Iceland Volcano: Not Yet A Global Cooling Eruption

Alister Doyle, PlanetArk 16 Apr 10;

A vast cloud from an intensifying volcanic eruption in Iceland is too small so far to slow global warming as happened in 1991 with the explosion of Mount Pinatubo in the Philippines, experts say.

Cataclysmic eruptions, led by Pinatubo and Mount Chichon in Mexico in 1982 in the 20th century, spewed so much debris into the upper atmosphere that they cooled the planet for months, briefly offsetting the effect of industrial heat-trapping gases.

"This is not like Pinatubo. So far the scale is not big enough to have a global effect," said Hans Olav Hygen, a climate researcher at the Norwegian Meteorological Institute.

The eruption under the Eyjafjallajokull glacier -- 10 times more powerful than another nearby last month -- threw up a 6 km (3.7 mile) cloud of ash and closed down air traffic across northern Europe.

"At the moment this is a relatively small eruption, not as big as some in the past from Iceland," said Colin Macpherson, a geologist at the University of Durham in England. Experts were monitoring to see possible impacts of ash on health.

A poison cloud from the eruption of Iceland's Laki volcano in 1783-84 killed thousands of people across Europe and undermined farm output by spewing an estimated 120 million metric tons of sulfur dioxide into the air, he said.

That amount of sulfur dioxide was three times European industrial output in 2006, he said.

STRATOSPHERE

Volcanic sulfur gases ejected high into the stratosphere and swept around the globe in the jetstream can linger for 12-14 months and dim sunlight, according to the U.N. panel of climate scientists.

Heavier ash generally falls back to Earth -- where it can cause respiratory problems -- within 3 months.

Some experts advocate the deliberate injection of sulfur dioxide in the stratosphere in a "geo-engineering" short cut to slow global warming and offset more floods, heatwaves, droughts, and rising sea levels.

That option has become attractive for some after a U.N. climate summit in Copenhagen in December failed to produce a binding global deal to cut emissions of greenhouse gases. Others say the risks are too big -- ranging from disruptions of weather patterns to acid rain.

"Pinatubo was the last major event. The levels of aerosols in the upper atmosphere have been fairly low of late," said Geoff Dollard, practice leader on air quality at the AEA consultancy which advises the British government.

"Generally there's a cooling effect from aerosols," he said. This is a lightish dust. We are keeping an eye on it" for possible threats to health. Dust in the air is nothing new -- storms from the Sahara can bring an orange-ish dust to northern Europe.

On an index of climate change since 1980 run by the International Geosphere-Biosphere Program, conditions got worse every year except 1982, 1992 and 1996. It links the dips to volcanic fallout from Chichon, Pinatubo and Monserrat in 1996.

Factbox: Volcanoes and ash clouds
Reuters 15 Apr 10;

(Reuters) - A huge cloud of ash from a volcano in Iceland turned the skies of northern Europe into a no-fly zone on Thursday, leaving hundreds of thousands of passengers stranded.

The eruption under the Eyjafjallajokull glacier -- 10 times more powerful than another one nearby last month -- showed no sign of abating after more than 24 hours of activity.

Here are a few facts on volcanic eruptions:

THE DANGERS:

* VOLCANIC GASES - The most dangerous gases released during an eruption are sulphur dioxide, carbon dioxide and hydrogen fluoride. High concentrations of sulphur dioxide injected into the atmosphere by large explosions can result in lung ailments, acid rain, lower surface temperatures and depletion of the earth's protective ozone layer. When carbon dioxide, which is heavier than air, settles in low-lying areas or collects in the soil, it can be lethal to people and animals.

* ERUPTION COLUMNS - Billowing clouds of gas and debris can reach more than 12 miles above a volcano, posing a serious threat to aviation. Some commercial jets have nearly crashed after flying into clouds of ash. Large rock fragments falling to the ground can kill people and destroy property.

* ASH FALL - Large volumes of ash can settle on buildings, resulting in their collapse. High levels of ash particles can cause increased coughing and irritate the eyes and skin and sometimes result in serious lung conditions. When the acid coating on ash is removed by rain, it can pollute local water supplies and damage vegetation. On the other hand, ash deposits can be beneficial by improving the fertility of soil.

* PYROCLASTIC FLOWS - An avalanche of hot ash, rock fragments and gas can flow down the side of a volcano at speeds of up to 150 miles an hour during explosive eruptions, burning everything in its path. People on the margins of the flows can suffer serious injury or even death from burns and inhalation of hot ash and gases.

THE RING OF FIRE:

* Of the world's 1,500 active volcanoes, almost 90 percent are in the Ring of Fire, a horseshoe-shaped band of volcanoes and fault lines circling the edges of the Pacific Ocean. It runs from Chile, northwards along the South American coast through Central America, Mexico, the west coast of the U.S. and the southern part of Alaska, through the Aleutian Islands to Japan, the Philippines and Indonesia before curving back to New Guinea, the southwest Pacific islands and New Zealand.

VOLCANIC ERUPTIONS IN HISTORY:

* Pompeii was buried under a deep layer of ash in an eruption of the Vesuvius volcano, which towers over the Bay of Naples in southern Italy, in AD 79.

* In 1815 the Tambora volcano eruption in Indonesia killed an estimated 92,000 people. It has been claimed that volcanic ashes swept all the way to Europe blanketing the continent in a veil and turning 1816 into a "year without summer."

* In 1883 Krakatoa erupted in Indonesia killing 36,000. The impact of the eruption spewed molten rock and sulphate aerosols into the atmosphere. The debris in the atmosphere created vivid red twilights in Europe from November 1883 through February 1884 - a fact reflected by painters of the period.

* An earthquake measuring 9.5 struck the coast of central Chile in May 1960, triggering tidal waves and volcanic eruptions. Some 5,000 people were killed and 2 million made homeless.

* Mount Pinatubo, 80 km (50 miles) north of Manila, has one of the 20th century's three largest eruptions. The June 1991 eruption killed more than 700 and 200,000 buildings are destroyed.

* The Mount St. Helens volcano in the U.S. state of Washington erupted in May 1980, creating a cloud of ash 2,500 miles long and 1,000 miles wide. The eruption was triggered by a 5.1 magnitude earthquake. 57 died.

* In June, 2006, eruptions at Mount Sakurajima, on the southern Japanese island of Kyushu, spews volcanic gases 2,000 meters (6,600 ft) into the air.

* An explosion from the 1,500-meter (5,000-ft) summit of Bulusan volcano in June 2006 in the Philippines sends ash and steam 1,000 meters (3,300 ft) into the air and showers ash on surrounding villages.

* In April 2010 an eruption from below the Eyjafjallajokull glacier in Iceland hurled a plume of ash six to 11 kilometers (3.8 to 7 miles) into the atmosphere.

(Writing by David Cutler, London Editorial Reference Unit; Editing by Dominic Evans)