Atmospheric CO2

A free, expert breakdown of this official LSAT Reading Comprehension question.

TopicsMain PointScience

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Passage

Experts anticipate that global atmospheric concentrations of carbon dioxide (CO2) will have doubled by the end of the twenty-first century. It is known that CO2 can contribute to global warming by trapping solar energy that is being reradiated as heat from the Earth’s surface. However, some research has suggested that elevated CO2 The level of CO2 would thus increase at a lower rate than many experts have predicted.

However, while a number of recent studies confirm that plant growth would be generally enhanced in an atmosphere rich in CO2, they also suggest that increased CO2 would differentially increase the growth rate of different species of plants, which could eventually result in decreased agricultural yields. Certain important crops such as corn potential increase may lead to greater numbers of and more severe wildfires in future rangeland communities.

It is clear that the CO2 fertilization effect does not guarantee the lush world of agricultural abundance that once seemed likely, but what about the potential for the increased uptake of CO2 to decrease the rate of global warming? Some studies suggest that the changes accompanying global warming will not improve the important because high-latitude habitats such as the tundra are expected to experience the greatest temperature increase.

What this question is testing

Main Point

Your task

Capture the passage's overall primary point — the claim everything else supports.

Common trap

Answers that are true but too narrow (a single paragraph) or too broad (beyond the passage's scope).

Winning move

Summarize the whole passage in one sentence first, then match it to a choice.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question

15.

Which one of the following best states the main point of

Answer choices

Opposite1% picked this
Elevated levels of CO2 would enhance photosynthetic rates, thus increasing plant growth
Our author is arguing (in the 2nd paragraph) that in the world of elevated CO2, there will be decreased agricultural yields.
1%
Out of Scope17% picked this
Recent studies have yielded contradictory findings about the benefits of increased levels of CO2
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).
17%
Correct67% picked this
The possible beneficial effects of increased levels of CO2 on plant growth and global warming
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.
67%
Too Narrow2% picked this
Increased levels of CO2 would enhance the growth rates of certain plants, but would inhibit the growth
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%
Missing 1st Objection13% picked this
Increased levels of CO2 would increase plant growth, but the rate of global warming
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%

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