I suspect the arguments to your plot() functions are reversed, When you type plot(a,b), Matlab puts 'a' on the x-axis ahd 'b' on the y axis. So, when you write 'plot(avgCO2, Time2);', it is going to put time on the vertical axis and avgCO2 on the horizontal axis. That's probably the opposite of what you wanted.
When it got to the bar-graph bar(prct_inc, Time2), it used prct_inc as the independent variable (the x-axis) and apparently found two or more values that were identical, which is not allowed in a bar-graph. If Time2 were plotted on the x-axis using bar(Time2,prct_inc), this probably wouldn't happen since you wouldn't normally have two identical values of time.