The graph below shows atmospheric carbon dioxide levels since the year 1880. Which of the following conclusions can be drawn from this graph?

Because the graph shows a curved line, instead of a straight one, you can conclude that as time has passed (on the x-axis) the levels of atmospheric carbon dioxide (on the y-axis) have risen at increasingly higher rates. If levels had increased at the same rate, the line would be diagonal from left to right, but it would be straight.