Homework 3
GEOG 313/513, Global Climate Change, Fall 2014
Due Tuesday, October 21, 2014 (beginning of class)
Your name: ___________________________________________________
Please answer the following questions in a different font (like this) to help me find your
answers. You may work in a group, but your answers and words must be your own (do not
copy!).
Turn in a print out of your homework in class. Your homework is due at the beginning of class.
If you turn it after that, you will incur late penalties (see syllabus).
1. Explain why “loading the dice” (or replacing the face with one dot with six dots on a die) is
an analogy for the link between climate change and extreme events like heat waves or
superstorms. (5 points)
2. Carbon cycle and paleoclimatology.
a. Why are “fossil fuels” called that? (2 points)
b. Your acquaintance from above points out that changes in CO2 “lagged” (followed) changes in
temperature during the Pleistocene (2 million to 12,000 years before present), and therefore even
if humans are emitted CO2, it isn’t having an effect on climate. How would you respond? (5
points)
3. Estimate your carbon footprint.
A carbon footprint is a “measure of the impact human activities have on the
environment in terms of the amount of greenhouse gases produced, measured in units
of carbon dioxide”. Your personal carbon footprint is defined by the total actions your
personally are accountable for over the course of one year, and their equivalent in
terms of kilograms of carbon dioxide. For this exercise, you will be estimating your
direct emissions (typically from home energy usage and transportation). This value
represents about one quarter of your total carbon footprint, as other activities include
indirect consumption and emission of carbon dioxide. As a second part of this
exercise you will be asked to think of your indirect carbon dioxide emissions, and means by
which you can reduce both your indirect and direct carbon footprint. Finally, food choices may
be important from a monetary and health perspective. However, food choices also have
ramifications in terms of carbon emissions. You will examine how your favorite food indirectly
contributes to anthropogenic emissions of greenhouses gases.
Part I. Calculate Your Personal CO2 Emissions (20 points)
To estimate your personal emissions you will need to gather a few pieces of data. Please show
your work in computing your estimated CO2 emissions!
Sources for emission factors: http://www.epa.gov/cleanenergy/energy-resources/refs.html,
http://www.carbonfund.org/how-we-calculate.
A. CO2 emissions at home
I. Electricity. You will need to estimate the number of kilowatt hours (kWh) used annually
(check a recent electricity bill) and divide by the number of people in your household. If
you happen to live on campus, then assume 1500kWh per year.
Next, we must consider where our electricity comes from. In Idaho we rely almost solely on
hydroelectric power generation, which lowers our emission of CO2 per kWh of electricity.
Find Idaho’s emission factor for electricity usage here: http://www.eia.gov/oiaf/1605/eefactors.html for (metric tons CO2/MWh, which equals kg CO2/kWh).
Monthly Usage
(kWh)
II.
Multiply by
12
Divide by People
Per Household
Multiply by emission factor for
Idaho from above
(i)
Natural Gas
Estimate your monthly gas bill using the same method as above. If you are in a dorm assume
0 emissions. The carbon dioxide emission factor for natural gas is 5.3 kg CO2 per therm.
Monthly
Usage
Multiply
by 12
Divide by People Per
Household
Multiply by 5.3 kg
CO2/therm
(ii)
Add (I+II) together to get your annual direct emissions from household use. _____________ (I)
B. Transportation
i) Personal Automobile
How many miles do you drive in a car each year :
_________________ (A)
Average number of people in car (including you) :
_________________ (B)
Average number of miles per gallon (MPG)
:
_________________ (C)
(look up your fuel usage efficiency on web at http://www.fueleconomy.gov/)
To convert between fuel consumption in gallons and carbon dioxide emissions, you need to
consider that roughly 8.9 kg CO2 are emitted for each gallon of fuel. That is 20 lbs of carbon
dioxide per gallon (yes, a gallon of gas weighs about 7 lbs…see why it results in 20 lbs of carbon
dioxide at http://www.fueleconomy.gov/feg/co2.shtml).
Annual Miles
Driven (A)
Divide by Average
People in Car (B)
Divide by MPG (C)
Multiply by 8.9 kg
CO2/gallon
(II)
ii) Public transit (excluding air travel)
Number of miles traveled per year :
Multiply by 0.107 kg CO2 /mile
Annual CO2 usage from public transit :
_____________________
x 0.107 kg CO2/mile
____________________ (III)
iii) Air Travel
Number of miles traveled per year
Multiply by 0.22 kg CO2/mile
Annual CO2 usage from air transit
:
___________________
x 0.22 kg CO2/mile
____________________ (IV)
Cumulative CO2 from Transportation (II+III+IV) :
____________________ (V)
Direct CO2 Emissions (I+V) :
____________________ (VI)
C. Indirect emissions
Typical CO2 emissions calculated in Part I (excluding extraordinary air travel) represent only
about 25% of your total CO2 emissions (for the US in general). Indirect emissions are notorious
challenging to quantify given the “life-cycle” of material goods. Estimate your indirect emissions
by clicking on the “Secondary” tab from the following site:
http://www.carbonfootprint.com/calculator.aspx. Remember to convert to kg CO2e.
Estimated indirect CO2 emissions :
____________________ (VII)
Estimated total annual CO2 emissions (VI+VII) :
____________________ (VIII)
Part II. Answer the following questions
a. What is your carbon footprint per year equivalent to in terms of (see
http://www.epa.gov/cleanenergy/energy-resources/calculator.html): (6 points)
i. passenger vehicles
ii. miles/year by average passenger vehicle
iii. gallons of gasoline
iv. homes’ energy use for one year
v. tree seedlings grown for 10 years
b. Use the following web page to answer the below questions:
http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions (use 2010
emissions; note that the units are metric tons (“t”; 1000 kg), so convert to kg). (6 points)
i. How does your C footprint compare with the average person (per capita) in the US?
ii. In the “World” (see entry in list)?
iii. What country is your carbon footprint closest to?
c. What realistic changes in your lifestyle would result in the largest reductions in your carbon
footprint? Subtract the difference from your total (show your work). What country would you
be closest to then? (5 points)
d. Electrical power is an important aspect of CO2 emissions. Redo the calculations using the
below values and add the difference to your totals (show your work). (4 points)
i. the US average of 0.69 kg CO2/kWh.
ii. the value for Wyoming (0.973 kg CO2/kWh).
Graduate student question
a. Using the global carbon budget figure from the IPCC AR5 Working Group I (shown in class),
calculate the percentage of human-caused emissions relative to the total amount of inputs to the
atmosphere. (4 points)
b. Given this, how can human emissions be causing any climate change? (5 points)