Question
About what is the highest level of parts per million of carbon dioxide (ppm) in the air in the 400,000 years before modern time? (In other words, what level of carbon dioxide was never exceeded?)
a. carbon dioxide levels never went over about 250ppm
b. carbon dioxide levels never went over about 275ppm
c. carbon dioxide levels never went over about 300ppm
a. carbon dioxide levels never went over about 250ppm
b. carbon dioxide levels never went over about 275ppm
c. carbon dioxide levels never went over about 300ppm
Answers
Bot
b. carbon dioxide levels never went over about 275ppm