QUESTION TEXT: The more sunlight our planet reflects back…
QUESTION TYPE: Strengthen
CONCLUSION: The more of Earth that is covered in ice and snow, the cooler the earth will be.
REASONING: Snowy land reflects more sunlight back into space than ocean or non-snowy land does. And reflection tends to cool the atmosphere.
ANALYSIS: This is nearly a rock-solid argument. But, the author forgets to address one thing: are there any other factors that affect whether land cools the earth.
For example, land might have a forest on it. And the forest could cool the earth by storing CO2. We need to show a reason that non-snowy land and ocean won’t cool the earth more than snow and ice do.
- This tells us how to make snow, but not what effect snow has compared to a forest.
- This weakens the argument. By showing reflectivity isn’t the only factor, it raises the possibility that some other factor might matter more.
- CORRECT. This helps. We already knew snow cooled the atmosphere. But the argument didn’t tell us whether ocean and non-snow land also cooled the atmosphere, by some other mechanism.
This answer eliminates that possibility, and now we can say:
1. Snowy land cools the earth
2. Other lands warm the earth
Therefore, replacing other land with snow will cool things.
- This is a tempting answer. It shows that heat is very important. But there are two problems:
1. This doesn’t show how important reflection of heat is.
2. It doesn’t address whether non-snow land has other properties which reduce heat, even if it doesn’t reflect.
- If you picked this, you may have thought you had to support the claim that snow and ice reflect sunlight. Not so. The stimulus says it’s true, so we can accept it as true. There’s no need to try to strengthen a premise.
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