppn as well-

http://www.agu.org/pubs/crossref/200...GL020044.shtml
GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L12217, doi:10.1029/2004GL020044, 2004
Detection of volcanic influence on global precipitation
N. P. Gillett et al

--
regards,
david
(add 17 to waghorne to reply)

"Paul Crabtree" (removespam) wrote in
message ...
I understand that Mt St Helens is likely to blow any day now - any
thoughts
on how this will change our weather this Autumn, or will it have to be a
huge event to have any effect here ?

live web cam of the mountain at

http://www.fs.fed.us/gpnf/volcanocams/msh/

Looking interesting now.

Joe

In article ,
says...

live web cam of the mountain at

http://www.fs.fed.us/gpnf/volcanocams/msh/

Looking interesting now.

You've missed it. What you're seeing now is just remnants. Should have
seen it an hour or two ago. It got quite dark.

Alan LeHun

"Waghorn" wrote in message


However, did it really cause changes to the regional/European climate in
the years 1783, 1784 etc?

No, see, sulphur is not easily converted to sulphuric acid. I don't know
the whys and wherefores but the underlying tendency to describe sulphur
oxides as sulphuric acid, while irritating from news reporters, is in
chronic bad taste from scientific journals.

One would suspect that there is an abject need for it to be sulphuric
acid to fit their needs and explanations.

http://www.cosis.net/abstracts/EGU04...04-J-05244.pdf

Is it anything to do with the fact that the peresence of sulphur dioxide
in dilute quantities is beneficial? Or does it not fit the climate
models or what?


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