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.

Assume that both Scientist 1 and Scientist 2 were correct. How would temperature change over the next 20,000 years?

The average atmospheric temperature will continue to rise at a constant rate.

There would be an increase in atmospheric temperature, however, the rate of increase would change depending on variances in the earth's orbit.

The temperatures in the summers will be hotter while the temperatures in the winter will be cooler.

The average atmospheric temperature will increase and decrease in a cyclical manner.

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