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Carbon
footprint
calculator
We all know that certain choices use energy
and cause pollution, but how do those things stack
up against each other? For example, how does
the pollution savings from ditching your car
compare to the savings from going vegetarian? And
how does the energy you save in your home compare
to the energy you save by not taking a certain
airline flight?
I wanted to know, and I found the
other online calculators lacking in important
ways, so I spent a solid week
researching the data and creating the calculator
below. Following the calculator are all my detailed
calculations and sources. So give the calculator a
whirl and see how you stack up!
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Electricity matters because most
electricity in the U.S. is generated by
burning coal. Coal-burning causes
tremendous pollution, and is a powerful
contributor to global warming. As a
result, the coal industry has been touting
what they call "Clean Coal", which is
little more than a marketing ploy. There
is no
such thing as clean coal.
You'll also note from the calculator
that your house has a bigger effect on the
climate than your car! That's why I
put home energy first in the
calculator.
Electricity used in different parts of
the country creates different amounts of
pollution, because some places get a
larger share of their electricity from
coal. This calculator keeps things simple
by using U.S. averages for pollution
caused by electricity.
You'll get the most accurate answer by
entering in the number of kWh you use
(which you can find on your electric bill)
rather than cost per month, since the cost
of electricity in the U.S. varies widely
from one area to another (7¢ to
30¢ per kWh as I write this). If you
enter $/mo. then I first subtract $10 to
estimate the fixed cost that the utility
charges you each month for the privilege
of being their customer, and then figure
the rest was for energy at 11¢/kWh,
the national average.
The average U.S. household uses 920
kWh per year of electricity. I assume
that single-person households use half
that. (There are 2.67 people per
household, but I don't divide by 2.67
because I want to account for the fact
that multi-person households are more
efficient. If I divide average household
use by 2.67 then I'll understate the
individual's use. For example, both a
3-person household and a 1-person
household will each have one refrigerator,
so the fridge in the 1-person house uses
more energy per person.)
On a separate page I have complete
sources,
references, and calculations.
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You can enter your gas usage either
as the amount you pay per month, or the
number of therms you use per month (which
you can get from your bill). If you
enter the cost, then I first subtract $10
as an estimate of the fixed cost your gas
company charges you no matter what, then
figure that the rest was charged at
$1.50/therm.
If you know your fixed monthly charge
is higher or lower than $10, you can
account for that to get a better estimate
from the calculator. For example, let's
say you enter in $14. The calculator
subtracts $10 and figures you bought $4
worth of gas. But say the gas company
charges you only $8/mo. to be a customer.
In that case you really used $6 worth of
gas ($14 - 8). So to get the calculator to
figure you bought $6 worth of gas, enter
in $16, and it will subtract $10, leaving
$6.
Only 64 million of the nation's 107
million households use natural gas. Of
those using gas, they use 688 therms per
year on average, or 57.3 therms per month.
To come up with the default figure for
single-person households, I assume they
use half of what a typical household uses.
(There are 2.67 people per household, but
I don't divide by 2.67 because I want to
account for the fact that multi-person
households are more efficient. If I divide
average household use by 2.67 then I'll
understate the individual's use. For
example, both a 3-person household and a
1-person household will each have one hot
water heater, but the water heater likely
won't use 3x as much energy in the
3-person household, so the heater in the
1-person household uses a little more
energy per person.)
To figure the tons of carbon from the
average household and the average person
for the right-hand column, I divide the
total amount of carbon generated by
natural gas by the total number of
households (107 million) and the total
number of people in the U.S. (300
million), respectively.
On a separate page I have complete
sources,
references, and calculations.
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You can enter your heating oil usage
either as the amount you pay per month, or
the number of gallons you use per month
(which you can get from your bill). If
you enter the cost, then I first subtract
$10 as an estimate of the fixed cost your
oil company charges you no matter what,
then figure that the rest was charged at
$4.00/gallon.
If you know your fixed monthly charge
is higher or lower than $10, you can
account for that to get a better estimate
from the calculator. For example, let's
say you enter in $14. The calculator
subtracts $10 and figures you bought $4
worth of oil. But say the oil company
charges you only $8/mo. to be a customer.
In that case you really used $6 worth of
oil ($14 - 8). So to get the calculator to
figure you bought $6 worth of oil, enter
in $16, and it will subtract $10, leaving
$6.
Only 8.1 million of the nation's 107
million households use fuel oil. Of those
using oil, they use 889 gallons per year
on average, or 74 gallons per month. To
come up with the default figure for
single-person households, I assume they
use half of what a typical household uses.
(There are 2.67 people per household, but
I don't divide by 2.67 because I want to
account for the fact that multi-person
households are more efficient. If I divide
average household use by 2.67 then I'll
understate the individual's use. For
example, both a 3-person household and a
1-person household have a furnace, but the
furnace likely won't use 3x as much energy
in the 3-person household, so the heater
in the 1-person household uses a little
more energy per person.)
To figure the tons of carbon from the
average household and the average person
for the right-hand column, I divide the
total amount of carbon generated by fuel
oil by the total number of households (107
million) and the total number of people in
the U.S. (300 million), respectively.
On a separate page I have complete
sources,
references, and calculations.
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As you can see from the calculator,
the average home pollutes more than the
average car.
The EPA reports the average fuel
economy of the U.S. fleet as 22.2 mpg, but
actual fuel economy is only 20.36, as
listed in the sources
section. Therefore, for whatever MPG you
enter, the calculator assumes your car
gets only 91.7% of that.
There are 107 million households in the
U.S. but only 99 million have a car. Of
those with a car, they use 1,141 gallons
of gas per year on average, or 95 gallons
per month. To come up with the default
figure per person, I divided the total
miles traveled (2.3 trillion) by average
MPG (20.36) and divided again by the
number of drivers in the U.S. (196
million), for 591 gallons per person. I
also use this in the right-hand column to
come up with the amount of carbon
generated by an individual's driving.
On a separate page I have complete
sources,
references, and calculations.
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Most people are surprised to learn
that the typical diet (what people
normally eat) uses 356% more energy to
produce than a typical vegan diet --
and therefore 356% more energy
pollution.
The reason is that livestock are food
factories in reverse: We put about 14
times more food into a steer than we get
out of it. So we're running 14x as many
tractors, using 14x as much labor, flying
14x as many crop-spraying planes, etc.
(The reasons a typical diet uses only 3.6x
as much as a meatless diet instead of 14x
are that other meats aren't quite as
inefficient as beef, and that meat-eaters
also eat plant foods.) As
a result, it takes 145 times more energy
to produce beef than potatoes.
Grass-fed beef is not the answer for a
whole host of reasons, the most important
being that there is not nearly enough
grazing land in the U.S. to raise as much
beef as Americans currently eat.
Food choices are so important that
the typical American could save more
carbon by going vegetarian than by giving
up flying. Vegans do even better,
saving two-and-a-half times as much
carbon. (source)
That's why I list Food higher in
the calculator than flying. It's also one
of the easier lifestyle factors to change.
It's easy to choose a bean burrito instead
of a hamburger. It's not as easy to get
from New York to California without
flying.
One buzzword these days is buying
locally-produced food, so that it takes
less energy to transport. While it can't
hurt to buy local, it's a small drop in
the bucket compared to the effect as going
vegetarian or vegan. Transportation of
food to the store accounts for only 4% of
the greenhouse emissionsn involved in
producing the food. A scientist who
analyzed food energy in a research paper
concludes, "Buying local is not as
important as what you eat." In
other words, it's much, much better to buy
a pound of carrots shipped from far away
than a pound of locally-produced beef.
(New
Scientist
reviews the research paper,
Actual
research paper,
source for the
quote)
For the calculator, I assume that kids
eat 60% as many calories as adults (and
therefore create 60% as much carbon).
On a separate page I have complete
sources,
references, and calculations.
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It's no surprise that planes use
huge amounts of energy -- and thus
produce huge amounts of climate-changing
gases. The airlines are on the defensive
about this and in their in-flight
magazines you will see big full-page
glossy ads touting their energy efficiency
initiatives. What they're not telling you
is that such changes make only a 2%
difference at best.
Most carbon calculators fail to
include radiative forcing and thus
underestimate the impact by a factor of
2.7. This calculator is one of the few
to include radiative forcing. Radiative
forcing is explained in more detail in pp.
26-27 a Dec. 2006 PDF
report from Tufts University, which
states:
"The IPCC has estimated total
radiative forcing of air travel to be
1-5 times larger in the stratosphere
than in the troposphere and calculated
the average for full radiative forcing
to be a factor of approximately 2.7
(IPCC, 1999.) Therefore to estimate the
impact of an airplane trip a multiplier
should be used on the CO2 emissions
from jet fuel to account for full
radiative forcing. ...
"Although more research is needed to
fully understand the chemical processes
in the stratosphere, the research used
by the IPCC is robust. We therefore
recommend using a calculator that
includes a multiplier for the increased
radiative forcing in its carbon
calculations."
Alternatives to flying
include:
- Taking a train or bus
- Taking a cargo
ship
- Vacationing closer to home
- Taking fewer trips, but staying for
longer periods of time
- Teleconferencing instead of
face-to-face business meetings
Would people consider not flying to
save the environment? Sure they would. A
BBC
poll found that over half would do
so.
In fact, most Americans already
don't fly. In a given year, only 43%
of Americans take a plane. That number
will surely decrease as airlines respond
to increased fuel costs by cutting flights
left and right (making travel less
convenient) and raising airfares
substantially.
If you can't give up flying, let me
give you an out: the typical American
could save more tons of carbon by going
vegetarian than by giving up flying.
Vegans do even better, saving
two-and-a-half times as much carbon
as flying.
(source)
Many people come to this page looking
for an answer to the question, "Which
is worse: driving or flying?" The
answer is flying. Planes effectively get
only 15.9 passenger
miles per gallon when considering
their special contributions to climate
change. That's less than just about any
car.
The calculator asks for hours of
flight rather than miles because most
people have a better idea of how many
hours they've flown than how many
miles. The calculator averages the
number of miles you took per trip, since
shorter flights use more energy per mile
than longer ones.
The default shown for flying by
household is equivalent to the total
number of passenger-miles flown (848
billion miles) divided by 107 million
households, multiplied by the percentage
of trips that are personal (non-business),
which comes out to 5548 miles, which I'm
figuring as a 2 round-trips of 1,387 miles
each way, which is closest to 13 hours
of flying time total.
On a separate page I have complete
sources,
references, and calculations.
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(see complete
sources and
references)
The best way to reduce your carbon footprint
is to use less energy.
(Drive less, fly
less, save energy at
home, and eat
vegetarian.)
The next-best way is to buy carbon
offsets.
Tons of carbon dioxide
emissions per capita
(I got this from the
Hinkle
Charitable Foundation
which credits the Energy Information
Administration,
"International Energy Outlook 2003", but I'm unable
to find that report, or a newer version, on EIA's
website.
Wikipedia has a Carbon
dioxide emissions per capita by
country
article.)
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Passenger
MPG
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Transportation
Mode
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125.0
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Bus
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81.6
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Typical U.S. car, 4 people
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61.2
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Typical U.S. car, 3 people
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43.0
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Airplane, w/o considering extra climate
change effect
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40.8
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Typical U.S. car, 2 people
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20.4
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Typical U.S. car, 1 person
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15.9
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Airplane after considering extra
climate change effect
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Flying is worse than
driving
Planes get a respectable 43 passenger miles
per gallon (pMPG), but they cause 2.7 times as much
climate change per gallon of fuel burned, by virtue
of their being up in the sky. So when we
consider climate change, the plane's efficiency is
more like 15.9 pMPG. That's worse than most cars.
And if there are two people traveling in the car
instead of flying, then the pMPG of the car is
doubled, while the plane is stuck at 15.9 pMPG,
because we're already figured the plane's pMPG on a
per-seat basis.
The most efficient way to travel in the U.S.
is by bus. Inter-city buses get a whopping 125
pMPG. By contrtast, Amtrak trains get only 45 pMPG.
Then again, you could consider that the train is
going anyway, so the energy used for an additional
passenger is "free". (You can't do that for the
plane, because your plane ticket could be what
causes the airline to either add a whole new
flight, or not cancel the flight you're booked on.
The same isn't true for Amtrak, since Amtrak trains
are so empty that there's no way your ticket
purchase will influence the schedule.)
(sources)
Carbon Footprint Calculators
Compared
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Carbon
calculators compared
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Michael
Bluejay.com
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Nature.org
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EPA
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Carbon
Counter
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Carbon
Fund
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An
Inconvenient
Truth
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Interaction and Results
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All data & results viewable on same
page
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✓
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✓
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✓
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✓
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Entire calculator viewable without
scrolling
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✓
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✓
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✓
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Shows sample data and results right off
the bat with no clicks required
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Compares your (or your household's)
results to the typical American (or
household), line by line
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(no, but
at bottom
of page)
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Shows total for each section
separately, on the same page
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✓
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✓
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Shows total of all sections
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✓
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✓
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✓
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✓
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Achieves brevity by omitting items that
are <2 tons per person on average
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✓
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✓
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✓
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Fast
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✓
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✓
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Calculates automatically without having
to click a "Calculate" button
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✓
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✓
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✓
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✓
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No annoying/distracting animations
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✓
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✓
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✓
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✓
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Results are not wildly inconsistent
with other calculators
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✓
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✓
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✓
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Home Energy
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Allows you to enter your exact home
energy use
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✓
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✓
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Allows entry of home energy in either
energy units or dollars
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Clearly shows whether data to be
entered is per month or per year
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n/a
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✓
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✓
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✓
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Doesn't require yearly data to be
entered (who gets a yearly electric
bill?!)
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n/a
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✓
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✓
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Food & Driving
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Includes food section
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✓
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Shows driving & flying
separately
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✓
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✓
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✓
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Allows you to enter MPG directly
(rather than making you
specify four different things about your
car so the calculator can guess your
MPG)
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✓
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✓
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✓
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Air Travel
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Includes air travel
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✓
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✓
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✓
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✓
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Doesn't restrict you to entering only
one single flight
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✓
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✓
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✓
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Good estimation of miles flown
(not just "# of short
& long trips" or "number of hours"
[without asking for number of
flights])
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✓
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Accounts for radiative
forcing (i.e., results are not off by
a factor of 2.7)
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?
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✓
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not by
default
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Other
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Sources and calculations provided and
explained well (esp. for "average person"
figure)
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✓
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(mixes
ind. &
household
figures)
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✓
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Shading is for the items I
consider most important.
Carbon
Calculator results compared (per
household)
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Activity (tons of CO2)
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(this page)
(2.67-person
household)
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EPA
(2-person
household)
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Nature.org
(3-person
household)
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CarbonCounter.org
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Home -
Electricity
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9.5
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8.1
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Home -
Gas
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2.4
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5.5
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Home -
Oil
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0.8
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7.3
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Home - Total
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12.7
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-
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29.0
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13.2
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Driving
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11.6
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6.0/vehicle
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34.0
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9.2
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Flying
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3.2
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-
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3.3
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Eating
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10.7
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-
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12.0
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-
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Total
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38.2
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20.8
(27.7 for 2.67
people)
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75
(66.8 for 2.67
people)
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25.7
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Notes
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(a)
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(b)
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Carbon
Calculators results compared (per
individual)
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Activity (tons of CO2)
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(this page)
(individual)
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CarbonFund.org
(individual)
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Nature.org
(individual)
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Home -
Electricity
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4.8
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3.0
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Home -
Gas
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1.2
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1.8
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Home -
Oil
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0.5
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3.2
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-
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Home - Total
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6.5
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8.0
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9.5
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Driving
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6.0
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6.1
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12.0
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Flying
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0
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-
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Eating
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4.1
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-
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4.1
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Total
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16.6
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23.8
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27
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Notes
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(c)
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(d)
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Other figures for individuals (U.S./short
tons):
- 22.5 tons - United
Nations, 2004
- 22 tons - Science
Daily
- 21 tons - Carbon
Trust, according to an article in The
Independent; note that I converted from
U.K./long tons
- 8.0 tons - FirmGreen
- 7.5 tons - An
Inconvenient Truth
(a) They figure the total
independently from the other figures; the total
is less than the individual values because the
figures for natural gas/oil are only for
households that use gas/oil.
(b) Their calculator doesn't include defaults,
so I had to enter my own figures, so this total
isn't really "their" estimate for household use,
since they don't tell us how much they think
households use. (They have a sources &
references section, but it mixes individual and
household data, and we don't know how they'd
separate that.)
(c) They cleverly figure the total by dividing
the U.S.' carbon output by the entire
population. If you add up their line items,
their total is 14.1.
(d) Their total is higher than the sum of the
line items because they include a section on
Household Waste, which I didn't include in the
table.
This page last modified
September 2008.
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