Self-study
The following passage was written in the mid-1990s.
P1
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Intro topic ·
Evidence that earth's atmosphere is warming unusually fast
Warmed about .5 degree Celsius over the last 100 years. This is unprecedented in the previous 1,000 years.
Hypothesis ·
Global warming is connected to the greenhouse effect
Elevated levels of certain gases can trap heat in the atmosphere. Some think this is one cause of global warming.
P2
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Challenge to hypothesis ·
Expected temperature increase from greenhouse effect is higher than actual increase
Opponents of the greenhouse effect connection to global warming used this data to question the theory.
New evidence that fixes problems with old ·
Actual temperatures now match expected temperatures, after accounting for sulfates
Sulfates can lead to cooler temperatures by reflecting energy back into space. After we account for this, models of the greenhouse effect match actual temperatures.
P3
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Another challenge to hypothesis ·
Warming might be due to variations in solar energy
Some scientific models show strong correspondence between solar activity and atmospheric temperature changes.
Challenge fails ·
Solar activity models can't explain entire recent rise in temperature
Average atmospheric temperature fluctuates over long term, but used to be very stable. The solar activity corresponds to those fluctuations. But the recent increase in temperature goes beyond the most extreme fluctuations; these don't fit the model.
Conclusion ·
Greenhouse effect is best explanation for global warming
Passage Style
Critique or debate
Phenomenon-hypothesis (RC)
3.
Which one of the following ██ █████████ ██ ███ ████████
a
the way in █████ ████████ ██ ███ ███████ ██████████ ███████ ██ ██████ ██ ████████████
b
that airborne sulfates ███ ███ ████ ██████████ █████
The author doesn’t state that sulfates are the main greenhouse gases. In fact, sulfates aren’t greenhouse gases; they’re things that can cause the earth’s temperature to be cooler.
c
the usual duration ██ ███ █████ ██ ███████ █████ ██████ ██████
Not stated. We have no information about the typical duration of a cycle of solar energy output.
d
predictions as to ███ ███████ ██ ██████ ███████ ██ ███████ ███
The author doesn’t make any predictions about what will happen to global ice. Ice is mentioned as something from which we can get evidence of sulfate concentration and evidence of global warming.
e
an example of █ █████████████ ██████ ██ ████████ ████████
The author doesn’t mention any technological sources of airborne sulfates. We do get mention of sulfates from natural sources — volcanoes — the author doesn’t mention any specific examples of technological sources of sulfates.