Hysteresis of the intertropical convergence zone to CO2 forcing

With the unprecedented rate of global warming in recent decades, whether or not anthropogenic climate change is irreversible an important question. Based on idealized CO2 ramp-up until 1,468 ppm and symmetric ramp-down model experiments, here we show that intertropical convergence zone (ITCZ) does respond linearly to forcing, but exhibits strong hysteresis behaviour. While location ITCZ changes minimally during period, it moves sharply south as soon begins decrease, its centre eventually resides Southern Hemisphere period. Such associated with delays energy exchanges between tropics extratropics. The delayed are explained by two distinct behaviours Atlantic Meridional Overturning Circulation slower warming/cooling Ocean. We also suggest can lead regional hydrological cycles. In experiments where increases four-fold before returning original level, temperature precipitation almost linear responses forcing. contrast, response Intertropical Convergence Zone lags behind changes, exchanges.