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Recent experiments in the Southern Ocean offer the promise

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Recent experiments in the Southern Ocean offer the promise  [#permalink]

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New post 31 Aug 2013, 07:11
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59% (01:44) correct 41% (02:00) wrong based on 396 sessions

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Recent experiments in the Southern Ocean offer the promise of controlling the threat of global warming by creating organic "sponges" for carbon dioxide, which is widely considered the main culprit for rising global temperatures. Scientists were able to grow a lush strip of phytoplankton 150 kilometers long by fertilizing a patch of the ocean with hundreds of kilograms of an iron compound. Phytoplankton presently accounts for over half of the photosynthesis on Earth, the process by which carbon dioxide is absorbed and converted into oxygen. A major limiting factor in the production of phytoplankton is lack of iron, but by fertilizing oceans with iron compounds scientists hope to be able to reduce carbon dioxide levels and reverse the greenhouse effect.

Which of the following, if true, casts the most serious doubt upon the advisability of using the fertilization method described above to control carbon dioxide levels?

(A) In some oceans, the growth of phytoplankton is also limited by how much nitrogen, phosphorus, and silicon are available.
(B) The cost of fertilizing the oceans with sufficient quantities of iron to reverse the greenhouse effect is likely to be very high.
(C) Iron naturally reaches the seas in the form of wind-blown mineral dust, which becomes more or less abundant as conditions on land change.
(D) Fertilization efforts will do nothing to curb the production of more carbon dioxide emissions.
(E) The oceans are a complex system, and the long-term consequences of ocean fertilization may be the opposite of what is predicted.
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Re: Recent experiments in the Southern Ocean offer the promise  [#permalink]

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New post 01 Sep 2013, 13:07
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Hi siddharthkanjilal
Let me try this one.

ANALYZE THE STIMULUS:

Fact: Scientists were able to grow a lush strip of phytoplankton 150 kilometers long by fertilizing a patch of the ocean with hundreds of kilogramsof an iron compound.
Fact: Phytoplankton presently accounts for over half of the photosynthesis on Earth, the process by which carbon dioxide – the main factor for rising global temperatures - is absorbed and converted into oxygen.
Fact: A major limiting factor in the production of phytoplankton is lack of iron.
Conclusion: Creating "sponges" organic for carbon dioxide can control the threat of global warming

Assumption:
- The amount of iron compound MUST be large enough to prove good effect.
- Organic sponges are GOOD and do NOT have negative effects in the long term.


ANALYZE EACH ANSWER:

Which of the following, if true, casts the most serious doubt upon the advisability of using the fertilization method described above to control carbon dioxide levels?

(A) In some oceans, the growth of phytoplankton is also limited by how much nitrogen, phosphorus, and silicon are available.
Wrong. Out of scope. Nothing about “nitrogen, phosphorus, and silicon”.

(B) The cost of fertilizing the oceans with sufficient quantities of iron to reverse the greenhouse effect is likely to be very high.
Wrong. Tempting. Scientists already know the limitation of the process is the lack of iron. It indirectly means the cost for having enough amount of iron is high. Thus, B does not weaken the conclusion.

(C) Iron naturally reaches the seas in the form of wind-blown mineral dust, which becomes more or less abundant as conditions on land change.
Wrong. SHELL GAME. The stimulus does not say iron will reduce the amount CO2. It says “hundreds of kilograms of an iron compound”, it means ONLY large amount of iron compound can help. What if iron reaches the seas, but its amount is TOO little. Clearly, It does not help. Hence, C does not weaken the conclusion.

(D) Fertilization efforts will do nothing to curb the production of more carbon dioxide emissions.
Wrong. SHELL GAME. Key word is “Sponges” which means fertilizing process ONLY absorbs CO2. The stimulus does not say the fertilizing process stops the production of CO2.

(E) The oceans are a complex system, and the long-term consequences of ocean fertilization may be the opposite of what is predicted
Correct. What if the fertilizing process has OPPOSITE effects in the long term. Thus, the process will create more CO2. E clearly weakens the conclusion.

Hope it helps.
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Re: Recent experiments in the Southern Ocean offer the promise  [#permalink]

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New post 03 Sep 2013, 14:58
Hi Pqhai,

How come A is wrong? Even though the fertilization method provides Iron, but without the other minerals phytoplankton wil not grow hence the plan fails => weakens.
Isn't E too vague?
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Re: Recent experiments in the Southern Ocean offer the promise  [#permalink]

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New post 03 Sep 2013, 15:37
summer101 wrote:
Hi Pqhai,

How come A is wrong? Even though the fertilization method provides Iron, but without the other minerals phytoplankton wil not grow hence the plan fails => weakens.
Isn't E too vague?


Hi summer101.

The stimulus says the "A major limiting factor in the production of phytoplankton is lack of iron". "A major limiting factor" means there are also other limiting factors, NOT only the lack of iron. Thus, A does not weaken the conclusion because it just rephrases the fact in other way.

E, however, says that the growth of phytoplankton may create negative effect in the future. Thus, the strategy may fail.

Hope it helps.
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Re: Recent experiments in the Southern Ocean offer the promise  [#permalink]

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New post 06 Dec 2017, 16:01
Hello from the GMAT Club VerbalBot!

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Re: Recent experiments in the Southern Ocean offer the promise &nbs [#permalink] 06 Dec 2017, 16:01
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