Logical Reasoning

PT148 · S1 · Q25 Oceanographer: To substantially reduce

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Oceanographer: To substantially reduce the amount of carbon dioxide in Earth's atmosphere, carbon dioxide should be captured and pumped deep into the oceans, where it would dissolve.

Conclusion (should = opinion)

In order to make a big reduction in atmospheric C02, we should capture CO2 and pump it deep into the oceans.

Intermediate Conclusion (so)

Any C02 pumped deep into the oceans would be trapped there for centuries.

Evidence

The cool, dense water that's deep in the ocean takes centuries to mix with the warmer water near the surface.

Evaluate

Since the argument contained multiple conclusions, we can scrutinize each of the reasoning moves.

Given that it takes centuries for the cold water at the bottom to mix with the warm water near the surface, does that convince us that any CO2 we pump down there will be trapped for centuries?

There's definitely a Linking assumption happening, if the cold hasn't → then the CO2 mixed with the warm is still trapped

What about the second reasoning move: if we accepted that the CO2 would be trapped down there for centuries, does that convince us that we should capture CO2 from the atmosphere and pump it deep into the ocean?

No, I'm not ready to sign-off on that plan yet.

Does it hurt the ocean wildlife? Does it cost too much money?

Does the pumping process send more CO2 into the atmosphere than the CO2 that gets pumped into the ocean (is there a net savings in atmospheric CO2 ?

In reality, only that last objection is relevant. The conclusion defines our goal as "substantially reducing CO2 in the atmosphere". So our objections can only be directed at the idea that this plan of pumping CO2 from air to deep-ocean would not result in a substantial reduction in atmospheric CO2.

Goal

Look for a Linking assumption like, or look for an answer ruling out an idea that would otherwise make it seem like this plan isn't really going to lead to a big decrease in atmospheric CO2.

25.

Which one of the following is an assumption that the oceanographer's argument requires?

  1. Carbon dioxide will dissolve much

    Out of Scope Comparison: thoroughly

    The author has committed to the idea that the CO2 pumped into the deep ocean would dissolve there, but that's it. There's no comparison between how thoroughly it dissolves here vs. there.

    3% picked this

  2. Evaporation of warmer ocean water

    Negation Doesn't Weaken

    This answer has that lovable Defender form; it's ruling out an idea using "not / no" language. But if we negate this, does it weaken to say, "The water that evaporates near the surface generally does release large amounts of CO2 from what ever CO2 is dissolved in that evaporating water"? At first this seems pretty tempting. If we wanted to argue that this plan wasn't going to work, then being able to say that "large amounts of CO2 were going be released into the atmosphere" definitely sounds up our alley. But this is talking about CO2 evaporating from the surface of the ocean. That doesn't have anything to do with the Plan we're evaluating. The plan is to pump CO2 deep into the cold depths of the sea. Supposedly it won't make it to the surface and evaporate until a few centuries from now. The author's plan implicitly accepts that this is a "short-term" fix, that allows us to reduce atmospheric CO2 for a few hundred years.

    11% picked this

  3. Correct

    Carbon dioxide dissolved in cool,

    Why this is right

    This has the lovable Defender ruling-out "not". If we negate it, does it weaken to say, "Hey, author --- the CO2 we pump into the cold, dense depths will escape back into the atmosphere way before the cold water mixes with the warm surface water". Sure, that weakens! The author's whole plan is about selling us a few centuries' worth of not having to worry about this CO22. Pump it down there now, and the cold water won't mix with the surface for a few centuries. The author was assuming that "if the cold water hasn't mixed with the warm, then the CO2 is still trapped". And if you believe that the CO2 is trapped until the cold mixes with the warm, then you synonymously believe that the CO2 won't escape back into the atmosphere long before the cold has mixed with the warm.

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

    75% picked this

  4. It is the density of

    Too Strong: main role

    The author is selling us on a plan to pump CO2 down to the cold, dense depths of the ocean in order to trap it there. There is no starring role there. Maybe the coldness of the water is the main reason it's trapped. Maybe the density is. Maybe the depth is. Maybe something else. The author's argument wouldn't change whether density was the biggest reason or smallest reason CO2 was trapped.

    4% picked this

  5. Carbon dioxide should be pumped

    Reversed Logic If-Conclusion

    When we see conditional answers on Necessary Assumption, we don't want to negate them. Instead, we should just look at them as a Left Side → Right Side reasoning move and ask ourselves whether that matches a move the author made. (Usually correct answers that are conditionals are written in contrapositive form) Here, we'd see the Conditional Indicator "only if" which always introduces the Right Side (necessary) idea: CO2 should be pumped the CO2 pumped into ocean depths → there would be to reduce atmosph CO2 trapped for 100's This does not match any of the Author's reasoning moves. Authors go from Evidence to Conclusion. But this answer is going from Conclusion on the left to an idea from the Evidence on the right. Putting the Conclusion on the left side of the arrow is always wrong.

    6% picked this

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