Test: ACT Science

Global warming is defined as the slow increase in the temperature of the earth’s atmosphere and is caused by pollutants and carbon dioxide (CO2). While the gradual increase in temperature cannot be refuted, scientists argue over the cause.

 Scientist 1:

Global warming is caused by increases in atmospheric CO2, which is directly created by humans and their consumption of fossil fuels. The natural CO2 released from carbon sinks has a different isotopic ratio from the CO2 released from fossil fuels. Current measurements of the radioactive isotopes of CO2 show that it is from human activity, not from nature. The Earth’s carbon sinks cannot absorb these large amounts of unnatural CO2 emissions. About fifty percent of the CO2 produced by mankind remains in the atmosphere, unable to be absorbed.

Scientist 2:

The rise in atmospheric CO2 levels are a result of global warming, not the cause of it. When the temperature increases, the CO2 in carbon sinks is released. While humans do cause release of CO2, the carbon sinks absorb it. The activity of the carbon sinks increases to allow for higher levels of CO2 absorption. Proponents for human causation of global warming point to the warming and cooling of the stratosphere, however, these temperature fluctuations are caused by changes in the sun’s heat. These proponents also look at the acidity of the ocean as evidence of human causation, however, the rise in ocean acidity is within the normal range of fluctuations over the past ten thousand years.

1.

Scientist 1 uses which of the following as evidence towards human causation of global warming?

While humans do cause releases of CO2, the carbon sinks absorb it.

Natural CO2 released from carbon sinks has a different isotopic ratio from the CO2 released from fossil fuels.

The Earth’s carbon sinks cannot absorb large amounts of natural CO2 emissions.

Natural CO2 released from carbon sinks has the same isotopic ratio from the CO2 released from fossil fuels.

When temperature increases, the CO2 in the carbon sinks is released.

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