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)
1.
Which one of the following ████ ██████████ ██████ ███ ████ █████ ██ ███ ████████
Question Type
Main point
In a Phenomenon-Hypothesis passage, if the author advocates for a hypothesis, the main point should capture that hypothesis and the author’s opinion about it. Here, the author
a
Though many accept ███ ██████ ████ ███ ██████████ ██████ ██ ███████ ███ ██████ ██████ ████████ ████ ██████ ██ ████████ ████████████ ██ █████ ██ ██████ ████ ██████████ ████████ ███ █████ ███████
The author
b
Scientific models of ███ ███████ ██ ██████████ ██████ ████████ ██ ███████████ ███ ███████ ██ ████████ █████████ ███ █████████ ███████ ████ ███████ ████ ███ ███████ ███████ ███████████ ████ ████████ ██ █████
The author doesn’t suggest that scientific models are important because they predict that the earth’s temperature will continue to rise. Rather, the author’s point is that the greenhouse effect is the best explanation for the increase in earth’s temperature observed over the past 100 years. The main point concerns what explains past temperature increase; it’s not about the future.
c
New scientific evidence █████ ████ ███ ███████ ███████████ ███████████ ███ ████ ██████ ██ █ ███ ████ ██ ██████████ ████ ███ ██████████ ███████ ███ ████ ███ ████████ ███ ████ ████ ████ ████ ██████ ██████████ ██████████
Although the author does acknowledge that early models charting the greenhouse effect predicted greater increases in temperature than that actually observed, the author explains that after the effects of sulfates were taken into account, the observed temperature increase is consistent with models of the greenhouse effect (see P2). The author then uses this consistency as part of the support for the greenhouse effect explanation. (C) doesn’t capture the author’s support for the greenhouse effect explanation.
d
Recent scientific data ███ ████████████ ███████ ███ ██████ ████ ███ ███████ ██████████ ██ ████████ ██████ ███ ████ ███ ██████████ ██████ ██ █ █████ █████ ██ ████ ███████ ██████
e
The greenhouse theory ██ █ ██████████ ███████████ ██ █ ██████ ██████ █████ ██ ███ ███████ ███████████ ████████████ ████ ██ ██ ██ ████████ ████ ███ █████████████████ ███████
The author doesn’t condition the reasonableness of the greenhouse theory on the solar-fluctuation theory. In fact, the author undermines the solar-fluctuation theory as an explanation for the increased temperature in P3.