Use the figure below CO Concentration (ppm) 400 350 300 250 200 150 20 CO Temperature 17.5 -10 years -20 years - 10,000 years 15 - 15,000 years - 20,000 years 12.5 10 7.5 Thousands of years ago 5 to answer this question. 2.5 0 15 12 07 49 f -9 Approximately how many years has the mean global temperature remained at the present value? -12 present (C) Temperature change from