Fig. 2.

Radiative forcing observed since 2000 (12), and projected over the 21st century due to scenarios RCP8.5, (thick blue), RCP4.5, (thick black), and RCP3PD (thick magenta) (18), and several geoengineering options (thin lines). Radiation management schemes are shown by thin solid lines: space mirror (red lines—the steeper gradient is -1 W m^-2 per decade from 2010 and the other ramping to -4 W m^-2 by 2100); aerosol forcing is set to either a constant -1.56 W m^-2 (the average forcing of a Pinatubo eruption every 4 years), or a -4 W m^-2, (black lines). Carbon cycle alteration is shown by broken lines: afforestation, (blue dashed); biochar, (magenta dotted); BECS, (blue dotted); and a combination of BECS + afforestation + bichar, (black dotted).