(May 22, 2012 at 11:17 am)Polaris Wrote:(May 21, 2012 at 9:44 pm)Chuck Wrote: That's untrue. There is no evidence the eruptive frequencies of separate volcanic systems flucturate together. Major volcanic induced climate disturbances are usually caused by extraordinarily high activity in a single volcanic system, such as a single large resurgent caldera or clusters of calderas, or a single hot spot driving a single flood basalt eruption. There simply has been no such truly huge eruptions in the last century or last several tens of thousands of years.
There has only one moderately large eruption in the last 2 thousand years, but at least 4 in the 4 thousand years before that. This suggest even by coincidence, there hasn't been any significant increase in rate of serious eruptions in the last thousand years. Couple this with the fact that the biggest eruption in the last 12000 years is only a fraction of the size of a major resurgent caldera eruption, which happen roughly once every 100,000 years or so somewhere on the globe, which in turn is a tiny fraction of large basalt igneous province eruptions, which happens every few tens of millions of years somewhere on earth.
So it is hard to argue volcanic activity is currently powering any major global climate change.
Atmospheric changes have a long-lasting affect. Krakatoa was the last but was actually almost a century past the worst of the volcanic eruption cycle. The worst is believed to have come from Iceland, the worst eruptions seen in several million years. These were not your typical volcanic eruptions you think about, but created mass magma fields which were much more devastating to the climate (it's these that are also believed to have lead to the end of the Cretaceous.
They ended near the beginning of the early 19th century...I had always assumed that the Industrial Revolution with its CO2 emissions had curtailed the affect of the SO2 until it was revealed in new data that there was a rebound effect from volcanic activity of this magnitude. Venus is the best example of this. It just does not end when you cut off the switch...that's why it's called a runaway greenhouse effect.
Erm, there are no known or demonstrably unambiguous volcanic cycles.
'The difference between a Miracle and a Fact is exactly the difference between a mermaid and seal. It could not be expressed better.'
-- Samuel "Mark Twain" Clemens
"I think that in the discussion of natural problems we ought to begin not with the scriptures, but with experiments, demonstrations, and observations".
- Galileo Galilei (1564-1642)
"In short, Meyer has shown that his first disastrous book was not a fluke: he is capable of going into any field in which he has no training or research experience and botching it just as badly as he did molecular biology. As I've written before, if you are a complete amateur and don't understand a subject, don't demonstrate the Dunning-Kruger effect by writing a book about it and proving your ignorance to everyone else! "
- Dr. Donald Prothero
-- Samuel "Mark Twain" Clemens
"I think that in the discussion of natural problems we ought to begin not with the scriptures, but with experiments, demonstrations, and observations".
- Galileo Galilei (1564-1642)
"In short, Meyer has shown that his first disastrous book was not a fluke: he is capable of going into any field in which he has no training or research experience and botching it just as badly as he did molecular biology. As I've written before, if you are a complete amateur and don't understand a subject, don't demonstrate the Dunning-Kruger effect by writing a book about it and proving your ignorance to everyone else! "
- Dr. Donald Prothero
