Air Quality - Airplanes

As air travel in affluent nations has increased, it has caused a number of environmental problems. The average American flew 1,739 miles a year by 2000. Europeans, though they flew fewer miles, had the world's most crowded skies, while the most rapid growth in flying was in Asia. Most air travel is done by a small portion of the world's population.

Flying carries an environmental price—it is the most energy-intensive form of transport. In much of the industrialized world, air travel is replacing more energy-efficient rail or bus travel. Although the fuel efficiency of jet engines has improved over the decades, overall jet fuel consumption has increased dramatically. According to the U.S. Bureau of Transportation's National Transportation Statistics, 2003 (March 2004), jet fuel consumption has nearly doubled in just over 30 years, from 7,847 million gallons in 1970 to 14,017 gallons in 2001.

Another problem with air travel is its impact on global warming. Airplanes spew millions of tons of nitrous oxide into the air every year, much of it while cruising in the tropospheric zone five to seven miles above Earth where ozone is formed. According to the February 2000 U.S. General Accounting Office (GAO) report Aviation's Effects on the

TABLE 5.8
Technical specifications and sales figures for hybrid car models, 1999–2002

	Honda Insight CVT1	Toyota Prius CVT1	Honda Civic Hybrid CVT SULEV1
Fuel economy (city/hwy)	57/56 mpg	52/45 mpg	47/48 mpg
Fuel tank capacity	10.6 gal.	11.9 gal.	11.9 gal.
Acceleration (0–60 mph)	11.5 sec.	12.3 sec.	11.6 sec.
Emissions rating	SULEV	SULEV	SULEV
Aerodynamics	0.25 Cd	0.29 Cd	0.28 Cd
Curb weight	1,967 lbs.	2,765 lbs.	2,740 lbs.
Passenger capacity	2	5	5
Dimensions:
Length	155.1 in.	169.6 in.	174.8 in.
Width	66.7 in.	66.7 in.	67.5 in.
Cargo capacity	16.3 ft3	11.8 ft3	10.1 ft3
Price	$21,280	$21,280	$20,550
Calendar year sales
1999	17	0	0
2000	3,788	5,562	0
2001	4,726	15,556	0
2002	2,216	20,119	∼12,0002
Total	10,747	41,237	∼12,0002
1Specifications are for the model containing a continuously variable transmission (CVT).
2Sales for the Civic Hybrid are not shown separately from other Civic models, but estimates of 2002 sales are approximately 12,000 vehicles since its March 2002 debut.
Note: SULEV Super ultra low emission vehicle.
SOURCE: Stacy C. Davis and Susan W. Diegel, "Table 6.5: Sales and Specifications of Available Advanced Technology Vehicles," in Transportation Energy Data Book: Edition 23, U.S. Department of Energy, Office of Planning, Budget Formulation and Analysis, Energy Efficiency and Renewable Energy, Washington, DC, October 2003

Global Atmosphere Are Potentially Significant and Expected to Grow, the EPA estimates that air traffic accounts for about 3 percent of all U.S. greenhouse gases. The Intergovernmental Panel on Climate Change (IPCC) notes that emissions deposited directly into the atmosphere do greater harm than those released at the Earth's surface. (See Figure 5.26.)