Page 204 - Fundamentals of Physical Volcanology

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VOLCANOES AND CLIMATE 181

10

Agung Hekla Katmai Krakatau Tambora Laki Katla Lanzarote Pacaya Komagatake Unknown 8 6 4

2
0
2000 1950 1900 1850 1800 1750 1700 1650 1600 1550 1500

10
Unknown Katla Hekla 8 6 Acidity

2 4
0
1500 1450 1400 1350 1300 1250 1200 1150 1100 1050 1000

Fig. 12.1 Occurrences of sudden 10
increases (spikes) of acidity in polar- Eldgja 8
ice cores marking known eruptions
over the past 1500 years. (Adapted by 6
permission from Macmillan Publishers 4
Ltd: Nature, Hammer, C.U., Clausen,
2
H.B. and Dansgaard, W., Greenland
ice sheet evidence of post-glacial 0
volcanism and its climatic impact, 1000 950 900 850 800 750 700 650 600 550 AD
288, 230–235, copyright (1980).)

eruption to affect climate (e.g., Hekla, 1947 and eruption. The difficulty of proving such a link
Katla, 1755). comes in part from the limitations of available data
• Frost rings are formed in years in which no known sets, and partly because the effects we are trying to
eruption is evident in either the ice-core records or detect are subtle and often complex, e.g., cooling
in historical records. It is unlikely therefore that the may occur in one region but warming in another.
cold conditions which generated these frost rings Our appreciation of the complexity of the effects
were caused by a volcanic eruption. of volcanic eruptions on climate has developed
• Overall the comparison suggests that, in some tremendously as the result of the new opportu-
instances, volcanic eruptions may have been respon- nities for detailed study offered with the advent of
sible for cooling which was severe enough to gen- satellite monitoring.
erate frost rings but that not all eruptions cause
cooling and not all frost rings are the result of
12.3 Satellite monitoring of climate change
volcanic activity.
after volcanic eruptions
Though individual studies, such as the one just
discussed, are not always conclusive, through a Until relatively recently our understanding of
range of different studies it has become evident that whether volcanic eruptions affect climate was
volcanic eruptions can induce mild climate change, based on historical records and studies such as
usually cooling, for a period of 2–3 years after an those just described. With the advent of the space