PT59.S2.Q25 - About 3 billion years ago

toniafisher1

I know I’m gonna feel like an idiot when this is explained, however, right now I feel like an even bigger idiot because the correct AC (B), is really confusing me. If there is much less methane in Earth’s atmosphere today than there was 3billion years ago, then less greenhouse gas equals less heat trapped, and therefore, cooler climate today than 3billion years ago. This appears to strengthen rather than weaken the argument. CAN SOMEONE PLEASE HELP ME WITH MY CONFUSION?

https://7sage.com/lsat_explanations/lsat-59-section-2-question-25/
Admin note: edited title

akistotle

P: There was water in oceans 3 billion years ago.
(Water 3B years ago)
P: Because there was less sunlight then, if oceans weren’t frozen, then there must have been more greenhouse gases than today.

(Water 3B years ago → More greenhouse gases than today)

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C: It’s likely that there was more CO2 3 billion years ago.

We know that there must have been more greenhouse gases 3 billion years ago. But does it have to be CO2? We learned that methane is also a type of greenhouse gas.

(B) says there was more methane 3 billion years ago. This weakens the argument because we can't really say it's "likely" that there was more CO2 than today. Maybe methane was the only gas that kept oceans from freezing 3 billion years ago.

toniafisher1

Wow, thank you! My mind was hurting!!