They share the same Y axis, the values are taken from simulations. From the article: "The colored temperature lines are the modeled estimates that each climate

They share the same Y axis, the values are taken from simulations. From the article: "The colored temperature lines are the modeled estimates that each climate factor contributes to the overall temperature. Each factor was simulated five times, with different initial conditions; each slide here shows the average of five runs. GISS researchers laid out their historical simulations in detail last year in this [0] article." [0] http://pubs.giss.nasa.gov/abs/mi08910y.html http://pubs.giss.nasa.gov/abs/mi08910y.html