Objectives:
After completing this activity, students will be able to:
- calculate how much CO2 a vehicle emits;
- differentiate between vehicles that are high- and low-emitters of CO2; and
- identify places in their daily transportation where they can reduce the emission of CO2.
Introduction
Human activities have been a major cause of warming temperatures around the world since the mid-20th century. The average global temperature has risen approximately 1°C (2°F) since 1880 (IPCC, 2018). Anthropogenic (human caused) CO2 emissions are a major culprit in the increase in global temperatures. The presence of CO2 and other greenhouse gases (GHG) found in the earth’s atmosphere function to trap heat from the sun and warm the planet. As we burn fossil fuels for energy, additional CO2 is released in the atmosphere, additional heat is trapped, further warming the planet. The concentration of CO2 in the atmosphere has increased from approximately 277 parts per million (ppm) at the start of the Industrial Revolution to 412 ppm in 2020 (Friedlingstein et al., 2021).
Impacts on natural systems from a warming planet have already been observed and future climate risks depend on our ability to limit emissions and further warming. Sea level rise has accelerated from 1.7 mm/year during most of the 20th century to 3.2 mm/year since 1993. Sea ice extent in the arctic is shrinking and the average thickness of glaciers has decreased more than 60 feet since 1980 (NOAA, n.d.). Extreme weather such as droughts, heat waves, and heavy precipitation have become more frequent since the 1950s (IPCC, 2021).
The transportation sector, which is made of up cars, trucks, railroads, and commercial aircraft, is one of the largest contributors to anthropogenic greenhouse gas emissions in the US. In 2020, the largest portion of total U.S. GHG emissions came from the transportation sector. Within the transportation sector, light-duty vehicles represented 57% of GHG emissions (EPA, 2022).
Automobiles are at the very heart of American social and economic relations. Environmentalists cannot simply demand the elimination of the modern automobile without providing a replacement. The questions, then, become: What do people want from the automobile, and how can these services be provided without the environmental consequences of current cars?
Activity 1: Analysis of Vehicles
In this activity, you will identify which vehicles you think emit the most or least amount of CO2 and research how much CO2 these cars release. There is a direct link between gas mileage and CO2 emissions. For each gallon of gas burned, 20 lbs of CO2 is emitted!
- Start by hypothesizing which characteristics you will look for in “high emitters” and “low emitters.” Then create one “If…then…” hypothesis about the relationship between these characteristics and emissions. State these characteristics and your hypothesis under Analysis Question number 1 below.
- Go outside and test your hypothesis by choosing 10 vehicles you think are high emitters of CO2. Record the makes and models in Table 1.
- Now choose 10 vehicles you think are the lowest CO2 emitters based on your hypothesis. Write down the makes, models, and year in Table 2.
- Use the Fuel Economy website to find information on the vehicles you found (see appendix at the end of the document for instructions on how to find gas mileage information).
- Record the following information in Table 1 and Table 2:
- Combined gas mileage (city and highway averaged together) for each vehicle in miles per gallon (mpg).
- Greenhouse Gas (GHG) Emissions from the tailpipe in grams per mile. After clicking on the link to the vehicle, click on the “Energy and Environment” tab and scroll down to the Greenhouse Gas Emissions information.
- Calculate the average metric tons of CO2 emitted per year for each vehicle.
- Assumption 1: The average American drives 15,000 miles each year
- Assumption 2: There are 1,000,000 g in a metric ton
- Calculate the averages for both the high- and low-emitters.
Table 1: High Emitter Vehicles
| Make, Model, and Year | Combined MPG | GHG Emissions (g/mile) | GHG Emissions (metric tons/yr) |
| 1. | |||
| 2. | |||
| 3. | |||
| 4. | |||
| 5. | |||
| 6. | |||
| 7. | |||
| 8. | |||
| 9. | |||
| 10. | |||
| Average: |
Table 2: Low Emitter Vehicles
| Make, Model, and Year | Combined MPG | GHG Emissions (g/mile) | GHG Emissions (metric tons/yr) |
| 1. | |||
| 2. | |||
| 3. | |||
| 4. | |||
| 5. | |||
| 6. | |||
| 7. | |||
| 8. | |||
| 9. | |||
| 10. | |||
| Average: |
Activity 2: Personal Car Emissions
In Activity 1, we investigated the connection between global warming and car fuel efficiency. For every one gallon of gasoline burned, 20 pounds of CO2 is produced. Now let’s see how much CO2 we individually produce driving our personal vehicles. If you do not drive, base this on a friend or relative’s car. You could also calculate how much you would use if you drove instead of using public transportation.
- Determine the number of miles you typically travel in car or bus each week. Record this information in Table 3.
- You can use Google Maps or other mapping software to estimate distances between your work, home, school, and other locations you visit on a weekly basis.
- Determine the combined gas mileage of the vehicle you typically travel in by using the Fuel Economy website.
- If you typically travel in a bus, go ahead and chose any car!
- Based on your vehicle’s gas mileage and the average number of miles you drive per week, calculate the number of gallons used per week. Record in Table 3. SHOW YOUR WORK!
- Calculate the amount of CO2 produced in one week if burning 1 gallon of gasoline produces 20 lbs of CO2 (if your vehicle runs on diesel, it produces 22 lbs of CO2 per gallon) and record in Table 3. SHOW YOUR WORK!
Table 3: Individual Emissions
| Make, model, year of your car | Combined MPG | Miles Driven Each Week | Number of Gallons of Gas Used Each Week | CO2 per week (lbs) |
Analysis Questions
Please answer the following questions in complete sentences. Remember to cite your sources in APA 7 format if necessary!
Activity 1
- Please explain what characteristics you looked for in your search of the parking lot or your neighborhood.
- Put your hypothesis statement here.
- Compare the average CO2 emissions for the high- and low-emitters. Did there seem to be a pattern among the vehicles that you chose? What was it?
- Using graphing software such as Excel, make a graph of your data (all 20 vehicles) comparing the following (make sure to put the information on the correct axes):
- The combined gas mileage (mpg)
- The CO2 emissions per vehicle in metric tons per year.
- Add a linear trendline to your data and make sure to include an appropriate title and axis titles. Copy and paste your graph below.
- According to your graph, is there a relationship between gas mileage and CO2 emissions? Please describe.
- Overall, were your hypotheses supported or refuted? Why?
- Describe circumstances in which larger or smaller vehicles are advantageous and ones in which they would not be.
- The average fuel economy of the U.S. car fleet has been improving recently but has not kept up with other countries. Refer to Figure 1 below to answer the following questions:
- Why do you think there are differences between the U.S. and Europe?
- What market factors (supply? demand? prices?) promote fuel efficiency?
Figure 1: Average new “light duty” vehicle fuel economy by country, 2005-2019 (IEA, 2021). “Light duty” refers to cars and light trucks. In this figure, fuel economy refers to the amount of gas/diesel (Lge) needed to go a set distance (100 km). A lower number is better.
- What would you suggest that the U.S. government do to promote fuel efficiency, other than banning cars? Try to be as realistic as possible.
- What should consumers do?
- What should car manufacturers do?
Activity 2
- Assuming you use the same amount of gas each week, approximately how much CO2 do you produce each year? SHOW YOUR WORK!
- Could you take alternative transportation (bike, walk, public transportation) for ANY of the times you typically drive during the week? Why or why not?
- Would you consider emissions of air pollutants in the purchase of your next car? What about gas mileage (and the money it could save you)? Why or why not?
References:
EPA (2022). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2020. U.S. Environmental Protection Agency, EPA 430-R-22-003. https://www.epa.gov/ghgemissions/draft-inventory-us-greenhouse-gas-emissions-and-sinks-1990-2020.
NOAA (n.d.). Global Climate Dashboard. Retrieved from https://www.climate.gov/climatedashboard
Friedlingstein et. al. (2021). Global Carbon Budget. Earth System Science Data, 14 (4),1917-2005. https://doi.org/10.5194/essd-14-1917-2022
International Energy Agency (2021). Vehicle fuel economy in major markets 2005-2019. https://iea.blob.core.windows.net/assets/79a0ee25-9122-4048-84fe-c6b8823f77f8/GlobalFuelEconomyInitiative2021.pdf
IPCC (2021). Climate Change 2021: The Physical Science Basis, the Working Group I contribution to the Sixth Assessment Report, Cambridge University Press, Cambridge, UK.
IPCC (2018). Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. Cambridge University Press, Cambridge, UK and New York, NY, USA.
NOAA National Centers for Environmental Information (2021), State of the Climate: Global Climate Report for 2021. https://www.ncdc.noaa.gov/sotc/global/202113.
List of full URLs used in this document
- Fuel Economy Website: https://www.fueleconomy.gov/feg/findacar.shtml
Appendix
Example for 2019 Subaru Outback:
Go to the Fuel Economy website
Use the dropdown menus to enter vehicle information.
Choose Go.
Find the combined MPG information under the MPG tab:
Choose the Energy & Environment tab to find greenhouse gas emission information:
