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Test: ACT Science
Since the early 1900s, there has been a steady increase in the earth’s atmospheric temperature, resulting in a phenomenon called “Global Warming.” While the steady temperature change has been well documented, the cause of global warming remains controversial.
Scientist 1
Scientist 1 believes that “external forcings” are the cause of increased temperature over the past century. “External forcings” can direct the change in temperature over thousands of years. One example of an external force is variation in the earth’s orbit around the sun. The earth orbital cycle lasts 26,000 years and causes general trends in warming and cooling.
Scientist 2
Scientist 2 believes that global warming is a man-made phenomenon due to an increase in greenhouse gases such as carbon dioxide or methane. Greenhouse gases have a natural warming effect, however, an increase in the amount of atmospheric greenhouse gases many enhance that effect. Since 1750, the concentration of carbon dioxide has increased 36 percent while the amount of atmospheric methane has increased 148 percent.
| 1. | What is a potential cause for an increase in greenhouse gases since 1750? |
An increase in gas released from melting ice caps
Production of greenhouse gases during the industrial revolution and population growth
An increase in the number of plants producing carbon dioxide
An increase in clorofluorocarbons resulting in depletion of the ozone layer
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