Which of the following is the best statement regarding the graph of atmospheric CO2 concentrations?
a) There has been negligible change in atmospheric CO2 concentrations over the past 50 years.
b) Atmospheric CO2 concentrations have increased by more than 15% over the past 50 years.
c) Atmospheric CO2 concentrations have increased by more than 100% over the past 50 years.
d) There has been a catastrophic increase in atmospheric CO2 concentrations over the past 50 years.
