Oil Spills in the Sky
Looking back at a 1997 Earth Island Journal report on pollution from the airline industry
On July 25, CBS News joined the rest of the mainstream media to acknowledge mounting concerns over atmospheric pollution from jet aircraft. "The government has found that jet engine exhaust is adding to climate change and endangering human health, and needs to be regulated," CBS reported. At the same time, the Environmental Protection Agency (EPA) announced plans to employ the Clean Air Act to reduce the impacts of jet-pollution.
photo by Aero Pixels, on Flickr
The EPA’s action came in the wake of a mid-April US District Court lawsuit filed by the nonprofits Friends of the Earth and The Center for Biological Diversity alleging that the EPA had failed "to enforce limits on heat-trapping greenhouse gas emissions from aircraft."
Meanwhile, a United Nations panel has suggested cutting airliner fuel consumption by an average of 4 percent — beginning in 2028. Unfortunately, the UN recommendation ignored the fact that aircraft fuel consumption (and, hence, pollution) is at its worst during takeoffs and landings — not while cruising at high altitudes.
These recent headlines brought to mind an Earth Island Journal cover story from the summer of 1997. Just as the Journal was the first magazine to feature a cover story on climate change ("The Climes They Are A-Changing," Summer 1988) it was also the first magazine to feature a cover story about the airline industry’s impact on Earth’s atmosphere ("Oil Spills in the Sky," Summer 1997).
Nearly 20 years have passed since the Journal first exposed these dangers. It is both gratifying and frustrating to see that action is finally being focused on addressing this serious environmental threat. In light of these recent developments here is a look back at our Summer 1997 report on aircraft pollution.
—Gar Smith, Editor Emeritus, Earth Island Journal
Oil Spills in the Sky
How Jet Aircraft Are Polluting the Skies and Changing the Weather
Viewed from space, there are four unmistakable signs that Earth is inhabited by humans: sprawling cities, forest fires, disappearing lakes, and aircraft contrails.
With 10,000 large commercial aircraft flying today and the number expected to double by the year 2020, contrails (short for "condensation trails") pose a growing environmental threat. Commercial jets have been crossing the skies since the 1950s, but scientists only recently have begun to notice evidence of climate change occurring beneath well-traveled jet routes.
One of the world’s most troubled routes, the North Atlantic Flight Corridor (NAFC) lies between 45 and 65 degrees north latitude and runs almost entirely over water. In 1990, between 700 and 800 aircraft traveled this route between the US and Europe each day – amounting to more than 200,000 flights per year.
Jet contrails are changing the weather and the number of jetliners could double in 20 years. Why isn’t this an issue?
Among the first to sound the climate change alarm was Stanley A. Changnon of the Illinois State Water Survey. In 1981, Changnon pointed out that the Midwest had grown cloudier since the 1960s and that the greatest changes had occurred in regions marked by heavy jet traffic.
University of Utah atmospheric physicist Kuo-Nan Liou found that high-level cirrus clouds in the skies above Salt Lake City had intensified by 5 to 10 percent between 1948 and 1984 – all major air-traffic hubs.
On the East Coast, Penn State meteorologist Tom Ackerman detected evidence of changes in surface temperature consistent with an increase in high-level cloudiness beneath the flight route connecting major cities of the east and west coasts.
In 1994, NASA scientists using GOES-8 satellite measurements reported that "in certain heavy air traffic corridors, cloud cover has increased by as much as 20 percent." In its May 1996 study, "Atmospheric Effects of Aviation," NASA estimated that subsonic flights in the NAFC had increased atmospheric soot by 10 percent, sulfur oxides (SOx) by nearly 10 percent and nitrogen oxides (NOx) from 10 to 100 percent.
Fry the Friendly Skies
Transatlantic jets burn between 2.5 and 3 tons of fuel per hour. In 1988, commercial aircraft consumed an estimated 70 percent of all jet fuel (with military and business craft accounting for another 24 percent). The world’s aircraft currently produce about 3 percent of the carbon dioxide gases attributed to human activity.
During take-off, a jumbo jet can devour 2 million liters (528,344 gallons) of air per second. In the first five minutes of flight, a commercial airliner can burn as much oxygen as 49,000 acres of forest produce in a day. According to Department of Transportation figures, flying a Boeing 747-400 from Washington, DC to San Francisco burns 17,232 gallons of jet fuel. (Fuel efficiency: 6.7 mpg.) A Boeing 747 averages 32 minutes taxiing, taking off and landing. During this time, it can generate 190 pounds of NOx – equal to the amount produced by driving a car 53,500 miles.
In addition to producing vapor trails that can stretch thousands of miles across the sky, jet exhaust also triggers the formation of artificial clouds by "seeding" the atmosphere with cloud-forming aerosols – droplets of sulfuric acid and particles of soot.
While NASA’s tests of jet engines at ground level found that less than 1% of the sulfur produced left the engines in the form of cloud-forming sulfuric acid droplets, researchers were startled to discover that, at jet-cruising altitudes, acid droplets accounted for at least 10% of the sulfur emissions.
The NOx ejected by jet engines contributes to global warming by helping to create ozone clouds that trap heat in the troposphere. In 1996, aircraft generated nearly half the NOx found in the mid-latitudes of the Northern Hemisphere between 26,000 and 40,000 feet, according to estimates cited by Ulrich Shumann of the DLR Institute in Oberpfaffenhofen, Germany.
During the day, contrails either can reflect heat back into space (the Albedo Effect) or trap heat below (the Greenhouse Effect). When jets travel at night, however, contrails only trap heat in the lower atmosphere. University of Wisconsin climatologist David T. Travis theorizes that this may explain an unusual narrowing of daytime and nighttime temperatures recorded across the US.
Contrails have the potential to change local and national weather patterns, as well. Temperature differences between ocean and land surfaces heavily influence circulation patterns in the atmosphere, and warmer land masses can increase the frequency, direction and intensity of winds and storms.
University of Munich meteorologist Werner Metz has observed that "aircraft emissions are the only significant man-made source of pollutants in the upper troposphere and in the stratosphere." In a 1993 issue of the Journal of Geophysical Research, Metz concluded that the best way to protect the stratosphere would be to move all transatlantic jet routes at least 2.5° South (to take advantage of a higher troposphere at that latitude) and lower cruising altitude by 6,000 feet. "This would result in a decrease in stratospheric NOx emission down to 9 percent," Metz calculated.
A Growing Problem
The Environmental Defense Fund (EDF) reported in 1994 that aviation fuel use and emissions were growing faster than other areas of energy use. While average world energy consumption rose 2.8 percent between 1983 and 1989, the annual use of aviation fuel crept up by 3.9 percent.
The EDF estimates that, in 1990, civil aviation consumed 133 million tons of fuel and generated four to 2 million tons of CO2.
According to a 1996 analysis by Boeing researcher Stephen L. Baughcum, in 1990, airline and cargo flights burned more than 10 billion tons of jet fuel and generated 125.6 million tons of NOx.
Baughcum estimated that military aircraft consumed 912 million tons of fuel and produced 21.4 million tons of NOx. The global total for 1990 came to 14.8 billion tons burned, which produced 160 million tons of NOx and 124.5 million tons of CO2.
The EDF has estimated that, even with a projected tripling of fuel efficiency, "fuel consumption and CO2 and water vapor emissions will jump more than six-fold by 2100." As in the case of automobiles, any efficiency gains in the air will be overwhelmed as the number of aircraft grows ten-fold over the next half-century. (The aircraft industry foresees these numbers doubling by the end of the 21st century.)
According to the EDF’s scenario, N0x emissions from subsonic aircraft could more than triple in the next century, while N0x and CO2 could "lead to as much as 10 percent of human caused global warming by 2050."
Meanwhile, a 1996 Natural Resources Defense Counsel survey has found that 75 percent of 50 major US airports we are undergoing expansion or planning to expand operations. Airport development promises to bring more air and noise pollution to nearby neighborhoods, while putting added stress on adjoining open spaces and wetlands. The Amicus Journal points out that airports "are exempt from some of the environmental standards that apply to industrial facilities" and also are exempt from the Community Right-to-Know Act requiring public disclosure of toxic hazards.
Under international agreement, jet fuel is not taxed – giving the airline industry subsidy to pollute. The Center for International Climate Change and Environmental Research in Oslo (CICERO) has suggested funding climate protection efforts by taxing fuel and passengers. A per-passenger tax of $8.70 would produce $10 billion by 2003. CICERO has proposed that the UN’s Global Environment Facility manage the revenue.
The Coming Superjets
By the year 2015, NASA estimates that aircraft fuel consumption will more than double, NOx emissions will nearly double and CO2 emissions will grow by 50 percent. But NASA’s figures specifically (and inexplicably) exclude the impacts of a "High-Speed Civil Transport (HSCT) fleet."
The new generation of supersonic HSCTs planned for the 21st century clearly will add to the impact of the world’s growing fleet of subsonic aircraft. The prototype HSCT now on the drawing boards could carry 300 passengers 60,000 feet above the Earth at twice the speed of sound. The first HSCT’s could be heading for the stratosphere as early as 2005.
Science News reports that superjets, ferrying VIP passengers between Tokyo and Los Angeles in under five hours, would create ground-rocking sonic booms capable of causing physiological harm or structural damage. With 500 ocean crossings each day, Science News predicts that superjets could have a serious impact on "whales, seals, sea lions and sea otters," not to mention "passengers on cruise ships and residents of Islands near ocean flightpaths."
In the 1960s, environmentalists grounded US plans to build a Supersonic Transport (SST) because of the damage the planes would wreak on the ozone layer. The only SSTs ever built were 13 British-French Concordes. The stakes are even higher as environmentalists prepare to fight the jet battle once again.