The graph below shows how the amount of carbon dioxide (CO2) in our atmosphere has changed since 1960. A graph that plots the amount of atmospheric carbon dioxide in the atmosphere from 1960 to approximately 2005. The x-axis shows the time in years. The y-axis shows the carbon dioxide concentration in parts per million. The concentration is increasing over time. Based on the information given in the graph, which of these phenomena has likely increased since 1960?
land erosion
coastal erosion
ozone depletion
greenhouse effect