Solving Environmental Problems through Engineering

CONTENTS OF CURRICULUM UNIT 20.04.10

  1. Unit Guide
  1. Introduction and Rationale
  2. The History of Climate Change
  3. Climate Change Basics: The science behind rising temperatures.
  4. The Greenhouse Gases: More than just CO2
  5. Climate Change: What happens as global temperatures rise.
  6. Climate Change: What are we going to do?
  7. Philadelphia: One city’s likely scenario in the coming climate crisis.
  8. Unit Planning for Middle School Students Studying Climate Change
  9. Pedagogy and Teaching Strategies for this Unit.
  10. Lesson Activities
  11. Bibliography
  12. Endnotes
  13. Appendix on Implementing District Standards

Engineers Wanted: Climate Change Experience Necessary!

Rachel Odoroff

Published September 2020

Tools for this Unit:

The Greenhouse Gases: More than just CO2

Greenhouse gases are comprised of many different gas compounds from a myriad of sources. Some of these compounds occur naturally but have been on a dramatic quantity increase since the start of the Industrial age around 1850. (See Figure 3) There is an accounting for the potential warming effect of each gas called the Global Warming Potential that combines the known heat trapping qualities of a gas with the life span of the gas. Carbon dioxide is defined as a “1” as it is the base against which all other gases are compared.16

Figure 3. Percent breakdown of the greenhouse gases globally including some of the attributed sources. epa.gov17

Methane Gas (CH4)

Methane gas is made of carbon bonded with hydrogen mainly released from animal waste. Manure and livestock production are the largest sources in the United States. Enteric Fermentation from ruminants is a large contributor to this. (Enteric fermentation is a scientific way to describe that cows pass gas.) Methane represents a slim 16% of the greenhouse gas blanket globally, but it’s a very warm part. The Environmental Protection Agency states that while methane has a shorter life span in the atmosphere than carbon dioxide, it is 25 times more efficient at trapping heat in the Earth’s atmosphere.18

Nitrous Oxide (N2O)

Nitrous Oxide represents a small portion of the greenhouse gas blanket. In the United States, most of it is contributed through the application of nitrogen-based fertilizers in agriculture, but it is also a by-product of fuel combustion.19

Carbon Dioxide (CO2)

CO2 represents the largest piece of the greenhouse pie, and the one we hear about the most. Carbon dioxide is a natural byproduct of respiration in many organisms, but the recent dramatic increase correlates directly to an increase in fossil fuel combustion and consumption. While not as efficient at trapping heat as methane, carbon dioxide is the largest single contributor to the GHG mixture. Carbon dioxide could also be part of a negative feedback loop: the more we cut down forests to create room for human development and agriculture, the fewer trees and plants we have to help utilize the gas.20 Carbon dioxide is measured in parts per million (ppm). Based on ice core samples, the CO2 level before the Industrial age was under 300 ppm. Figure 4 shows the relative stability of carbon dioxide concentrations in the atmosphere until quite recently, when levels began topping 400 ppm. (See Figure 4)

Figure 4. National Oceanic and Atmospheric Administration graph charting historic carbon dioxide levels (ppm). Noaa.gov21

Additional Greenhouse Gases

F-Gases include a class of compounds with fluorine that are used in industrial processes and refrigeration. While not included in this graph, water vapor (H2O) and ozone (O3) are also classified as greenhouse gases though they are not considered to be major contributors to the problem of climate change as their concentrations are not significantly increasing due to anthropogenic activity.22

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