18.104.22.168 Uncertainties Due to Atmospheric Dynamics
Changes in atmospheric dynamics could affect ozone. For example, sub-grid scale processes such as gravity wave propagation (e.g., Warner and McIntyre, 2001), prescribed for past and present conditions, may change in the future. Tropospheric climate changes will also alter planetary-scale waves. Together with changes in orographic gravity waves, these waves give rise to the increase in the Brewer-Dobson circulation seen in most models (Butchart et al., 2006). The magnitude of this effect varies from model to model and leads to increased adiabatic heating of the polar regions, compensating in part the increased radiative cooling from CO2 increases. Hence, the net heating or cooling is subject to large uncertainty, and available model simulations do not give a consistent picture of future development of ozone, particularly in the Arctic (Figure 7.18).