Your Friend Insists That Any Changes in Atmospheric CO₂ Levels

Your friend insists that any changes in atmospheric CO₂ levels or global temperature are nothing to worry about. He claims that these are actually normal fluctuations that have occurred for thousands of years on Earth, and that human activities play no role in these processes. What evidence could you provide to counter this argument?

A) An increase in global temperature can't be the result of normal processes such as volcanic eruptions, as these typically result in a drop in temperature.
B) Isotopic carbon evidence (especially atmospheric levels of ¹³C) demonstrates that human processes are in fact contributing to atmospheric CO₂ levels.
C) Current global temperature changes are occurring much faster than would happen under normal circumstances.
D) All of these choices are correct.