Volcanic eruptions may be an agent of rapid and long-term climate change

Volcanic eruptions may be an agent of rapid
and long-term climate change, according to new research by British scientists.
Vincent Gauci and co-authors Nancy Dise and Steve Blake of the Open University
simulated the volcanic acid rain from one of Europe’s largest historical eruptions,
the Icelandic Laki eruption of 1783, which caused widespread crop damage
and deaths around Europe.

Their finding are scheduled for
publication in the American Geophysical Union journal, Geophysical Research
Letters, later this month.

Gauci says, ‘we know that volcanic
aerosol [airborne] particles reflect the Sun’s rays back out to space and
also create more clouds that have the same effect. It all helps to cool the
planet for a year or two. These simple physical relationships have been known
for a while.

‘Our findings show that volcanic
eruptions have another, more indirect, effect: the resulting sulfuric acid
from the volcano helps to biologically reduce an important source of atmospheric
greenhouse gases. At the extreme, this effect could cause significant cooling
for up to 10 years or more.’

Blake says, ‘The amount of sulfur
dioxide put out by Laki in nine months was ten times more than the amount
that now comes from all of western European industrial sources in a year.
That would have caused a major natural pollution event.’

The researchers found that such
eruptions create a microbial battleground in wetlands, with sulfate-reducing
bacteria suppressing the microbes that would normally produce the powerful
greenhouse gas methane. In other words, the sulfate-loving bacteria are
victorious over the microbes producing methane, leading to a cooling effect.

‘We did the simulation on a peat
bog in Moray in northeast Scotland, an area we know was affected by the volcanic
fallout from the Laki eruption,’ adds Gauci, ‘and found that the reduced
methane emission lasts several years beyond the end of the acid rain. Our
calculations show that the emissions would take many years to recover – far
longer than volcanoes are currently understood to impact on the atmosphere.’

The researchers now think that
volcanoes may exert a more powerful influence over Earth’s atmosphere than
was thought. Volcanoes may even be a more important regulator of wetland
greenhouse gases than modern industrial sources of acid rain.

‘Wetland ecosystems are the biggest
source of methane and for the most part are located in areas of the world
that are remote from industrial activity.

But many of Earth’s wetlands
seem to be located in volcanically active regions such as Indonesia, Patagonia,
Kamchatka, and Alaska. Even some wetlands that are quite far away from volcanoes,
such as those in Scandinavia or Siberia, will be regularly affected by Laki-like
pollution events from Icelandic eruptions’ says Gauci.

Gauci adds that there was a period
of Earth’s pre-history when this effect may have created important climate

‘This interaction may have been
particularly important 50 million years ago, when the warm greenhouse climate
of the day was due, in large part, to methane from the extensive wetlands
that covered the Earth at that time. During that time, large volcanic eruptions
could have been real agents of rapid climate change due to this mechanism.’

The research also points to a
long recovery period for wetland ecosystems that have experienced industrially-derived
acid rain. Gauci says, ‘We’ve been getting on top of the sulfur pollution
problem in Europe and the U.S. for a long time now. Our findings show, however,
that the effects of acid rain can still linger for a long time.’

Source : www.physorg.com