Reading Comprehension

PT109 · S2 · P3 · Q15 Atmospheric CO2

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Experts anticipate that global atmospheric concentrations of carbon dioxide (CO2) will have doubled by the end of the twenty-first century.

Topic

The potential effects of elevated CO2 levels on agriculture and global warming.

Framework

Challenge Position

Main Point

While some initially believed that increased CO2 levels could lead to lush agricultural growth and aid in decreasing global warming, research suggests that it might actually disrupt ecosystems, decrease crop yields, and exacerbate global warming. *The Most Valuable Sentence: (start of paragraph 3).*

P1: Introduction to CO2's Anticipated Impact

This paragraph sets up an initial optimistic view that increased CO2 levels might boost plant growth and lessen global warming by enhancing photosynthetic rates and trapping more carbon.

P2: Challenge to the Optimistic View

Recent studies show that while plant growth could increase with more CO2, it would vary between species, potentially reducing agricultural yields and harming ecosystem stability. For example, certain crops might suffer compared to weeds, leading to ecological changes and increased wildfire risks.

P3: Doubts About CO2 Reducing Global Warming

The paragraph discusses how in some conditions, such as warming tundras, enhanced plant growth won’t offset CO2 emissions from decomposing peat, hence the increased uptake of CO2 might not significantly curb global warming.

15.

Which one of the following best states the main point of the passage?

Elevated levels of CO2 would
Opposite
Our author is arguing (in the 2nd paragraph) that in the world of elevated CO2, there will be decreased agricultural yields.
1% picked this
Recent studies have yielded contradictory
Out of Scope
Out of Scope: contradictory Too Narrow: what about global warming The recent studies don't contradict each other -- they say that there will be more plant growth in general (due to higher photosynthetic rates), but that will lead to worse outcomes for some specific plants, such as agricultural crops. But the easiest way to get rid of this is that it's only shooting down lush agricultural abundance. It doesn't address the 2nd big prediction that the author was undermining, that there would be decreased global warming (paragraph 3).
18% picked this
Correct
The possible beneficial effects of
Why this is right
Even though this is test 33, this is a very "modern style" Main Point answer, in that it's surprisingly vague and gist-y. But because it says the possible beneficial effects (plural), it allows us to capture the fact that the author was attacking two different ideas: - we'll benefit from more CO2 because it will help beneficial plants (crops / agriculture) - we'll benefit from more CO2 because that first thing will lead to decreased global warming If we were looking for an answer choice that matched our Challenge a Position framework, then only (B) and (C) would sound like the passage was written to undermine a point of view.
Skill tested: Main Point · how this choice captures the passage's function is the move to repeat next time.
66% picked this
Increased levels of CO2 would
Too Narrow
Yes, this is basically said in the beginning of the 2nd paragraph (although we're never saying that more CO2 would directly inhibit growth rates. We're just saying that indirectly some plants would be outcompeted by other plants, and so some of them would suffer. But the bigger/easier way to get rid of this would be that it fails to mention the 3rd paragraph aspect of shooting down the idea that more CO2 will decrease global warming.
2% picked this
Increased levels of CO2 would
Missing 1st Objection
This answer captures the idea that our author resists the prediction that we'll have less global warming, but it fails to capture the idea that our author also resists the prediction that we'll have more agricultural abundance.
13% picked this

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