Answer:
raised atmospheric concentrations of CO2 by 47% above pre-industrial levels
Explanation:
Over the past 170 years, human activities have raised atmospheric concentrations of CO2 by 47% above pre-industrial levels found in 1850. This is more than what had happened naturally over a 20,000 year period (from the Last Glacial Maximum to 1850, from 185 ppm to 280 ppm).
