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‘Compelling evidence’ discovered of previously unknown volcanic eruption, 1809 AD 31 October 2009

Posted by admin in climate.
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News that a U.S./French team of chemists claim to have found ‘compelling evidence’ of a previously unknown volcanic eruption that occurred 1809 and that may have been responsible for the global cooling noted during the period 1810-19. The evidence comes from ice samples from Greenland and the Antarctic:

‘We’ve never seen any evidence of this eruption in Greenland that corresponds to a simultaneous explosion recorded in Antarctica before in the glacial record’, said Mark Thiemens, Dean of the Division of Physical Sciences at UC San Diego and one of the co-authors of the study. ‘But if you look at the size of the signal we found in the ice cores, it had to be huge. It was bigger than the 1991 eruption of Mount Pinatubo in the Philippines, which killed hundreds of people and affected climate around the world’.

Read on: ‘Previously unknown volcanic eruption helped trigger cold decade’ (UC San Diego news release, 27 October 2009).

[H/T: commenter Perry.]

UPDATE. The 1809 eruption may be unidentified but it’s certainly not ‘unknown’: see comments below.

The Volcanism Blog



1. Guillermo - 1 November 2009

There is a clue about the volcano that caused that eruption?

2. The Bobs - 1 November 2009

This may be new evidence, but the “unknown” tropical eruption of 1809 has been talked about for years. For example, here: http://atlas-conferences.com/c/a/h/i/24.htm

That is from 2001.

3. Paul Callander - 1 November 2009

Reproduced below is a comment on WUWT from Leif Svalgaard about this article. It appears that this is not new news but was reported in 1991 and again in 2001 in science journals!

“We have seen this kind of hype again and again [“never before seen”, “unprecedented”, etc]

This story is old hat:

Title: Ice core evidence for an explosive tropical volcanic eruption 6
years preceding Tambora
Authors: Dai, Jihong; Mosley-Thompson, Ellen; Thompson, Lonnie G.
Publication: Journal of Geophysical Research (ISSN 0148-0227), vol.
96, Sept. 20, 1991, p. 17,361-17,366. (JGR Homepage)

High-resolution analyses of ice cores from Antarctica and Greenland
reveal an explosive volcanic eruption in the tropics in A.D. 1809
which is not reflected in the historical record. A comparison in the
same ice cores of the sulfate flux from the A.D. 1809 eruption to that
from the Tambora eruption (A.D. 1815) indicates a near-equatorial
location and a magnitude roughly half that of Tambora. Thus this event
should be considered comparable to other eruptions producing large
volumes of sulfur-rich gases such as Coseguina, Krakatau, Agung, and
El Chichon. The increase in the atmospheric concentration of sulfuric
acid may have contributed to the Northern Hemisphere cooling observed
in the early nineteenth century and may account partially for the
decline in surface temperatures which preceded the eruption of Tambora
in A.D. 1815.

Title: Two major volcanic cooling episodes derived from global marine
air temperature, AD 1807-1827
Authors: Chenoweth, Michael
Publication: Geophysical Research Letters, Volume 28, Issue 15, p.
2963-2966 (GeoRL Homepage), 2001
DOI: 10.1029/2000GL012648

A new data set of global marine air temperature data for the years
1807-1827 is used to show the impact of volcanic eruptions in ~1809
(unlocated) and 1815 (Tambora, Indonesia). Both eruptions produced
cooling exceeding that after Krakatoa, Indonesia (1883) and Pinatubo,
Philippines (1991). The ~1809 eruption is dated to March-June 1808
based on a sudden cooling in Malaysian temperature data and maximum
cooling of marine air temperature in 1809. Two large-scale calibrated
proxy temperature records, one from tree-ring-density data, the other
using multi-proxy sources are compared to the marine air temperature
data. Correlation is highest with maximum latewood density data and
lowest with the multi-proxy data.”

I wonder if the identity of the volcano will be identified.



4. admin - 2 November 2009

Mea culpa – I wrote this post hurriedly and worded it badly, rehashing what the UC San Diego press release said. The ~1809 eruption has indeed been known about for years: ‘unidentified’ rather than ‘unknown’. And it’s clearly still ‘unidentified’.

So what is in the new paper? Perhaps the UC San Diego press office is getting excited about nothing, which is certainly not unknown for university press offices. What seems less likely is that Geophysical Research Letters would be publishing something that is nothing but ‘old hat’. Perhaps someone with access to the article, which I don’t have at the moment, will take a look and let us know? It’s here:

Cole-Dai, J., D. Ferris, A. Lanciki, J. Savarino, M. Baroni, and M. H. Thiemens (2009), Cold decade (AD 1810-1819) caused by Tambora (1815) and another (1809) stratospheric volcanic eruption, Geophys. Res. Lett., doi:10.1029/2009GL040882, in press.


5. Henry Gaudru - European Volcanological Society (SVE) - 6 November 2009

Piton de la Fournaise – Reunion Island – France

As of the 6th of November OVPLF reported that following a short seismic crisis yesterday evening between 7:30 pm – 8:30 pm then a 30 mn of pause, a signal of tremor occured and a new eruption started at 9 pm (GMT + 4). The lava has issued from the East flank of the Dolomieu crater as lava fountains and lava flows.Scientists carried out an flight over the voclano at 6:45 am (GMT 4) with the helicopter allowed to confirmed that two fractures opened in the south, south side is and is of the crater sommital Dolomieu. Each of the cracks let escape a lava flow reaching the elevation of approximately 1970 metres. At 7:30 am on the morning, lava flows were not any more fed, consequence of a progressive decrease of the intensity of eruptive trémor since 3:00 am this morning ( GMT+4). At 9:00 am (GMT 4) the eruptive trémor was practically non-existent. (From OVPLF)

6. admin - 6 November 2009

Thank you to Henry Gaudru for the note about Piton de la Fournaise. I haven’t time to write anything up now, but will catch up with events on Reunion as soon as I can. In the meantime, Erik Klemetti has a report at his Eruptions blog:


7. Setting it straight - 14 November 2009

The reason this is “new” is that there were 2 camps of scientists – those who believed 2 nearly simultaneous tropospheric events occurred around 1809, and those who believed it was one stratospheric event. Tropospheric eruptions don’t nearly have the same climatic effect which is why this study was important. Based on isotopic data, it was found that this eruption in 1809 was a stratospheric one. THAT is the reason this paper was published since this is the first time the “simultaneous tropospheric” camp of scientists can be put to rest because of the evidence. The identity of this volcano could be done with tephra analysis, which the lab in this paper does not do. Also, note the same author here and of the 1991 paper… he got married (note the slight name change).

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