JERUSALEM, April 19 (Xinhua) -- One of the world's pre-eminent authorities on volcanic activity and its effects on the atmosphere said there should not have been a ban on commercial flights over much of Europe in the past five days, though he agrees currently there is no enough information to accurately assess the extent of potential damage to aircraft.
Satellite imagery developed by Professor Daniel Rosenfeld of the Institute of Earth Sciences at the Hebrew University of Jerusalem shows the rate at which the ash plumes and subsequent dust clouds have dissipated as they made their way across northern Europe.
However, the visualization created by Rosenfeld for the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) clearly shows fresh volcanic activity emanating from Iceland on Monday.
When the volcano erupted under Iceland's Eyjafjallajokull glacier last week, spewing forth lava with ash rising skywards, the thoughts of scientists went back to an eruption in the Philippines in 1991.
When Mount Pinatubo erupted, causing massive disruption to human existence in the central Luzon region, aircraft were told to avoid the area as a heavy ash cloud formed. Even so, aircraft flying well to the west of the Philippines island chain sustained considerable damage amounting to tens of millions of dollars.
However, as far as the environmental impact was concerned, the effects of Pinatubo were far more serious than those of the current Icelandic eruption.
Some of the volcanic ash from Pinatubo succeeded in blocking solar radiation, meaning there was a significant cooling in temperatures, Rosenfeld said on Sunday. That is unlikely to take place on a similar scale around Iceland, because of the height difference between the eruptions.
"The volcanic eruption in the Philippines was very explosive and threw ash into the stratosphere -- that is at an elevation above the highest clouds where precipitation cannot occur and that lingered for more than a year and cooled the globe," said Rosenfeld.
In the Icelandic case, the ash has remained within the lowest 10 kilometers above the earth's surface. While that may be causing aviation havoc, from an environmental perspective it means there is less cause for concern.
Given precipitation at those levels, it is possible for the ash to all but disappear within a week to two. In order to see a real climactic effect, the volcano must continue producing the ash for an extended period and even then the areas affected will only be those reached by the airborne ash.
"Therefore there should be more limited cooling in the region around the site of the eruption. That could mean Europe or North America depending on which way the winds will blow -- Europe most likely -- and this effect will only be felt while the volcano is still erupting," Rosenfeld predicted.
From the point of view of air pollution, he argues that there is very little difference between the ash and the desert dust that affects many countries.
Indeed, as Rosenfeld was talking, the skies above his native Israel were turning a brownish-grey as north-easterly winds brought with them Sahara sands that they had picked up in North Africa.
Both desert sands and volcanic ash present health problems and in Israel, for example, the national radio stations broadcast warnings on particularly sandy days. Those with breathing problems, pregnant women and children are advised not to participate in strenuous exercise and it is recommended they remain indoors.
In the case of the Icelandic ash though, the effects are really only felt where it is at its densest.
A quick look at the EUMETSAT dust imagery shows vast tracts of the world covered in thick dust clouds. These show in a deep red on the animated maps. The dust and ash clouds created by the Eyjafjallajokull volcano are in far paler colors and dissipate far more quickly as the time lapse images show.
While aviation authorities argue with airline companies as to whether the shutdown of European airspace was justified, scientists like Rosenfeld are trying to improve ways of predicting such volcanic activity and improving the science so it is possible to measure the potential dangers posed by the ash clouds.
Rosenfeld agrees that one of the differences between the desert sands and the ash is the composition and the materials spewed by volcanoes can be a real danger to aircraft, as gooey residual lava interferes with engines.
In terms of forecasting when a volcano is about to erupt, he said the current methods are not totally accurate. However, once can monitor volcanic activity and when there are increases, it is possible to prepare a few weeks in advance.
That having been said, the last time the Icelandic volcano erupted was 190 years ago and for the last two years there has been heightened activity but only now did it actually erupt.
There has been concern that a larger volcano in the Eyjafjallajokull area may be about to erupt but because this is not an exact science all the experts seem able to say is that this will not take place in the next week or so.
Even if experts predict a volcano is about to erupt, they cannot say just how big that eruption will be and for how long it will last.
On the aviation front, while Rosenfeld maintains planes should have continued flying, he says that there is currently not enough information available to accurately assess the extent of potential damage to aircraft.
"We don't have sufficient knowledge about what are the safe levels of the size and amounts of volcanic particles. Because of that, you take very wide margins of safety," he said.
If the science was more precise then the areas where flying was banned could have been much more limited, he added.
Britain sent a research aircraft towards the Icelandic clouds to collect particles for examination. Aircraft companies also sent empty planes into the danger zone to monitor the potential damage.
"They couldn't find any scratches on the airplanes, which supports my thinking that we are overly cautious," Rosenfeld said.
According to the expert, the decisions not to fly this time are based on guesstimates rather than science and the sooner advances are made in this direction the less the likelihood of a repeat performance of this week's aviation mayhem.