## Sierra Club quiz on travel: CO2 emissions: cars, planes, trains

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• Quiz results: http://www.sierraclub.org/howgreen/getaway/answer.asp A Los Angeles resident is planning a vacation to Seattle. Which way to get there and back
Message 1 of 1 , May 1, 2008
Quiz results:

A Los Angeles resident is planning a vacation to Seattle. Which way to
get there and back generates the least amount of global-warming carbon
dioxide?
15-miles-to-the-gallon SUV.
0 out of 10 points.

The plane, but in this case, just barely. The roundtrip flight would
generate the equivalent of 0.93 tons of CO2, compared to the SUV's
1.18 tons. Jet fuel and gasoline both generate about 20 pounds of CO2
per gallon burned, according to Tuft University's Climate Initiative.

Consider the same vacation, but this time for a family of four and a
third travel choice. Which generates the least CO2?
10 out of 10 points.

The 30-mpg car would generate the least CO2. But even the SUV beats
the plane in this match-up because it's carrying four people at the
same mileage and CO2 emissions.

Does it really matter whether I take a plane or train or drive? That
plane's going to fly even if I'm not on it.
0 out of 10 points.

If you're not on board next Tuesday, Southwest probably isn't going to
ground the plane or Amtrak cancel its run. But your day-by-day
decisions -- and those of everyone else -- absolutely drive overall
market demand. Carriers hate empty seats and constantly fine-tune the
number of departures in response.

While jet fuel and vehicle gasoline both generate about the same
amount of CO2 per gallon burned, the mile-for-mile effect of jets is
more than twice that of autos and trucks.
10 out of 10 points.

True. For a clue to the difference, think about what happens to those
jet trails six to eight miles up in the air. They coalesce into
clouds, which trap the earth's heat, even though they also reduce the
sun's incoming warmth. Known as radiative forcing, this problem's not
driven strictly by the CO2, but by all the other things jets emit,
including water vapor and nitrogen oxides. Still, the end result is
that a single ton of high-altitude aircraft CO2 does as much damage as
2.7 tons of ground-level vehicle C02.

When you do fly, it's easier on the environment if you take non-stop flights.
10 out of 10 points.

True. Just as your car's gas mileage plummets if you jackrabbit off a
stoplight, planes use more fuel -- and create more CO2 -- taking off
than at cruising speed. Really long flights of more than 10,000 miles,
say New York to New Zealand, generate 40 percent less C02 per mile
than those under 1,500 miles. Assuming your legs still work once you
arrive.

Given the role gas mileage plays into the drive-or-fly decision, would
it be better to take the smaller car instead of the van or SUV?
10 out of 10 points.

the smaller car's probably better for the planet. Just as backpackers
know that every item they carry has a cost, make some hard choices
before hitting the road. Bigger vehicles easily swallow all the kids'
toys, all the clothes, and all the gear you might use. But choosing to
leave behind some of that stuff could make for a more relaxing trip --
and a little practice at living lighter when you get back home.

How do passenger trains stack up against commercial airlines?
than planes.
5 out of 10 points.

All three of the above choices apply. According to the U.S. Department
of Energy, Amtrak's passenger trains are 18 percent more efficient per
passenger mile than commercial flights. Secondly, among the dozens of
products refineries extract from a single 42-gallon barrel of crude
oil, 7.9 gallons of diesel are produced but only 4.1 gallons of jet
fuel. It's true that refineries can adjust the overall product mix,
but it takes less crude to generate a gallon of diesel than jet fuel.
(Gasoline, by the way, accounts for almost half of a barrel's yield.)
Finally, until trains can fly they won't contribute to heat-trapping
cloud formations as much as planes do.

While Amtrak's limited route choices may make the train an impractical
choice in many parts of the U.S., vacationers along the East Coast
still have plenty of options. Trains' green edge over planes also
might mean rethinking hopping on one of Europe's cheap city-to-city
flights when a rail connection exists.

When one must fly, does it help to buy so-called carbon offsets?
10 out of 10 points.

Yes -- if you do your homework and choose a reputable vendor. The idea
of carbon offsets is simple: the money you pay is used to fund
projects worldwide that reduce or slow the production of
global-warming gases. Buying an offset for that Los Angeles to Seattle
roundtrip flight, for example, would cost only \$5.14. Just remember
that the first step in fighting global warming is reducing your
overall energy demands everywhere you can. Carbon offsets definitely
help, but none of us can buy our way out of the problem. (If you're
interested in how the Sierra Club's Outings program handles offsets,

How do commercial airplanes, trains, and cars rank from most to least
efficient per passenger mile?
Your Answer: Trains are the most efficient, followed by cars, and then planes.
10 out of 10 points.

B is the right answer: Trains are the most efficient, followed by
cars, and then planes. You get partial credit if you guessed A since
you realized that planes are the least efficient. According to the
DOE, passenger trains use 2,978 British thermal units per passenger
mile, while cars use 3,496 BTUs/passenger mile, and airplanes use
3,959 BTUs/passenger mile. However, if you include personal trucks and
SUVs along with cars, the nation's vehicle fleet uses 4,329 BTUs per
passenger mile, which is worse than airplanes. You could vacation Easy
Rider style on a motorcycle, which uses 2,272 BTUs for every passenger
mile. Or consider a bicycle trip: just as breezy as the Harley but
gasoline free.

Are ship cruises a more environmentally friendly way to travel?
10 out of 10 points.

CO2 emissions are almost the least of a cruise ship's environmental
problems. According to Climate Care, a UK firm that sells carbon
offsets, large cruise ships can emit up to three times as much CO2 as
airliners. A larger issue, however, has been proper disposal of the
sewage and garbage generated by mega-cruisers, which carry as many as
3,000 passengers at a time. After a spate of lawsuits and unfavorable
publicity six to eight years ago, cruise lines have reduced such
discharges, at least within three miles of shore. Still, environmental
critics and congressional allies continue to press for tighter
controls.

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