Volcanic ash unlikely to cool planet==5pm Melbourne -- Moon

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Date Posted: 00:01:01 04/16/10 Fri
Author: waxing Crescent 7% of full==Friday April 16th 2010
Subject: Volcanic ash unlikely to cool planet==5pm Melbourne

Home ť Weather News ť Volcanic ash unlikely to cool planet

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Volcanic ash unlikely to cool planet
Darren Osborne for ABC Science Online, Friday April 16, 2010 - 16:26 EST

To have a significant global cooling effect the ash cloud would have to reach the stratosphere, say experts - Reuters
The volcanic ash cloud that exploded from an Icelandic volcano this week is not expected to have an impact on global temperatures, says an Australian climatologist.

The volcano, located under the Eyjafjallajokull glacier, erupted on Thursday producing a 10-kilometre high plume of ash and rock that has extended across most of northern Europe.

The debris has caused the closure of airports in the UK, Norway, Denmark, Belgium and Sweden, and produced spectacular sunsets in the region.

While the particles may have an effect on local temperatures in the short-term, experts don't believe it will have the same impact as the Pinatubo eruption two decades earlier.

In June 1991, Mount Pinatubo, an active volcano in the Philippines, launched ten cubic kilometres of material into the atmosphere.

Particles from the eruption entered the Earth's stratosphere resulting in a 10% reduction in sunlight reaching the Earth's surface, and a 0.4°C drop in global average temperatures.

Dr Blair Trewin of the National Climate Centre in Melbourne says, in its current form the ash cloud is unlikely to have the same impact on global temperatures.

"For a volcano to have a significant global cooling effect it has to get its ash up into the stratosphere," he says. "If it doesn't, the ash will get rained out fairly quickly."

Even if the material reaches the stratosphere, Trewin believes the volcano's location will result in the ash staying in the northern hemisphere.

"Once you're in the stratosphere the winds tend to flow out from the equator to the poles," he says. "So if you get a big eruption in the tropics the winds in the stratosphere will tend to spread out material over the whole globe.

"Whereas if it happens in the polar regions the stuff tends to get stuck - it doesn't spread up to lower latitudes."

But Trewin says the volcanic ash cloud may have an impact locally.

"When Mount St Helens erupted in 1980 it had no significant global impacts, but in the days immediately after the eruption you had cooling of daylight temperatures by 10°C or more in some parts of the northwestern United States."

Dr Jeff Masters, Director of Meteorology at Weather Underground says the eruption isn't expected to have a significant impact on weather patterns in the northern hemisphere.

"However, the ash could bring spectacular sunsets to Europe over the next week, and to North America by sometime next week, as the jet stream wraps the ash cloud eastwards across the northern hemisphere."

- ABC

Š ABC 2010

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