AVIATION

Aircraft produce the same types of emissions as cars and trucks. In particular, aircraft jet engines produce carbon dioxide (CO2), water vapor (H2O), nitrogen oxides (NOx), carbon monoxide (CO), oxides of sulfur (SOx), unburned or partially combusted hydrocarbons (also known as volatile organic compounds, or VOCs), particulates, and other trace compounds. Aircraft engine emissions are roughly composed of about 70 percent CO2, a little less than 30 percent H2O, and less than 1 percent each of NOx, CO, SOx, VOC, particulates, and other trace components.

As with surface vehicles, aircraft produce carbon dioxide through combustion of petroleum-based fuel. Aircraft can have complex effects on climate through contrail formation and by emitting water vapor into the dry stratosphere. Aviation accounts for about 10 percent of greenhouse gas emissions from transportation in the U.S., or about 2.7 percent of total national greenhouse gas emissions.

Change is coming as the industry works to come to terms with climate change, but, by all measures, it will be slow. A wide range of technologies and innovations are being designed in a bid to tackle aviation’s environmental footprint. For example,

• NASA is researching ideas that could lead to the development of electric propulsion-powered aircraft, which would be quieter, more efficient and environmentally friendly than today's commuter aircraft.
• The U.S. Air Force's Agility Prime program is working with private industry to explore building innovative aircraft, such as “flying taxis”, also being developed by United Airlines.
• Emitting 90% less carbon dioxide than a standard airplane, blimps are also coming. Bill McKibben found the best description of what they might feel like, in a new world of aviation, in Kim Stanley Robinson’s brilliant sci-fi novel, The Ministry for the Future. "In the novel", he writes "that takeoff felt strange, lofting up over the bay, bouncing a little on the wind, not like a jet, not like a helicopter. Strange but interesting. Dynamic lift; the electric motors, on sidecars up the sides of the bag, could get them to about two hundred kilometers an hour over the land, depending on the winds.”