Friday, February 21, 2014

Which Emits the Most Greenhouse Gases- Car Trips or Plane Trips?

The climate impact of travel behavior: A German case study with illustrative mitigation options( Aamaas B, Borken-Kleefeld J, Peters GP, Environmental Science & Policy, Nov. 2013)

Also discussed here: Policy Analysis - Mode, Load, and Specific Climate Impact from Passenger Trips(Abstract, Jens Borken-Kleefeld, Jan Fuglestvedt, and Terje Berntsen, Environmental Science & Technology, Jun. 13, 2013)

And here: Going by car, plane, coach or train?– Climate impact from passenger travel re-calculated(11 page pdf, Jens Borken-Kleefeld, International Institute for Applied Systems Analysis, 2011)

And here: Cars and planes dominate the climate impact from travel(CICERO, Center for International Climate and Environmental Research-Oslo, May 8, 2013)

And here: Study finds climate impact of long distance trip can vary by factor of 10 depending upon mode, efficiency and occupancy(Green Care Congress, Jun. 27, 2013)

Today we review several articles that examined the greenhouse gas contributions made to atmospheric by various modes of travel. As to which is worst- car or plane trips, the short answer is: it depends. It depends on how many passengers travel together in a car and how energy efficient the car is and in terms of annual emissions how many car or plane trips are taken (in Germany the average is 1,000 car trips per year, likely close to what it is in US/Canada or Western Europe). On a single passenger per km travel basis, the plane trip is the winner (or, I should say, loser), not only because of the CO2 in the fuel emissions but also as a result of contrails which impact the climate. Travel in a small car with 3 or more passengers has less impact per passenger on the climate than rail or bus public transit which, otherwise, win.

The biggest issue for transit is passenger occupancy – they work best when full to capacity but usually they are not which leaves a heavy vehicle, wasting fuel to carry a few passengers. I’d bet on a small electric  robot car, wouldn’t you?

travel ghg  

Key Quotes:

“The climate impact from a long-distance trip can easily vary by a factor of 10 per passenger depending on mode choice, vehicle efficiency, and occupancy”

“[in Germany]Car and air travel are responsible for about 90% of the climate impact. Air travel has a higher specific climate impact per person kilometer, but after adjusting for travel volumes, the split between car and air travel is equal.”

“The climate impact of air travel is almost doubled due to the additional impact from contrail formation”.

“The climate impact from the highest income group is 250% larger than from the lowest income group. However, the middle classes account for more than two thirds of the total impact. The relatively few trips beyond 100 km contribute more than half of the total impact because of the trip distance and use of aircraft.”

“Two inner-European trips by aircraft can equal the climate impact from a whole year's driving,”

“One long-distance holiday return trip has the same impact as more than two months of regular urban travel…Likewise, a medium distance leisure round trip has the same impact as 7 days of regular urban travel”

“the climate impact from a long-distance trip (500–1,000 km, or 310–621 miles) can easily vary by a factor of 10 per passenger depending on mode choice, vehicle efficiency, and occupancy”

“The impact from short-lived climate forcers (SLCFs) and notably of contrails and cirrus clouds is particularly strong for aircraft; as a result, their specific climate impacts are strongly influenced by the choice of metric and time horizon. …Cirrus clouds and contrails contribute more than four-fifths of extra warming”
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