RCP8.5 predicts an atmospheric CO₂ concentration of over 1200 ppm within 100 years. When is the last time that Earth experienced such high CO₂ concentrations?
A) 2.5 million years ago, just before Greenland became covered by glacial ice
B) 20,000 years ago during the Last Glacial Maximum
C) 35 million years ago when neither Greenland nor Antarctica has massive ice sheets
D) 120,000 years ago during the previous Interglacial episode