Saturday, March 19, 2011

The Environmental Impact of Finding a Job

This time of year marks the tail end of the season known to economics PhD students as “the job market.”  The season begins in early January at the AEA meetings (which this year were in Denver), where a large fraction of schools and non-academic employers interview candidates.

During most of grad school I monastically confined myself within a few square miles of Boston and Cambridge, but my careful conservation efforts were drastically upheaved last year when I went on the job market.  After going to the AEA meetings in Atlanta, I traveled to ten employers for site visits (this is a typical number among my peers, but I realize ten is obscenely high for most fields).

So how much environmental damage did I do?  *Note: the following calculations do NOT take into account the hot air emitted from my mouth during my seminar presentations.

I used three modes of transportation (car, train, and plane) during the 17 trips I took on the job market, not counting layovers.  I used three different online calculators (Atmosfair, Terrapass, and Carbonfund) to compute the carbon emissions from each trip.  All of the calculators compute emissions for air travel, but they vary on coverage of car and train travel (Carbonfund is Amtrak’s official calculator).  I also tallied up all the nights I stayed in hotels using Carbonfund’s estimates of 29.55 Kg CO2 / night for regular hotels and 33.38 Kg CO2 / night for upscale hotels (the hotels I stayed at were likely fancier than average).  I’ve never thought much about the energy use associated with hotel stays, so this was a good chance to get a benchmark on that.
In the end, I traveled 18,028 miles and consumed 5.37 metric tons of CO2.  That’s about 28% of the average American’s total annual energy use, although it’s more than the per capita energy use of 65% of countries.  The total costs of travel and lodging were $5,625.  Are these numbers high or low?  While I was on the job market, it felt like I was wasting huge amounts of resources with my jetsetting lifestyle.  And by objectively reasonable measures, I still think that’s true.  But the final numbers leave me on a note of optimism; they’re modest enough that my conservation efforts during the previous five years of grad school might have a chance of making up for them.

I think of my relationship to the environment like a savings account.  If I withdraw resources (and do harm through pollution and climate change), then I should make sure to do something extra to replenish my account.  By forgoing discretionary energy consumption when I can, I can bank conservation for times when resource use is necessary for things that are important to me, without becoming an energy hog.

One of the most regrettable things about the job market is that it finally gave me a legitimate reason to go to a lot of cool places, yet I had very little time to explore and learn from my travels.  The timing of the market necessitates continent-crossing journeys from hotel room to seminar room to hotel room.  But something is lost when we travel for only one narrow purpose that’s removed from the sense of place.  The universality of academic exchange neutralizes place, yet at the same time, it’s a wonderful thing to behold in itself.
Details of the calculations:

Travel summary

# of trips (one-way)


Cost / mile

Kg CO2
Kg CO2/mile

# of nights


Kg CO2




Kg CO2


Kg CO2


Kg CO2



w/o RF
w/o RF
w RF
Kg CO2

For the plane calculations, I include numbers both with and without radiative forcing.

Sidebar: Marginal vs. Average?

All the calculations are done assuming that my CO2 emissions are the average emissions per traveler, e.g. the total emissions of an airplane flying from Boston to Los Angeles divided by the number of travelers on the plane. 

Another way to calculate my emissions is to assume that the plane would run anyway whether or not I am on it, so the only emissions I am personally responsible for come from the extra fuel it takes to carry me and my luggage.  This marginal calculation would end up being much smaller than the average calculation.  All of the carbon calculators I use and that know of use the average calculation, and I think that’s the correct way to think about it. 

Slate gives a nice, simple explanation why.  Each consumer contributes to the demand for that aircraft to be in the air, so it lets us off too easy to say that our travel contributes absolutely zero to additional flights being run.  My guess is that airlines are quite sensitive to how many people book a particular flight.  If no one booked it, it would be canceled.  Thus, even if taking one trip contributes only a small amount to demand for flights, a person who travels a lot could eventually account for entire flights.  And I know more than one economist in the “million miles” club.  In this context, small but nonzero is a world away from precisely, absolutely zero.

Another way to think about it is that we don’t know who the marginal person is who causes an airline to add one additional flight.  If we did know, the correct way to do the marginal calculation would be to place the burden of the entire fixed energy costs of flying the plane on the one marginal person, and let every subsequent passenger count only marginal fuel costs toward their energy usage.  This doesn’t seem sensible, or fair to that poor marginal fellow.  Thus, I think the reasonable way to account for energy use on airlines is the average method.

For car trips, the average method also makes sense unless you’re hitching a ride with someone who would be driving the same route anyway.  Public transportation is slightly trickier.  While airlines are probably quite sensitive to the number of people who book flights, subways and Amtrak trains are probably almost completely insensitive.  Thus, as Slate argues, the marginal calculation makes sense in this context.  One of the carbon calculators I used, Atmosfair, thus attributes no emissions to train travel.  Just to be fair however, all of my calculations for trains use the average method.

Miscellaneous details
  • Hotel stays do not count 8 nights spent staying with friends.
  • I also do not include costs and carbon emissions from within-city travel (e.g. from the airport to the hotel).  Here are the cities where I used public transportation:
    • Boston (T)
    • New York (Metro)
    • Washington, DC (Metrorail)
    • Vancouver (Trans link)

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