Based on data collected in Hawaii, since about 1960 the amount of CO₂ in the atmosphere has:

A) decreased as more trees are cut down
B) increased and then decreased
C) decreased and then increased
D) consistently increased, except for yearly variations

Since about 1960, the amount of CO2 in the atmosphere has consistently increased, except for yearly variations, primarily due to the burning of fossil fuels and deforestation. This trend has been observed globally, including in Hawaii, where the Mauna Loa Observatory has collected some of the longest-running data on atmospheric CO2 levels.