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Ash clouds and airplanes

If the western world needed a reminder that nature, not the human race, is in charge – and that distant, unexpected events can suddenly and radically alter people’s lives – it need only look to Eyjafjallajökull. One of Iceland’s smaller glaciers, the icecap covers a volcano that had lain dormant for nearly two centuries before erupting on March 20. It did so, as a fissure, after a few months ago of seismic activity: thousands of small earthquakes.

The volcano erupted again on April 14, this time more powerfully and from beneath the centre of the glacier. This explosion melted snow and ice, causing floodwaters to swell nearby rivers. Volcanic ash and steam were expelled several kilometres into the earth’s atmosphere. The next day, as the cloud drifted south-east toward the British Isles and mainland Europe, a ban on flights to and from most European airspace was imposed. It had, naturally, a knock-on effect across an inter-dependent world reliant on trade (particularly perishable food products). In a world in which so many people have come to take their short hops and long-haul journeys for granted, the ash cloud put their feet firmly back on the ground.

The chaos and confusion, frustration and disappointment, that ensued from the flight ban is only beginning to ease today, after aviation authorities re-evaluated their April 15 decision and reopened the skies. Along with some planes, recriminations, too, are flying. Did officials overreact six days ago to the dangers the volcano presented to jet aircraft engines? Are flights being allowed again because of a change in the nature of the eruption, commercial pressures or a greater understanding of the ash’s effects and the contamination levels? The answer appears to be a combination of all three factors. Still, the question niggles: is it really safe to fly in the vicinity of the volcanic ash?

The fine particles – which the World Meteorological Organisation (WMO) said were made up of tiny jagged pieces of rock, mineral and volcanic glass the size of sand, salt or silt -- are hazardous, in numerous ways, to jet engines. And at 30,000 feet (roughly 10,000 metres) and above, airliners and ash cloud would share the same cruising altitudes.

As of this morning, the volcano under the Eyjafjallajökull glacier was still erupting, though with a decline in ash. “There is ongoing activity in the volcano and we don’t see any signs of it coming to an end,” an Icelandic meteorological official said. “There is less ash production; it is probably the same as yesterday. The plume is very low, so most of the ash is falling here and keeping itself under 20,000 feet.”

According to the WMO, a low-pressure weather system moving into Iceland should help clear the cloud within days.

That may not be the end of the story though. Scientists fear that tremors at Eyjafjallajökull could trigger an even more dangerous eruption at the Katla volcano, 20 kilometres away, creating a greater nightmare for the airline industry, businesses and travelers. An eruption at Katla, they said, would be 10 times stronger and shoot higher and larger plumes of ash into the air. The two volcanoes are thought to be connected by a network of magma channels.

What happens next, and when, is anyone’s guess. For the time being, though, many people have observed, the volcano has done what years of climate talks and protests against airport noise and runway expansions have not. It grounded every airliner in northern Europe and many more around the world.

So, has Eyjafjallajökull done us a favour, environmentally, by grounding the planes? Or is its output of gases and particles far worse than those caused by aviation? Like many scientists, Grant Allen, of the University of Manchester’s Centre for Atmospheric Science, sees “a double-edged sword” in the comparative emissions of carbon dioxide (CO2) and sulfur dioxide (SO2).

“I believe that the volcano is emitting a very broad estimate of 200,000 tonnes CO2 per day,” he told chinadialogue on Tuesday, “whereas the planes would be emitting 10 times that, so we are currently seeing a large reduction in the emitted CO2 over Europe on net. SO2 is emitted in much larger amounts -- about five times more SO2 than CO2 is emitted from the volcano and this is very bad for the environment; so the volcano could be considered to be a double-edged sword in terms of the greenhouse and noxious gases it emits.”

Experts cited by Agence France-Presse also expressed caution regarding any climate benefit from the eruption. AFP quoted European Environmental Agency (EAA) sources as saying that daily carbon emissions from the 27-nation European Union’s aviation sector are about 440,000 tonnes per day. Not all of this, however, is “saved” because of the eruption. Some airports in southern Europe remained open for traffic; carbon is emitted when people travel in ways other than by air; and many flights are merely being deferred until the ash crisis ends.

“CO2 is dangerous because it stays in the atmosphere for about 100 years,” a French climatologist told the news agency. “Its short-term effect is not a big problem.”

Still, the absence of the planes and an immediate benefit has not gone unnoticed, particularly by those living near European airports such as London’s Heathrow, the world’s third-busiest.

A Guardian reporter strolled through Kew Gardens and imagined a world permanently without planes. A BBC correspondent, writing in the Observer, exulted in the respite from the roar of jet engines. “So what difference does it make without the planes? Birdsong, that’s what you hear. Blackbirds, robins, wood pigeons, even song thrushes.”

Indeed, at London’s 43-hectare Wetland Centre over the weekend, birds of various species and plumage crisscrossed the contrail-free blue sky, circling, swooping and diving before coming to rest in the wildlife preserve. Until a volcano in Iceland changed things for six days, the small birds had shared the sky with larger, noisier metal ones, their bodies glistening in colourful corporate plumage as they proceeded along their flight path into Heathrow.

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匿名 | Anonymous


航空公司的老板们,让我们不要忘记英国航空公司009航班于1982 年6月24日所发生的事故。大型喷气式客机——从吉隆坡到澳大利亚珀斯的航班上载有263名乘客——在机组成员能够重新启动之前所有4个引擎已经在印度洋上空可怕的失灵了。什么引起的呢?一片来自爪哇Galunggung火山的灰云。它并没有显现在雷达上,因为它是由干燥的粒子,而不由是水组成的。除了堵塞飞机的引擎外,火山颗粒还可以破坏驾驶舱的窗户和金属表面。其他商用飞机也在过去几年里经历了引擎失灵和灰云带来的损害。

Safety first

Authorities are right to be extremely cautious, even to the point of "over-reacting", in these situations. A Belgian air force F-16 fighter plane -- one of several NATO jets that flew through the ash cloud -- was reported this week to have been damaged by the volcanic material. Glass-like deposits were found inside its engine.
And let's not forget, you airline bosses, about British Airways flight 009 on 24 June 1982. The jumbo jet -- en route from Kuala Lumpur to Perth, Australia, with 263 passengers -- terrifyingly lost all four engines over the Indian Ocean before its crew was able to restart them. The cause? An ash cloud from the Galunggung volcano in Java. It hadn't appeared on the radar because it was made up of dry particles, not water. In addition to clogging plane engines, volcanic particles can chip away at cockpit windows and metal surfaces. Other commercial jets also have experienced dramatic engine failures and ash-cloud damage over the years.
Airlines face huge economic problems now because their planes were grounded and passengers are demanding compensation. But nothing would drive them out of business faster than a crash when they shouldn't have been flying at all.

Default avatar
匿名 | Anonymous



Space radiation

The sulphur spewed out by the volcanic eruption in Iceland should also stop a considerable amount of space radiation, and may significantly reduce the greenhouse effect on Earth.

Default avatar
匿名 | Anonymous



由Jieping Hu翻译

Safety update

Britain's Royal Air Force temporarily grounded its Typhoon Eurofighter jets on 22 April after tests showed volcanic ash deposits in one of the planes' engines. The planes were back in the air today -- "doing loop-the-loops and the rest of it", as The Independent quoted a squadron leader as saying -- after no damage was found. "There was just a little bit of dust found on one of the jets and in the engine air intakes."
The jets cost £69 million apiece, apparently. A very costly bit of equipment to lose had anything gone wrong, not to mention the life of a highly skilled pilot.


Default avatar
匿名 | Anonymous




The British Really Have Guts

Thanks for the update in comment 3.

The British really have guts, but I'm guessing that the military should have a good understanding of exactly how much volcanic ash affects jets, and it presumably doesn't amount to much.