Researchers have been studying how emissions from both volcanoes and human activities, such as the burning of fossil fuels, impact the atmosphere. Both types of emissions contribute to the total CO2 levels in the atmosphere. Graph 2 shows that atmospheric CO2 levels have been steadily increasing over time. This increase in CO2 levels has been linked to the increase in global surface temperatures. Explain why the total mass of carbon must be decreasing in a different step of the slow carbon cycle based on the on the increase in atmospheric CO2.