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)
4.
It can be reasonably inferred ████ ███ ███████ ████ ███ ██████ █████████ █████ ███ ██ ███ █████████ ████ ███████ ██ ███████ ███ ███████ ██ █ █████ █████████ ██ ███████ ███ ██████ ███████ █████ ██ ███ ████████ ███ ██████
a
a strong correspondence ███████ ███ ███████ ██████████ ███████ ██████ ████████████ ██ ███ ████ ███ █████ ███ ████ ████ ██████ ███████████ ████████████
Not supported, because there’s no indication the author believes correspondence concerning “the last few years” is crucial in determining the success of a model. Rather, what the author finds important is correspondence with the
b
that the model ████████ ██ ████████ ██ ███ ███████ ███████████ ██ ███ █████ ██ █ ██████ ███████████ █████████
There’s no evidence the author finds the simplicity of an explanation important. She doesn’t reject solar fluctuation on the basis of lack of simplicity, nor does she find the greenhouse theory persuasive because of simplicity.
c
the extent to █████ ███ █████ ███ ████ ███████ ██ █████ ██ ████████████ ████████
The author doesn’t reject the solar fluctuation theory because of how little or how much it has been revised. Nor does she accept the greenhouse theory because of how little or how much it has been revised. So there’s no evidence the author finds the extent to which a model has been revised important.
d
a close fit ███████ ███ ███████ ██████████ ██████████ ██ ███ ██████ ███ █████ ████ ███ █████████ ████████████ ██ ██ ████ ██ █████ ███████████ ████████████
The author doesn’t reject the solar fluctuation theory because of a lack of fit between warming mechanisms and those postulated by the solar fluctuation theory. She doesn’t say, for example, that solar energy isn’t something that is typically thought to change temperature. Nor does she accept the greenhouse theory on the basis of a close fit between its postulated mechanisms and those acknowledged to raise temperatures. She doesn’t say, for example, that the greenhouse theory is the best explanation because we know greenhouse gases merely because we know greenhouse gases can warm the atmosphere.
e
a long-term match ███████ ███ ███████ █████████ ███████ ██ ███ ███████ ███████████ ███ ████ ██████████ ███ ██████ ████████████ ████ ████ ████████
Supported, because the author finds it important that a model’s estimated changes correspond with the