Fig. 5

Model simulations of the changes in total column ozone over the tropics (25°S–25°N) between 1960 and 2100 relative to the 1980 baseline (coloured lines). Each model follows a different scenario for future greenhouse gas emissions, known as the Representative Concentration Pathways (RCP), and correspond to +2.6 (dark blue), +4.5 (light blue), +6.0 (orange), and +8.5 W m⁻² (red) of global radiative forcing (radiative forcing is the difference between the incoming and outgoing energy in the Earth-atmosphere system with increasing positive values indicating an increasing warming effect). Except for RCP 8.5, which specifies large increases in methane, significant decreases in total column ozone over the tropics are projected during the twenty-first century. Also shown are the total column ozone values recorded from ground-based observations relative to the 1964–1978 average (grey line). From [14]