Oceanographer: To substantially reduce the amount of carbon dioxide in Earth's atmosphere, carbon dioxide should be c...

shunhe on May 31, 2020

Hi @CassGabriel,

Thanks for the question! So let’s take a look at what the stimulus is telling us. The oceanographer is saying that to reduce the amount of CO2 in the atmosphere, we should capture and pump it deep into the oceans, where it’d dissolve. Then, it’d stay down therefore centuries because the cool, dense water down there would take centuries to mix with the warm water nearer the surface.
?Now we’re asked to find an assumption that this argument requires, and when anticipating answers, one clear one comes to mind. The author is assuming that there’s some relation between the water mixing and the carbon dioxide being released, and in particular, she’s assuming that the carbon dioxide won’t be released before the water mixes. Otherwise, there’d be no point in saying the last sentence of the prompt.

Taking a look at the answer choices, we can see that this matches what’s written in (C), though (C) says it in a very convoluted way. Basically, (C) is saying that the author assumes that CO2 dissolved in cold water down below won’t escape a long time before it mixes with warmer water. Using the assumption negation technique, if we say that it could escape back into Earth’s atmosphere a long time before the mixing happens, then the oceanographer’s argument has a huge hole in it.

(E), on the other hand, is just outside the scope of the passage. (E) is a mistaken reversal, because remember we diagram X only if Y as X — > Y. So diagramming (E), we get

CO2 should be pumped —> CO2 would be trapped for hundreds of years

And this is definitely not an assumption the argument requires, and is actually irrelevant to the argument.

Hope this helps! Feel free to ask any other questions that you might have.