DISCUSSION: Billings is mentioned in lines 43-54. It’s a long excerpt. He found that plants grew more when CO2 was high, but that the tundra released more CO2 as well.
It’s related to the question of whether the rate of CO2 growth will slow due to plant growth.
- This is mentioned in lines 54-60, but it’s not clear that the information is based on Billings’ research.
- Billing estimated what would happen if summer temperatures rose. He didn’t say whether they would.
- CORRECT. Billings findings suggest that plant growth won’t be enough to lower the rate of CO2’s increase. CO2 causes plant growth, but it also leads to more CO2 leakage from permafrost. This accelerates warming.
- This is very tempting. But we’re not told if Billing was researching the year 2100, or whether Billing was just researching a doubling of CO2 at any time. C is a better answer, because it’s more general and thus easier to support in this case.
- Billing only researched tundra. He didn’t compare it to other habitats.
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