LONDON — As volcanic ash cast a shadow over millions of lives, Londoners and other city dwellers across Europe were treated to a rare spectacle of nature: Pristine, blue skies brighter than any in recent memory.
The remarkable sight happened in part because mass flight groundings prevented busy airspace from being crisscrossed with plumes of jet exhaust that create a semi-permanent haze — and other effects beyond the white contrails themselves.
Just as city lights make it necessary for us to go to the desert to appreciate the true glitter of stars, so has modern aviation dulled us to what the noontime sky can really look like — until the erupting volcano in Iceland offered a reminder.
Britain's poet laureate, Carol Ann Duffy, was inspired to write verses about the unusually clear skies above London: "Five miles up the hush and shush of ash/Yet the sky is as clean as a white slate/I could write my childhood there."
Scientists cast the phenomenon in more prosaic terms. Without aircraft contrails, "the skies have been particularly blue," said meteorology professor Chris Merchant of the University of Edinburgh.
The clearer skies are primarily due to a high pressure system in the region, but Merchant said the blue tone has been deeper than normal because of the lack of vapor from aircraft engines. Depending on weather conditions, the vapor trials can expand into thin cirrus clouds.
On an average day, European air travel generates more than 400,000 tons of carbon dioxide — representing about 3 percent of total greenhouse emissions, according to the European Environment Agency. Those aircraft emissions have been cut by more than half in recent days as aircraft were grounded across the continent.
But many of the stranded passengers have chosen to travel by road — in some cases thousands of miles — burning fuel that otherwise would have been left in the tanks.
It's hard to estimate the added emissions, since it remains unclear how many extra vehicles are on the road as a result of the airspace closures and how far they are traveling.
Then there's the volcano's own CO2 emissions.
Colin Macpherson, a professor in earth sciences at Britain's Durham University, estimates that the volcano belched out 150,000 tons of CO2 a day over the first three days of the eruption and then progressively less.
By comparison, the world's volcanoes release an average of 44 million tons of CO2 annually, Macpherson said.
Alice Bows, a climate scientist at the University of Manchester, said "a back-of-the-envelope calculation" suggests that because aviation is so carbon-intensive, there should be a net reduction in emissions.
Even if the flight stoppage yielded only a small reduction in man-made emissions, Bows wondered whether the travel chaos would have a more lasting effect — on people's minds.
"In the grand scheme of things, the interesting thing for me is, does this change behavior in any way? Does it make people consider different forms of travel?" she said. "Anecdotally we're hearing about people using video conferencing to conduct interviews with people abroad, when they would normally have flown for the interview."
Ash cloud grounds jet fighters
When the Icelandic volcano erupted last week, it didn't just wreak havoc with commercial flights. It grounded American jet fighters and some of the most advanced air forces in the world.
Like their commercial cousins, fighters, reconnaissance planes, helicopters and other military aircraft around the region sat idle for days. They are just now beginning to come back to life, although fighter jets — which have highly sensitive engines — remain grounded across Europe.
The U.S. Air Force's biggest fighter wing in Europe, at England's RAF Lakenheath air base, was under no-fly orders and many of its F-15s were being kept in protective shelters. U.S. military officials at their European headquarters in Germany said they were keeping all aircraft on routine missions on the ground regionwide as a precaution.
Getting supplies to Afghanistan has also gotten more complicated, and troops have had to deal with mail not being delivered properly and low supplies at base stores.
Two U.S. military bases in southern Spain are seeing big increases in stopovers by transport planes heading to or from Afghanistan because the planes can no longer stop over in Germany for refueling or maintenance, meaning longer flying times and delays. Medical flights to Landstuhl Regional Medical Center near Ramstein for troops injured in Afghanistan and Iraq have been halted although hospitals in the war zones are not short of supplies or overwhelmed by patients, said spokeswoman Marie Shaw.
Airlines struggle to recoup costs, get passengers home
Airlines toted up losses topping $2 billion and struggled to get hundreds of thousands of travelers back home Wednesday after a week of crippled air travel, as questions and recriminations erupted over Europe's chaotic response to the volcanic ash cloud.
Electronic boards in Europe's biggest hubs — London's Heathrow, Paris' Charles de Gaulle and Germany's airport at Frankfurt — showed about 80 percent of flights on schedule as airlines began filling vacant seats with those who had been stranded for days. But with 102,000 flights scrapped worldwide over the last week, it could take more than a week to get everyone home.
In Iceland, the volcano under the Eyjafjallajokull (ay-yah-FYAH-lah-yer-kuhl) remained active Wednesday — throwing magma chunks the size of cars into the air, bubbling lava and producing tremors. But it was not shooting ash and smoke four to six miles into the air like it did previously.
"There is much, much less ash production and the plume is low," said Gudrun Nina Petersen, meteorologist at the Icelandic Met Office, adding that mild winds kept the ash away from crowded air flight corridors.
But scientists at Zurich's Federal Institute of Technology said an initial analysis of samples collected over Zurich last weekend by special weather balloons concluded that safety concerns were warranted and the volcano could be getting more dangerous.
The concentration of particles was "very high" at up to 600 micrograms per cubic meter, according to Professor Thomas Peter.
In Berlin, Giovanni Bisignani, the head of the International Air Transport Association, called the economic fallout "devastating" and urged European governments to compensate airlines for lost revenues like the U.S. government did following the 9/11 terror attacks.
At one stage, he said 29 percent of global aviation and 1.2 million passengers a day were affected by the airspace closures. Airlines were on track to lose $2.2 billion, he said.