Feds Say Planes Emitting Less CO2. Um, Not Quite.

The Environmental Protection Agency has released a report with the surprising conclusion that carbon dioxide emissions from commercial aircraft in the United States have grown only slightly since 1990 while also decreasing during the past 13 years.

That's an amazing claim that looks like a bit of Orwellian doublespeak given the huge increase in air travel we've seen in the past two decades. Here's how the report sums it up:

"CO2 from the domestic operation of commercial aircraft increased by 4 percent (5.4 Tg) from 1990 to 2006, well below the growth in travel activity (passenger miles traveled grew by 69 percent from 1990 to 2005, the most recent year of available data)."

So if carbon dioxide emissions are up 4 percent, how can they also be down?

They aren't.

A table in the EPA report, "CO2 Emissions From Fossil Fuel
Combustion in Transportation End-Use Sector," backs up their findings.
We pulled a column of numbers from the chart that shows CO2 emitted by all jet-fuel burning aircraft (including military and general aviation aircraft) and another that measures only commercial planes. The figures listed are in Tg CO2 Eq, or teragrams of carbon dioxide equivalents. One Tg equals one million metric tons.

Year Total jet fuel Commercial aircraft –
consumption: domestic:

1995 222.1 __ 143.1 __
2000 253.8 164.2
2001 242.8 __ 152.9 __
2002 236.8 146.1
2003 231.5 143.9
2004 239.8 1__42.9__
2005 246.3 150.4
2006 239.5 142.1

Here's the EPA's explanation for this .69 percent drop since 1995:

"The operational efficiency of commercial aircraft improved substantially because of a growing percentage of seats occupied per flight, improvements in the fuel efficiency of new aircraft, and the accelerated retirement of older, less fuel efficient aircraft."

They got it right, sort of.

It's true that airlines have dumped their gas guzzling 727s, DC-10s and L1011s and replaced them with sleeker, sexier, more fuel efficient aircraft. And rather than flying half-empty jets around the country, they're bumping up their load factors - which means more crowded flights but less CO2 per passenger.

Before breathing a big sigh of relief that you can once again fly guilt-free, consider this: when calculating US airlines' emissions, the EPA looks only at fuel used on commercial routes. Anything purchased in the US for international flights gets lumped into a different category called bunker fuels. That's like saying gassing up an SUV doesn't count if you're driving it to Mexico.

Emissions from bunker fuels have jumped by 55 percent since 1995, which means means total CO2 emissions for commercial aircraft have actually grown by 10%. And as US airlines continue to shifting planes onto more lucrative international routes, the EPA numbers will become increasingly skewed.

And you've also got to remember that when it comes to aircraft emissions, CO2 isn't the only thing to worry about. Planes spew plenty of other pollutants, including nitrogen oxides, sulfur oxides, soot and water vapor. Yup, water vapor. It traps heat, and trapped heat contributes to global warming.

The EPA report was about measuring CO2. That's cool, and it's good to see that commercial aviation has at least managed to stabilize its emissions. But the people who think these finding vindicate the industry need to take a closer look at the numbers.

*Photo by Flickr user mytimemachine. *