Between 400,000 years ago until 1950, the levels of carbon dioxide in the atmosphere never exceeded ____ parts per million. Today, carbon dioxide levels have exceeded ____ parts per million

fill in the blanks
400
300
200
100 for blank one

300
500
550
410 blank 2

1 answer

Between 400,000 years ago until 1950, the levels of carbon dioxide in the atmosphere never exceeded 300 parts per million. Today, carbon dioxide levels have exceeded 410 parts per million.