In 2013, the sea ice in Antarctica reached a record high (GMAT CR Assumption)

In 2013, the sea ice in Antarctica reached a record high. 80% of the increase in ice volume can be attributed to the strong westerly winds in the South Pole. The ice level is much higher than the recorded ice level during the 1970s. This proves that Global Warming is a hoax.

The argument above is based on which of the following assumptions?

a) Global warming and sea ice level are correlated.
b) Sea Ice Level in Antarctica has a stronger correlation to Global Warming
c) One of the effects of Global Warming is the melting of sea ice.
d) Increase in Ice Volume is the result of low temperature
e) There was no interruption in collecting data about sea ice level from 1970 to 2013

This is an interesting assumption question. Some of the answer choices look similar and equally relevant. Before we go into answer choices, let us look into the arguments and conclusion.

Fact 1: In 2013, the sea ice in Antarctica reached a record high.

Fact 2: 80% of the increase in ice volume can be attributed to the strong westerly winds in the South Pole

Fact 3: The ice level is much higher than the recorded ice level during the 1970s

Conclusion: Global Warming is a hoax

Most GMAT Critical Reasoning questions will have 1 to 2 facts. The third fact supports Fact 1.

a) Global warming and sea ice level are correlated.

This is a basic assumption but there is a difference between correlation and causation. Two independent variables can be correlated but it does not prove that one caused the other.
For the above argument to work , the assumption is that Global Warming causes sea ice level to melt.

Eliminate Option A

b) Sea Ice Level in Antarctica has a stronger correlation to Global Warming

Similar reasoning to Option a. Even though Sea Ice Level in Antarctica and Global Warming has a stronger correlation, the causation is not clear.

c) One of the effects of Global Warming is the melting of sea ice.

This is a much direct assumption that is relevant for the argument. In fact, this statement shows that Global warming causes melting of sea ice.

Keep Option C

d) Increase in Ice Volume is the result of low temperature

Although this is relevant information, this information just adds to the fact that strong winds causes increase in Ice Volume.

Not Relevant. Eliminate Option D

e) There was no interruption in collecting data about sea ice level from 1970 to 2013

Although this is an assumption that is required to compare Ice Volume in 1970 with that of 2013, interruption in itself does not prove that the trend of decreasing ice volume cannot be attributed to Global Warming.

From the above options, C is the only relevant assumption for the argument.