Background: Carbon molecules move between living and nonliving components of the Earth system in the carbon cycle. Biological processes, such as photosynthesis, cellular respiration, digestion, and excretion tranfer the molecules into and out of living beings. Physical and geological processes transfer the molecules between non-living reservoirs where carbon compounds are in high supply. Transfers between living and non-living reservoirs in the cycle are called fluxes. The relative amounts of carbon stored in the reservoirs are called carbon loads. For example, there are carbon loads in the air, plants, animals, soils, fossil fuels, and oceans. Changes in human activities over time influence fluxes in the carbon cycle.
What human activities seen in the picture below can increase carbon load?
What activities seen in the picture below can decrease carbon load?
Student Exploration: Greenhouse Effect
Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.
Vocabulary: global warming, greenhouse effect, greenhouse gas, heat flow
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
What do you notice when you get into a car that has been sitting in the Sun for a while?
Why is the inside of the car so hot?
How would things be different if the car’s windows were left open?
Gizmo Warm-up
Like the windows of a car, greenhouse gases play a major role in regulating Earth’s climate. Without the gases that trap heat in Earth’s atmosphere, Earth would be a frigid desert like Mars (average temperature -55°C, or -67°F). Too much greenhouse gas and Earth could be a fiery inferno like Venus (average temperature 450°C, or 850°F).
On the Greenhouse Effect Gizmo, set the Greenhouse gases to 0% and the Simulation speed to fast.
Click Play () and view the BAR CHART tab. The temperature will go up and down every day, but try to look at the overall trend. What happens to the temperature over time?
Now set the Greenhouse gases to 100% and let the simulation run for a while. How does a maximum amount of greenhouse gas affect the temperature?
Activity:
Heat in, heat out
Get the Gizmo ready:
Click Reset ().
Set Simulation speed to slow.
Be sure the Greenhouse gases level is 10%.
Question: How do greenhouse gases affect Earth’s climate?
Observe: Select the BAR CHART tab and click Play. After about 24 simulated hours, click Pause (). What do you notice about the heat flow into and out of Earth’s atmosphere?
Analyze: Select the TABLE tab.
At what time of day is heat flow into the atmosphere (Hin) greatest?
At what time of day is heat flow into the atmosphere (Hin) least?
Does heat flow out of the atmosphere (Hout) change during the day?
At what time of day is surface temperature highest? Lowest?
Highest:
Lowest:
Predict: Click Reset. When you change the amounts of greenhouse gases in the atmosphere, which factor(s) do you expect to change? (✏️Circle your answer/answers.)
Experiment: Select the BAR CHART tab, and click Play. While the simulation is playing, move the Greenhouse gases slider back and forth. What do you notice?
Experiment: Click Play, and this time observe the GRAPH tab as you change the Greenhouse gases. What do you notice?
Draw conclusions: The influence of greenhouse gases on temperature is called the greenhouse effect. Based on what you have seen, how do greenhouse gases affect the heat flow into and out of Earth’s atmosphere?
Extend your thinking: Atmospheric concentrations of greenhouse gases such as carbon dioxide have risen dramatically in the past century. Most scientists agree that this has begun to result in global warming, a slow increase in average temperature worldwide.
What are the possible consequences of global warming?
Note: The reason greenhouse gases raise the temperature of Earth’s atmosphere is similar to, but not identical to, the way that the glass in a greenhouse raises the temperature inside.
In a greenhouse, sunlight passes through the transparent glass and is absorbed by the plants and soil below. Heat is then radiated from plants and soil, which heats the air inside the greenhouse. The hot air is trapped by the glass. If the glass were not there, the hot air would mix with the colder air outside, and the result would be similar temperatures inside and outside the greenhouse.
In Earth’s atmosphere, greenhouse gases are transparent to visible light but absorb heat that is emitted from Earth’s surface. Some of this heat is then reflected back to Earth. If the greenhouse gases were not present, all of the heat would radiate into space instead.
In the picture, human activities that can increase carbon load can include burning fossil fuels, deforestation, and industrial processes that release carbon dioxide into the atmosphere.
Activities that can decrease carbon load can include reforestation and the use of renewable energy sources, such as solar or wind power, that do not release carbon dioxide into the atmosphere.